METHODS AND COMPOSITIONS FOR ACCELERATED TRAIT INTROGRESSION
Compositions and methods are provided for the use of pollen-inhibitor genes and/or color marker genes in accelerated trait introgression. Compositions and methods are also provided for introducing a pollen-inhibitor gene and/or a color marker gene in close proximity to a trait locus of interest. Breeding methods and methods for selecting plants comprising a trait locus of interest in close proximity to at least one pollen-inhibitor gene and/ or color marker gene are also disclosed. The methods and compositions employ at least one pollen-inhibitor gene and /or color marker gene to provide an effective system for accelerated trait introgression in the genome of a plant.
Latest PIONEER HI-BRED INTERNATIONAL, INC. Patents:
This application claims the benefit of U.S. patent application Ser. No. 15/554,234 (Published as US Patent Publication Number 2018-0119162), filed on Aug. 29, 2017, which claims the benefit of PCT Application Serial Number PCT/US16/22621, filed Mar. 16, 2016, which claims the benefit of U.S. Provisional Application No. 62/135,261, filed Mar. 19, 2015, both of which are incorporated herein in its entirety by reference.
FIELDThe disclosure relates to the field of plant molecular biology. In particular, methods and compositions are provided for introducing and using pollen-inhibitor loci and color marker loci in accelerated trait introgression.
REFERENCE TO A SEQUENCE LISTING SUBMITTED AS A TEXT FILE VIA EFS-WEBThe official copy of the sequence listing is submitted electronically via EFS-Web as an XML formatted sequence listing with a file name of BB2237-US-PCN.xml created on Aug. 31, 2022 and is filed concurrently with the specification. The sequence listing contained in this XML formatted document is part of the specification and is herein incorporated by reference in its entirety.
BACKGROUNDRecombinant DNA technology has made it possible to insert foreign DNA sequences into the genome of an organism, as well as altering endogenous genes of an organism, thus, altering the organism's phenotype. The most commonly used plant transformation methods are Agrobacterium infection and biolistic particle bombardment in which transgenes integrate into a plant genome in a random fashion and in an unpredictable copy number.
Site-specific integration techniques, which employ site-specific recombination systems, as well as, other types of recombination technologies, have been used to generate targeted insertions of genes of interest in a variety of organism. Other methods for inserting or modifying a DNA sequence involve homologous DNA recombination by introducing a transgenic DNA sequence flanked by sequences homologous to the genomic target. U.S. Pat. No. 5,527,695 describes transforming eukaryotic cells with DNA sequences that are targeted to a predetermined sequence of the eukaryote's DNA. Transformed cells are identified through use of a selectable marker included as a part of the introduced DNA sequences. While such systems have provided useful techniques for targeted insertion of sequences of interest, there remains a need for methods and compositions which improve these systems and allow for improved breeding methods and compositions and methods useful for accelerated trait introgression.
BRIEF SUMMARYCompositions and methods are provided for the use of pollen-inhibitor genes and/or color maker genes in accelerated trait introgression. Compositions and methods are also provided for introducing a pollen-inhibitor gene and/or a color marker gene in close proximity to a trait locus of interest. Breeding methods and methods for selecting plants comprising a trait locus of interest in close proximity to at least one pollen-inhibitor gene and/or a color marker gene are also disclosed.
In one embodiment of the disclosure, the method comprises a method for introducing a pollen-inhibitor gene in close proximity to a trait locus of interest in the genome of a progeny plant, said method comprising: (a) providing a first plant having within a genomic window at least one trait gene of interest integrated into a first target site located proximal to a telomere, wherein said genomic window is about 10 cM in length, wherein said first plant does not comprise a pollen-inhibitor gene; (b) breeding to said first plant a second plant, wherein said second plant comprises in said genomic window a pollen-inhibitor gene integrated into a second target site located proximal to both the telomere and the trait gene of interest of (a); and (c) selecting a progeny plant from step (b) comprising said trait gene of interest and said pollen-inhibitor gene, wherein said trait gene of interest and said pollen-inhibitor gene are genetically linked
In another embodiment, the method comprises a method for introducing two pollen-inhibitor genes in close proximity to a trait locus of interest in the genome of a progeny plant, said method comprising: (a) providing a first plant having within a genomic window a first pollen-inhibitor gene integrated into a first target site, wherein said genomic window is about 10 cM in length; (b) breeding to said first plant a second plant having a trait gene of interest integrated into a second target site within said genomic window; (c) selecting a progeny plant from step (b) comprising said first pollen-inhibitor gene and said trait gene of interest in said genomic widow; (d) providing a third plant having a second pollen-inhibitor gene integrated into a third target site within said genomic window; (e) breeding to said third plant a fourth plant, wherein said fourth plant comprises a pollen-inhibitor maintainer (PIM) gene; (f) selecting a progeny plant from step (e) comprising said second pollen-inhibitor gene and said pollen-inhibitor maintainer (PIM) gene; and, (g) cross pollinating the progeny plant of (c) with the progeny plant of (f) and selecting for a progeny plant that comprises said first pollen-inhibitor gene, said trait gene of interest, and said second pollen-inhibitor gene, wherein said first pollen-inhibitor gene, said trait gene of interest, and said second pollen-inhibitor gene are genetically linked. Optionally, the PIM gene is not genetically linked or has been segregated away from said first pollen-inhibitor gene said trait gene of interest and said second pollen-inhibitor gene. The target sites as described herein can be selected from the group consisting of a recombinase target site, a transgenic SSI target site, a single-strand-break-inducing-agent target site, and a double-strand-break-inducing-agent target site, or any one combination thereof. The double-strand-break-inducing-agent target site includes a target site any double strand break inducing agent. For example, but not limiting to an agent selected from the group of a Cas9 endonuclease, a zinc-finger nuclease, a Tal Effector nuclease (TALEN), a meganuclease and an engineered endonuclease.
In one embodiment, the method comprises a method for introducing a pollen-inhibitor gene and a color marker gene in close proximity to a trait locus of interest in the genome of a plant, said method comprising: (a) providing a first plant having a trait of interest located within a genomic window, wherein said genomic window is about 10 cM in length; (b) introducing into said genomic window of the plant of (a) a color marker gene; (c) breeding to the plant of (b) a second plant, wherein said second plant is a haploid inducer line capable of producing haploid embryos; (d) selecting haploid embryos from the plant of (c) and introducing into said haploid embryos, a pollen-inhibitor gene; and, (e) producing a double haploid plant from the haploid embryo of (d).
In one embodiment, the method comprises a method for introducing two color marker genes in close proximity to a trait locus of interest in the genome of a plant, said method comprising: (a) providing a first plant having a trait of interest located within a genomic window, wherein said genomic window is about 10 cM in length; (b) introducing into said genomic window of the plant of (a) a color marker gene; (c) breeding to the plant of (b) a second plant, wherein said second plant is a haploid inducer line capable of producing haploid embryos; (d) selecting haploid embryos from the plant of (c) and introducing into said haploid embryos, a second color marker gene; and (e) producing a double haploid plant from the haploid embryo of for introducing. As described herein, the color marker or the pollen-inhibitor gene can be introduced into any target site of a double-strand-break-inducing-agent.
In another embodiment, the method comprises a method for introducing a pollen-inhibitor gene in close proximity to a trait locus of interest in the genome of a progeny plant, said method comprising: (a) providing a first plant having within a genomic window at least a first transgenic SSI target site located proximal to a telomere, wherein said first transgenic SSI target site comprises at least one trait gene of interest, wherein said genomic window is about 5 cM in length and located within 0.1 cM to 10 cM of the telomere, and wherein said first plant does not comprise a pollen-inhibitor gene; (b) breeding to said first plant a second plant, wherein said second plant comprises in said genomic window a second transgenic SSI target site located proximal to both the telomere and the trait gene of interest, wherein said second transgenic SSI target site comprises a pollen-inhibitor gene, wherein said second plant does not comprise said first transgenic target site; and (c) selecting a progeny plant from step (b) comprising said trait gene of interest and said pollen-inhibitor gene, wherein said trait gene of interest and said pollen-inhibitor gene are genetically linked in said genomic window.
In another embodiment, the method comprises a method for accelerated trait introgression in the genome of a plant, the method comprising: (a) providing a first progeny plant having within a genomic window at least a first transgenic SSI target site located proximal to a telomere and a second transgenic SSI target site located proximal to both the telomere and the trait gene of interest, wherein said first transgenic SSI target site comprises at least one trait gene of interest, wherein said second transgenic SSI target site comprises a pollen-inhibitor gene, wherein said first transgenic target site and said pollen-inhibitor gene are genetically linked in said genomic window, wherein said genomic window is about 5 cM in length and located within 10 cM of the telomere;(b) cross pollinating the first plant of (a) with pollen from a second plant; and (c) selecting a progeny plant from step (b) comprising said first transgenic target site and said pollen-inhibitor gene. The second plant can be an elite inbred line.
In another embodiment, the method comprises a method for introducing two pollen-inhibitor genes in close proximity to a trait locus of interest in the genome of a progeny plant, said method comprising: (a) providing a first plant having within a genomic window at least a first transgenic SSI target site, wherein said first transgenic SSI target site comprises a first pollen-inhibitor gene, wherein said genomic window is about 5 cM in length; (b) breeding to said first plant a second plant, wherein said second plant comprises in said genomic window a second transgenic SSI target site, wherein said second transgenic SSI target site comprises at least one trait gene of interest wherein said second plant does not comprise said first transgenic target site; (c) selecting a progeny plant from step (b) comprising said first transgenic target site and said second transgenic target site genetically linked in said genomic widow, (d) providing a third plant having within said genomic window at least a third transgenic SSI target site and a pollen-inhibitor maintainer (PIM), wherein said third transgenic SSI target site comprises a second pollen-inhibitor gene, (e) using the third plant of step (d) to pollinate the plant of step (c) and selecting a progeny plant wherein said first transgenic SSI target site, said second transgenic SSI target site, and said third transgenic SSI target site are genetically linked to each other, and optionally, wherein the PIM gene has been segregated away
In one embodiment, the method comprises a method for introducing two pollen-inhibitor genes in close proximity to a trait locus of interest in the genome of a progeny plant, said method comprising: (a) providing a first plant having within a genomic window at least a first transgenic SSI target site, wherein said first transgenic SSI target site comprises a first pollen-inhibitor gene, wherein said genomic window is about 5 cM in length; (b) breeding to said first plant a second plant, wherein said second plant comprises in said genomic window a second transgenic SSI target site, wherein said second transgenic SSI target site comprises at least one trait gene of interest wherein said second plant does not comprise said first transgenic target site; (c) selecting a progeny plant from step (b) comprising said first transgenic target site and said second transgenic target site genetically linked in said genomic widow; (d) providing a third plant having within said genomic window at least a third transgenic SSI target site, wherein said third transgenic SSI target site comprises a second pollen-inhibitor gene; (e) breeding to said third plant a fourth plant, wherein said fourth plant comprises a pollen-inhibitor maintainer (PIM) gene; (f) selecting a progeny plant from step (e) comprising said third transgenic target site and pollen-inhibitor maintainer (PIM) gene; and (g) cross pollinating the progeny plant of (c) with the progeny plant of (f) and selecting for a progeny plant that comprises said first transgenic SSI target site, said second transgenic SSI target site and said third transgenic SSI target site, wherein said first transgenic SSI target site, said second transgenic SSI target site and said third transgenic SSI target site, are genetically linked. Compositions and methods are provided for the use of pollen-inhibitor genes and/or color maker genes in accelerated trait introgression.
In one embodiment, the method comprises a method of accelerated trait introgression in the genome of a plant, the method comprising: (a) providing a first plant having within a genomic window at least one trait of interest located proximal to a telomere, and at least one pollen-inhibitor gene located proximal to both the telomere and the trait of interest, wherein said trait of interest and said pollen-inhibitor gene are genetically linked in said genomic window, wherein said genomic window is about 5 cM in length and located within 10 cM of the telomere; (b) cross pollinating the first plant of (a) with pollen from a second plant; and, (c) selecting a progeny plant from step (b) comprising said trait of interest and said pollen-inhibitor gene; and, (d) optionally, backcrossing the progeny plant of (c) as the pollen donor onto a recurrent parent plant and selecting progeny plants comprising the trait of interest.
In one embodiment, the method comprises a method of accelerated trait introgression in the genome of a plant, the method comprising: (a) providing a first plant having within a genomic window at least one trait of interest located proximal to a telomere, and at least one color marker gene located proximal to both the telomere and the trait of interest, wherein said trait of interest and said color marker gene are genetically linked in said genomic window, wherein said genomic window is about 5 cM in length and located within 10 cM of the telomere; (b) cross pollinating the first plant of (a) with pollen from a second plant; and, (c) selecting a progeny plant from step (b) comprising said trait of interest site and said color marker gene; and, (d) optionally, backcrossing the progeny plant of (c) as the pollen donor onto a recurrent parent plant and selecting progeny plants comprising the trait of interest.
In one embodiment, the method comprises a method of accelerated trait introgression in the genome of a plant comprising: (a) providing a first plant having within a genomic window at least one trait of interest, a first pollen-inhibitor gene, and a second pollen-inhibitor gene wherein said genomic window is about 5 cM in length, and wherein said trait of interest is flanked by said first and second pollen-inhibitor gene; (b) cross-pollinating the first plant of (a) with pollen from a second plant; and (c) selecting a progeny plant from step (b) comprising said first pollen-inhibitor gene, said trait of interest, and said second pollen-inhibitor gene; and, (d) optionally, cross pollinating the progeny plant from step (c) to a recurrent parent plant and selecting progeny plants comprising the trait of interest.
In one embodiment, the method comprises a method of accelerated trait introgression in the genome of a plant comprising: (a) providing a first plant having within a genomic window at least one trait of interest, a pollen-inhibitor gene and a color marker gene, wherein said genomic window is about 5 cM in length, and wherein trait of interest is flanked by said first and second pollen-inhibitor gene; (b) cross-pollinating the first plant of (a) with pollen from a second plant; and, (c) selecting a progeny plant from step (b) comprising said first pollen-inhibitor gene, said trait of interest, and said second pollen-inhibitor gene; and (d) optionally, cross pollinating the progeny plant from step (c) to a recurrent parent plant and selecting progeny plants comprising the trait of interest.
In one embodiment, the method comprises a method accelerated trait introgression in the genome of a plant comprising: (a) providing a first plant having within a genomic window at least one trait of interest and at least a first color marker gene integrated into a first target site, a second color marker gene integrated into a second target site for, wherein said genomic window is about 5 cM in length, and wherein trait of interest is flanked by said first and second pollen-inhibitor gene;(b) cross-pollinating the first plant of (a) with pollen from a second plant; and, (c) selecting a progeny plant from step (b) comprising said first pollen-inhibitor gene, said trait of interest, and said second pollen-inhibitor gene; and (d) optionally, cross pollinating the progeny plant from step (c) to a recurrent parent plant and selecting progeny plants comprising the trait of interest.
Also provided are nucleic acid constructs, plants, plant cells, explants, seeds and grain having at least one pollen-inhibitor gene and/or color marker linked to a trait locus of interest. Additional embodiments of the methods and compositions of the present disclosure are shown herein.
The invention can be more fully understood from the following detailed description and the accompanying drawings and Sequence Listing that form a part of this application.
The sequence descriptions summarize the Sequence Listing attached hereto. The Sequence Listing contains one letter codes for nucleotide sequence characters and the single and three letter codes for amino acids as defined in the IUPAC-IUB standards described in Nucleic Acids Research 13:3021-3030 (1985) and in the Biochemical Journal 219(2):345-373 (1984). The symbols and format used for nucleotide and amino acid sequence data comply with the rules set forth in 37 C.F.R. § 1.822.
Many modifications and other embodiments of the disclosures set forth herein will come to mind to one skilled in the art to which this disclosure pertains having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the disclosure is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.
Compositions and methods are provided herein for use of a pollen-inhibitor gene, a color marker gene or a pollen-inhibitor and/or color marker expression cassette in the genome of a plant.
As used herein, a “Pollen-Inhibitor gene” refers to a gene that when expressed in pollen or during pollen development, encodes a protein that renders the pollen grain incapable of germinating to produce a pollen tube, or produces a compromised pollen tube incapable of reaching the ovule and fertilizing the egg. Pollen-inhibitor genes also include genes that, when suppressed or silenced, render the pollen grain incapable of germinating to produce a pollen tube, or produces a compromised pollen tube incapable of reaching the ovule and fertilizing the egg.
A pollen-inhibitor gene (pollen inhibitor gene) can be expressed by a pollen-inhibitor expression cassette. A pollen-inhibitor expression cassette refers to a recombinant DNA construct comprising a promoter that stimulates transcription in pollen or during pollen development operably linked to a pollen-inhibitor gene and a 3′ regulatory sequence such as a terminator.
A pollen-inhibitor locus (pollen inhibitor locus) refers to a genomic location defined by a genetic and physical position, where a pollen-inhibitor gene is located, or into which a pollen-inhibitor expression cassette has integrated. The genomic location defined by a genetic and physical position, into which a pollen-inhibitor expression cassette has integrated is referred to as a “pollen-inhibitor locus”.
A non-conditional pollen-inhibitor gene includes a gene that when expressed in pollen produces a protein that will inhibit pollen germination or pollen tube elongation. Examples of genes that can be used as pollen inhibition include, but are not limited to, the maize alpha-amylase gene (Albertsen, et al., (1999) U.S. Pat. No. 5,962,769), the barnase gene from Bacillus amyloliquefaciens (Mariani, et al., (1990) Nature 347:737-741) and the KID gene from Escherichia coli (de al Cueva-Mendez, et al., (2003) EMBO J. 22:246-251). Other pollen-inhibitor genes are well known in the art (see, van Melderen and de Bast, (2009) PIOS Genetics 5:1-6 and Yamaguchi, et al., (2001) Ann Rev Genetics 45:61-79 and Leplae, et al., (2001) Nuc Acids Res 1-13).
A conditional pollen-inhibitor gene includes a gene that when expressed to encode a protein in pollen grains is not inhibitory until the protein cognate substrate is supplied to the pollen. At this point, the non-inhibitory substrate is converted to an inhibitory molecule. Conditional inhibitory genes include, but are not limited to, the codA gene (Danielsen, et al., (1993) Mol. Microbiol. 6:1335-1344), the dhlA gene (Naested, et al., Plant J. 18:571-576), the tms2 gene (Sundaresan, et al., (1995) Genes Dev. 9:1797-1810) or the CYP105A gene (O'Keefe, et al., Plant Physiol. 105:473-482). When expressed in plants, the encoded gene products are themselves neutral. However, when a non-inhibitory substrate is supplied, the encoded protein converts this compound to an inhibitory compound or inhibitory derivative. The coda encoded protein converts 5-fluorocytosine (5-FC) to cytotoxic 5-fluorouracil (5-FU), the dhlA-encoded protein hydrolyzes haloalkanes such as 1,2 dichloroethane to the cytotoxic halogenated alcohol, the tms2-encoded protein converts indole-3 acetamide to the auxin indole-3-acetic acid, and the P450-monooxygenase gene CYP105A encodes a protein that converts the non-herbicidal sufonylurea R7402 into a potent herbicide.
Promoters useful for expressing pollen-inhibitor genes include included promoters that are expressed after tetrad formation within the maturing pollen grain, the mature pollen grain or during pollen germination, for example, the maize Zm13 promoter (Hamilton, et al., (1998) Plant Mol Biol. 38:663-669), the tomato LAT52 promoter (Twell, (1990) et al., Development 109:705-713), the Brassica Bp19 promoter (Albani, et al., (1991) PMB 16:501-513), the tobacco NTP303 promoter (Weterings, et al., (1995) Plant J. 8:55-63), the wheat TaPSG719 promoter (Chen, et al., (2010) Mol. Biol. Rep. 37:737-744), maize SEQ ID NO:1 (Allen and Lonsdale, (1995) U.S. Pat. No. 5,412,085), the maize pollen-specific promoter described in Fearing, et al. ((1997) Mol Breeding 3:169-176, the tobacco NTPp13 promoter (Yang, et al., (2010) Genetika 46:458-463) and promoters of pollen-specific genes described in Khurana, et al. ((2012) Critical Rev in Plant Science 31:359-390).
Inducible expression can be driven by a promoter that is activated by a specific ligand or by an environmental stimulus. Examples include, but are not limited to, the tetracyclin-responsive repressor system (Gatz and Quail, (1988) PNAS 85:1394-1397), the ethametsulfuron-responsive repressor system (DuPont Patent Applications, McBride, et al.), the safener-inducible In2 promoter from maize (DeVelder, et al., (1997) Plant Cell Physiol 38:568-577), the copper-inducible ACE1 system (McKenzie, et al., (1998)), the ethanol-inducible AlcA system (Cadick, et al., (1988) Nat. Biotechnol. 16:177-180; Runzhi, et al., (2005) Plant Sci. 169:463-469), the glucocorticoid GVG inducible expression system (Aoyama and Chua, (1997) Plant J. 11:605-612), estradiol-inducible expression system (Bruce, et al., (2000) Plant Cell 12:65-79; Zuo, et al., (2000) Plant J. 24:265-273) and the methoxyfenozide-inducible VGE system (Koo, et al., (2004) Plant J. 37:439-448; Padidum, et al., (2003) Curr. Opin. Plant Biol. 6:87-91)
As described herein, color markers can be useful for screening kernels for the presence of a specific locus. Seed color markers represent an alternative method to the pollen-inhibitor screen described herein, to screen for progeny that have broken the linkage between the trait and the seed-color locus.
A color marker gene can be expressed by a color marker expression cassette. A color marker expression cassette refers to a recombinant DNA construct comprising a promoter operably linked to a gene encoding a color maker. Color maker genes include genes whose expression result in anthocyanin accumulation including ZM-R (X15806, see, Perrot and Cone, (1989) Nucl. Acids Res 17:8003), ZM-C1 (NCBI Locus NM_001158182, see, Alexandrov, et al., (2009) Plant Mol. Biol 69:179-194) monocot orthologs of the maize R and Cl, genes and the fusion of these two genes as CRC (The Cl DNA-Binding domain, the R gene and the Cl activation domain, fused together in that order). Color markers that could be useful also include genes that encode fluorescent proteins such as Am-CYAN1, AcGFP1, ZS-GREEN, ZS-YELLOW1, DS-RED2, DS-RED-EXPRESS (Clontech).
A color marker locus refers to a genomic location defined by a genetic and physical position, where a color marker gene is located, or into which color marker expression cassette has integrated. The genomic location defined by a genetic and physical position, into which a color marker expression cassette has integrated is referred to as a “color marker locus”.
Promoters to control expression of color markers in the seed include, but are not limited to, outer endosperm promoters or aleurone promoters such as the barley LTP1 promoter (Skriver, et al., (1992) Plant Mol. Biol. 18:585-589), the barley LTP2 promoter (Kalla, et al., (1994) Plant J. 6:849-860), the barley GAmyb and High-pl Alpha amylase promoters (Gubler, et al., (1995) Plant Cell 7:1879-1891), the wheat Early Methionine promoter (Furtado and Henry, (2005) Plant Biotechnol. J. 3:421-434), the rice Chi26 and LTP2 promoters (Hwang, et al., (2001) Plant Cell Rep. 20:647-654), the maize BETL1 promoter (Hueros, et al., (1999) Plant Physiol. 121:1143-1152), the maize cystatin (CC7) promoter (U.S. Pat. No 8,481,811, issued on Jul. 9, 2013), the maize LEG1A promoter (US Patent Application Publication Number US2011/0271405 A1, published Nov. 3, 2011), maize End 2 promoter (U.S. Pat. No. 6,903,205, issued on Mar. 4, 2003), and monocot orthologs or paralogs of the above promoters. Provided herein are plants, plant parts, plant cells or seeds having in its genome a genomic window. A genomic window refers to a segment of a chromosome in the genome of a plant that is desirable for producing at least one trait locus, or the segment of a chromosome comprising at least one trait locus that was produced by the methods provided herein.
