METHOD FOR PRODUCING TRANSGENIC SURFACE LAYER CHIMERIC PLANT
A rose is produced in which an introduced gene is only present in a part of the cells thereof, such as cells of the L1 layer of flower petals, but is not present in germ cells such as pollen cells or ovule cells. Since the introduced gene is not propagated to other roses even when this rose is crossed with other roses, the possibility of dispersal of the introduced gene can be completely negated.
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The present invention provides a method for producing a chimeric transgenic plant having an introduced gene in a part of the cells thereof.
BACKGROUND ARTIndividuals composed of a plurality of genetically different cell groups are referred to as chimeras. Plant chimeras are classified as periclinal chimeras, partial chimeras and sectorial chimeras according to their structure, and can be produced by, for example, grafting as well as accidental or radiation-induced somatic mutations or chromosome doubling induced by chemical treatment.
Sectorial chimeras are non-structural chimeras derived from the layered structure of plants, and occur due to proliferation of mutant cells present non-structurally at growth points. Namely, sectorial chimeras refer to chimeras in which a single tissue layer itself is chimeric, and frequently appear in the form of different colored stripes in flowers, leaves, stems and other organs. Although sectorial chimeras usually disappear due to their instability, periclinal chimeras occasionally continue to develop.
Periclinal chimeras refer to structural chimeras derived from the tissue layer structure of plants in which sectorial chimeras develop and a single cell layer is completely substituted with mutant cells. In the case of periclinal chimeras, a single tissue layer itself is homogeneous and not chimeric. Periclinal chimeras are stable and the frequency at which they disappear is said to be low. Plant cell tissue is basically composed of three cell layers, having a tissue layer structure consisting of a first layer (L1), a second layer (L2) and a third layer (L3) moving inward from the outside.
The L1 and L2 layers arise from the two layers of tunica of growth points, while the L3 layer arises from the corpus. In nearly all plant species, the epidermis is entirely formed from the L1 layer, while the L2 layer is involved with the germ cell system. Although numerous periclinal chimeras having different properties for each of these cell layers are horticulturally important and have high industrial value, the probability of obtaining a periclinal chimera accidentally or by a means in which mutations are induced artificially in the manner of radiation exposure or chemical treatment is extremely low.
When introducing a foreign gene into a plant body, it is not easy to artificially produce a chimeric plant having an introduced gene in only a part of the cells. Previously, there is an example of the production of a chimeric plant having an introduced gene in only a part of germ cells or the L2 cell layer by introducing a gene into an immature corn embryo by a method using a particle gun (Japanese Unexamined International Publication No. H10-503374). However, in the case of introducing a gene mediated by Agrobacterium, it is even more difficult to produce a chimeric plant. In methods of Agrobacterium-mediated gene introduction, single cells in which the gene has been introduced are selected by using as an indicator a trait such as drug resistance as determined through expression of a marker gene, and a single individual transgenic plant is obtained from the single cell in which the gene has been introduced.
Accordingly, normally obtained transgenic plants are composed of genetically a single kind of cell, and all of the cells have the introduced gene. Even if a plant that only had a foreign gene in a part of the cells (chimeric plant) was obtained, it would merely constitute an accidental result, and it is extremely difficult to control gene introduction so that the gene is only introduced into cells of a specific portion of a plant with the current level of technology. In addition, even if such a plant were obtained accidentally, the probability of the plant being a periclinal chimera having the gene only in a part of the cell layers is considered to be extremely low as previously described.
During the course of selecting cells having an introduced gene, although chimeric cell clusters or chimeric plant bodies may appear in which a foreign gene has been introduced into only a part thereof, in this case, the chimeric cell cluster or plant body is either chimeric throughout all cell layers or only a single tissue layer itself is chimeric, and is not a true periclinal chimera (that in which a foreign gene is introduced in only a specific cell layer while the cell layer itself is homogeneous). There have previously been very few examples of the production of a truly periclinal chimeric transgenic plant that has been verified by molecular biological techniques. Although an example has previously been reported of having found that a periclinal chimeric body can be produced by using a vector containing rol gene and a leaving factor (Japanese Unexamined Patent Publication No. 2002-315460), this case is a periclinal chimera of the L3 layer.