The genomic window can be about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 or more centimorgans (cM) in length. In one embodiment, the genomic window can be about 1-2 cM, about 1-3 cM, about 1-4 cM, about 1-5 cM, about 1-6 cM, about 1-7 cM, about 1-8 cM, about 1-9 cM, about 1-10 cM, about 2-3 cM, about 2-4 cM, about 2-5 cM, about 2-6 cM, about 2-7 cM, about 2-8 cM, about 2-9 cM, about 2-10 cM, about 3-4 cM, about 3-5 cM, about 3-6 cM, about 3-7 cM, about 3-8 cM, about 3-9 cM, about 3-10 cM, about 4-5 cM, about 4-6 cM, about 4-7 cM, about 4-8 cM, about 4-9 cM, about 4-10 cM, about 5-6 cM, about 5-7 cM, about 5-8 cM, about 5-9 cM, about 5-10 cM, about 6-7 cM, about 6-8 cM, about 6-9 cM, about 6-10 cM, about 7-8 cM, about 7-9 cM, about 7-10 cM, about 8-9 cM, or about 8-10 cM in length.
A “centimorgan” (cM) or “map unit” is the distance between two linked genes, markers, target sites, genomic loci of interest, loci, or any pair thereof, wherein 1% of the products of meiosis are recombinant. Thus, a centimorgan is equivalent to a distance equal to a 1% average recombination frequency between the two linked genes, markers, target sites, loci, genomic loci of interest or any pair thereof.
The genomic window can be located proximal to a telomere of a chromosome or in a non-telomeric (internal) region of a chromosome. The location of the genomic window proximal to a telomere can be about 0.1 to 1 cM, 0.1 to 10 cM, 1-10 cM, 5-15 cM or 20-25 cM distant from telomeric end of the chromosome. The genomic window can comprise various components. Such components can include, for example, but not limited to, recombination target sites, target sites for site-specific integration (such as, but not limited to, transgenic SSI target sites), single-strand break target sites, double-strand break target sites, genomic loci of interest, native genes, mutated genes, edited genes, trait loci of interest, pollen-inhibitor genes, and polynucleotides of interest. The genomic window can comprise at least 1, 2, 3, 4, 5 or more target sites for a recombinase, a single-strand-break-inducing agent (such as but not limited to a nickase, a Cas endonuclease), a double-strand-break-target site (such as but not limited to a Cas endonuclease, a Zinc finger nuclease, a TALEN, a meganuclease and/or an engineered endonuclease) such that each target site has a different genomic insertion site within the genomic window. In addition, the genomic window can comprise at least 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more trait loci of interest each having a different genomic insertion site. By a “different genomic insertion site” is meant that each component of the genomic window (such as for example target sites and trait loci of interest) is inserted into the genome at a different location and as such each component can segregate independently from one another. For example, the genomic window can comprise a combination of target sites and/or trait loci of interest such that each target site or trait loci of interest has a different genomic insertion site within the genomic window.
The components of the genomic windows provided herein have different genomic insertion sites and as such can segregate independently from one another. As used herein, “segregate independently”, is used to refer to the genetic separation of any two or more genes, transgenes, native genes, mutated genes, target sites, genomic loci of interest, markers and the like from one another during meiosis. Assays to measure whether two genetic elements segregate independently are known in the art. As such, any two or more genes, transgenes, native genes, mutated genes, target sites, genomic loci of interest, markers and the like within a genomic window provided herein, have genomic insertion sites located at an appropriate distance from one another so that they generally segregate independently at a rate of about 10% or less. Thus, the components of the genomic windows provided herein can segregate independently from one another at a rate of about 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%, 0.3%, 0.2%, 0.1% or 0.05%. Alternatively, the components of the genomic windows provided herein can segregate independently from one another at a rate of about 10-0.1%, about 10-0.5%, about 10-1%, about 10-5%, about 9-0.1%, about 9-0.5%, about 9-1%, about 9-5%, about 8-0.1%, about 8-0.5%, about 8-1%, about 8-4%, about 7-0.1%, about 7-0.5%, about 7-1%, about 7-4%, about 6-0.1%, about 6-1%, about 6-0.5%, about 6-3%, about 5-0.1%, about 5-1%, about 5-0.5%, about 4-0.1%, about 4-1%, about 4-0.5%, about 3-0.1%, about 3-1%, about 3-0.5%, about 2-0.1%, about 2-0.5%, about 1-0.1%, about 1-0.5%, or less than 0.1%. For example, if the genomic window comprises a target site and a trait locus of interest that are about 5 cM from each other, the target site and the trait locus trait locus of interest would segregate independently at a rate of about 5%.
As used herein, a “genomic locus of interest” (plural “genomic loci of interest”) comprises a collection of specific polymorphisms that are inherited together. The terms “trait locus” and “trait locus of interest” (plural “trait loci of interest”) are used interchangeably herein and refer to a genomic locus of interest that comprises a trait of interest. A given trait locus of interest can include but is not limited to, a modified or edited native gene, a transgene, an altered double-strand-break target site, a native gene, or a transgenic SSI target site.
As used herein, a “trait” refers to the phenotype conferred from a particular gene or grouping of genes. A trait gene of interest includes any one gene or grouping of genes that encodes a trait. Any desired trait (also referred to as trait of interest) can be introduced into the genome at a given trait locus of interest. Such traits include, but are not limited to, traits conferring insect resistance, disease resistance, herbicide tolerance, male sterility, abiotic stress tolerance, altered phosphorus, altered antioxidants, altered fatty acids, altered essential amino acids, altered carbohydrates, or sequences involved in site-specific recombination. In terms of relative position of two loci on a chromosome, a locus is more “proximal” if it is closer to the centromere (and farther from the telomere) of that chromosome, and a locus is more “distal” if it is closer to the telomere (and farther from the centromere).
The trait locus of interest can include, for example, any modification that confers a trait, such as a transgene or a native trait. The trait locus of interest can also include a native trait or a selectable marker. Selectable markers are described in more detail further herein and include DNA segments that encode products which provide resistance against otherwise toxic compounds. As used herein, a “native trait” refers to a trait found in nature. In another embodiment, the trait locus of interest comprises a transgene.
A given trait locus of interest has its own genomic insertion site within the genomic window. For example, a trait locus of interest and a target site (for a recombinase, a single-strand-break-inducing agent, a double-strand-break-target site, or others) within the genomic window will have different genomic insertion sites within the genome. A given target site can be found within about 10 cM, 9 cM, 8 cM, 7 cM, 6 cM, 5 cM, 4 cM, 3 cM, 2 cM, 1 cM, 0.9 cM, 0.8 cM, 0.7 cM, 0.6 cM, 0.5 cM, 0.4 cM, 0.3 cM, 0.2 cM, 0.1 cM or 0.05 cM from the trait locus of interest such that the target site and trait locus of interest have different genomic insertion sites.
Compositions and methods are provided for introducing a pollen-inhibitor gene and/or a color marker gene in close proximity to a trait locus of interest in the genome of a progeny plant. In one embodiment of the disclosure, the method comprises: (a) providing a first plant having within a genomic window at least one trait gene of interest integrated into a first target site located proximal to a telomere, wherein said genomic window is about 10 cM in length, wherein said first plant does not comprise a pollen-inhibitor gene; (b) breeding to said first plant a second plant, wherein said second plant comprises in said genomic window a pollen-inhibitor gene integrated into a second target site located proximal to both the telomere and said trait gene of interest; and, (c) selecting a progeny plant from step (b) comprising said trait gene of interest and said pollen-inhibitor gene, wherein said trait gene of interest and said pollen-inhibitor gene are genetically linked.
In one embodiment of the disclosure, the method comprises: (a) providing a first plant having within a genomic window a first pollen-inhibitor gene integrated into a first target site, wherein said genomic window is about 10 cM in length; (b) breeding to said first plant a second plant having a trait gene of interest integrated into a second target site within said genomic window; (c) selecting a progeny plant from step (b) comprising said first pollen-inhibitor gene and said trait gene of interest in said genomic widow; (d) providing a third plant having a second pollen-inhibitor gene integrated into a third target site within said genomic window; (e) breeding to said third plant a fourth plant, wherein said fourth plant comprises a pollen-inhibitor maintainer (PIM) gene within said genomic window; (f) selecting a progeny plant from step (e) comprising said second pollen-inhibitor gene and said pollen-inhibitor maintainer (PIM) gene; and, (g) cross pollinating the progeny plant of (c) with the progeny plant of (f) and selecting for a progeny plant that comprises, genetically linked to each other. Optionally, the PIM gene is segregated away from said first pollen-inhibitor gene, said trait gene of interest, and said second pollen-inhibitor gene.
As used herein, by “target site” is intended a polynucleotide comprising a nucleotide sequence comprising at least one recognition sequence for an agent such as, but not limited to, a recombinase, a single-strand-break-inducing agent (such as but not limited to a nickase or a Cas endonuclease) or a double-strand-break-inducing target site (such as but not limited to a Cas endonuclease, a Zinc finger nuclease, a TALEN, a meganuclease, an engineered endonuclease, or any one combination thereof).
By “transgenic target site” is meant a target site that is non-native in sequence and/or in genomic location to the plant genome. In some embodiments, the transgenic target site can comprise at least 1, 2, 3, 4, 5 or more recombination sites for site-specific recombination (also referred to as transgenic SSI target site). Site-specific recombination system employ various components which are described herein and in U.S. Pat. Nos. 6,187,994, 6,262,341, 6,331,661 and 6,300,545, each of which is herein incorporated by reference.
The terms “transgenic SSI target site”, “transgenic target site for site specific integration (SSI)”, and “transgenic target site for SSI” are used interchangeably herein and refer to a polynucleotide comprising a nucleotide sequence flanked by at least two recombination sites (see, for example, US Patent Publication Number US 2013/0198888 A1, published on Aug. 1, 2013, and US Patent Publication Number US 2014/0338070 A1, published on Nov. 13, 2014, each of which is herein incorporated by reference. In some embodiments, the recombination sites of the transgenic SSI target site are dissimilar and non-recombinogenic with respect to one another. One or more intervening sequences may be present between the recombination sites of the transgenic SSI target site. Intervening sequences of particular interest would include linkers, adapters, selectable markers, pollen-inhibitor genes, polynucleotides of interest, promoters and/or other sites that aid in vector construction or analysis. In addition, the recombination sites of the transgenic SSI target site can be located in various positions, including, for example, within intronic sequences, coding sequences, or untranslated regions.
The transgenic SSI target site can comprise 1, 2, 3, 4, 5, 6 or more recombination sites. In one embodiment, the target site comprises a first recombination site and a second recombination site wherein the first and the second recombination site are dissimilar and non-recombinogenic to each other. In a further embodiment, the target site comprises a third recombination site between the first recombination site and the second recombination site. In such embodiments, the first, second and third recombination sites may be dissimilar and non-recombinogenic with respect to one another. Such first, second and third recombination sites are able to recombine with their corresponding or identical recombination site when provided with the appropriate recombinase.
Pollen-inhibitor genes, color marker genes, or trait loci employed in the methods and compositions provided herein can be integrated into recombination sites that are “corresponding” sites or “dissimilar” sites. By “corresponding recombination sites” or a “set of corresponding recombination sites” is intended that the recombination sites have the same or corresponding nucleotide sequence. A set of corresponding recombination sites, in the presence of the appropriate recombinase, will efficiently recombine with one another (i.e., the corresponding recombination sites are recombinogenic). The recombination sites can also be dissimilar. By “dissimilar recombination sites” or a “set of dissimilar recombination sites” is intended that the recombination sites are distinct (i.e., have at least one nucleotide difference). The recombination sites within “a set of dissimilar recombination sites” can be either recombinogenic or non-recombinogenic with respect to one other. By “recombinogenic” is intended that the set of recombination sites are capable of recombining with one another. Thus, suitable sets of “recombinogenic” recombination sites for use in the methods and compositions provided herein include those sites where the relative excision efficiency of recombination between the recombinogenic sites is above the detectable limit under standard conditions in an excision assay, typically, greater than 2%, 5%, 10%, 20%, 50%, 100%, or greater. By “non-recombinogenic” is intended the set of recombination sites, in the presence of the appropriate recombinase, will not recombine with one another or recombination between the sites is minimal. Thus, suitable “non-recombinogenic” recombination sites for use in the methods and compositions provided herein include those sites that recombine (or excise) with one another at a frequency lower than the detectable limit under standard conditions in an excision assay, typically, lower than 2%, 1.5%, 1%, 0.75%, 0.5%, 0.25%, 0.1%, 0.075, 0.005%, 0.001%.
Each recombination site within the “set of non-recombinogenic sites” is biologically active and therefore can recombine with an identical site. Accordingly, it is recognized that any suitable non-recombinogenic recombination sites may be utilized, including a FRT site or an active variant thereof, a LOX site or active variant thereof, any combination thereof, or any other combination of non-recombinogenic recombination sites known in the art. FRT sites that can be employed in the methods and compositions disclosed herein can be found, for example, in U.S. Pat. No. 8,586,361 issued on Nov. 19, 2013, herein incorporated by reference.
By “recombination site” is intended a recombination site and active variants thereof. Many recombination systems are known in the art and one of skill will recognize the appropriate recombination site to be used with the recombination system of interest. Any suitable recombination site or set of recombination sites may be utilized herein, including a FRT site, a biologically active variant of a FRT site (i.e., a mutant FRT site), a LOX site, a biologically active variant of a LOX site (i.e., a mutant LOX site), any combination thereof, or any other combination of recombination sites known in the art. Examples of FRT sites include, for example, the wild type FRT site (FRT1) (SEQ ID NO: 1), and various mutant FRT sites, including but not limited to, FRTS (SEQ ID NO: 120), FRT6 (SEQ ID NO: 121), FRT12 (SEQ ID NO: 122) and FRT87 (SEQ ID NO: 2). See, for example, U.S. Pat. No. 6,187,994 issued on Jan. 13, 2001, U.S. Pat. No. 8,586,361 issued on Nov. 19, 2013, and US Patent Publication US 2013/0198888 A1, published on Aug. 1, 2013, each of which are herein incorporated by reference.
Recombination sites from the Cre/Lox site-specific recombination system can also be used. Such recombination sites include, for example, wild type LOX sites and mutant LOX sites. An analysis of the recombination activity of mutant LOX sites is presented in Lee, et al. (1998) Gene 216:55-65, herein incorporated by reference. Also, see for example, Schlake and Bode, (1994) Biochemistry 33:12746-12751; Huang, et al., (1991) Nucleic Acids Research 19:443-448; Sadowski (1995) In Progress in Nucleic Acid Research and Molecular Biology 51:53-91; Cox (1989) In Mobile DNA, Berg and Howe (eds) American Society of Microbiology, Washington D.C., pages 116-670; Dixon, et al., (1995) Mol. Microbiol. 18:449-458; Umlauf and Cox, (1988) EMBO 7:1845-1852; Buchholz, et al., (1996) Nucleic Acids Research 24:3118-3119; Kilby, et al., (1993) Trends Genet. 9:413-421; Rossant and Geagy, (1995) Nat. Med. 1:592-594; Albert, et al., (1995) The Plant J. 7:649-659; Bayley, et al., (1992) Plant Mol. Biol. 18:353-361; Odell, et al., (1990) Mol. Gen. Genet. 223:369-378; Dale and Ow, (1991) Proc. Natl. Acad. Sci. USA 88:10558-10562; Qui, et al., (1994) Proc. Natl. Acad. Sci. USA 91:1706-1710; Stuurman, et al., (1996) Plant Mol. Biol. 32:901-913; Dale, et al., (1990) Gene 91:79-85; Albert, et al., (1995) The Plant J. 7:649-659 and WO 2001/00158; all of which are herein incorporated by reference.
Active variants and fragments of recombination sites are also encompassed by the compositions and methods provided herein. Fragments of a recombination site retain the biological activity of the recombination site and hence facilitate a recombination event in the presence of the appropriate recombinase. Thus, fragments of a recombination site may range from at least about 5, 10, 15, 20, 25, 30, 35, 40 nucleotides, and up to the full-length of a recombination site. Active variants can comprise at least 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or more sequence identity to the native recombination site, wherein the active variants retain biological activity and hence facilitate a recombination event in the presence of the appropriate recombinase. Assays to measure the biological activity of recombination sites are known in the art. See, for example, Senecoll, et al., (1988) J. Mol. Biol. 201:406-421; Voziyanov, et al., (2002) Nucleic Acid Research 30:7, U.S. Pat. No. 6,187,994, WO 2001/00158, and Albert, et al., (1995) The Plant Journal 7:649-659.
By “recombinase” is intended a polypeptide that catalyzes site-specific recombination between compatible recombination sites. For reviews of site-specific recombinases, see, Sauer (1994) Current Opinion in Biotechnology 5:521-527, and Sadowski (1993) FASEB 7:760-767; the contents of which are incorporated herein by reference. The recombinase can be a naturally occurring recombinase or a biologically active fragment or variant of the recombinase. Recombinases include recombinases from the Integrase and Resolvase families, biologically active variants and fragments thereof, and any other naturally occurring or recombinantly produced enzyme or variant thereof that catalyzes conservative site-specific recombination between specified DNA recombination sites.
The Integrase family of recombinases has over one hundred members and includes, for example, FLP, Cre, Int, and R. For other members of the Integrase family, see for example, Esposito, et al., (1997) Nucleic Acid Research 25:3605-3614 and Abremski, et al., (1992) Protein Engineering 5:87-91, both of which are herein incorporated by reference. Other recombination systems include, for example, the streptomycete bacteriophage phi C31 (Kuhstoss, et al., (1991) J. Mol. Biol. 20:897-908); the SSV1 site-specific recombination system from Sulfolobus shibatae (Maskhelishvili, et al., (1993) Mol. Gen. Genet. 237:334-342), and a retroviral integrase-based integration system (Tanaka, et al., (1998) Gene 17:67-76). Some recombinase do not require cofactors or a supercoiled substrate. Such recombinases include Cre recombinase, FLP recombinase, or active variants or fragments thereof (see, for example, U.S. Pat. No. 8,586,361, issued on Nov. 19, 2013, which is herein incorporated by reference).
The FLP recombinase is a protein that catalyzes a site-specific reaction that is involved in amplifying the copy number of the two-micron plasmid of S. cerevisiae during DNA replication. As used herein, FLP recombinase refers to a recombinase that catalyzes site-specific recombination between two FRT sites. The FLP protein has been cloned and expressed. See, for example, Cox (1993) Proc. Natl. Acad. Sci. USA. 80:4223-4227. The FLP recombinase for use in the methods and with the compositions may be derived from the genus Saccharomyces. One can also synthesize a polynucleotide comprising the recombinase using plant-preferred codons for optimal expression in a plant of interest. A recombinant FLP enzyme encoded by a nucleotide sequence comprising maize preferred codons (FLPm) (SEQ ID NO: 119) that catalyzes site-specific recombination events is known. See, for example, U.S. Pat. No. 5,929,301, herein incorporated by reference. Additional functional variants and fragments of FLP are known. See, for example, Buchholz, et al., (1998) Nat. Biotechnol. 16:617-618, Hartung, et al., (1998) J. Biol. Chem. 273:22884-22891, Saxena, et al., (1997) Biochim Biophys Acta 1340(2):187-204, and Hartley, et al., (1980) Nature 286:860-864, all of which are herein incorporated by reference.
The bacteriophage recombinase Cre catalyzes site-specific recombination between two lox sites. The Cre recombinase is known in the art. See, for example, Guo, et al., (1997) Nature 389:40-46; Abremski, et al., (1984) J. Biol. Chem. 259:1509-1514; Chen, et al., (1996) Somat. Cell Mol. Genet. 22:477-488; Shaikh, et al., (1977) J. Biol. Chem. 272:5695-5702; and Buchholz, et al., (1998) Nat. Biotechnol. 16:617-618, all of which are herein incorporated by reference. The Cre polynucleotide sequences may also be synthesized using plant-preferred codons. Such sequences (moCre) are described in WO 1999/25840, herein incorporated by reference. It is further recognized that a chimeric recombinase can be used in the methods. By “chimeric recombinase” is intended a recombinant fusion protein which is capable of catalyzing site-specific recombination between recombination sites that originate from different recombination systems. That is, if a set of functional recombination sites, characterized as being dissimilar with respect to one another, is utilized in the methods and compositions and comprises a FRT site and a LoxP site, a chimeric FLP/Cre recombinase or active variant or fragment thereof will be needed or, alternatively, both recombinases may be separately provided. Methods for the production and use of such chimeric recombinases or active variants or fragments thereof are described in WO 1999/25840, herein incorporated by reference.
As used herein, the terms “double-strand-break target site”, “DSB target site”, “DSB target sequence”, “double-strand-break—inducing-agent target site”, and “target site for a double-strand-break-inducing-agent” are used interchangeably and refer to a polynucleotide sequence in the genome of a plant cell (including choloroplastic and mitochondrial DNA) that comprises a recognition sequence for a double-strand-break-inducing agent at which a double-strand-break is induced in the cell genome by a double-strand-break-inducing-agent.
As used herein, the terms “single-strand-break-inducing-agent target site”, “single-strand-break target site”, “SSB target site”, “SSB target sequence”, and “target site for a single-strand-break-inducing-agent” are used interchangeably and refer to a polynucleotide sequence in the genome of a plant cell (including choloroplastic and mitochondrial DNA) that comprises a recognition sequence for an agent (such as but not limited to a nickage, a nuclease) at which a single-strand-break is induced in the cell genome.
As used herein, the terms “altered double-strand-break target site”, “altered DSB target site”, “aDSB target site”, and “altered target site for a double-strand-break-inducing-agent” are used interchangeably and refer to a DSB target sequence comprising at least one alteration when compared to a non-altered DSB target sequence. “Alterations” can include, for example: (i) replacement of at least one nucleotide, (ii) a deletion of at least one nucleotide, (iii) an insertion of at least one nucleotide, or (iv) any combination of (i)-(iii).
The DSB target site can be an endogenous site in the plant genome, or alternatively, the DSB target site can be heterologous to the plant and thereby not be naturally occurring in the genome, or the DSB target site can be found in a heterologous genomic location compared to where it occurs in nature. As used herein, the term “endogenous DSB target site” refers to an DSB target site that is endogenous or native to the genome of a plant and is located at the endogenous or native position of that DSB target site in the genome of the plant.
The length of the SSB or DSB target site can vary, and includes, for example, DSB target sites that are at least 4, 6, 8, 10, 12, 14, 16, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70 or more nucleotides in length. It is further possible that the DSB target site could be palindromic, that is, the sequence on one strand reads the same in the opposite direction on the complementary strand. The nick/cleavage site could be within the recognition sequence or the nick/cleavage site could be outside of the recognition sequence. In another variation, the cleavage could occur at nucleotide positions immediately opposite each other to produce a blunt end cut or, in other cases, the incisions could be staggered to produce single-stranded overhangs, also called “sticky ends”, which can be either 5′ overhangs, or 3′ overhangs. Pollen-inhibitor genes, color marker genes, or trait loci employed in the methods and compositions provided herein can be integrated into a double-strand-break target site by a double-strand-break-inducing-agent.
A “double-strand-break-inducing agent” (also referred to as “DSB-inducing-agent”) refers to any nuclease which produces a double-strand break in the target sequence. The double-strand break target site can be, but is not limited to a zinc finger endonuclease target site, an engineered endonuclease target site, a meganuclease target site, a TALENs target site and a Cas endonuclease target site.
Any nuclease that induces a single or double-strand break into a desired target site can be used in the methods and compositions disclosed herein. A naturally-occurring or native endonuclease can be employed so long as the endonuclease induces a single or double-strand break in a desired target site. Alternatively, a modified or engineered endonuclease can be employed. An “engineered endonuclease” refers to an endonuclease that is engineered (modified or derived) from its native form to specifically recognize and induce a single or double-strand break in the desired target site. Thus, an engineered endonuclease can be derived from a native, naturally-occurring endonuclease or it could be artificially created or synthesized. The modification of the endonuclease can be as little as one nucleotide. Producing a single or double-strand break in a target site or other DNA can be referred to herein as “cutting” or “cleaving” the DSB target site or other DNA.
Active variants and fragments of the SSB or DSB target sites can comprise at least 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or more sequence identity to the given DSB target site, wherein the active variants retain biological activity and hence are capable of being recognized and cleaved by an DSB-inducing-agent. Assays to measure the double-strand break of a DSB target site by an endonuclease are known in the art and generally measure the ability of an endonuclease to cut the DSB target site.
Endonucleases are enzymes that cleave the phosphodiester bond within a polynucleotide chain, and include restriction endonucleases that cleave DNA at specific sites without damaging the bases. Restriction endonucleases include Type I, Type II, Type III, and Type IV endonucleases, which further include subtypes. In the Type I and Type III systems, both the methylase and restriction activities are contained in a single complex. Restriction enzymes are further described and classified, for example in the REBASE database (Roberts, et al., (2003) Nucleic Acids Res 31:418-20, Roberts, et al., (2003) Nucleic Acids Res 31:1805-12, and Belfort, et al., (2002) in Mobile DNA II, pp. 761-783, Eds. Craigie, et al., ASM Press, Washington, DC).
Endonucleases also include meganucleases, also known as homing endonucleases (HEases), which like restriction endonucleases, bind and cut at a specific DSB target site, however the DSB target sites for meganucleases are typically longer, about 18 bp or more. Meganuclease domains, structure and function are known, see, for example, Guhan and Muniyappa, (2003) Crit Rev Biochem Mol Biol 38:199-248; Lucas, et al., (2001) Nucleic Acids Res 29:960-9; Jurica and Stoddard, (1999) Cell Mol Life Sci 55:1304-26; Stoddard, (2006) Q Rev Biophys 38:49-95, and Moure, et al., (2002) Nat Struct Biol 9:764. In some examples a naturally occurring variant, and/or engineered derivative meganuclease is used. Any meganuclease can be used herein, including, but not limited to, I-Scel, I-ScelI, I-ScelII, I-SceIV, I-SceV, I-SceVI, I-SceVII, I-CeuI, I-CeuAIIP, I-CreI, I-CrepsbIP, I-CrepsbIIP, I-CrepsbIIIP, I-CrepsbIVP, I-PpoI, PI-PspI, F-SceI, F-SceII, F-SuvI, F-TevI, F-TevII, I-AmaI, I-AniI, I-ChuI, I-CmoeI, I-CpaI, I-CpaII, I-CsmI, I-CvuI, I-CvuAIP, I-DdiI, I-DdiII, I-DirI, I-DmoI, I-HmuI, I-HmuII, I-HsNIP, I-LlaI, I-MsoI, I-NaaI, I-NanI, I-NcIIP, I-NgrIP, I-NitI, I-NjaI, I-Nsp236IP, I-Pakl, I-PboIP, I-PcuIP, I-PcuAI, I-PcuVI, I-PgrIP, 1-PobIP, I-PorI, I-PorIIP, I-PbpIP, I-SpBetaIP, I-ScaI, 1-SexIP, I-SneIP, I-Spoml, I-SpomCP, I-SpomIP, I-Spom IIP, I-SquIP, I-Ssp6803I, I-SthPhiJP, I-SthPhiST3P, I-SthPhiSTe3bP, I-TdeIP, I-TevI, 1-TevII, 1-TevIII, I-UarAP, I-UarHGPAIP, I-UarHGPA13P, I-VinIP, I-ZbiIP, PI-MtuI, PI-MtuHIP PI-MtuHIIP, PI-Pful, PI-Pfull, PI-Pkol, PI-Pkoll, PI-Rma43812IP, PI-SpBetaIP, PI-SceI, PI-TfuI, PI-TfuII, PI-ThyI, PI-TliI, PI-TliII, or any active variants or fragments thereof.
TAL effector nucleases (also referred to as TALENs) can be used to make double-strand breaks at specific target sequences in the genome of a plant or other organism. TAL effector nucleases can be created by fusing a native or engineered transcription activator-like (TAL) effector, or functional part thereof, to the catalytic domain of an endonuclease, such as, for example, Fokl. The unique, modular TAL effector DNA binding domain allows for the design of proteins with potentially any given DNA recognition specificity. Thus, the DNA binding domains of the TAL effector nucleases can be engineered to recognize specific DNA target sites and thus, used to make double-strand breaks at desired target sequences. See, WO 2010/079430; Morbitzer, et al., (2010) PNAS 10.1073/pnas.1013133107; Scholze and Boch, (2010) Virulence 1:428-432; Christian, et al., (2010) Genetics 186:757-761; Li, et al., (2010) Nuc. Acids Res. (2010) doi:10.1093/nar/gkq704, and Miller, et al., (2011) Nature Biotechnology 29:143-148; all of which are herein incorporated by reference.
CRISPR (clustered regularly interspaced short palindromic repeats) loci refers to certain genetic loci encoding factors of DNA cleavage systems, for example, used by bacterial and archaeal cells to destroy foreign DNA (Horvath and Barrangou, (2010) Science 327:167-170). A CRISPR locus can consist of a CRISPR array, comprising short direct repeats separated by short variable DNA sequences (called ‘spacers’), which can be flanked by diverse Cas (CRISPR-associated) genes. Multiple CRISPR-Cas systems have been described including Class 1 systems, with multisubunit effector complexes, and Class 2 systems, with single protein effectors (such as but not limiting to Cas9, Cpf1, C2c1, C2c2, C2c3). (Zetsche, et al., (2015) Cell 163,1-13; Shmakov, et al., (2015) Molecular Cell 60:1-13; Makarova, et al., (2015) Nature Reviews Microbiology 13:1-15). The type II CRISPR/Cas system from bacteria employs a crRNA (CRISPR RNA) and tracrRNA (trans-activating CRISPR RNA) to guide a Cas9 endonuclease to its DNA target. The crRNA contains a region complementary to one strand of the double strand DNA target and a region that base pairs with the tracrRNA (trans-activating CRISPR RNA) forming a RNA duplex that directs the Cas9 endonuclease to cleave the DNA target. CRISPR systems belong to different classes, with different repeat patterns, sets of genes, and species ranges. The number of CRISPR-associated genes at a given CRISPR locus can vary between species (Haft, et al., (2005) Computational Biology, PLoS Comput Biol 1(6):e60. doi:10.1371/journal.pcbi.0010060; Makarova, et al., (2015) Nature Reviews Microbiology 13:1-15).
The term “Cas gene” herein refers to a gene that is generally coupled, associated or close to, or in the vicinity of flanking CRISPR loci. The terms “Cas gene”, “CRISPR-associated (Cas) gene” are used interchangeably herein.
The term “Cas endonuclease” herein refers to a protein encoded by a Cas gene. A Cas endonuclease herein, when in complex with a suitable polynucleotide component, is capable of recognizing, binding to, and optionally nicking or cleaving all or part of a specific DNA target sequence. A Cas endonuclease described herein comprises one or more nuclease domains. Cas endonucleases of the disclosure includes those having a HNH or HNH-like nuclease domain and/or a RuvC or RuvC-like nuclease domain. A Cas endonuclease of the disclosure includes a Cas9 protein, a Cpf1 protein, a C2c1 protein, a C2c2 protein, a C2c3 protein, Cas3, Cas 5, Cas7, Cas8, Casio, or complexes of these.
“Cas9” (formerly referred to as Cas5, Csn1, or Csx12) herein refers to a Cas endonuclease of a type II CRISPR system that forms a complex with a crNucleotide and a tracrNucleotide, or with a single guide polynucleotide, for specifically recognizing and cleaving all or part of a DNA target sequence. Cas9 protein comprises a RuvC nuclease domain and an HNH (H-N-H) nuclease domain, each of which can cleave a single DNA strand at a target sequence (the concerted action of both domains leads to DNA double-strand cleavage, whereas activity of one domain leads to a nick).
As used herein, the term “guide polynucleotide”, relates to a polynucleotide sequence that can form a complex with a Cas endonuclease (such as but not limited to a Cas9 endonuclease) and enables the Cas endonuclease to recognize and optionally cleave a DNA target site (U.S. Provisional Patent Application No. 62/023,239, filed Jul. 11, 2014). The guide polynucleotide can be a single molecule or a double molecule. The guide polynucleotide sequence can be a RNA sequence, a DNA sequence, or a combination thereof (a RNA-DNA combination sequence). Optionally, the guide polynucleotide can comprise at least one nucleotide, phosphodiester bond or linkage modification such as, but not limited, to Locked Nucleic Acid (LNA), 5-methyl dC, 2,6-Diaminopurine, 2′-Fluoro A, 2′-Fluoro U, 2′-O-Methyl RNA, phosphorothioate bond, linkage to a cholesterol molecule, linkage to a polyethylene glycol molecule, linkage to a spacer 18 (hexaethylene glycol chain) molecule, or 5′ to 3′ covalent linkage resulting in circularization. A guide polynucleotide that solely comprises of ribonucleic acids is also referred to as a “guide RNA”. A guide RNA can include a fusion of two RNA molecules, a crRNA (CRISPR RNA) comprising a variable targeting domain, and a tracrRNA. In one embodiment, the guide RNA comprises a variable targeting domain of 12 to 30 nucleotide sequences and a RNA fragment that can interact with a Cas endonuclease.
The guide polynucleotide can be a double molecule (also referred to as duplex guide polynucleotide) comprising a first nucleotide sequence domain (referred to as Variable Targeting domain or VT domain) that is complementary to a nucleotide sequence in a target DNA and a second nucleotide sequence domain (referred to as Cas endonuclease recognition domain or CER domain) that interacts with a Cas endonuclease polypeptide. The CER domain of the double molecule guide polynucleotide comprises two separate molecules that are hybridized along a region of complementarity. The two separate molecules can be RNA, DNA, and/or RNA-DNA-combination sequences. In some embodiments, the first molecule of the duplex guide polynucleotide comprising a VT domain linked to a CER domain is referred to as “crDNA” (when composed of a contiguous stretch of DNA nucleotides) or “crRNA” (when composed of a contiguous stretch of RNA nucleotides), or “crDNA-RNA” (when composed of a combination of DNA and RNA nucleotides). The crNucleotide can comprise a fragment of the cRNA naturally occurring in Bacteria and Archaea. In one embodiment, the size of the fragment of the cRNA naturally occurring in Bacteria and Archaea that is present in a crNucleotide disclosed herein can range from, but is not limited to, 2, 3, 4, 5, 6, 7, 8, 9,10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more nucleotides. In some embodiments the second molecule of the duplex guide polynucleotide comprising a CER domain is referred to as “tracrRNA” (when composed of a contiguous stretch of RNA nucleotides) or “tracrDNA” (when composed of a contiguous stretch of DNA nucleotides) or “tracrDNA-RNA” (when composed of a combination of DNA and RNA nucleotides). In one embodiment, the RNA that guides the RNA/Cas9 endonuclease complex, is a duplexed RNA comprising a duplex crRNA-tracrRNA.
The guide polynucleotide can also be a single molecule comprising a first nucleotide sequence domain (referred to as Variable Targeting domain or VT domain) that is complementary to a nucleotide sequence in a target DNA and a second nucleotide domain (referred to as Cas endonuclease recognition domain or CER domain) that interacts with a Cas endonuclease polypeptide. By “domain” it is meant a contiguous stretch of nucleotides that can be RNA, DNA, and/or RNA-DNA-combination sequence. The VT domain and/or the CER domain of a single guide polynucleotide can comprise a RNA sequence, a DNA sequence, or a RNA-DNA-combination sequence. In some embodiments the single guide polynucleotide comprises a crNucleotide (comprising a VT domain linked to a CER domain) linked to a tracrNucleotide (comprising a CER domain), wherein the linkage is a nucleotide sequence comprising a RNA sequence, a DNA sequence, or a RNA-DNA combination sequence. The single guide polynucleotide being comprised of sequences from the crNucleotide and tracrNucleotide may be referred to as “single guide RNA” (when composed of a contiguous stretch of RNA nucleotides) or “single guide DNA” (when composed of a contiguous stretch of DNA nucleotides) or “single guide RNA-DNA” (when composed of a combination of RNA and DNA nucleotides). In one embodiment of the disclosure, the single guide RNA comprises a cRNA or cRNA fragment and a tracrRNA or tracrRNA fragment of the type II CRISPR/Cas system that can form a complex with a type II Cas endonuclease, wherein said guide RNA/Cas endonuclease complex can direct the Cas endonuclease to a plant genomic target site, enabling the Cas endonuclease to introduce a double strand break into the genomic target site. One aspect of using a single guide polynucleotide versus a duplex guide polynucleotide is that only one expression cassette needs to be made to express the single guide polynucleotide.
The term “variable targeting domain” or “VT domain” is used interchangeably herein and includes a nucleotide sequence that is complementary to one strand (nucleotide sequence) of a double strand DNA target site. The % complementation between the first nucleotide sequence domain (VT domain) and the target sequence can be at least 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 63%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100%. The variable target domain can be at least 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 or 30 nucleotides in length. In some embodiments, the variable targeting domain comprises a contiguous stretch of 12 to 30 nucleotides. The variable targeting domain can be composed of a DNA sequence, a RNA sequence, a modified DNA sequence, a modified RNA sequence, or any combination thereof.
The term “Cas endonuclease recognition domain” or “CER domain” of a guide polynucleotide is used interchangeably herein and includes a nucleotide sequence (such as a second nucleotide sequence domain of a guide polynucleotide), that interacts with a Cas endonuclease polypeptide. The CER domain can be composed of a DNA sequence, a RNA sequence, a modified DNA sequence, a modified RNA sequence (see, for example, modifications described herein), or any combination thereof.
The nucleotide sequence linking the crNucleotide and the tracrNucleotide of a single guide polynucleotide can comprise a RNA sequence, a DNA sequence, or a RNA-DNA combination sequence. In one embodiment, the nucleotide sequence linking the crNucleotide and the tracrNucleotide of a single guide polynucleotide can be at least 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99 or 100 nucleotides in length. In another embodiment, the nucleotide sequence linking the crNucleotide and the tracrNucleotide of a single guide polynucleotide can comprise a loop sequence, such as, but not limiting to a GAAA loop sequence.
Nucleotide sequence modification of the guide polynucleotide, VT domain and/or CER domain can be selected from, but not limited to , the group consisting of a 5′ cap, a 3′ polyadenylated tail, a riboswitch sequence, a stability control sequence, a sequence that forms a dsRNA duplex, a modification or sequence that targets the guide poly nucleotide to a subcellular location, a modification or sequence that provides for tracking , a modification or sequence that provides a binding site for proteins, a Locked Nucleic Acid (LNA), a 5-methyl dC nucleotide, a 2,6-Diaminopurine nucleotide, a 2′-Fluoro A nucleotide, a 2′-Fluoro U nucleotide; a 2′-0-Methyl RNA nucleotide, a phosphorothioate bond, linkage to a cholesterol molecule, linkage to a polyethylene glycol molecule, linkage to a spacer 18 molecule, a 5′ to 3′ covalent linkage, or any combination thereof. These modifications can result in at least one additional beneficial feature, wherein the additional beneficial feature is selected from the group of a modified or regulated stability, a subcellular targeting, tracking, a fluorescent label, a binding site for a protein or protein complex, modified binding affinity to complementary target sequence, modified resistance to cellular degradation, and increased cellular permeability.
Polynucleotides of interest are reflective of the commercial markets and interests of those involved in the development of the crop. Crops and markets of interest change, and as developing nations open up world markets, new crops and technologies will emerge also. In addition, as our understanding of agronomic traits and characteristics such as yield and heterosis increase, the choice of genes for gene editing or transformation will change accordingly. Polynucleotides/polypeptides of interest include, but are not limited to, herbicide-tolerance coding sequences, insecticidal coding sequences, nematicidal coding sequences, antimicrobial coding sequences, antifungal coding sequences, antiviral coding sequences, abiotic and biotic stress tolerance coding sequences, or sequences modifying plant traits such as yield, grain quality, nutrient content, starch quality and quantity, nitrogen fixation and/or utilization, and oil content and/or composition. More specific polynucleotides of interest include, but are not limited to, genes that improve crop yield, genes encoding polypeptides that improve desirability of crops, genes encoding proteins conferring resistance to abiotic stress, such as drought, nitrogen, temperature, salinity, toxic metals or trace elements, or those conferring resistance to toxins such as pesticides and herbicides, or to biotic stress, such as attacks by fungi, viruses, bacteria, insects, and nematodes, and development of diseases associated with these organisms.
An herbicide resistance protein or a protein resulting from expression of an herbicide resistance-encoding nucleic acid molecule includes proteins that confer upon a cell the ability to tolerate a higher concentration of an herbicide than cells that do not express the protein, or to tolerate a certain concentration of an herbicide for a longer period of time than cells that do not express the protein. Herbicide resistance traits may be introduced into plants by genes coding for resistance to herbicides that act to inhibit the action of acetolactate synthase (ALS), in particular the sulfonylurea-type herbicides, genes coding for resistance to herbicides that act to inhibit the action of glutamine synthase, such as phosphinothricin or basta (e.g., the bar gene), glyphosate (e.g., the EPSP synthase gene and the GAT gene), HPPD inhibitors (e.g, the HPPD gene) or other such genes known in the art. See, for example, U.S. Pat. Nos. 7,626,077, 5,310,667, 5,866,775, 6,225,114, 6,248,876, 7,169,970, 6,867,293, each of which is herein incorporated by reference.
Agronomically important traits such as oil, starch, and protein content can be genetically altered in addition to using traditional breeding methods. Modifications include increasing content of oleic acid, saturated and unsaturated oils, increasing levels of lysine and sulfur, providing essential amino acids, and also modification of starch. Hordothionin protein modifications are described in U.S. Pat. Nos. 5,703,049, 5,885,801, 5,885,802 and 5,990,389, herein incorporated by reference. Another example is lysine and/or sulfur rich seed protein encoded by the soybean 2S albumin described in U.S. Pat. No. 5,850,016, and the chymotrypsin inhibitor from barley, described in Williamson, et al., (1987) Eur. J. Biochem. 165:99-106, the disclosures of which are herein incorporated by reference.
Commercial traits can also be encoded on a polynucleotide of interest that could increase for example, starch for ethanol production, or provide expression of proteins. Another important commercial use of transformed plants is the production of polymers and bioplastics such as described in U.S. Pat. No. 5,602,321. Genes such as β-Ketothiolase, PHBase (polyhydroxyburyrate synthase), and acetoacetyl-CoA reductase (see, Schubert, et al., (1988) J. Bacteriol. 170:5837-5847) facilitate expression of polyhyroxyalkanoates (PHAs).
Derivatives of the coding sequences can be made by site-directed mutagenesis to increase the level of preselected amino acids in the encoded polypeptide. For example, the gene encoding the barley high lysine polypeptide (BHL) is derived from barley chymotrypsin inhibitor, U.S. patent application Ser. No. 08/740,682, filed Nov. 1, 1996, and WO 1998/20133, the disclosures of which are herein incorporated by reference. Other agronomically important genes encode latex, Floury 2, growth factors, seed storage factors, and transcription factors. Polynucleotides that improve crop yield include dwarfing genes, such as Rht1 and Rht2 (Peng, et al., (1999) Nature 400:256-261) and those that increase plant growth, such as ammonium-inducible glutamate dehydrogenase. Polynucleotides that improve desirability of crops include, for example, those that allow plants to have reduced saturated fat content, those that boost the nutritional value of plants, and those that increase grain protein. Polynucleotides that improve salt tolerance are those that increase or allow plant growth in an environment of higher salinity than the native environment of the plant into which the salt-tolerant gene(s) has been introduced.
Polynucleotides/polypeptides that influence amino acid biosynthesis include, for example, anthranilate synthase (AS; EC 4.1.3.27) which catalyzes the first reaction branching from the aromatic amino acid pathway to the biosynthesis of tryptophan in plants, fungi, and bacteria. In plants, the chemical processes for the biosynthesis of tryptophan are compartmentalized in the chloroplast. See, for example, US Patent Publication Number US 2008/0050506, herein incorporated by reference. Additional sequences of interest include Chorismate Pyruvate Lyase (CPL) which refers to a gene encoding an enzyme which catalyzes the conversion of chorismate to pyruvate and pHBA. The most well characterized CPL gene has been isolated from E. coli and bears the GenBank accession number M96268. See, U.S. Pat. No. 7,361,811, herein incorporated by reference.
These polynucleotide sequences of interest may encode proteins involved in providing disease or pest resistance. By “disease resistance” or “pest resistance” is intended that the plants avoid the harmful symptoms that are the outcome of the plant-pathogen interactions. Pest resistance genes may encode resistance to pests that have great yield drag such as rootworm, cutworm, European Corn Borer, and the like. Disease resistance and insect resistance genes such as lysozymes or cecropins for antibacterial protection, or proteins such as defensins, glucanases or chitinases for antifungal protection, or Bacillus thuringiensis endotoxins, protease inhibitors, collagenases, lectins, or glycosidases for controlling nematodes or insects are all examples of useful gene products. Genes encoding disease resistance traits include detoxification genes, such as against fumonosin (U.S. Pat. No. 5,792,931); avirulence (avr) and disease resistance (R) genes (Jones, et al., (1994) Science 266:789; Martin, et al., (1993) Science 262:1432; and Mindrinos, et al., (1994) Cell 78:1089), and the like.
Furthermore, it is recognized that the polynucleotide of interest may also comprise antisense sequences complementary to at least a portion of the messenger RNA (mRNA) for a targeted gene sequence of interest. Antisense nucleotides are constructed to hybridize with the corresponding mRNA. Modifications of the antisense sequences may be made as long as the sequences hybridize to and interfere with expression of the corresponding mRNA. In this manner, antisense constructions having 70%, 80%, or 85% sequence identity to the corresponding antisense sequences may be used. Furthermore, portions of the antisense nucleotides may be used to disrupt the expression of the target gene. Generally, sequences of at least 50 nucleotides, 100 nucleotides, 200 nucleotides, or greater may be used.
In addition, the polynucleotide of interest may also be used in the sense orientation to suppress the expression of endogenous genes in plants. Methods for suppressing gene expression in plants using polynucleotides in the sense orientation are known in the art. The methods generally involve transforming plants with a DNA construct comprising a promoter that drives expression in a plant operably linked to at least a portion of a nucleotide sequence that corresponds to the transcript of the endogenous gene. Typically, such a nucleotide sequence has substantial sequence identity to the sequence of the transcript of the endogenous gene, generally greater than about 65% sequence identity, about 85% sequence identity, or greater than about 95% sequence identity. See, U.S. Pat. Nos. 5,283,184 and 5,034,323; herein incorporated by reference.
The polynucleotide of interest can also be a phenotypic marker. A phenotypic marker is a screenable or a selectable marker that includes visual markers and selectable markers whether it is a positive or negative selectable marker. Any phenotypic marker can be used. Specifically, a selectable or screenable marker comprises a DNA segment that allows one to identify, or select for or against a molecule or a cell that contains it, often under particular conditions. These markers can encode an activity, such as, but not limited to, production of RNA, peptide, or protein, or can provide a binding site for RNA, peptides, proteins, inorganic and organic compounds or compositions and the like.
Examples of selectable markers include, but are not limited to, DNA segments that comprise restriction enzyme sites; DNA segments that encode products which provide resistance against otherwise inhibitory compounds including antibiotics, such as, spectinomycin, ampicillin, kanamycin, TET-repressor, acycline, Basta, neomycin phosphotransferase II (NEO) and hygromycin phosphotransferase (HPT)); DNA segments that encode products which are otherwise lacking in the recipient cell (e.g., tRNA genes, auxotrophic markers); DNA segments that encode products which can be readily identified (e.g., phenotypic markers such as β-galactosidase, GUS; fluorescent proteins such as green fluorescent protein (GFP), cyan (CFP), yellow (YFP), red (RFP), and cell surface proteins); the generation of new primer sites for PCR (e.g., the juxtaposition of two DNA sequence not previously juxtaposed), the inclusion of DNA sequences not acted upon or acted upon by a restriction endonuclease or other DNA modifying enzyme, chemical, etc.; and, the inclusion of a DNA sequences required for a specific modification (e.g., methylation) that allows its identification.
Additional selectable markers include genes that confer resistance to herbicidal compounds, such as glufosinate ammonium, bromoxynil, imidazolinones, and 2,4-dichlorophenoxyacetate (2,4-D).
Methods are provided herein for introducing a pollen-inhibitor gene in close proximity to a trait locus of interest in the genome of a progeny plant.