In transgenic plants, an introduced gene incorporated in a chromosome is stably transferred to progeny thereof in accordance with Mendel's laws. By then using these transgenic plants as crossing parents, new varieties of plants can be further produced by utilizing traits derived from the introduced gene.
In addition, there are concerns over transgenic plants regarding effects on the ecosystem (environment) (such as the dispersal of an introduced gene into the natural world). Known examples of technologies for preventing gene dispersal from transgenic plants to non-transformants and wild plants include (1) use of maternal inheritance, (2) use of male sterility, and (3) use of sterile seeds. The use of maternal inheritance refers to a method for preventing gene dispersal by pollen by introducing a foreign gene into a chloroplast genome that is not passed to pollen cells.
The use of male sterility refers to a method for inhibiting pollen formation or not allowing pollen to have the ability to reproduce, and makes it possible to carry out genetic isolation. For example, this method consists of tissue-specifically producing a harmful gene product using a promoter specifically expressed in male reproductive organs to inhibit pollen formation. The use of sterile seeds refers to a method for preventing both crossing or seed dispersal by directly inhibiting seed formation of a transgenic plant, and is equivalent to “terminator technology” and the like which prevents seed saving.
If it were possible to produce a transgenic plant not having an introduced gene in its germ cells, even in the case of using that transgenic plant as a pollen parent or as a seed parent, the possibility of dispersal of the introduced gene by crossing would be completely eliminated. This means that for a person engaged in cultivation of the transgenic plant in the wild or utilization of the transgenic plant industrially, the burden incurred by regulatory procedures for cultivating the transgenic plant would be reduced. In Japan, such procedures include an assessment of biodiversity effects based on the “Law Concerning the Conservation and Sustainable Use of Biological Diversity through Regulations on the Use of Living Modified Organisms” (Cartagena protocol), and include assessments based on similar laws in other countries.
- Patent Document 1: Japanese Unexamined International Publication No. H10-503374
- Patent Document 2: Japanese Unexamined Patent Publication No. 2002-503374
- Patent Document 3: U.S. Pat. No. 5,480,789
- Patent Document 4: WO 2005/017147
- Patent Document 5: PCT/JP96/00348
- Non-Patent Document 1: Firoozababy et al., Bio/Technology, 12: 883-888, 1994
- Non-Patent Document 2: Lazo et al., Bio/Technology, 9: 963-967, 1991
- Non-Patent Document 3: Fujiwara et al., Plant J., 16, 421-431, 1998
- Non-Patent Document 4: Mitsuhara et al., Plant Vell. Physiol., 37, 45-59, 1996
Thus, the present invention provides a floricultural plant such as a rose in which an introduced gene is only present in a part of the cells of the plant body, for example, is absent in germ cells.
As a result of conducting various studies to overcome the aforementioned problems, the inventors of the present invention that introduction of a foreign gene into a floricultural plant mediated by Agrobacterium tumefaciens can result in the regenerated floricultural plant being a chimeric plant. Moreover, it was also found that a target transgenic floricultural plant can be obtained by selecting a periclinal chimeric plant there from, thereby leading to completion of the present invention. Thus, the present invention provides a floricultural plant such as a rose in which an introduced gene is only present in a part of the cells and not present in the other cells.
The aforementioned part of the cells preferably composes a part of the cell layers. For example, the aforementioned other cells are pollen or ovule cells. More specifically, the portion of the cell layers is either the L1 layer or the L1 layer and the L3 layer. Examples of an introduced gene include genes involved in flavonoid synthesis, and particularly genes relating to flower color such as genes involved in anthocyanin synthesis.
In the case the floricutural plant is a rose, it is important that the introduced gene be, for example, a flavonoid 3′,5′-hydroxylase gene derived from a plant belonging to the violet family or an aromatic acyl group transferase gene derived from a plant belonging to the snapdragon family. An example of a plant belonging to the violet family is a pansy, while an example of a plant belonging to the snapdragon family is a torenia.
Examples of roses include hybrid tea rose such as rose variety WKS82, floribunda and miniature rose. Due to the effect of the introduced gene, the rose of the present invention, for example, changes its flower color to a bluish color as compared with prior to gene introduction.