A trait locus of interest can be integrated into a target site by use of a double-strand-break (DSB) inducing agent. The DSB-inducing agent may be provided by any means known in the art. For example, the DSB-inducing agent can be provided via a polynucleotide encoding the nuclease. Such a polynucleotide encoding a nuclease can be modified to substitute codons having a higher frequency of usage in a plant, as compared to the naturally occurring polynucleotide sequence. The polynucleotide encoding the DSB-inducing agent can be modified to substitute codons having a higher frequency of usage in a maize or soybean plant, as compared to the naturally occurring polynucleotide sequence. A plant having the DSB target site in its genome can also be provided. The DSB-inducing agent may be transiently expressed or the polypeptide itself can be directly provided to the cell. Alternatively, a nucleotide sequence capable of expressing the DSB-inducing agent may be stably integrated into the genome of the plant. In the presence of the corresponding DSB target site and the DSB-inducing agent, a donor DNA comprising the trait of interest can be inserted into the plant's genome. Alternatively, the components of the system (double strand break inducing agent, DSB target site and donor DNA) may be brought together by sexually crossing transformed plants. Thus a sequence encoding the DSB-inducing agent and/or target site (and optionally a donor DNA comprising a trait of interest) can be sexually crossed to one another to allow each component of the system to be present in a single plant. The DSB-inducing agent may be under the control of a constitutive or inducible promoter. Such promoters of interest are discussed in further detail elsewhere herein. Examples of such double-strand-break inducing systems can be guide polynucleotide/Cas endonuclease systems described herein. See also, U.S. patent application Ser. No. 14/463,687, filed Aug. 20, 2014, which is hereby incorporated in its entirety by reference.
As used herein, a “genomic region” is a segment of a chromosome in the genome of a plant cell that is present on either side of a target site or, alternatively, also comprises a portion of the target site. The genomic region can comprise at least 5-10, 5-15, 5-20, 5-25, 5-30, 5-35, 5-40, 5-45, 5-50, 5-55, 5-60, 5-65, 5-70, 5-75, 5-80, 5-85, 5-90, 5-95, 5-100, 5-200, 5-300, 5-400, 5-500, 5-600, 5-700, 5-800, 5-900, 5-1000, 5-1100, 5-1200, 5-1300, 5-1400, 5-1500, 5-1600, 5-1700, 5-1800, 5-1900, 5-2000, 5-2100, 5-2200, 5-2300, 5-2400, 5-2500, 5-2600, 5-2700, 5-2800. 5-2900, 5-3000, 5-3100 or more bases such that the genomic region has sufficient homology to undergo homologous recombination with the corresponding region of homology.
The structural similarity between a given genomic region and the corresponding region of homology found on the donor DNA can be any degree of sequence identity that allows for homologous recombination to occur. For example, the amount of homology or sequence identity shared by the “region of homology” of the donor DNA and the “genomic region” of the plant genome can be at least 50%, 55%, 60%, 65%, 70%, 75%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100% sequence identity, such that the sequences undergo homologous recombination.
The region of homology on the donor DNA can have homology to any sequence flanking the target site. While in some embodiments the regions of homology share significant sequence homology to the genomic sequence immediately flanking the target site, it is recognized that the regions of homology can be designed to have sufficient homology to regions that may be further 5′ or 3′ to the target site. In still other embodiments, the regions of homology can also have homology with a fragment of the target site along with downstream genomic regions. In one embodiment, the first region of homology further comprises a first fragment of the target site and the second region of homology comprises a second fragment of the target site, wherein the first and second fragments are dissimilar.
Homologous recombination includes the exchange of DNA fragments between two DNA molecules at the sites of homology. The frequency of homologous recombination is influenced by a number of factors. Different organisms vary with respect to the amount of homologous recombination and the relative proportion of homologous to non-homologous recombination. Generally, the length of the region of homology affects the frequency of homologous recombination events, the longer the region of homology, the greater the frequency. The length of the homology region needed to observe homologous recombination is also species-variable. In many cases, at least 5 kb of homology has been utilized, but homologous recombination has been observed with as little as 25-50 bp of homology. See, for example, Singer, et al., (1982) Cell 31:25-33; Shen and Huang, (1986) Genetics 112:441-457; Watt, et al., (1985) Proc. Natl. Acad. Sci. USA 82:4768-4772, Sugawara and Haber, (1992) Mol Cell Biol 12:563-575, Rubnitz and Subramani, (1984) Mol Cell Biol 4:2253-2258; Ayares et al., (1986) Proc. Natl. Acad. Sci. USA 83:5199-5203; Liskay et al., (1987) Genetics 115:161-167.
Once a single or double-strand break is induced in the DNA, the cell's DNA repair mechanism is activated to repair the break. Error-prone DNA repair mechanisms can produce mutations at double-strand break sites. The most common repair mechanism to bring the broken ends together is the nonhomologous end-joining (NHEJ) pathway (Bleuyard, et al., (2006) DNA Repair 5:1-12). The structural integrity of chromosomes is typically preserved by the repair, but deletions, insertions, or other rearrangements are possible (Siebert and Puchta, (2002) Plant Cell 14:1121-1131; Pacher, et al., (2007) Genetics 175:21-29).
Alternatively, the single or double-strand break can be repaired by homologous recombination between homologous DNA sequences. Once the sequence around the double-strand break is altered, for example, by exonuclease activities involved in the maturation of double-strand breaks, gene conversion pathways can restore the original structure if a homologous sequence is available, such as a homologous chromosome in non-dividing somatic cells, or a sister chromatid after DNA replication (Molinier, et al., (2004) Plant Cell 16:342-352). Ectopic and/or epigenic DNA sequences may also serve as a DNA repair template for homologous recombination (Puchta, (1999) Genetics 152:1173-1181).
DNA double-strand breaks appear to be an effective factor to stimulate homologous recombination pathways (Puchta, et al., (1995) Plant Mol Biol 28:281-292; Tzfira and White, (2005) Trends Biotechnol 23:567-569; Puchta, (2005) J Exp Bot 56:1-14). Using DNA-breaking agents, a two- to nine-fold increase of homologous recombination was observed between artificially constructed homologous DNA repeats in plants (Puchta, et al., (1995) Plant Mol Biol 28:281-292). In maize protoplasts, experiments with linear DNA molecules demonstrated enhanced homologous recombination between plasmids (Lyznik, et al., (1991) Mol Gen Genet 230:209-218).
Once a double-strand break is introduced in the DSB target site by the DSB inducing agent, the first and second regions of homology of the donor DNA can undergo homologous recombination with their corresponding genomic regions of homology resulting in exchange of DNA between the donor and the genome. As such, the provided method results in the integration of the donor DNA (comprising for example a trait of interest or a polynucleotide of interest) into the double-strand break in the DSB target site in the plant genome (as described in U.S. patent application Ser. No. 14/463,687, filed Aug. 20, 2014, which is hereby incorporated in its entirety by reference.
The donor DNA may be introduced by any means known in the art. For example, the donor DNA may be provided transiently to a plant or plant cell by any method known in the art. The donor DNA may be provided by any transformation method known in the art including, for example, Agrobacterium-mediated transformation or biolistic particle bombardment. The donor DNA may be present transiently in the cell or it could be introduced via a viral replicon. In the presence of a DBS inducing agent and the DSB target site, the donor DNA can be inserted into the transformed plant's genome.
A trait locus of interest can also be integrated (introduced; inserted) into a target site (located proximal or distal to a telomere) by use of a site-specific integration (SSI) system discussed in further detail elsewhere herein. The site-specific recombination system employs various components which are described in detail below and in U.S. Pat. Nos. 6,187,994, 6,262,341, 6,331,661 and 6,300,545, each of which is herein incorporated by reference. A recombinase is provided that recognizes and implements recombination at the recombination sites of the transgenic SSI target site and the transfer cassette. The recombinase can be provided by any means known in the art and is described in detail elsewhere herein. The coding region of a transfer cassette can encode a recombinase that facilitates recombination between the first and the second recombination sites of the transfer cassette and the transgenic SSI target site, the second and the third recombination sites of the transfer cassette and the transgenic SSI target site, or the first and the third recombination sites of the transfer cassette and the transgenic SSI target site.
Methods for selecting plant cells with integration at the target site, such as selecting for cells expressing a trait of interest, a polynucleotide of interest, or a selectable marker, are known in the art.
As discussed above, various methods can be used to introduce a trait gene of interest and/or pollen-inhibitor genes into the genome of a plant or plant cell, thereby creating a plant having within a genomic window at least one trait locus of interest and/or a pollen-inhibitor gene integrated into a target site.
Non-limiting examples of various DNA constructs, transgenic SSI target sites, and transfer cassettes that can be used to insert a polynucleotide of interest into a plant or plant cell are described in PCT/US2012/47202 application filed Jul. 18, 2012, incorporated by reference in its entirety herein. In short, once the trait gene of interest has integrated into the target site or once the pollen-inhibitor cassette has integrated into the target site, the appropriate selective agent can be employed to identify the plant cell having the desired DNA construct. Once a target site has been established within the genome, additional target sites may be introduced by incorporating such sites within the nucleotide sequence of the transfer cassette. Thus, once a SSI target site has been established, it is possible to subsequently add or alter sites through recombination or DSB technology. Such methods are described in detail in WO 1999/25821, herein incorporated by reference.
Transformation protocols as well as protocols for introducing polypeptides or polynucleotide sequences into plants may vary depending on the type of plant or plant cell, i.e., monocot or dicot, targeted for transformation. By “stably incorporated” or “stably introduced” is intended the introduction of a polynucleotide into the plant such that the nucleotide sequence integrates into the genome of the plant and is capable of being inherited by progeny thereof. Any protocol may be used for the stable incorporation of the DNA constructs or the various components of the pollen-inhibitor system employed herein.
Suitable methods of introducing polypeptides and polynucleotides into plant cells include microinjection (Crossway, et al., (1986) Biotechniques 4:320-334), electroporation (Riggs, et al., (1986) Proc. Natl. Acad. Sci. USA 83:5602-5606), Agrobacterium-mediated transformation (U.S. Pat. Nos. 5,563,055 and 5,981,840), direct gene transfer (Paszkowski, et al., (1984) EMBO J. 3:2717-2722), and ballistic particle acceleration (see, for example, U.S. Pat. Nos. 4,945,050; 5,879,918; 5,886,244 and 5,932,782; Tomes, et al., (1995) in Plant Cell, Tissue, and Organ Culture: Fundamental Methods, ed. Gamborg and Phillips (Springer-Verlag, Berlin); McCabe, et al., (1988) Biotechnology 6:923-926); and Lec1 transformation (WO 2000/28058). Also see, Weissinger, et al., (1988) Ann. Rev. Genet. 22:421-477; Sanford, et al. (1987) Particulate Science and Technology 5:27-37 (onion); Christou, et al., (1988) Plant Physiol. 87:671-674 (soybean); McCabe, et al., (1988) Bio/Technology 6:923-926 (soybean); Finer and McMullen, (1991) In Vitro Cell Dev. Biol. 27P:175-182 (soybean); Singh, et al., (1998) Theor. Appl. Genet. 96:319-324 (soybean); Datta, et al., (1990) Biotechnology 8:736-740 (rice); Klein, et al., (1988) Proc. Natl. Acad. Sci. USA 85:4305-4309 (maize); Klein, et al., (1988) Biotechnology 6:559-563 (maize); U.S. Pat. Nos. 5,240,855; 5,322,783 and, 5,324,646; Klein, et al., (1988) Plant Physiol. 91:440-444 (maize); Fromm, et al., (1990) Biotechnology 8:833-839 (maize); Hooykaas-Van Slogteren, et al., (1984) Nature (London) 311:763-764; U.S. Pat. No. 5,736,369 (cereals); Bytebier, et al., (1987) Proc. Natl. Acad. Sci. USA 84:5345-5349 (Liliaceae); De Wet, et al., (1985) in The Experimental Manipulation of Ovule Tissues, ed. Chapman, et al., (Longman, N.Y.), pp. 197-209 (pollen); Kaeppler, et al., (1990) Plant Cell Reports 9:415-418 and Kaeppler, et al., (1992) Theor. Appl. Genet. 84:560-566 (whisker-mediated transformation); D'Halluin, et al., (1992) Plant Cell 4:1495-1505 (electroporation); Li, et al., (1993) Plant Cell Reports 12:250-255 and Christou and Ford, (1995) Annals of Botany 75:407-413 (rice); Osjoda, et al., (1996) Nature Biotechnology 14:745-750 (maize via Agrobacterium tumefaciens); all of which are herein incorporated by reference.
In other embodiments, any of the polynucleotides employed herein may be introduced into plants by contacting plants with a virus or viral nucleic acids. Generally, such methods involve incorporating a desired polynucleotide within a viral DNA or RNA molecule. It is recognized that a sequence employed in the methods or compositions provided herein may be initially synthesized as part of a viral polyprotein, which later may be processed by proteolysis in vivo or in vitro to produce the desired recombinant protein. Further, it is recognized that promoters employed herein also encompass promoters utilized for transcription by viral RNA polymerases. Methods for introducing polynucleotides into plants and expressing a protein encoded therein, involving viral DNA or RNA molecules, are known in the art. See, for example, U.S. Pat. Nos. 5,889,191, 5,889,190, 5,866,785, 5,589,367, 5,316,931, and Porta, et al., (1996) Molecular Biotechnology 5:209-221; herein incorporated by reference.
The trait gene(s) of interest, color marker genes, and/or pollen-inhibitor gene(s) can be provided to a plant using a variety of transient transformation methods. “Transient transformation” is intended to mean that a polynucleotide is introduced into the host (i.e., a plant) and expressed temporally. Such transient transformation methods include, but are not limited to, the introduction of any of the components of the pollen-inhibitor system or active fragments or variants thereof directly into the plant or the introduction of the transcript into the plant. Such methods include, for example, microinjection or particle bombardment. See, for example, Crossway, et al., (1986) Mol Gen. Genet. 202:179-185; Nomura, et al., (1986) Plant Sci. 44:53-58; Hepler, et al., (1994) Proc. Natl. Acad. Sci. 91:2176-2180 and Hush, et al., (1994) The Journal of Cell Science 107:775-784, all of which are herein incorporated by reference. Alternatively, the polynucleotide can be transiently transformed into the plant using techniques known in the art. Such techniques include viral vector system and the precipitation of the polynucleotide in a manner that precludes subsequent release of the DNA. Thus, the transcription from the particle-bound DNA can occur, but the frequency with which it is released to become integrated into the genome is greatly reduced. Such methods include the use particles coated with polyethylimine (PEI; Sigma #P3143).
The cells that have been transformed may be grown into plants in accordance with conventional ways. See, for example, McCormick, et al., (1986) Plant Cell Reports 5:81-84. These plants may then be grown, and either pollinated with the same transformed strain or different strains, and the resulting progeny having constitutive expression of the desired phenotypic characteristic identified. Two or more generations may be grown to ensure that expression of the desired phenotypic characteristic is stably maintained and inherited and then seeds harvested to ensure expression of the desired phenotypic characteristic has been achieved. In this manner, transformed seed having the recited DNA construct stably incorporated into their genome is provided.
In specific embodiments, the transgenic SSI target site of the plant cell, plant, plant part and seed further comprises a third recombination site between the first and the second recombination site, wherein the third recombination site is dissimilar and non-recombinogenic to the first and the second recombination sites. The first, second, and third recombination sites can comprise, for example, FRT1, FRTS, FRT6, FRT12, FRT62 (described in U.S. Pat. No. 8,318,493 issued on Nov. 27, 2012, herein incorporated by reference), or FRT87. Also, provided is a plant cell, plant, or seed wherein the first recombination site is FRT1, the second recombination site is FRT12 and the third recombination site is FRT87.
Plants, plant cells, or seeds having in their genome a genomic window comprising at least one trait locus and at least one pollen-inhibitor gene or a color marker gene provided herein are also encompassed.
Plants described herein include plants that comprise a trait locus that is flanked by a pollen-inhibitor gene on each side; plants that comprise a trait locus that is flanked by a color maker gene on each side, or plants that comprise a trait locus that is flanked by a color marker gene on one side and a pollen-inhibitor gene on the opposite side of the trait locus. The proximity of the pollen-inhibitor gene or color marker gene to the trait locus of interest can be about at least 0.05 cM, 0.1 cM, 0.2 cM, 0.3 cM, 0.4 cM, 0.5 cM, 0.6 cM, 0.7 cM, 0.8 cM, 0.9 cM, 1.0 cM, 1.1 cM, 1.2 cM, 1.3 cM, 1.4 cM, 1.5 cM, 1.6 cM, 1.7 cM, 1.8 cM, 1.9 cM, 2.0 cM, 2.1 cM, 2.2 cM, 2.3 cM, 2.4 cM, 2.5 cM, 2.6 cM, 2.7 cM, 2.8 cM, 2.9 cM, 3.0 cM, 3.1 cM, 3.2 cM, 3.3 cM, 3.4 cM, 3.5 cM, 3.6 cM, 3.7 cM, 3.8 cM, 3.9 cM, 4.0 cM or 5.0 cM.
In one embodiment the composition comprises a plant comprising at least one trait gene of interest, a first recombinant DNA construct comprising a color marker gene, and a second recombinant DNA construct comprising a second color marker gene, wherein said first recombinant DNA construct and said second recombinant DNA construct are genetically linked and flank said trait gene of interest.
In one embodiment the composition comprises a plant comprising at least one trait locus of interest and a recombinant DNA construct comprising a color marker gene, wherein said trait locus of interest and said color marker gene segregate independently from one another at a rate of about 10% to about 0.1%.
In one embodiment the composition comprises a plant comprising at least one trait locus of interest and a recombinant DNA construct comprising a pollen-inhibitor gene, wherein said trait locus of interest and said a pollen-inhibitor gene segregate independently from one another at a rate of about 10% to about 0.1%.
Compositions as described herein include plants wherein the first pollen-inhibitor gene (or color maker gene), the second pollen-inhibitor gene (or color maker gene) and the trait gene of interest are located within 0.05 cM, 0.1 cM, 0.2 cM, 0.3 cM, 0.4 cM, 0.5 cM, 0.6 cM, 0.7 cM, 0.8 cM, 0.9 cM, 1.0 cM, 1.1 cM, 1.2 cM, 1.3 cM, 1.4 cM, 1.5 cM, 1.6 cM, 1.7 cM, 1.8 cM, 1.9 cM, 2.0 cM, 2.1 cM, 2.2 cM, 2.3 cM, 2.4 cM, 2.5 cM, 2.6 cM, 2.7 cM, 2.8 cM, 2.9 cM, 3.0 cM, 3.1 cM, 3.2 cM, 3.3 cM, 3.4 cM, 3.5 cM, 3.6 cM, 3.7 cM, 3.8 cM, 3.9 cM , 4.0 cM or 5.0 cM of each other.
Compositions as described herein include plants wherein the first pollen-inhibitor gene and the second pollen-inhibitor is selected from the group consisting of barnase, alpha amylase, KID, or any combination thereof. Compositions as described herein include plants wherein the second pollen-inhibitor gene is selected from the group consisting a non-conditional gene, a conditional gene and an inducible gene.
As used herein, the term plant includes plant cells, plant protoplasts, plant cell tissue cultures from which a plant can be regenerated, plant calli, plant clumps, and plant cells that are intact in plants or parts of plants such as embryos, pollen, ovules, seeds, leaves, flowers, branches, fruit, kernels, ears, cobs, husks, stalks, roots, root tips, anthers, and the like. Grain is intended to mean the mature seed produced by commercial growers for purposes other than growing or reproducing the species. Progeny, variants, and mutants of the regenerated plants are also included herein, provided that these parts comprise the recited DNA construct.
A transgenic plant includes, for example, a plant which comprises within its genome a heterologous polynucleotide introduced by a transformation step. The heterologous polynucleotide can be stably integrated within the genome such that the polynucleotide is passed on to successive generations. The heterologous polynucleotide may be integrated into the genome alone or as part of a recombinant DNA construct. A transgenic plant can also comprise more than one heterologous polynucleotide within its genome. Each heterologous polynucleotide may confer a different trait to the transgenic plant. A heterologous polynucleotide can include a sequence that originates from a foreign species, or, if from the same species, can be substantially modified from its native form. Transgenic can include any cell, cell line, callus, tissue, plant part or plant, the genotype of which has been altered by the presence of heterologous nucleic acid including those transgenics initially so altered as well as those created by sexual crosses or asexual propagation from the initial transgenic. The alterations of the genome (chromosomal or extra-chromosomal) by conventional plant breeding methods, by the genome editing procedure described herein that does not result in an insertion of a foreign polynucleotide, or by naturally occurring events such as random cross-fertilization, non-recombinant viral infection, non-recombinant bacterial transformation, non-recombinant transposition, or spontaneous mutation are not intended to be regarded as transgenic.
In certain embodiments of the disclosure, a fertile plant is a plant that produces viable male and female gametes and is self-fertile. Such a self-fertile plant can produce a progeny plant without the contribution from any other plant of a gamete and the genetic material contained therein. Other embodiments of the disclosure can involve the use of a plant that is not self-fertile because the plant does not produce male gametes, or female gametes, or both, that are viable or otherwise capable of fertilization. As used herein, a “male sterile plant” is a plant that does not produce male gametes that are viable or otherwise capable of fertilization. As used herein, a “female sterile plant” is a plant that does not produce female gametes that are viable or otherwise capable of fertilization. It is recognized that male-sterile and female-sterile plants can be female-fertile and male-fertile, respectively. It is further recognized that a male fertile (but female sterile) plant can produce viable progeny when crossed with a female fertile plant and that a female fertile (but male sterile) plant can produce viable progeny when crossed with a male fertile plant.
In one embodiment, the plant is a soybean or maize plant, wherein the genomic window described herein is not more than 0.1, 0.2, 0.3, 0.4, 0.5, 1, 2, 5, 10 cM in length.
In one embodiment the plant is a plant comprising at least one trait gene of interest, a first recombinant DNA construct comprising a first pollen-inhibitor gene, and a second recombinant DNA construct comprising a second pollen-inhibitor gene, wherein said first recombinant DNA construct and said second recombinant DNA construct are genetically linked and flank said trait gene of interest. The first pollen-inhibitor gene and the second pollen-inhibitor can be selected from the group consisting of barnase, alpha amylase, KID, coda or CYP105A, or any combination thereof. The second pollen-inhibitor gene can be, a non-conditional gene, a conditional gene and an inducible gene.
In one embodiment the plant is a plant comprising at least one trait locus of interest and a recombinant DNA construct comprising a pollen-inhibitor gene, wherein said trait locus of interest and said a pollen-inhibitor gene segregate independently from one another at a rate of about 10% to about 0.1%.
In one embodiment, the plant is a soybean or maize plant, wherein the genomic window comprises at least one transgene and at least one pollen-inhibitor gene, wherein the transgene confers a trait selected from the group consisting of herbicide tolerance, insect resistance, disease resistance, male sterility, site-specific recombination, abiotic stress tolerance, altered phosphorus, altered antioxidants, altered fatty acids, altered essential amino acids, altered carbohydrates, herbicide tolerance, insect resistance and disease resistance.
The trait gene(s) of interest, color marker gene(s), and/or pollen-inhibitor gene(s) described herein can be of used in any plant species, including, but not limited to, monocots and dicots. Examples of plant species of interest include, but are not limited to, corn (maize) (Zea mays), Brassica sp. (e.g., B. napus, B. rapa, B. juncea), particularly those Brassica species useful as sources of seed oil, alfalfa (Medicago sativa), rice (Oryza sativa), rye (Secale cereale), sorghum (Sorghum bicolor, Sorghum vulgare), millet (e.g., pearl millet (Pennisetum glaucum), proso millet (Panicum miliaceum), foxtail millet (Setaria italica), finger millet (Eleusine coracana)), sunflower (Helianthus annuus), safflower (Carthamus tinctorius), wheat (Triticum aestivum), soybean (Glycine max), tobacco (Nicotiana tabacum), potato (Solanum tuberosum), peanuts (Arachis hypogaea), cotton (Gossypium barbadense, Gossypium hirsutum), sweet potato (Ipomoea batatus), cassava (Manihot esculenta), coffee (Coffea spp.), coconut (Cocos nucifera), pineapple (Ananas comosus), citrus trees (Citrus spp.), cocoa (Theobroma cacao), tea (Camellia sinensis), banana (Musa spp.), avocado (Persea americana), fig (Ficus casica), guava (Psidium guajava), mango (Mangifera indica), olive (Olea europaea), papaya (Carica papaya), cashew (Anacardium occidentale), macadamia (Macadamia integrifolia), almond (Prunus amygdalus), sugar beets (Beta vulgaris), sugarcane (Saccharum spp.), oats, barley, vegetables, ornamentals, and conifers.
Vegetables include tomatoes (Lycopersicon esculentum), lettuce (e.g., Lactuca sativa), green beans (Phaseolus vulgaris), lima beans (Phaseolus limensis), peas (Lathyrus spp.), and members of the genus Cucumis such as cucumber (C. sativus), cantaloupe (C. cantalupensis), and musk melon (C. melo). Ornamentals include azalea (Rhododendron spp.), hydrangea (Macrophylla hydrangea), hibiscus (Hibiscus rosasanensis), roses (Rosa spp.), tulips (Tulipa spp.), daffodils (Narcissus spp.), petunias (Petunia hybrida), carnation (Dianthus caryophyllus), poinsettia (Euphorbia pulcherrima), and chrysanthemum.
Conifers that may be employed include, for example, pines such as loblolly pine (Pinus taeda), slash pine (Pinus elliotii), ponderosa pine (Pinus ponderosa), lodgepole pine (Pinus contorta), and Monterey pine (Pinus radiata); Douglas-fir (Pseudotsuga menziesii); Western hemlock (Tsuga canadensis); Sitka spruce (Picea glauca); redwood (Sequoia sempervirens); true firs such as silver fir (Abies amabilis) and balsam fir (Abies balsamea); and cedars such as Western red cedar (Thuja plicata) and Alaska yellow-cedar (Chamaecyparis nootkatensis). In specific embodiments, plants are crop plants (for example, corn, alfalfa, sunflower, Brassica, soybean, cotton, safflower, peanut, sorghum, wheat, millet, tobacco, etc.). In other embodiments, corn and soybean plants are optimal, and in yet other embodiments corn plants are optimal.
Other plants of interest include grain plants that provide seeds of interest, oil-seed plants, and leguminous plants. Seeds of interest include grain seeds, such as corn, wheat, barley, rice, sorghum, rye, etc. Oil-seed plants include cotton, soybean, safflower, sunflower, Brassica, maize, alfalfa, palm, coconut, etc. Leguminous plants include beans and peas. Beans include guar, locust bean, fenugreek, soybean, garden beans, cowpea, mungbean, lima bean, fava bean, lentils, chickpea, etc.
The terms “polynucleotide,” “polynucleotide sequence,” “nucleic acid sequence,” and “nucleic acid fragment” are used interchangeably herein. These terms encompass nucleotide sequences and the like. A polynucleotide may be a polymer of RNA or DNA that is single- or double-stranded, that optionally contains synthetic, non-natural or altered nucleotide bases. A polynucleotide in the form of a polymer of DNA may be comprised of one or more segments of cDNA, genomic DNA, synthetic DNA, or mixtures thereof. The use of the term “polynucleotide” is not intended to limit the present invention to polynucleotides comprising DNA. Those of ordinary skill in the art will recognize that polynucleotides, can comprise ribonucleotides and combinations of ribonucleotides and deoxyribonucleotides. Such deoxyribonucleotides and ribonucleotides include both naturally occurring molecules and synthetic analogues. The polynucleotides provided herein also encompass all forms of sequences including, but not limited to, single-stranded forms, double-stranded forms, hairpins, stem-and-loop structures, and the like.
The compositions provided herein can comprise an isolated or substantially purified polynucleotide. An “isolated” or “purified” polynucleotide is substantially or essentially free from components that normally accompany or interact with the polynucleotide as found in its naturally occurring environment. Thus, an isolated or purified polynucleotide is substantially free of other cellular material, or culture medium when produced by recombinant techniques, or substantially free of chemical precursors or other chemicals when chemically synthesized. Optimally, an “isolated” polynucleotide is free of sequences (optimally protein encoding sequences) that naturally flank the polynucleotide (i.e., sequences located at the 5′ and 3′ ends of the polynucleotide) in the genomic DNA of the organism from which the polynucleotide is derived. For example, in various embodiments, the isolated polynucleotide can contain less than about 5 kb, 4 kb, 3 kb, 2 kb, 1 kb, 0.5 kb, or 0.1 kb of nucleotide sequence that naturally flank the polynucleotide in genomic DNA of the cell from which the polynucleotide is derived.
The terms “recombinant polynucleotide” and “recombinant DNA construct” are used interchangeably herein. A recombinant construct can comprise an artificial or heterologous combination of nucleic acid sequences, e.g., regulatory and coding sequences that are not found together in nature. For example, a transfer cassette can comprise restriction sites and a heterologous polynucleotide of interest. In other embodiments, a recombinant construct may comprise regulatory sequences and coding sequences that are derived from different sources, or regulatory sequences and coding sequences derived from the same source, but arranged in a manner different than that found in nature. Such a construct may be used by itself or may be used in conjunction with a vector. If a vector is used, then the choice of vector is dependent upon the method that will be used to transform host cells as is well known to those skilled in the art. For example, a plasmid vector can be used. The skilled artisan is well aware of the genetic elements that must be present on the vector in order to successfully transform, select and propagate host cells comprising any of the isolated nucleic acid fragments provided herein. The skilled artisan will also recognize that different independent transformation events will result in different levels and patterns of expression (Jones, et al., (1985) EMBO J. 4:2411-2418; De Almeida, et al., (1989) Mol. Gen. Genetics 218:78-86), and thus that multiple events must be screened in order to obtain lines displaying the desired expression level and pattern. Such screening may be accomplished by Southern analysis of DNA, Northern analysis of mRNA expression, immunoblotting analysis of protein expression, or phenotypic analysis, among others.
The trait gene(s) of interest, color marker gens, and/or pollen-inhibitor gene(s) described herein can be provided in an expression cassette for expression in a plant or other organism or cell type of interest. The cassette can include 5′ and 3′ regulatory sequences operably linked to a polynucleotide provided herein. “Operably linked” is intended to mean a functional linkage between two or more elements. For example, an operable linkage between a polynucleotide of interest and a regulatory sequence (i.e., a promoter) is a functional link that allows for expression of the polynucleotide of interest. Operably linked elements may be contiguous or non-contiguous. When used to refer to the joining of two protein coding regions, by operably linked is intended that the coding regions are in the same reading frame. The cassette may additionally contain at least one additional gene to be cotransformed into the organism. Alternatively, the additional gene(s) can be provided on multiple expression cassettes. Such an expression cassette is provided with a plurality of restriction sites and/or recombination sites for insertion of a recombinant polynucleotide to be under the transcriptional regulation of the regulatory regions. The expression cassette may additionally contain selectable marker genes.
The expression cassette can include in the 5′-3′ direction of transcription, a transcriptional and translational initiation region (i.e., a promoter), a recombinant polynucleotide provided herein, and a transcriptional and translational termination region (i.e., termination region) functional in plants. The regulatory regions (i.e., promoters, transcriptional regulatory regions, and translational termination regions) and/or a polynucleotide provided herein may be native/analogous to the host cell or to each other. Alternatively, the regulatory regions and/or a polynucleotide provided herein may be heterologous to the host cell or to each other. As used herein, “heterologous” in reference to a sequence is a sequence that originates from a foreign species, or, if from the same species, is substantially modified from its native form in composition and/or trait locus by deliberate human intervention. For example, a promoter operably linked to a heterologous polynucleotide is from a species different from the species from which the polynucleotide was derived, or, if from the same/analogous species, one or both are substantially modified from their original form and/or genomic locus, or the promoter is not the native promoter for the operably linked polynucleotide. Alternatively, the regulatory regions and/or a recombinant polynucleotide provided herein may be entirely synthetic.
The termination region may be native with the transcriptional initiation region, may be native with the operably linked recombinant polynucleotide, may be native with the plant host, or may be derived from another source (i.e., foreign or heterologous) to the promoter, the recombinant polynucleotide, the plant host, or any combination thereof. Convenient termination regions are available from the Ti-plasmid of A. tumefaciens, such as the octopine synthase and nopaline synthase termination regions. See also, Guerineau, et al., (1991) Mol. Gen. Genet. 262:141-144; Proudfoot, (1991) Cell 64:671-674; Sanfacon, et al., (1991) Genes Dev. 5:141-149; Mogen, et al., (1990) Plant Cell 2:1261-1272; Munroe, et al., (1990) Gene 91:151-158; Ballas, et al., (1989) Nucleic Acids Res. 17:7891-7903; and Joshi, et al., (1987) Nucleic Acids Res. 15:9627-9639.
In preparing the expression cassette, the various DNA fragments may be manipulated, so as to provide for the DNA sequences in the proper orientation. Toward this end, adapters or linkers may be employed to join the DNA fragments or other manipulations may be involved to provide for convenient restriction sites, removal of superfluous DNA, removal of restriction sites, or the like. For this purpose, in vitro mutagenesis, primer repair, restriction, annealing, resubstitutions, e.g., transitions and transversions, may be involved.
A number of promoters can be used in the expression cassettes provided herein. The promoters can be selected based on the desired outcome. It is recognized that different applications can be enhanced by the use of different promoters in the expression cassettes to modulate the timing, location and/or level of expression of the polynucleotide of interest. Such expression constructs may also contain, if desired, a promoter regulatory region (e.g., one conferring inducible, constitutive, environmentally- or developmentally-regulated, or cell- or tissue-specific/selective expression), a transcription initiation start site, a ribosome binding site, an RNA processing signal, a transcription termination site, and/or a polyadenylation signal.
In some embodiments, an expression cassette provided herein can be combined with constitutive, tissue-preferred, or other promoters for expression in plants. Examples of constitutive promoters include the cauliflower mosaic virus (CaMV) 35S transcription initiation region, the 1′- or 2′-promoter derived from T-DNA of Agrobacterium tumefaciens, the ubiquitin 1 promoter, the Smas promoter, the cinnamyl alcohol dehydrogenase promoter (U.S. Pat. No. 5,683,439), the Nos promoter, the pEmu promoter, the rubisco promoter, the GRP1-8 promoter and other transcription initiation regions from various plant genes known to those of skill. If low level expression is desired, weak promoter(s) may be used. Weak constitutive promoters include, for example, the core promoter of the Rsyn7 promoter (WO 1999/43838 and U.S. Pat. No. 6,072,050), the core 35S CaMV promoter, and the like. Other constitutive promoters include, for example, U.S. Pat. Nos. 5,608,149; 5,608,144; 5,604,121; 5,569,597; 5,466,785; 5,399,680; 5,268,463; and 5,608,142. See also, U.S. Pat. No. 6,177,611, herein incorporated by reference.
Examples of inducible promoters are the Adh1 promoter which is inducible by hypoxia or cold stress, the Hsp70 promoter which is inducible by heat stress, the PPDK promoter and the pepcarboxylase promoter which are both inducible by light. Also useful are promoters which are chemically inducible, such as the In2-2 promoter which is safener induced (U.S. Pat. No. 5,364,780), the ERE promoter which is estrogen induced, and the Axig1 promoter which is auxin induced and tapetum specific but also active in callus (PCT/US2001/22169).
Examples of promoters under developmental control include promoters that initiate transcription preferentially in certain tissues, such as leaves, roots, fruit, seeds, or flowers. An exemplary promoter is the anther specific promoter 5126 (U.S. Pat. Nos. 5,689,049 and 5,689,051). Examples of seed-preferred promoters include, but are not limited to, 27 kD gamma zein promoter and waxy promoter, Boronat, et al., (1986) Plant Sci. 47:95-102; Reina, et al., Nucl. Acids Res. 18(21):6426; and Kloesgen, et al., (1986) Mol. Gen. Genet. 203:237-244. Promoters that express in the embryo, pericarp, and endosperm are disclosed in U.S. Pat. No. 6,225,529 and PCT Publication Number WO 2000/12733. The disclosures for each of these are incorporated herein by reference in their entirety.
Chemical-regulated promoters can be used to modulate the expression of a gene in a plant through the application of an exogenous chemical regulator. Depending upon the objective, the promoter may be a chemical-inducible promoter, where application of the chemical induces gene expression, or a chemical-repressible promoter, where application of the chemical represses gene expression. Chemical-inducible promoters are known in the art and include, but are not limited to, the maize In2-2 promoter, which is activated by benzenesulfonamide herbicide safeners, the maize GST promoter, which is activated by hydrophobic electrophilic compounds that are used as pre-emergent herbicides, and the tobacco PR-1 a promoter, which is activated by salicylic acid. Other chemical-regulated promoters of interest include steroid-responsive promoters (see, for example, the glucocorticoid-inducible promoter in Schena, et al., (1991) Proc. Natl. Acad. Sci. USA 88:10421-10425 and McNellis, et al., (1998) Plant J. 14(2):247-257) and TET repressoracycline-inducible and TET repressoracycline-repressible promoters (see, for example, Gatz, et al., (1991) Mol. Gen. Genet. 227:229-237, and U.S. Pat. Nos. 5,814,618 and 5,789,156), herein incorporated by reference.
Tissue-preferred promoters can be utilized to target enhanced expression of a polynucleotide of interest within a particular plant tissue. Tissue-preferred promoters are known in the art. See, for example, Yamamoto, et al., (1997) Plant J. 12(2):255-265; Kawamata, et al., (1997) Plant Cell Physiol. 38(7):792-803; Hansen, et al., (1997) Mol. Gen Genet. 254(3):337-343; Russell, et al., (1997) Transgenic Res. 6(2):157-168; Rinehart, et al., (1996) Plant Physiol. 112(3):1331-1341; Van Camp, et al., (1996) Plant Physiol. 112(2):525-535; Canevascini, et al., (1996) Plant Physiol. 112(2):513-524; Yamamoto, et al., (1994) Plant Cell Physiol. 35(5):773-778; Lam, (1994) Results Probl. Cell Differ. 20:181-196; Orozco, et al., (1993) Plant Mol Biol. 23(6):1129-1138; Matsuoka, et al., (1993) Proc Natl. Acad. Sci. USA 90(20):9586-9590; and Guevara-Garcia, et al., (1993) Plant J. 4(3):495-505. Such promoters can be modified, if necessary, for weak expression.
Leaf-preferred promoters are known in the art. See, for example, Yamamoto, et al., (1997) Plant J. 12(2):255-265; Kwon, et al., (1994) Plant Physiol. 105:357-367; Yamamoto, et al., (1994) Plant Cell Physiol. 35(5):773-778; Gotor, et al., (1993) Plant J. 3:509-518; Orozco, et al., (1993) Plant Mol. Biol. 23(6):1129-1138; and Matsuoka, et al., (1993) Proc. Natl. Acad. Sci. USA 90(20):9586-9590. In addition, the promoters of cab and rubisco can also be used. See, for example, Simpson, et al., (1958) EMBO J 4:2723-2729 and Timko, et al., (1988) Nature 318:57-58.
Root-preferred promoters are known and can be selected from the many available from the literature or isolated de novo from various compatible species. See, for example, Hire, et al., (1992) Plant Mol. Biol. 20(2):207-218 (soybean root-specific glutamine synthetase gene); Keller and Baumgartner, (1991) Plant Cell 3(10):1051-1061 (root-specific control element in the GRP 1.8 gene of French bean); Sanger, et al., (1990) Plant Mol. Biol. 14(3):433-443 (root-specific promoter of the mannopine synthase (MAS) gene of Agrobacterium tumefaciens); and Miao, et al., (1991) Plant Cell 3(1):11-22 (full-length cDNA clone encoding cytosolic glutamine synthetase (GS), which is expressed in roots and root nodules of soybean). See also, Bogusz, et al., (1990) Plant Cell 2(7):633-641, where two root-specific promoters isolated from hemoglobin genes from the nitrogen-fixing nonlegume Parasponia andersonii and the related non-nitrogen-fixing nonlegume Trema tomentosa are described. The promoters of these genes were linked to a β-glucuronidase reporter gene and introduced into both the nonlegume Nicotiana tabacum and the legume Lotus corniculatus, and in both instances root-specific promoter activity was preserved. Leach and Aoyagi (1991) describe their analysis of the promoters of the highly expressed rolC and rolD root-inducing genes of Agrobacterium rhizogenes (see, Plant Science (Limerick) 79(1):69-76). They concluded that enhancer and tissue-preferred DNA determinants are dissociated in those promoters. Teeri, et al., (1989) used gene fusion to lacZ to show that the Agrobacterium T-DNA gene encoding octopine synthase is especially active in the epidermis of the root tip and that the TR2′ gene is root specific in the intact plant and stimulated by wounding in leaf tissue, an especially desirable combination of characteristics for use with an insecticidal or larvicidal gene (see, EMBO J. 8(2):343-350). The TR1′ gene, fused to nptll (neomycin phosphotransferase II) showed similar characteristics. Additional root-preferred promoters include the VfENOD-GRP3 gene promoter (Kuster, et al., (1995) Plant Mol. Biol. 29(4):759-772); and rolB promoter (Capana, et al., (1994) Plant Mol. Biol. 25(4):681-691). See also, U.S. Pat. Nos. 5,837,876; 5,750,386; 5,633,363; 5,459,252; 5,401,836; 5,110,732; and 5,023,179. The phaseolin gene (Murai, et al., (1983) Science 23:476-482 and Sengopta-Gopalen, et al., (1988) PNAS 82:3320-3324.
The expression cassette containing the polynucleotides provided herein can also comprise a selectable marker gene for the selection of transformed cells. Selectable marker genes are utilized for the selection of transformed cells or tissues. Marker genes include genes encoding antibiotic resistance, such as those encoding neomycin phosphotransferase II (NEO) and hygromycin phosphotransferase (HPT), as well as genes conferring resistance to herbicidal compounds, such as glufosinate ammonium, bromoxynil, imidazolinones, and 2,4-dichlorophenoxyacetate (2,4-D) and sulfonylureas. Additional selectable markers include phenotypic markers such as beta-galactosidase and fluorescent proteins such as green fluorescent protein (GFP) (Su, et al., (2004) Biotechnol. Bioeng. 85:610-619 and Fetter, et al., (2004) Plant Cell 16:215-228), cyan fluorescent protein (CYP) (Bolte, et al., (2004) J. Cell Science 117:943-954 and Kato, et al., (2002) Plant Physiol. 129:913-942), and yellow fluorescent protein (PhiYFP™ from Evrogen; see, Bolte, et al., (2004) J. Cell Science 117:943-54). Such disclosures are herein incorporated by reference. The above list of selectable marker genes is not meant to be limiting. Any selectable marker gene can be used in the compositions presented herein.
Where appropriate, the sequences employed in the methods and compositions (i.e., the polynucleotide of interest, the recombinase, the endonuclease, etc.) may be optimized for increased expression in the transformed plant. That is, the genes can be synthesized using plant-preferred codons for improved expression. See, for example, Campbell and Gowri, (1990) Plant Physiol. 92:1-11 for a discussion of host-preferred codon usage. Methods are available in the art for synthesizing plant-preferred genes. See, for example, U.S. Pat. Nos. 5,380,831 and 5,436,391, and Murray, et al., (1989) Nucleic Acids Res. 17:477-498, herein incorporated by reference.
Fragments and variants of the various components of the DSB-inducing-agent system, such as for example the guide polynucleotide/Cas endonuclease system and the site-specific integration system (transgenic SSI target site, a donor DNA, a transfer cassette, various site-specific recombination sites, site-specific recombinases, polynucleotides of interest or any active variants or fragments thereof) are also encompassed herein. By “fragment” is intended a portion of the polynucleotide or a portion of the amino acid sequence and hence protein encoded thereby. Fragments of a polynucleotide may encode protein fragments that retain the biological activity of the native protein (i.e., a fragment of a recombinase implements a recombination event). As used herein, a “native” polynucleotide or polypeptide comprises a naturally occurring nucleotide sequence or amino acid sequence, respectively. Thus, fragments of a polynucleotide may range from at least about 20 nucleotides, about 50 nucleotides, about 100 nucleotides, and up to the full-length polynucleotide. A fragment of a polynucleotide that encodes a biologically active portion of a protein employed in the methods or compositions will encode at least 15, 25, 30, 50, 100, 150, 200, or 250 contiguous amino acids, or up to the total number of amino acids present in a full-length protein. Alternatively, fragments of a polynucleotide that are useful as a hybridization probe generally do not encode fragment proteins retaining biological activity. Thus, fragments of a nucleotide sequence may range from at least about 10, 20, 30, 40, 50, 60, 70, 80 nucleotides or up to the full length sequence.
A biologically active portion of a polypeptide can be prepared by isolating a portion of one of the polynucleotides encoding the portion of the polypeptide of interest and expressing the encoded portion of the protein (e.g., by recombinant expression in vitro), and assessing the activity of the portion of the polypeptide. For example, polynucleotides that encode fragments of a recombinase polypeptide can comprise nucleotide sequence comprising at least 16, 20, 50, 75, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 800, 900, 1,000, 1,100, 1,200, 1,300, or 1,400 nucleotides, or up to the number of nucleotides present in a nucleotide sequence employed in the methods and compositions provided herein.
“Variants” is intended to mean substantially similar sequences. For polynucleotides, a variant comprises a polynucleotide having deletions (i.e., truncations) at the 5′ and/or 3′ end; deletion and/or addition of one or more nucleotides at one or more internal sites in the native polynucleotide; and/or substitution of one or more nucleotides at one or more sites in the native polynucleotide. For polynucleotides, conservative variants include those sequences that, because of the degeneracy of the genetic code, encode the amino acid sequence of one of the polypeptides employed in the compositions and methods provided herein. Naturally occurring allelic variants such as these, or naturally occurring allelic variants of polynucleotides can be identified with the use of well-known molecular biology techniques, as, for example, with polymerase chain reaction (PCR) and hybridization techniques as outlined below. Variant polynucleotides also include synthetically derived polynucleotides, such as those generated, for example, by using site-directed mutagenesis. Generally, variants of a particular polynucleotide employed in the methods and compositions provided herein will have at least about 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or more sequence identity to that particular polynucleotide as determined by sequence alignment programs and parameters as described elsewhere herein.
Variants of a particular polynucleotide employed in the methods and compositions provided herein (trait gene(s) of interest and/or pollen-inhibitor gene(s), recombinases, nucleases) can also be evaluated by comparison of the percent sequence identity between the polypeptide encoded by a variant polynucleotide and the polypeptide encoded by the reference polynucleotide. Thus, for example, an isolated polynucleotide that encodes a polypeptide with a given percent sequence identity to the polypeptide are disclosed. Percent sequence identity between any two polypeptides can be calculated using sequence alignment programs and parameters described elsewhere herein. Where any given pair of polynucleotides provided herein is evaluated by comparison of the percent sequence identity shared by the two polypeptides they encode, the percent sequence identity between the two encoded polypeptides is at least about 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or more sequence identity.
“Variant” protein is intended to mean a protein derived from the native protein by deletion (so-called truncation) of one or more amino acids at the N-terminal and/or C-terminal end of the native protein; deletion and/or addition of one or more amino acids at one or more internal sites in the native protein; or substitution of one or more amino acids at one or more sites in the native protein. Variant proteins employed in the methods and compositions provided herein are biologically active, that is they continue to possess the desired biological activity of the native protein. Such variants may result from, for example, genetic polymorphism or from human manipulation. Biologically active variants of a native protein provided herein will have at least about 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or more sequence identity to the amino acid sequence for the native protein as determined by sequence alignment programs and parameters described elsewhere herein. A biologically active variant of a protein provided herein may differ from that protein by as few as 1-15 amino acid residues, as few as 1-10, such as 6-10, as few as 5, as few as 4, 3, 2, or even 1 amino acid residue.
Proteins may be altered in various ways including amino acid substitutions, deletions, truncations, and insertions. Methods for such manipulations are generally known in the art. For example, amino acid sequence variants of the recombinase proteins can be prepared by mutations in the DNA. Methods for mutagenesis and nucleotide sequence alterations are well known in the art. See, for example, Kunkel, (1985) Proc. Natl. Acad. Sci. USA 82:488-492; Kunkel, et al., (1987) Methods in Enzymol. 154:367-382; U.S. Pat. No. 4,873,192; Walker and Gaastra, eds. (1983) Techniques in Molecular Biology (MacMillan Publishing Company, New York) and the references cited therein. Guidance as to appropriate amino acid substitutions that do not affect biological activity of the protein of interest may be found in the model of Dayhoff, et al., (1978) Atlas of Protein Sequence and Structure (Natl. Biomed. Res. Found., Washington, D.C.), herein incorporated by reference. Conservative substitutions, such as exchanging one amino acid with another having similar properties, may be preferable.
Thus, the polynucleotides used herein can include the naturally occurring sequences, the “native” sequences, as well as mutant forms. Likewise, the proteins used in the methods provided herein encompass both naturally occurring proteins as well as variations and modified forms thereof. Obviously, the mutations that will be made in the polynucleotide encoding the variant polypeptide must not place the sequence out of reading frame and preferably will not create complementary regions that could produce secondary mRNA structure. See, EP Patent Application Publication Number 75,444.
The deletions, insertions, and substitutions of the protein sequences encompassed herein are not expected to produce radical changes in the characteristics of the protein. However, when it is difficult to predict the exact effect of the substitution, deletion, or insertion in advance of doing so, one skilled in the art will appreciate that the effect will be evaluated by routine screening assays.
Variant polynucleotides and proteins also encompass sequences and proteins derived from a mutagenic and recombinogenic procedure such as DNA shuffling. With such a procedure, for example, one or more different recombinase coding sequences can be manipulated to create a new recombinase protein possessing the desired properties. In this manner, libraries of recombinant polynucleotides are generated from a population of related sequence polynucleotides comprising sequence regions that have substantial sequence identity and can be homologously recombined in vitro or in vivo. Strategies for such DNA shuffling are known in the art. See, for example, Stemmer, (1994) Proc. Natl. Acad. Sci. USA 91:10747-10751; Stemmer, (1994) Nature 370:389-391; Crameri, et al., (1997) Nature Biotech. 15:436-438; Moore, et al., (1997) J. Mol. Biol. 272:336-347; Zhang, et al., (1997) Proc. Natl. Acad. Sci. USA 94:4504-4509; Crameri, et al., (1998) Nature 391:288-291; and U.S. Pat. Nos. 5,605,793 and 5,837,458.
The following terms are used to describe the sequence relationships between two or more nucleic acids or polynucleotides. As used herein, “reference sequence” is a defined sequence used as a basis for sequence comparison. A reference sequence may be a subset or the entirety of a specified sequence; for example, as a segment of a full-length cDNA or gene sequence, or the complete cDNA or gene sequence. As used herein, “comparison window” makes reference to a contiguous and specified segment of a polynucleotide sequence, wherein the polynucleotide sequence in the comparison window may comprise additions or deletions (i.e., gaps) compared to the reference sequence (which does not comprise additions or deletions) for optimal alignment of the two sequences. Generally, the comparison window is at least 20 contiguous nucleotides in length, and optionally can be 30, 40, 50, 100, or longer. Those of skill in the art understand that to avoid a high similarity to a reference sequence due to inclusion of gaps in the polynucleotide sequence a gap penalty is typically introduced and is subtracted from the number of matches.
Sequence relationships can be analyzed and described using computer-implemented algorithms. The sequence relationship between two or more polynucleotides, or two or more polypeptides can be determined by determining the best alignment of the sequences, and scoring the matches and the gaps in the alignment, which yields the percent sequence identity, and the percent sequence similarity. Polynucleotide relationships can also be described based on a comparison of the polypeptides each encodes. Many programs and algorithms for the comparison and analysis of sequences are well-known in the art.
“Sequence identity” or “identity” in the context of nucleic acid or polypeptide sequences refers to the nucleic acid bases or amino acid residues in two sequences that are the same when aligned for maximum correspondence over a specified comparison window.
The term “percentage of sequence identity” refers to the value determined by comparing two optimally aligned sequences over a comparison window, wherein the portion of the polynucleotide or polypeptide sequence in the comparison window may comprise additions or deletions (i.e., gaps) as compared to the reference sequence (which does not comprise additions or deletions) for optimal alignment of the two sequences. The percentage is calculated by determining the number of positions at which the identical nucleic acid base or amino acid residue occurs in both sequences to yield the number of matched positions, dividing the number of matched positions by the total number of positions in the window of comparison and multiplying the results by 100 to yield the percentage of sequence identity. Useful examples of percent sequence identities include, but are not limited to, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90% or 95%, or any integer percentage from 50% to 100%. These identities can be determined using any of the programs described herein.
Sequence alignments and percent identity or similarity calculations may be determined using a variety of comparison methods designed to detect homologous sequences including, but not limited to, the MegAlign™ program of the LASERGENE bioinformatics computing suite (DNASTAR Inc., Madison, Wis.). Within the context of this application it will be understood that where sequence analysis software is used for analysis, that the results of the analysis will be based on the “default values” of the program referenced, unless otherwise specified. As used herein “default values” will mean any set of values or parameters that originally load with the software when first initialized.
The “Clustal V method of alignment” corresponds to the alignment method labeled Clustal V (described by Higgins and Sharp, (1989) CABIOS 5:151-153; Higgins, et al., (1992) Comput Appl Biosci 8:189-191) and found in the MegAlign™ program of the LASERGENE bioinformatics computing suite (DNASTAR Inc., Madison, Wis.). For multiple alignments, the default values correspond to GAP PENALTY=10 and GAP LENGTH PENALTY=10. Default parameters for pairwise alignments and calculation of percent identity of protein sequences using the Clustal method are KTUPLE=1, GAP PENALTY=3, WINDOW=5 and DIAGONALS SAVED=5. For nucleic acids these parameters are KTUPLE=2, GAP PENALTY=5, WINDOW=4 and DIAGONALS SAVED=4. After alignment of the sequences using the Clustal V program, it is possible to obtain a “percent identity” by viewing the “sequence distances” table in the same program.
The “Clustal W method of alignment” corresponds to the alignment method labeled Clustal W (described by Higgins and Sharp, (1989) CABIOS 5:151-153; Higgins, et al., (1992) Comput Appl Biosci 8:189-191) and found in the MegAlign™ v6.1 program of the LASERGENE bioinformatics computing suite (DNASTAR Inc., Madison, Wis.). Default parameters for multiple alignment (GAP PENALTY=10, GAP LENGTH PENALTY=0.2, Delay Divergen Seqs (%)=30, DNA Transition Weight=0.5, Protein Weight Matrix=Gonnet Series, DNA Weight Matrix=IUB). After alignment of the sequences using the Clustal W program, it is possible to obtain a “percent identity” by viewing the “sequence distances” table in the same program.
“BLAST” is a searching algorithm provided by the National Center for Biotechnology Information (NCBI) used to find regions of similarity between biological sequences. The program compares nucleotide or protein sequences to sequence databases and calculates the statistical significance of matches to identify sequences having sufficient similarity to a query sequence such that the similarity would not be predicted to have occurred randomly. BLAST reports the identified sequences and their local alignment to the query sequence.
It is well understood by one skilled in the art that many levels of sequence identity are useful in identifying polypeptides from other species or modified naturally or synthetically wherein such polypeptides have the same or similar function or activity. Useful examples of percent identities include, but are not limited to, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90% or 95%, or any integer percentage from 50% to 100%. Indeed, any integer amino acid identity from 50% to 100% may be useful in describing the present disclosure, such as 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99%.
Sequence identity/similarity values can also be obtained using GAP Version 10 (GCG, Accelrys, San Diego, Calif.) using the following parameters: % identity and % similarity for a nucleotide sequence using GAP Weight of 50 and Length Weight of 3, and the nwsgapdna.cmp scoring matrix; % identity and % similarity for an amino acid sequence using GAP Weight of 8 and Length Weight of 2, and the BLOSUM62 scoring matrix (Henikoff and Henikoff, (1989) Proc. Natl. Acad. Sci USA 89:10915); or any equivalent program thereof. By “equivalent program” is intended any sequence comparison program that, for any two sequences in question, generates an alignment having identical nucleotide or amino acid residue matches and an identical percent sequence identity when compared to the corresponding alignment generated by GAP Version 10.
GAP uses the algorithm of Needleman and Wunsch, (1970) J. Mol. Biol. 48:443-453, to find the alignment of two complete sequences that maximizes the number of matches and minimizes the number of gaps. GAP considers all possible alignments and gap positions and creates the alignment with the largest number of matched bases and the fewest gaps. It allows for the provision of a gap creation penalty and a gap extension penalty in units of matched bases. GAP must make a profit of gap creation penalty number of matches for each gap it inserts. If a gap extension penalty greater than zero is chosen, GAP must, in addition, make a profit for each gap inserted of the length of the gap times the gap extension penalty. Default gap creation penalty values and gap extension penalty values in Version 10 of the GCG Wisconsin Genetics Software Package for protein sequences are 8 and 2, respectively. For nucleotide sequences the default gap creation penalty is 50 while the default gap extension penalty is 3. The gap creation and gap extension penalties can be expressed as an integer selected from the group of integers consisting of from 0 to 200. Thus, for example, the gap creation and gap extension penalties can be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65 or greater.
GAP presents one member of the family of best alignments. There may be many members of this family, but no other member has a better quality. GAP displays four figures of merit for alignments: Quality, Ratio, Identity, and Similarity. The Quality is the metric maximized in order to align the sequences. Ratio is the quality divided by the number of bases in the shorter segment. Percent Identity is the percent of the symbols that actually match. Percent Similarity is the percent of the symbols that are similar. Symbols that are across from gaps are ignored. A similarity is scored when the scoring matrix value for a pair of symbols is greater than or equal to 0.50, the similarity threshold.
As used herein, “breeding” is the genetic manipulation of living organisms. Plants are bred through techniques that take advantage of the plant's method of pollination. A plant is self-pollinated if pollen from one flower is transferred to the same or another flower of the same plant. A plant is sib-pollinated when individuals within the same family or line are used for pollination. A plant is cross-pollinated if the pollen comes from a flower on a different plant from a different family or line. In a breeding application, a breeder initially selects and crosses two or more parental plants. As used herein, “crossing” can refer to a simple X by Y cross, or the process of backcrossing, depending on the context.
The introduction of transgenes (transgenic trait of interest) into many major crops is typically performed in a single plant variety that is most amenable to the transformation, tissue culture and regeneration processes. For example, in corn, the readily transformable genotype referred to Hi-II (Armstrong and Green, (1985) Planta 164(2):207-214) has been used for many years across the industry for genetic transformation. However, the agronomic characteristics of this genotype are not commercially desirable, so once a transgenic trait locus (genomic locus where transgene has integrated into the plant genome) has been created, the transgenic trait locus must be introgressed from Hi-II into commercially relevant inbreds. Introgression, also known as introgressive hybridization, refers to the movement of a gene (gene flow) from one species into the gene pool of another, which can be accomplished by repeated backcrossing of an interspecific hybrid with one of its parent species.
A transgenic inbred (A) can be crossed to a non-transgenic inbred (B) in order to introgress (or transfer) the transgenic trait into the new germplasm by repeated back-crossing to the recurrent parent (B). The result of the first cross between inbred A and inbred B is the F1 hybrid. The F1 hybrid can then be used as the pollen donor to again cross with the recurrent parent (inbred B) to produce the first backcross generation (the BC1 generation). Successive backcrosses can be performed until the majority of genetic material from the original inbred A has been lost through meiotic recombination and segregation, leaving the transgenic locus in the new inbred background.
Commercial corn seed companies typically work with hundreds of inbreds in different heterotic groups, and thus the transgenic trait locus must be introgressed into numerous inbreds for further efficacy testing—a process that can take up to many successive generations to completely eliminate as much of the undesired germplasm (such as for example the Hi-II germplasm in maize) as possible. A major impediment in the introgression process is identifying progeny in successive crosses in which meiotic recombination has occurred in close proximity on either side of the transgenic locus, replacing as much of the flanking undesired germ plasm chromosome with the new inbred chromosome. To identify progeny where closely-spaced (such as but not limited to less than 0-1 cM, 0-2 cM, 0-3 cM, 0-4 cM, 0-5 cM, 0-6 cM, 0-7 cM, 0-8 cM, 0-9 cM, 0-10 cM, 1-1 cM, 1-2 cM, 1-3 cM, 1-4 cM, 1-5 cM, 1-6 cM, 1-7 cM, 1-8 cM, 1-9 cM, 1-10 cM) meiotic recombination on either side of a transgenic locus has occurred a molecular screening using genetic markers can be used thereby adding more work and cost to each generation of screening. In addition, for certain crop species which naturally self-pollinate such as soybean, making crosses through emasculation and hand-pollination on the scale needed in order to identify low-frequency recombination events is extremely labor intensive.
In order to accelerate the introgression process (also referred to as “Accelerated Trait Introgression” and greatly reduce the labor involved, a (screening) method that selects for recombination in the gametes would be of great benefit. One method of accomplishing such as screen is to position a gamete-specific inhibitor gene (or gamete inhibitor gene) in close proximity to the transgenic locus of interest. One can also position at least one color marker gene in close proximity of a trait locus of interest, in combination with or without a pollen-inhibitor gen as described herein. Described herein are compositions and methods to position a pollen-inhibitor gene and/or a color marker in close proximity to a trait locus of interest in the genome of a progeny plant. As described herein the trait locus can be flanked by a pollen-inhibitor gene on each side, a color maker gene on each side, or a combination of a color marker gene and a pollen-inhibitor gene. The proximity of the pollen-inhibitor gene or color marker gene to the trait locus of interest can be about at least 0.05 cM, 0.1 cM, 0.2 cM, 0.3 cM, 0.4 cM, 0.5 cM, 0.6 cM, 0.7 cM, 0.8 cM, 0.9 cM, 1.0 cM, 1.1 cM, 1.2 cM, 1.3 cM, 1.4 cM, 1.5 cM, 1.6 cM, 1.7 cM, 1.8 cM, 1.9 cM, 2.0 cM, 2.1 cM, 2.2 cM, 2.3 cM, 2.4 cM, 2.5 cM, 2.6 cM, 2.7 cM, 2.8 cM, 2.9 cM, 3.0 cM, 3.1 cM, 3.2 cM, 3.3 cM, 3.4 cM, 3.5 cM, 3.6 cM, 3.7 cM, 3.8 cM, 3.9 cM , 4.0 cM or 5.0 cM.
Compositions and methods are provided herein for the use of pollen-inhibitor genes and/or color maker genes in accelerated trait introgression.
In one embodiment, the method comprises a method of accelerated trait introgression in the genome of a plant, the method comprising: (a) providing a first plant having within a genomic window at least one trait of interest located proximal to a telomere, and at least one pollen-inhibitor gene located proximal to both the telomere and the trait of interest, wherein said trait of interest and said pollen-inhibitor gene are genetically linked in said genomic window, wherein said genomic window is about 5 cM in length and located within 10 cM of the telomere; (b) cross pollinating the first plant of (a) with pollen from a second plant; and (c) selecting a progeny plant from step (b) comprising said trait of interest and said pollen-inhibitor gene; and (d) optionally, backcrossing the progeny plant of (c) as the pollen donor onto a recurrent parent plant and selecting progeny plants comprising the trait of interest.
In one embodiment, the method comprises a method of accelerated trait introgression in the genome of a plant, the method comprising: (a) providing a first plant having within a genomic window at least one trait of interest located proximal to a telomere, and at least one color marker gene located proximal to both the telomere and the trait of interest, wherein said trait of interest and said color marker gene are genetically linked in said genomic window, wherein said genomic window is about 5 cM in length and located within 10 cM of the telomere; (b) cross pollinating the first plant of (a) with pollen from a second plant; and (c) selecting a progeny plant from step (b) comprising said trait of interest site and said color marker gene; and (d) optionally, backcrossing the progeny plant of (c) as the pollen donor onto a recurrent parent plant and selecting progeny plants comprising the trait of interest.
In one embodiment, the method comprises a method of accelerated trait introgression in the genome of a plant comprising: (a) providing a first plant having within a genomic window at least one trait of interest, a first pollen-inhibitor gene, and a second pollen-inhibitor gene wherein said genomic window is about 5 cM in length, and wherein said trait of interest is flanked by said first and second pollen-inhibitor gene; (b) cross-pollinating the first plant of (a) with pollen from a second plant; and, (c) selecting a progeny plant from step (b) comprising said first pollen-inhibitor gene, said trait of interest, and said second pollen-inhibitor gene; and, (d) optionally, cross pollinating the progeny plant from step (c) to a recurrent parent plant and selecting progeny plants comprising the trait of interest.
In one embodiment, the method comprises a method of accelerated trait introgression in the genome of a plant comprising: (a) providing a first plant having within a genomic window at least one trait of interest, a pollen-inhibitor gene and a color marker gene, wherein said genomic window is about 5 cM in length, and wherein trait of interest is flanked by said first and second pollen-inhibitor gene; (b) cross-pollinating the first plant of (a) with pollen from a second plant; and, (c) selecting a progeny plant from step (b) comprising said first pollen-inhibitor gene, said trait of interest, and said second pollen-inhibitor gene; and, (d) optionally, cross pollinating the progeny plant from step (c) to a recurrent parent plant and selecting progeny plants comprising the trait of interest.
In one embodiment, the method comprises a method accelerated trait introgression in the genome of a plant comprising: (a) providing a first plant having within a genomic window at least one trait of interest and at least a first color marker gene integrated into a first target site, a second color marker gene integrated into a second target site for, wherein said genomic window is about 5 cM in length, and wherein trait of interest is flanked by said first and second pollen-inhibitor gene; (b) cross-pollinating the first plant of (a) with pollen from a second plant; and, (c) selecting a progeny plant from step (b) comprising said first pollen-inhibitor gene, said trait of interest, and said second pollen-inhibitor gene; and, (d) optionally, cross pollinating the progeny plant from step (c) to a recurrent parent plant and selecting progeny plants comprising the trait of interest.
The location of the trait locus can determine how many pollen-inhibitor loci (or color marker loci) are introduced and where the pollen-inhibitor or color marker loci are positioned. If the trait locus is in close proximity (such as but not limited to less than 0-1 cM, 0-2 cM, 0-3 cM, 0-4 cM, 0-5 cM, 0-6 cM, 0-7 cM, 0-8 cM, 0-9 cM, 0-10 cM, 1-1 cM, 1-2 cM, 1-3 cM, 1-4 cM, 1-5 cM, 1-6 cM, 1-7 cM, 1-8 cM, 1-9 cM, 1-10 cM) to a telomere (near the end of the chromosome), only a single pollen-inhibitor locus, located just proximal to the trait locus of interest (i.e. 0.5 to 1.0 cM closer to the centromere) is required. As described in Example 1 and illustrated in
For trait loci in internal (for example, in non-telomeric locations (more toward the centromere of the chromosome), two flanking pollen-inhibitor loci located one on either side of the trait locus can be used (as described in Example 2). As described in Example 2 and illustrated in
Another alternative for setting up three linked loci without the use of a maintainer, while also obviating the need for conventional breeding methods to establish the linkage, is to use CRISPR-mediated introduction of the pollen-inhibitors directly into the flanking sites in a chromosome that already contains the trait locus. For pollen inhibition, the alpha-amylase gene can be particularly useful, since the breakdown of starch by the expressed protein renders the pollen incapable of forming a pollen tube.
Methods are provided for introducing a pollen-inhibitor gene in close proximity to a trait locus of interest in the genome of a progeny plant using breeding techniques. For example, a first plant having within a genomic window at least one trait locus of interest integrated into a first target site located proximal to a telomere, wherein said genomic window is about 10 cM in length and located within 10 cM of the telomere, wherein said first plant does not comprise a pollen-inhibitor gene; can be crossed with a second plant, wherein said second plant comprises in said genomic window a pollen-inhibitor gene integrated into a second target site located distal to the telomere, wherein said second plant does not comprise said first target site. A progeny plant in then selected comprising said trait locus of interest and said pollen-inhibitor gene, wherein said trait locus of interest and said pollen-inhibitor gene are genetically linked. Selecting a progeny plant comprising both the trait locus of interest and the pollen-inhibitor gene can be done through various methods. For example, a phenotypic analysis can be performed whereby the activity of the trait of interest or said pollen-inhibitor is detected in the progeny plant. Alternative methods that assay for the presence of said trait locus of interest and said pollen-inhibitor gene which are specific to the said trait locus of interest and said pollen-inhibitor gene include techniques such as PCR, hybridization, Isozyme electrophoresis, Restriction Fragment Length Polymorphisms (RFLPs), Randomly Amplified Polymorphic DNAs (RAPDs), Arbitrarily Primed PCR (AP-PCR), DNA Amplification Fingerprinting (DAF), Sequence Characterized Amplified Regions (SCARs), Amplified Fragment length Polymorphisms (AFLPs), Simple Sequence Repeats (SSRs), and Single Nucleotide Polymorphisms (SNPs).
The meaning of abbreviations is as follows: “sec” means second(s), “min” means minute(s), “h” means hour(s), “d” means day(s), “μL” means microliter(s), “mL” means milliliter(s), “L” means liter(s), “μM” means micromolar, “mM” means millimolar, “M” means molar, “mmol” means millimole(s), “pmole” mean micromole(s), “g” means gram(s), “μg” means microgram(s), “ng” means nanogram(s), “U” means unit(s), “bp” means base pair(s) and “kb” means kilobase(s).
Non-limiting examples of compositions and methods disclosed herein are as follows:
- 1. A method for introducing a pollen-inhibitor gene in close proximity to a trait locus of interest in the genome of a progeny plant, said method comprising:
- (a) providing a first plant having within a genomic window at least one trait gene of interest integrated into a first target site located proximal to a telomere, wherein said genomic window is about 10 cM in length, wherein said first plant does not comprise a pollen-inhibitor gene;
- (b) breeding to said first plant a second plant, wherein said second plant comprises in said genomic window a pollen-inhibitor gene integrated into a second target site located proximal to both the telomere and the trait gene of interest of (a); and,
- (c) selecting a progeny plant from step (b) comprising said trait gene of interest and said pollen-inhibitor gene, wherein said trait gene of interest and said pollen-inhibitor gene are genetically linked.
- 2. A method for introducing two pollen-inhibitor genes in close proximity to a trait locus of interest in the genome of a progeny plant, said method comprising:
- (a) providing a first plant having within a genomic window a first pollen-inhibitor gene integrated into a first target site, wherein said genomic window is about 10 cM in length;
- (b) breeding to said first plant a second plant having a trait gene of interest integrated into a second target site within said genomic window;
- (c) selecting a progeny plant from step (b) comprising said first pollen-inhibitor gene and said trait gene of interest in said genomic widow;
- (d) providing a third plant having a second pollen-inhibitor gene integrated into a third target site within said genomic window;
- (e) breeding to said third plant a fourth plant, wherein said fourth plant comprises a pollen-inhibitor maintainer (PIM) gene;
- (f) selecting a progeny plant from step (e) comprising said second pollen-inhibitor gene and said pollen-inhibitor maintainer (PIM) gene; and,
- (g) cross pollinating the progeny plant of (c) with the progeny plant of (f) and selecting for a progeny plant that comprises said first pollen-inhibitor gene said trait gene of interest and said second pollen-inhibitor gene, wherein said first pollen-inhibitor gene, said trait gene of interest and said second pollen-inhibitor gene are genetically linked.
- 3. The method of embodiments 1-2, wherein the first target site and the second target site is selected from the group consisting of a recombinase target site, a transgenic SSI target site, a single-strand-break-inducing-agent target site, and a double-strand-break-inducing-agent target site, or any one combination thereof.
- 4. The method of embodiments 1-2, wherein the double-strand-break-inducing-agent target site is a target site for an agent selected from the group of a Cas9 endonuclease, a zinc-finger nuclease, a Tal Effector nuclease (TALEN), a meganuclease, and an engineered endonuclease.
- 5. A method for introducing a pollen-inhibitor gene and a color marker gene in close proximity to a trait locus of interest in the genome of a plant, said method comprising:
- (a) providing a first plant having a trait of interest located within a genomic window, wherein said genomic window is about 10 cM in length;
- (b) introducing into said genomic window of the plant of (a) a color marker gene;
- (c) breeding to the plant of (b) a second plant, wherein said second plant is a haploid inducer line capable of producing haploid embryos;
- (d) selecting haploid embryos from the plant of (c) and introducing into said haploid embryos, a pollen-inhibitor gene; and,
- (e) producing a double haploid plant from the haploid embryo of (d).
- 6. A method for introducing two color marker genes in close proximity to a trait locus of interest in the genome of a plant, said method comprising:
- (a) providing a first plant having a trait of interest located within a genomic window, wherein said genomic window is about 10 cM in length;
- (b) introducing into said genomic window of the plant of (a) a color marker gene;
- (c) breeding to the plant of (b) a second plant, wherein said second plant is a haploid inducer line capable of producing haploid embryos;
- (d) selecting haploid embryos from the plant of (c) and introducing into said haploid embryos, a second color marker gene; and,
- (e) producing a double haploid plant from the haploid embryo of (d).
- 7. The method of embodiments 5-6, wherein color marker or the pollen-inhibitor gene are introduced into a target site of a double-strand-break-inducing-agent target site.
- 8. A method of accelerated trait introgression in the genome of a plant, the method comprising:
- (a) providing a first plant having within a genomic window at least one trait of interest located proximal to a telomere, and at least one pollen-inhibitor gene located proximal to both the telomere and the trait of interest, wherein said trait of interest and said pollen-inhibitor gene are genetically linked in said genomic window, wherein said genomic window is about 5 cM in length and located within 10 cM of the telomere;
- (b) cross pollinating the first plant of (a) with pollen from a second plant; and,
- (c) selecting a progeny plant from step (b) comprising said trait of interest and said pollen-inhibitor gene; and,
- (d) optionally, backcrossing the progeny plant of (c) as the pollen donor onto a recurrent parent plant and selecting progeny plants comprising the trait of interest.
- 9. A method of accelerated trait introgression in the genome of a plant, the method comprising:
- (a) providing a first plant having within a genomic window at least one trait of interest located proximal to a telomere, and at least one color marker gene located proximal to both the telomere and the trait of interest, wherein said trait of interest and said color marker gene are genetically linked in said genomic window, wherein said genomic window is about 5 cM in length and located within 10 cM of the telomere;
- (b) cross pollinating the first plant of (a) with pollen from a second plant; and,
- (c) selecting a progeny plant from step (b) comprising said trait of interest site and said color marker gene; and,
- (d) optionally, backcrossing the progeny plant of (c) as the pollen donor onto a recurrent parent plant and selecting progeny plants comprising the trait of interest.
- 10. A method of accelerated trait introgression in the genome of a plant comprising:
- (a) providing a first plant having within a genomic window at least one trait of interest, a first pollen-inhibitor gene, and a second pollen-inhibitor gene wherein said genomic window is about 5 cM in length, and wherein said trait of interest is flanked by said first and second pollen-inhibitor gene;
- (b) cross-pollinating the first plant of (a) with pollen from a second plant; and,
- (c) selecting a progeny plant from step (b) comprising said first pollen-inhibitor gene, said trait of interest, and said second pollen-inhibitor gene; and,
- (d) optionally, cross pollinating the progeny plant from step (c) to a recurrent parent plant and selecting progeny plants comprising the trait of interest.
- 11. A method of accelerated trait introgression in the genome of a plant comprising:
- (a) providing a first plant having within a genomic window at least one trait of interest, a pollen-inhibitor gene and a color marker gene, wherein said genomic window is about 5 cM in length, and wherein trait of interest is flanked by said first and second pollen-inhibitor gene;
- (b) cross-pollinating the first plant of (a) with pollen from a second plant; and,
- (c) selecting a progeny plant from step (b) comprising said first pollen-inhibitor gene, said trait of interest, and said second pollen-inhibitor gene; and,
- (d) optionally, cross pollinating the progeny plant from step (c) to a recurrent parent plant and selecting progeny plants comprising the trait of interest.
- 12. A method of accelerated trait introgression in the genome of a plant comprising:
- (a) providing a first plant having within a genomic window at least one trait of interest and at least a first color marker gene integrated into a first target site, a second color marker gene integrated into a second target site for, wherein said genomic window is about 5 cM in length, and wherein trait of interest is flanked by said first and second pollen-inhibitor gene;
- (b) cross-pollinating the first plant of (a) with pollen from a second plant; and,
- (c) selecting a progeny plant from step (b) comprising said first pollen-inhibitor gene, said trait of interest, and said second pollen-inhibitor gene; and,
- (d) optionally, cross pollinating the progeny plant from step (c) to a recurrent parent plant and selecting progeny plants comprising the trait of interest.
- 13. A method for introducing a pollen-inhibitor gene in close proximity to a trait locus of interest in the genome of a progeny plant, said method comprising:
- (a) providing a first plant having within a genomic window at least a first transgenic SSI target site located proximal to a telomere, wherein said first transgenic SSI target site comprises at least one trait gene of interest, wherein said genomic window is about 5 cM in length and located within 0.1 cM to 100 cM of the telomere, and wherein said first plant does not comprise a pollen-inhibitor gene;
- (b) breeding to said first plant a second plant, wherein said second plant comprises in said genomic window a second transgenic SSI target site located proximal to both the telomere and the trait gene of interest, wherein said second transgenic SSI target site comprises a pollen-inhibitor gene, wherein said second plant does not comprise said first transgenic target site; and,
- (c) selecting a progeny plant from step (b) comprising said trait gene of interest and said pollen-inhibitor gene, wherein said trait gene of interest and said pollen-inhibitor gene are genetically linked in said genomic window.
- 14. A method of accelerated trait introgression in the genome of a plant, the method comprising:
- (a) providing a first progeny plant having within a genomic window at least a first transgenic SSI target site located proximal to a telomere and a second transgenic SSI target site located proximal to both the telomere and the trait gene of interest, wherein said first transgenic SSI target site comprises at least one trait gene of interest, wherein said second transgenic SSI target site comprises a pollen-inhibitor gene, wherein said first transgenic target site and said pollen-inhibitor gene are genetically linked in said genomic window, wherein said genomic window is about 5 cM in length and located within 10 cM of the telomere;
- (b) cross pollinating the first plant of (a) with pollen from a second plant (elite inbred); and,
- (c) selecting a progeny plant from step (b) comprising said first transgenic target site and said pollen-inhibitor gene;
- 15. The method of embodiment 8, further comprising:
- (d) backcrossing the progeny plant of (c) as the pollen donor onto a recurrent parent plant and selecting progeny plants comprising the trait gene of interest.
- 16. The method of any one of embodiments 13-14, wherein the pollen-inhibitor gene is selected from the group consisting of barnase, alpha amylase and KID.
- 17. The method of anyone of embodiments 13-14 wherein the trait gene of interest is selected from the group consisting of a selectable marker, a modified or edited native gene, a transgene, an altered double-strand-break target site, a native gene, or a transgenic SSI target site.
- 18. The method of anyone of embodiments 13-14, wherein the trait gene of interest and the pollen-inhibitor gene are genetically linked and located within 0.5 cM to 1 cM from each other.
- 19. A method for introducing two pollen-inhibitor genes in close proximity to a trait locus of interest in the genome of a progeny plant, said method comprising:
- (a) providing a first plant having within a genomic window at least a first transgenic SSI target site, wherein said first transgenic SSI target site comprises a first pollen-inhibitor gene, wherein said genomic window is about 5 cM in length;
- (b) breeding to said first plant a second plant, wherein said second plant comprises in said genomic window a second transgenic SSI target site, wherein said second transgenic SSI target site comprises at least one trait gene of interest wherein said second plant does not comprise said first transgenic target site;
- (c) selecting a progeny plant from step (b) comprising said first transgenic target site and said second transgenic target site genetically linked in said genomic widow;
- (d) providing a third plant having within said genomic window at least a third transgenic SSI target site and a pollen-inhibitor maintainer (PIM), wherein said third transgenic SSI target site comprises a second pollen-inhibitor gene; and,
- (e) using the third plant of step (d) to pollinate the plant of step (c) and selecting a progeny plant wherein said first transgenic SSI target site, said second transgenic SSI target site, and said third transgenic SSI target site are genetically linked to each other.
- 20. A method of accelerated trait introgression in the genome of a plant comprising:
- (a) providing a first plant having a pollen-inhibitor maintainer gene and a genomic window, wherein said genomic window is about 5 cM in length and wherein said genomic window comprises at least a first transgenic SSI target site, a second transgenic SSI target site and a third transgenic SSI target site, wherein said first transgenic SSI target site comprises a first pollen-inhibitor gene, wherein said second transgenic SSI target site comprises at least one trait gene of interest, wherein said third transgenic SSI target site comprises a second pollen-inhibitor gene, wherein said second transgenic target site is flanked by said first transgenic SSI target site and said third transgenic SSI target site;
- (b) cross-pollinating the first plant of (a) with pollen from a second plant; and,
- (c) selecting a progeny plant from step (b) comprising said first transgenic target site, said second transgenic target site and said third transgenic target site.
- 21. The method of embodiment 20, further comprising cross pollinating the progeny plant from step (c) to a recurrent parent plant and selecting progeny plants by exposing germinating seedlings to said selectable marker.
- 22. A method of accelerated trait introgression in the genome of a plant comprising:
- (a) providing a first plant having within a genomic window a trait of interest and at least a first pollen-inhibitor gene integrated into a first target site for a Cas9 endonuclease, a second pollen-inhibitor gene integrated into a second target site for a Cas9 endonuclease, wherein said genomic window is about 5 cM in length, and wherein trait of interest is flanked by said first and second pollen-inhibitor gene;
- (b) cross-pollinating the first plant of (a) with pollen from a second plant; and,
- (c) selecting a progeny plant from step (b) comprising said first pollen-inhibitor gene, said trait of interest, and said second pollen-inhibitor gene;
- 23. The method of embodiment 22, further comprising cross pollinating the progeny plant from step (c) to a recurrent parent plant and selecting progeny plants by exposing germinating seedlings to said selectable marker.
- 24. A method for introducing two pollen-inhibitor genes in close proximity to a trait gene of interest in the genome of a progeny plant, said method comprising:
- (a) providing a first plant having within a genomic window at least a first transgenic SSI target site, wherein said first transgenic SSI target site comprises at least one trait gene of interest, wherein said genomic window is about 5 cM in length;
- (b) introducing into the plant of (a) a first pollen-inhibitor gene, wherein said first pollen-inhibitor gene is genetically linked to said trait gene of interest
- (c) selecting a progeny plant from (b) comprising the pollen-inhibitor gene genetically linked to the trait gene of interest.
- (d) breeding to said progeny plant of (c) a haploid-inducer plant and producing haploid immature embryos.
- (e) introducing into the haploid immature embryos of (d) a second pollen-inhibitor gene linked to said trait gene of interest and said first pollen-inhibitor gene, wherein the trait gene of interest is flanked by the first and second pollen-inhibitor gene; and,
- (f) producing a homozygous plant from the haploid immature embryo of (e);
- 25. A method of accelerated trait introgression in the genome of a plant comprising
- (a) providing a first plant having a genomic window comprising a trait gene of interest flanked by and genetically linked to a first pollen-inhibitor gene and a second pollen-inhibitor gene, wherein said genomic window is about 5 cM in length;
- (b) cross pollinating the first plant of (a) with pollen from a second plant; and,
- (c) selecting a progeny plant from step (b) comprising said trait gene of interest flanked by and genetically linked to said first pollen-inhibitor gene and said second pollen-inhibitor gene.
- 26. The method of embodiment 25 further comprising cross-pollinating the progeny plant from step (c) to a recurrent parent plant and selecting progeny plants by exposing germinating seedlings to said selectable marker.
- 27. A plant comprising at least one trait gene of interest, a first recombinant DNA construct comprising a first pollen-inhibitor gene, and a second recombinant DNA construct comprising a second pollen-inhibitor gene, wherein said first recombinant DNA construct and said second recombinant DNA construct are genetically linked and flank said trait gene of interest.
- 28. A plant comprising at least one trait locus of interest and a recombinant DNA construct comprising a pollen-inhibitor gene, wherein said trait locus of interest and said a pollen-inhibitor gene segregate independently from one another at a rate of about 10% to about 0.1%.
- 29. The plant of embodiment 27, wherein the first pollen-inhibitor gene, the second pollen-inhibitor gene and the trait gene of interest are located within 5 cM of each other.
- 30. The plant of embodiment 27, wherein the first pollen-inhibitor gene and the second pollen-inhibitor is selected from the group consisting of barnase, alpha amylase, KID, or any combination thereof.
- 31. The plant of embodiment 27, wherein the second pollen-inhibitor gene is selected from the group consisting a non-conditional gene, a conditional gene and an inducible gene.
- 32. A plant comprising at least one trait gene of interest, a first recombinant DNA construct comprising a color marker gene, and a second recombinant DNA construct comprising a second color marker gene, wherein said first recombinant DNA construct and said second recombinant DNA construct are genetically linked and flank said trait gene of interest.
- 33. A plant comprising at least one trait locus of interest and a recombinant DNA construct comprising a color marker gene, wherein said trait locus of interest and said color marker gene segregate independently from one another at a rate of about 10% to about 0.1%.
- 34. The plant of embodiment 33, wherein the first color marker gene, the second color marker gene and the trait gene of interest are located within 5 cM of each other.
In the following Examples, unless otherwise stated, parts and percentages are by weight and degrees are Celsius. It should be understood that these Examples, while indicating embodiments of the disclosure, are given by way of illustration only. From the above discussion and these Examples, one skilled in the art can make various changes and modifications of the disclosure to adapt it to various usages and conditions. Such modifications are also intended to fall within the scope of the appended claims.
Example 1 Using a Single Pollen-Inhibitor Locus to Screen for Accelerated Trait Introgression of a Telomeric Trait LocusIllustrated in
-
- a. If the linkage between GAT and PI is broken during meiosis then the pollen is viable and GAT can be transmitted to progeny.
- b. Spray with glyphosate to eliminate any progeny derived from wild-type pollen grains.
- c. The surviving plants will have GAT gene with a minimal linkage drag from the transformation inbred.
A donor sequence for site specific integration (SSI) (SEQ ID NO: 44) was introduced into a pre-existing transgenic SSI target site containing a first expression cassette comprising a ubiquitin promoter driving a phosphomannose isomerase (PMI) and a pin II terminator, wherein the PMI was preceded by a FRT1 recombination site (UBI PRO::FRT1::PMI::pinII) linked to a second expression cassette comprising an actin promoter driving a moPAT selectable marker and a pin II terminator, followed by a FRT87 recombination site (ACTIN PRO::moPAT::pinII-FRT87) located on chromosome 3 at genetic position 0.9 cM (close to the end of the short arm of the chromosome), replacing the PMI and moPAT genes with FRT1-NPTII:PINII TERM, 3x 35S ENH:UBI PRO:UBI INTRON:GAT891G3:UBQ3 TERM AND LTP2:GZ-W64A TERM-FRT87 (SEQ ID NO: 44). In a second independent transformation experiment, the pollen-inhibitor cassette PG47::barnase (comprising a PG47 [a maize promoter from a polygalacturonase gene] promoter driving the pollen-inhibitor gene barnase and a pinII terminator; bp 4438 to bp 8039 in PHP70154, SEQ ID NO: 43) was introduced into a pre-existing SSI target site also containing FRT1-PMI+Actin::moPAT-FRT87) located on chromosome 3 at genetic position 3.2 cM, replacing PMI and moPAT with PG47::Barnase.
These two transgenic events were crossed together, creating an F1 generation. Progeny in the F2 generation are then screened for linkage and a progeny plant (maize Pioneer inbred line 1, such as for example PHN46) is selected comprising the linked GAT (glyphosate resistant trait locus of interest) and barnase (pollen-inhibitor gene loci).
B. Use of a Pollen-Inhibitor Gene Barnase to Break Linkage with a Glyphosate Resistance Trait (GAT) on Chromosome Three of Maize for Accelerated Trait Introgression.
The maize Pioneer inbred line 1carrying the linked GAT (glyphosate resistant trait locus of interest) and barnase (pollen-inhibitor gene) described above, can be used as the female in a cross with an (elite) inbred into which GAT will be introgressed. The resultant F1 plants can then be used as pollen-donors back onto the recurrent parent. Pollen that carries both the GAT locus and the pollen-specific barnase expression cassette are non-viable. Progeny of this cross can be screened by exposing the germinating seedlings to glyphosate which eliminates any progeny not carrying the trait locus. In viable progeny that pass this screen (i.e., progeny that contains the GAT trait and is resistant to the herbicide), the linkage between GAT and the pollen-specific barnase inhibitor would have been broken during meiosis. The resultant progeny now carry only the terminal end of the original Pioneer inbred line 1chromosome 3 carrying the GAT locus, and the remainder of chromosome 3 has been replaced by chromosome 3 from the recurrent parent inbred (
A Pioneer inbred Line 1 (PHN46) was identified that comprised a pre-existing transgenic SSI target site located at 152 cM on chromosome 10 containing a first expression cassette comprising a ubiquitin promoter driving a phosphomannose isomerase (PMI) and a pin II terminator, wherein the PMI was preceded by a FRT1 recombination site (UBI PRO::FRT1::PMI::pinII) linked to a second expression cassette comprising an actin promoter driving a moPAT selectable marker and a pin II terminator, followed by a FRT87 recombination site (ACTIN PRO::moPAT::pinII-FRT87). That Pioneer inbred line 1 was then used as the transformation target for particle-gun-mediated delivery and introduction of a GAT-resistance expression cassette between two dissimilar FLP-recombinase sites (FRT sites FRT1-NPTII::PINII TERM+3X(35S ENH): UBI1ZM PRO:UBI1ZM INTRON::GAT891G3::UBQ3 TERM+LTP2 PRO::DS-RED2::GZ-W64a TERM-FRT87 (SEQ ID NO: 44), along with a separate plasmid cassette (comprising a ubiquitin promoter driving a FLP recombinase terminated by a pinII terminator, UBI1ZM PRO:UBI1ZM INTRON:FLPM::PINII TERM (bp 411 to bp 4012 of PHP5096, SEQ ID NO: 50), resulting in RMCE and the replacement of PMI and moPAT by GAT in the pre-existing transgenic SSI target site located at 152 cM on chromosome 10. At a position 2 cM proximal (150 cM on chromosome 10), an SSI donor sequence (SEQ ID NO: 46) containing FRT1-NPT-II:pinII+35S ENH:LTP2 PRO::TAGBFP::GZ-W64A TERM +ZM-PG47-PRO::Zm-AA1::IN2-1 TERM-FRT87 (comprising a PG47 promoter driving the Zea mays alpha amylase (Zm-AA1) gene) was also introduced via particle-gun-mediated RMCE in a separate transformation experiment with Pioneer inbred line 1. The expression of alpha amylase in maize plant comprising the expression cassette PG47-PRO::Zm-AA1::pinII inhibits pollen tube growth and these plants must therefore be crossed with plants containing the GAT locus through the female ear in order to establish linkage.
D. Use of a Pollen-Inhibitor Gene—Alpha Amylase—To Break Linkage With a Glyphosate Resistance Trait (GAT) on Chromosome Three of Maize for Accelerated Trait Introgression.The maize Pioneer inbred line 1 carrying the linked GAT (glyphosate resistant trait locus of interest) and alpha-amylase (pollen-inhibitor gene) described above, can be used as the female in a cross with an (elite) inbred into which GAT will be introgressed. The resultant F1 plants can then be used as pollen-donors back onto the recurrent parent. Pollen that carries both the GAT locus and the pollen-specific alpha-amylase expression cassette are non-viable. Progeny of this cross can be screened by exposing the germinating seedlings to glyphosate which eliminates any progeny not carrying the trait locus. In viable progeny that pass this screen (i.e., progeny that contains the GAT trait and is resistant to the herbicide), the linkage between GAT and the pollen-specific alpha-amylase inhibitor would have been broken during meiosis. The resultant progeny now carry only the terminal end of the original Pioneer inbred line 1 chromosome 10 carrying the GAT locus, and the remainder of chromosome 10 has been replaced by chromosome 3 from the recurrent parent inbred (
In a fashion similar to Example 1 A-D described above, a trait locus of interest located at position of 0.9 cM on chromosome 1 containing the trait expression cassette ACTIN PRO::moPAT::pinII and the PG47 PRO::ZmAA1::pinII cassette can be introduced into on chromosome 1, at position 3.2 cM of the Pioneer Proprietary genomic map (PHD 3.2 cM). Establishing linkage (between the pollen-inhibitor genes such as ZM-AA1 and the trait loci of interest such as GAT891G3) and using this linked pair to cross to many different commercially important inbreds, can create a population of F1 hybrids. Each of the F1 hybrids can be used as a pollen donor back onto the same commercially-important inbred and progeny can be screened for accelerated introgression of the trait into each of the commercially-important inbreds.
Example 2 Using Two Pollen-Specific Inhibitor Loci Flanking a Trait of Interest for Accelerated Trait Introgression of a Non-Telomeric Trait LocusIllustrated in
A transgenic trait locus containing the GAT expression locus (GAT,
Pollen inhibition can be accomplished by using a pollen-specific promoter driving the alpha-amylase gene (AA) which is introduced both at positions 22.7 cM and 24.7 cM on chromosome six using SSI-mediated integration of the seed-specific DS-RED2 and PG47:Top3:ZM-AA1 contained in PHP02 (
B. Use of Two Pollen-Inhibitor Genes Flanking a Trait Locus on Interest (ZMAA1-GAT-ZMAA1) to Break Linkage with a Glyphosate Resistance Trait (GAT) for Accelerated Trait Introgression in Maize.
Once all three loci are physically linked (ZMAA1-GAT-ZMAA1), this material can then be used to cross with other inbreds (for example, Pioneer Inbred Line 3,
Using marker-assisted background selection methods has been widely used in agriculture since the 1990's (for example, see, Frisch, et al., (1999) Crop Science 39(5):1295-1301). However, the difficulty in introgressing a single trait is actually identifying meiotic recombination events that have occurred close the trait of interest. Out method provides a genetic selection at the gamete level (pollen) that identifies cells and progeny in which this has occurred. Once the chromosome that contains the trait has been substantially converted to the new inbred background, marker-assisted background selection can be used to more rapidly convert the remaining nine chromosomes.
C. Use of One Flanking Pollen-Inhibitor and a Seed Color Marker on the Other Flank of an Internal Trait Locus for Accelerated Trait Introgression in Maize.In Step 6, pollen is carried from a different Elite inbred (the recurrent parent into which the trait will be introgressed) onto the triple-linked plants (containing RK-Trait-PI) and use molecular markers to screen for F1 progeny that contain the triple-linked RK-GAT-PI. In Step 7, pollen is carried from the RK-Trait-PI F1 progeny back to the Recurrent Parent (the elite inbred) to generate a progeny pool. Kernels are screened for red color. If the kernel is red, it is discarded or set aside for another round of crossing. Yellow kernels were produced by pollen that had lost the pollen-inhibitor through breaking the linkage between the Trait and the PI locus, and had also lost the Red Kernel phenotype by breaking the linkage between the Trait and RK. Yellow kernels are then germinated in herbicide (or germinated and then sprayed with herbicide) to eliminate wild-type progeny, and the surviving seedlings contain the trait locus that has been rapidly introgressed into the trait-carrier chromosome.
D. Use of Two Flanking Seed Color Markers for Accelerated Trait Introgression in Maize.In Step 6, pollen is carried from a different Elite inbred (the recurrent parent into which the trait will be introgressed) onto the triple-linked plants (containing RK-Trait-RP) and use molecular markers to screen for F1 progeny that contain the triple-linked RK-GAT-RP. In Step 7, pollen is carried from the RK-Trait-RP F1 progeny back to the Recurrent Parent (the elite inbred) to generate a progeny pool. Kernels are screened for red color. If the kernel has a red crown or a red base, or both, it is discarded or set aside for another round of crossing (with the expression patern being an indication or which side broke linkage). Yellow kernels are produced by pollen that had lost the both the RC and RP phenotypes by breaking the linkage between the Trait both flanking loci. Yellow kernels are then germinated in herbicide (or germinated and then sprayed with herbicide) to eliminate wild-type progeny, and the surviving seedlings contain the trait locus that has been rapidly introgressed into the trait-carrier chromosome.
Example 3 Using Guide Polynucleotide/Cas Endonuclease Mediated Integration to Introduce Two Pollen-Specific Inhibitor Loci Flanking a Trait Locus for Accelerated Introgression of a Non-Telomeric Trait LocusIllustrated in
In this example, the trait locus can be a GAT expression cassette (UBLGAT::pinII) integrated into chromosome 1 at genetic position 53.14 cM. A pollen-inhibitor expression cassette (PG47-PRO::ZM-AA1::pinII) can be introduced at positions 52.56 cM and 54.56 cM on chromosome 1 using guide polynucleotide/Cas endonuclease mediated integration of the a sequence containing three expression cassettes, an expression cassette with PG47 PRO::ZM-AA1::PINII TERM, a cassette with the LTP2 PRO::YFP::PINII TERM (or with DS-RED2 in place of YFP), and a cassette with UBI1ZM PRO: UBI1ZM INTRON::PMI::PINII TERM (
Illustrated in
A SSI-generated trait locus can be established at a chromosomal location that is confirmed to be agronomically neutral, have no deleterious impacts on expression patterns of surrounding endogenous genes, and that supports good transgene expression levels. For example, as shown in
Any proven PATI site with a trait locus linked to a pollen-inhibition locus (for a telomeric trait locus) or to two pollen-inhibition loci (for an internal or non-telomeric trait locus) that has been demonstrated to support appropriate transgene expression and not be deleterious to plant growth and productivity can be used in this fashion, as a pre-established site for transgene introduction and accelerated trait introgression. Pre-existing Targeted Accelerated Integration Sites such as these can be used to introduce the trait gene, and can be used to introduce either single genes or molecular stacks and then rapidly introgressed these into many new inbreds for testing.
Example 5 Two Flanking Pollen-Inhibitor Intein Halves Used in Two-Stage Screening for Two Sequential RecombinationsThis experiment utilizes a bacterial endoribonuclease from Escherichia coli referred to as KID (Ruiz-Echevarria, et al., (1991) Mol. Microbiol. 5:2685-2693). This gene was split into two fragments and then the sequences encoding the amino-(KID-N, SEQ ID NO: 67) and carboxy-(KID-C, SEQ ID NO: 69) fragments were fused to the amino (NP-INTE-N, SEQ ID NO: 65) and the carboxy (NP-INTE-C, SEQ ID NO: 63) intein halves, respectively. These intein halves (from Nostoc, puncteforma, see, Iwai, et al., (2006) FEBS Lett. 580:1853-1858) encode two cognate intein, that when expressed in the same cell when fused to two cognate protein fragments peptides (fusing KID-N with NP-INTE-N in that order, and fusing NP-INTE-C with KID-C in that order) will bind with each other and catalyze their own excision, effectively splicing the two protein fragments (i.e., KID-N AND KIDC) together to form a fully functional protein (i.e., KID).
An internal trait locus such as the RMCE locus at position 23.7 cM on chromosome 6 (
As an alternative to the fluorescent proteins used in the second screening step (to monitor the second recombination and breakage of the linkage), a conditional negative selection marker such as the coda gene, the dhlA gene or the CYP105A gene can be used. When these genes are expressed in plant cells there is no adverse effect until their cognate substrates (5-fluorocytosine, dihaloalkanes or sulfonylurea R4702, respectively) are provided to the plant cell at which point these non-inhibitory substrates are converted to an inhibitor. Using such as marker, fluorescent microscopy is not needed to identify plant cells or tissues in which the genetic linkage has been broken and there is also no need for a maintainer line to render the inhibitor (coda, dhlA or CYP105A) inactive when not needed.
A trait such as resistance to the glufosinate herbicides such as Basta and Liberty (OS-ACTIN PRO & INTRON::MOPAT::35S TERM (SEQ ID NO: 95) can be integrated at Chromosome 6, 23.7 cM in inbred Pioneer inbred line 1 (
In this example we describe the use of sequential guide polynucleotide/Cas endonuclease system mediated integration to introduce a first flanking pollen-inhibitor cassette, followed by SSI-mediated targeting along with haploid embryo transformation to produce two flanking pollen-specific inhibitor loci linked to an intervening trait locus (illustrated in
The Pioneer inbred Line 3 homozygous for a specific trait locus referred to as TRAIT1 located at 53.1 cM (Pioneer Proprietary genomic map) on chromosome 1 can be transformed using particle bombardment of immature embryos to introduce via guide polynucleotide/Cas endonuclease systems (
A trait locus located on Chr1-50.5 cM in Pioneer inbred line 1 has been demonstrated to be efficacious and is to be introgressed into many new inbreds for testing. Cas9-mediated targeted integration using immature embryo transformation can be used to introduce a pollen-specific promoter driving expression the pollen-tube inhibitor AA1 at Chr1-49.5 cM, and single-copy targeted-integration T0 plants can be identified using PCR. These plants can then be pollinated using wild-type pollen of Pioneer inbred line 1, and the T1 immature embryos can be isolated for a second round of CAS9-mediated integration of a second AA1 Marker at Chr1-51.5 cM. Using two back-to-back transformations of immature embryos permits rapid creation of the triple-linked AA1-Trait-AA1 that can then be used for rapid introgression.
Example 7 Flanking an Internal Trait Locus with a Non-Conditional Pollen-Inhibitor Gene on One Side and a Conditional Lethal Gene on the Other, for Two-Step Screening for an Introgressed Trait LocusThis example describes a method for flanking an internal (non-telomeric) trait locus with a non-conditional pollen-inhibitor gene on one side and a conditional lethal gene on the other. This can be used for traits where breaking the linkage on both sides of the trait simultaneously (using back-crossing for introgression) occurs at too low a frequency (for example, due to very short genetic distances (between the trait locus and the flanking pollen-inhibitor loci on both sides) or due to meiotic recom binational-interference).
The two pollen-inhibitor flanking loci can be as follows: one flanking locus can contain a non-conditional pollen-inhibitor such as PG47 PRO::ZM-BT1 TP-ZM-AA1::IN2-1 TERM (SEQ ID NO: 77) or PG47 PRO::BA-BARNASE::PINII TERM (SEQ ID NO: 78), and the opposite flanking locus can contain a conditional pollen-inhibitor expression cassette. Examples of a conditional expression cassette can be PG47 PRO::CODAcodA::PINII TERMpinII (Ffor CODA gene, see, SEQ ID NO: 81, and for encoded protein see SEQ ID NO: 82). The encoded CODA protein has been shown to be non-inhibitory when expressed in plant cells, until a non-inhibitory substrate is added (5-fluorocytosine, see, Koprek, et al., (1999) Plant Journal 6:719-726). Upon addition of the substrate, 5-fluorocytosine is converted by the encoded protein into the inhibitory product 5-fluorouracil (see, Koprek, et al., (1999) Plant Journal 6:719-726).
Expressing a non-conditional pollen-inhibitor such as AA on one side can indicate that this locus can be crossed through the female to establish linkage, while the conditional codA locus does not inhibit pollen in the absence of 5-FC and can be crossed through the male to establish the three-way linkage and can be made homozygous. The Triple-linked plant (AA-GAT-codA) can be crossed to the inbred-of-interest to create the F1. At this juncture, the F1 can be crossed back to the recurrent parent with no 5-FC application. Of the pollen-grains containing the triple-stacked locus, only those that have lost AA will be viable. The progeny can be sprayed with glyphosate to recover the GAT-codA progeny. These can again be crossed back to the recurrent parent but this time the plants can be sprayed with the non-toxic 5-FC immediately before pollen-shed. Of the pollen grains containing codA before meiosis, only those pollen grains in which the linkage was broken will be viable.
This strategy can be used in the following, non-limiting examples:
1) when the genetic distances on either side are very small (and thus the frequency of a double cross-over can be very small)
2) when recominbinational-interference makes it impractical to screen for two simultaneous cross-overs
3) in crops where the number of pollen grains is not as great as in maize.
Example 8 Creating a Cas9 Mediated System for Pollen InhibitionIn this example we describe how one can create a Cas9 mediated system for pollen inhibition useful for providing an alternative for accomplishing pollen inhibition for use in accelerated trait introgression (see,
There are three components to the Cas9 mediated pollen-inhibitor system:
First, expressing a catalytically inactive double mutant of CAS9 (referred to as dCas9 and containing mutations in the RuvC1 and HNH nuclease domains) which can still associated with a guide-RNA and bind to a specific genomic sequence but without inducing a double strand break. While it's been demonstrated in E. coli that simple binding of dCas9 protein to a promoter can interfere with transcription (see, Qi, et al., (2013) Cell 152:1173-1183), the transcriptional interference can be enhanced, as described herein, namely by fusing a second component of the system to dCas9. The second component of the system comprises at least one repressor peptide that can be fused to dCas9. These repressor peptides comprise highly conserved motifs, such as “EAR-motifs” (with consensus signatures such as LxLxL or LxLxPP) that actively repress transcription (see, Kagale and Rozwadowski, (2011) Epigenetics 6:141-146). By fusing the repressor to dCas9, and expressing the protein behind a pollen-specific promoter, and using the third component, namely at least one expressed guide-RNA that direct the dCas9-LxLxPP fusion protein to an endogenous promoter (or multiple endogenous promoters) whose encoded protein(s) is(are) required for either pollen development or pollen tube growth, the result will be non-viable pollen.
Examples of genes that can be targeted to produce non-viable pollen;
a) A GT1 (glycosyltransferase gene) gene. It has been demonstrated in rice that knocking out the GT1 gene results in non-viable pollen. The maize ortholog of the rice GT1 gene (glycosyltransferase 1) is located on the short arm of chromosome 3 relatively near the centromere.
b) It has been documented that in the triple-mutant oas-tLABC (in which the A, B and C family members for the gene encoding O-acetylserine(thiol)lyase are knocked out, pollen germination does not occur or is so impaired as to be non-functional (see, Birke, et al., (2013) Plant Physiol 163:959-972). However, trying to create a triple-mutant and have all three mutant isoforms segregate together is impractical. By using a pollen-specific promoter to express dcas9-LxLxPP and the guide-RNA's that will target dcas9-LxLxPP to the promoters of oar-tlA, oar-tlB and oar-tlC—pollen tube growth in that pollen grain is blocked, and because these are expressed only in the pollen, there are no whole-plant pleiotropic effects.
c) This system can be used for any gene whose encoded product is essential for pollen viability and function. Another example of maize genes whose down-regulation will result in non-viable pollen are the maize chalcone synthase genes Whp (white pollen) and C2 which both encode a chalcone synthase protein necessary for pollen viability (Coe, et al., (1981) J Heredity 72:318-320; Franken, et al., (1991) EMBO J. 10(9):2605-2612).
Example 9 Use of a Two-Component Expression System to Control Pollen-Inhibition in the First of a Two-Step Screening Process, and a Conditional Negative Marker as the Second Screen to Rapidly Identify Introgressed Trait Loci in Two GenerationsTwo component transactivation expression systems have been used for many years in plants, (for example, see, Schwechheiner, et al., (1998) Plant Mol. Biol. 36:195-204) in which a fusion protein consisting of the GAL4 DNA-binding domain and the herpes simplex virus PV16 activation domain is expressed behind a promoter such as CaMV 35S, which binds to upstream activation sequences (UAS) in front of a minimal −45 CaMV promoter and the reporter gene beta-glucuronidase. However, it is also known that the GAL4 UAS is methylated in plants which inhibits binding (Galweiler, et al., (2000) Plant J. 23:143-157). As an alternative to GAL4˜VP16, the use of alternative DNA-binding domains such as LEXA (REF) fused to plant activation domains and the cognate UAS sequence for LEXA make a good alternative for two component expression in plants (Boddepalli, et al., US Patent Publication Number 2013/055791). One such plant transcriptional activation domain comes from the Arabidopsis CBF1A protein (Stockinger, et al., (1997) PNAS 94:1035-1040; Wang, et al., (2005) Plant Mol. Biol. 58:543-559).
A two-step (two-generations) method comprising a two-component transactivation system to drive expression of a pollen-inhibitor gene (step one), along with a pollen-specific conditional-inhibitor gene (step two) can be used to break linkage on both sides of an internal trait locus in two successive crosses. In the constructs described herein, moLEXA is a maize-optimized gene (SEQ ID NO: 97) which encodes the DNA binding domain of the Esherichia coli LEXA protein (LEXA described in Brent and Ptashne, (1985) Cell 43:729-736; see, SEQ ID NO: 98), UAS is the upstream activation sequence to which the LEXA fragment binds (SEQ ID NO: 99), and CBF1A is the polynucleotide sequences encoding the activation domain from the Arabidopsis CBF1A transcription factor (SEQ ID NO: 100).
An RTL exists at Chr1-52 cM in Pioneer Inbred Line 3 is used to introduce a trait expression cassette (labeled “GAT” in
Illustrated in
-
- a. If the linkage between GAT and PI is broken during meiosis then the pollen is viable and GAT can be transmitted to progeny.
- b. Spray with glyphosate to eliminate any progeny derived from wild-type pollen grains.
- c. The surviving plants will contain the GAT locus with minimal linkage drag from the transformation (donor) inbred.
A Pioneer Inbred Line1 (PHN46) (the target line) was identified that comprised a pre-existing transgenic SSI target site located at 150.7 cM on chromosome 10 containing a first expression cassette comprising a ubiquitin promoter driving a phosphomannose isomerase (PMI) and a pin II terminator, wherein the PMI was preceded by a FRT1 recombination site (UBI PRO::FRT1::PMI::pinII) linked to a second expression cassette comprising an actin promoter driving a moPAT selectable marker and a pin II terminator, followed by a FRT87 recombination site (ACTIN PRO::moPAT::pinII-FRT87). The target line was then used as the transformation target for particle-gun-mediated delivery and introduction of a GAT-resistance expression cassette between two dissimilar FLP-recombinase sites (FRT sites FRT1-NPTII::PINII TERM+3X(35S ENH):UBI1ZM PRO:UBI1ZM INTRON::GAT891G3::UBQ3 TERM+LTP2 PRO::DS-RED2::GZ-W64a TERM-FRT87 (SEQ ID NO:44), along with a separate plasmid cassette (comprising a ubiquitin promoter driving a FLP recombinase terminated by a pinII terminator, UBI1ZM PRO:UBI1ZM INTRON:FLPM::PINII TERM (bp 411 to bp 4012 of PHP5096, SEQ ID NO:50), which resulted in RMCE and the replacement of PMI & moPAT by GAT in the pre-existing transgenic SSI target site located at 150.7 cM on chromosome 10. At a position 0.5 cM proximal (150 cM on chromosome 10), an SSI donor sequence (SEQ ID NO:46) containing FRT1-NPT-II:pinII+35S ENH:LTP2 PRO::TAGBFP::GZ-W64A TERM+ZM-PG47-PRO::Zm-AA1::IN2-1 TERM-FRT87 (comprising a PG47 promoter driving the Zea mays alpha amylase (Zm-AA1) gene) was also introduced via particle-gun-mediated RMCE in a separate transformation experiment with Pioneer Inbred Line 1.
To confirm that the PG47::AA1::pinII expression cassette targeted to Chr10-150 cM resulted in pollen tube inhibition, we first verified that AA1 protein was being produced and then assessed the efficacy to inhibit pollen tube growth. For the first step (assessing expression), protein extracted from segregating pollen produced by eight SSI-targeted events (all at this same location) was analyzed by ELISA to assess AAI protein levels. In these assays, wild-type Pioneer Inbred Line 1 pollen was used as the negative control and no AA1 protein was detected (labeled “Inbred 1” in
B. Use of a Pollen-Inhibitor Gene Alpha Amylase (AA1) to Break Linkage with a Glyphosate Resistance Trait (GAT) on Chromosome Ten of Maize for Accelerated Trait Introgression.
An efficacious event containing AAI+BFP at Chr10-250 cM (referred to as PI in
The next step of the experiment was the first step in testing whether this closely linked pollen-inhibitor locus would facilitate more rapid and more precise introgression into another inbred. First, Pioneer Inbred line 1 plants containing the linked AA1 and GAT loci were crossed to Pioneer inbred Line 2 (such as inbred line PHH5G, the inbred into which the trait would be introgressed), using Pioneer inbred Line 2 as the pollen donor and producing the first filial generation (more commonly called the F1 hybrid) in the first step of the introgression process (Step 5 in
These results demonstrated that using a closely-located pollen-inhibitor locus next to a trait of interest could be effectively used to rapidly (with one generation from the F1 hybrid) screen and identify progeny that had converted the transgene-carrier chromosome (Chr10) to the recurrent parent Pioneer Inbred Line 2.
C. Use of the AA1 Pollen-Inhibitor Locus for Accelerated Trait Introgression of a Telomeric Trait Located at 0.9 cM on the Short Arm of Chromosome One.A trait locus on Chr 1 of Pioneer Inbred Line 1 (PHN46) at genetic position 0.9 cM contained both a moPAT (maize-optimized phosphinithricin acetyl transferase) and PMI (phosphomannose isomerase) (illustrated as GAT on
Pollen from wild-type Pioneer Inbred Line 2 (PHH5G) was used to pollinate ears of the doubly-linked (Traits+AA1) Pioneer Inbred Line 1 to produce the F1 hybrid (
Both of the above examples on the long arm of Chr10 and the short arm of Chr1 demonstrated the ability to use pollen-inhibitor loci to rapidly and precisely introgress a transgenic trait locus into a new inbred with a minimum of yield drag (unwanted flaking donor inbred chromosome segments remaining next to the introgressed trait).
Example 11 Use of Two Sequential Screenings Using a Pollen-Inhibitor Locus on One Side of the Trait Locus and a Locus Encoding a Visible Kernel Phenotype on the Other Side, In Order to Rapidly Identify Progeny in Which the Linkage had been Broken on Both Sides of the TraitAn internal trait locus containing at least one trait gene of interest in the Pioneer Inbred Line 1 (such as PHN46) is located at Chr1-51.8 cM. Using Cas9-mediated targeted integration, a pollen tube inhibitor expression cassette (PG47::Zm-AA1::pinII) is positioned at Chr1-50.8 cM, and in a second round of CAS9-medaited targeted integration, a seed-specific color marker (LTP2 PRO::CRC::pinII) is introduced at Chr1-52.8 cM. The seed is bulked up by pollinating with the wild-type Pioneer Inbred Line 1.
To begin the introgression process, ears of the triple-linked transgenic inbred are pollinated with pollen from the various inbreds (for example, Pioneer Inbred Line 2, such as PHH5G) into which trait of interest will be introgressed to produce F1 hybrids. The F1 hybrids are then used as the male to pollinate the recurrent parent (i.e., Pioneer Inbred Line 2) and the BC1F1 seed are examined. Kernels are separated into two pools; the red-kernel phenotype imparted by the anthocyanin fusion-gene CRC and yellow kernels (non-red). Because of the pollen-inhibitor locus that was originally on the distal flank of the trait, any F1 pollen grains containing this locus would not form pollen tubes, and only wild-type pollen grains or transgenic pollen grains that had lost the AA1 locus due to meiotic recombination would produce a pollen tube and hence BC1F1 progeny. Non-red kernels are germinated in the presence of herbicide (which kills all the progeny derived from wild-type pollen) and only the non-red kernels (that had lost the color marker due to meiotic recombination) will survive.
If no surviving progeny are recovered in the first BC1F1 screening, the red BC1F1 seeds can be germinated and used to again pollinate the wild-type recurrent parent (i.e. Pioneer Inbred Line 2). The resultant BC2 seed are again separated into red and non-red kernels and the yellow kernels are germinated in herbicide. Resultant plants that germinate in the presence of herbicide have broken linkage on both sided of the trait and the trait has been introgressed in the RP with <1.0 cM of remaining Pioneer Inbred Line 1 chromosome on either side of the trait.
Example 12 Using a Flanking Pollen-Inhibitor Proximal to a Telomeric Trait Along with a Meiotically-Expressed Targeted Nuclease Between the Pollen-Inhibitor and the Trait Locus to Simulate Targeted Recombination and Chromosome ExchangeA trait locus in Pioneer Inbred line 1 (such as PHN46) containing a moPAT and PMI at Chr1-0.9 cM is produced, and a T-DNA containing a pollen-inhibitor expression cassette is positioned at Chr1-1.0 cM (0.1 cM proximal to the trait) using Cas9/CRISPR systems. In addition to the pollen-inhibitor expression cassette (PI), the T-DNA contains a 2 kb spacer sequence, an expression cassette containing a meiosis-specific promoter such as the SPI11 PRO in front of Cas9 (CAS9 locus) and an expression cassette driving expression of a guide-RNA that will target a Double-Stranded Break in between the T-DNA and the trait locus.
After establishing these two linked loci (the trait locus and the PI/CAS9 locus) on the same chromosome, pollen from various inbreds (for example Pioneer Inbred Line 1) is used to pollinate the ears of Pioneer Inbred Line 1 comprising the Trait-PI/CAS9 to produce the F1 hybrid. The F1 hybrids are grown to maturity and then used to pollinate the recurrent parent, Pioneer Inbred Line 2. BC1F1 progeny are screened for introgression of the Trait Locus into the Pioneer Inbred Line2 Chromosome 1, which normally is predicted to occur in 1/1000 progeny, based on a genetic distance between the two loci of 0.1 cM. However, because of the targeted cutting activity of the CAS9 protein during meiosis, targeted meiotic recombination between the trait and the pollen-inhibitor is stimulated resulting in a higher frequency of progeny that have introgressed the trait into the Pioneer Inbred Line 1 chromosome 1 at very close genetic distance (i.e., <0.1 cM).
In addition to using Cas9, other double strand break inducing systems can be used in the methods described herein. One can express a fusion between a well-established DNA-binding-domain (DBD) such as GAL4 or LEXA and a nuclease (or meganuclease; abbreviated MN) such I-SceI, I-CreI, I-DmoI, PI-SceI, PI-PfuI, Fok1. One can also use the DBD fused to Spoil in this type of a scenario. One can include the pollen-inhibitor (or the red-aleurone marker) in the T-DNA followed by a meiosis-specific promoter driving expression of fusion protein (comprising a DNA-binding domain and a meganuclease (or a topoisomerase), a 2-3 kb spacer and then the DNA sequence that is bound by the DNA-binding-domain), which positions the MN at this cleavage site. This provides the pollen-inhibitor (or the seed color marker) to be used as the screening method(s) to identify the progeny in which the linkage has been broken within a specified nearby genetic interval, a meiosis-specific catalyst to create double-strand breaks, and the cutting target site provided by the target sequence of the DNA-binding domain. Targeted double-strand breaks in this region during meiosis will stimulate localized homologous recombination (crossovers) and the pollen and/or seed screening tools will permit rapid identification.
Claims
1.-34. (canceled)
35. A method of accelerated trait introgression in the genome of a plant, the method comprising:
- (a) providing a first plant having within a genomic window at least one trait of interest located proximal to a telomere, and at least one color marker gene located proximal to both the telomere and the trait of interest, wherein said trait of interest and said color marker gene are genetically linked in said genomic window, wherein said genomic window is about 5 cM in length and located within 10 cM of the telomere;
- (b) cross pollinating the first plant of (a) with pollen from a second plant; and,
- (c) selecting a progeny plant from step (b) comprising said trait of interest site and said color marker gene; and,
- (d) backcrossing the progeny plant of (c) as the pollen donor onto a recurrent parent plant and selecting progeny plants comprising the trait of interest but lacking the color marker gene.
36. A method of accelerated trait introgression in the genome of a plant comprising:
- (a) providing a first plant having within a genomic window at least one trait of interest, a pollen-inhibitor gene and a color marker gene, wherein said genomic window is about 5 cM in length, and wherein trait of interest is flanked by said first and second pollen-inhibitor gene;
- (b) cross-pollinating the first plant of (a) with pollen from a second plant; and,
- (c) selecting a progeny plant from step (b) comprising said first pollen-inhibitor gene, said trait of interest, and said second pollen-inhibitor gene; and,
- (d) cross pollinating the progeny plant from step (c) to a recurrent parent plant and selecting progeny plants comprising the trait of interest but lacking the color marker gene.
37. The method of claim 36, further comprising: a second color marker gene integrated into a second target site.
38. A plant comprising at least one trait gene of interest, a first recombinant DNA construct comprising a color marker gene, and a second recombinant DNA construct comprising a second color marker gene, wherein said first recombinant DNA construct and said second recombinant DNA construct are genetically linked and flank said trait gene of interest, and wherein the first and second color markers segregate independently from the trait gene of interest ata rate of about 10% to about 0.1%.
39. The plant of claim 38, wherein the first color marker gene, the second color marker gene and the trait gene of interest are located within 5 cM of each other.
Type: Application
Filed: Sep 12, 2022
Publication Date: Jan 19, 2023
Applicant: PIONEER HI-BRED INTERNATIONAL, INC. (JOHNSTON, IA)
Inventors: MICHAEL T. ELSING (URBANDALE, IA), WILLIAM JAMES GORDON-KAMM (URBANDALE, IA), LEANDRO DANIEL PERUGINI (URBANDALE, IA), HUAXUN YE (JOHNSTON, IA)
Application Number: 17/931,142