In the case the floricultural plant is a carnation, the introduced gene is one or a plurality of genes such as flavonoid 3′,5′-hydroxylase gene cDNA derived from salvia under the control of a promoter of a chalcone synthase gene derived from common snapdragon, a genomic gene of petunia dihydroflavonol 4-reductase, or an anthocyanin synthase gene derived from carnation. The carnation may be of the standard type or spray type. Due to the effect of the introduced gene, the carnation of the present invention, for example, changes flower color to a bluish color as compared with prior to gene introduction.
However, the foreign gene is not limited to the genes described above, but rather may be a gene that functions in a wide range of pigment synthesis systems, and for example, may be a gene that functions in the flavonoid synthesis system. In addition, the foreign gene may be a selectable marker gene in the manner of GFP gene, NPTII gene, GUS gene or SURB gene. Moreover, the foreign gene may be a gene that encodes a transcription factor, such as a gene that encodes myb-like transcription factor, and more specifically, PHR1 gene or Psr1 gene.
In addition, the present invention also provides a tissue of the rose or other floricultural plant as described above having the same properties thereof, or a nutritive growth product thereof.
Moreover, the present invention further provides the method for producing a floricultural plant such as a rose comprising a step for introducing a foreign gene into the rose mediated by Agrobacterium, and selecting a rose in which the foreign gene is only present in a part of the cells thereof. The present invention further provides a method for preventing dispersal of an introduced gene into the natural world by producing a floricultural plant not having a foreign gene in the germ cells thereof as described in any of claims 3 to 27.
There are no particular limitations on the floricultural plant used in the present invention provided it is a floricultural plant in which a foreign gene can be introduced mediated by Agrobacterium. Examples of floricultural plants include rose, carnation, petunia, torenia, tobacco, verbena, Nierembergia, chrysanthemum, lily, morning glory, common snapdragon, cyclamen, orchid, prairie gentian, freesia, gerbera, gladiola, baby's breath, kalanchoe, pelargonium, geranium, tulip, rapeseed, potato, tomato, poplar, banana, eucalyptus, sweet potato, soybean, alfalfa, lupine and cauliflower. In particular, rose, carnation, petunia, torenia, tobacco, verbena and Nierembergia are preferable, with rose and carnation being able to be used particularly preferably.
The foreign gene used in the present invention is preferably a gene of an enzyme that functions in cells of the L1 layer following introduction. For example, genes related to flower color, selectable marker genes, and genes encoding transcription factors are preferable. Examples of genes related to flower color include gene of enzymes involved in flavonoid synthesis such as genes related to anthocyanin synthesis, genes encoding proteins related to aurone synthesis, genes encoding aliphatic acyl group transferases, and genes encoding flavone synthases. Examples of selectable marker genes include GFP gene and NPTII gene, GUS gene and SURB gene. Examples of genes encoding transcription factors include genes encoding MYB-like transcription factor, and more specifically, PHR1 gene and Psr1 gene. However, the present invention is not limited to the genes specifically listed here.
The rose used in the present invention may be a horticultural variety or a wild variety. In particular, commercially useful horticultural varieties (Rosa hebrida) such as hybrid tea rose, floribunda and miniature rose are preferable. There are no particular limitations on these varieties.
T-DNA composed of an expression cassette of flavonoid 3′,5′-hydroxylase gene derived from pansy and an expression cassette of aromatic acyl group transferase gene NPTII derived from torenia was inserted into a rose callus mediated by Agrobacterium. Since the resulting transformant underwent a color change due to the action of the introduced genes, the introduced genes were suggested to be present in petal cells, and particularly in cells of the L1 layer of those petals engaged in pigment synthesis. The introduced genes were not suggested to be present in pollen cells based on PCR using as a template genomic DNA extracted from various rose organs.
In addition, in the case of having carried out a crossing test with other horticultural and wild varieties of rose using pollen obtained from the transgenic plants, there were no introduced genes detected whatsoever in the resulting seeds. On the basis of this as well, the introduced genes were suggested to not be contained in pollen cells. Moreover, the introduced genes were clearly determined to be present in the L1 cell layer only based on in situ hybridization. This finding verifies that the introduced genes are not present in germ cells such as pollen that are formed by originating in the L2 cell layer. Accordingly, a chimeric plant having an introduced gene in only a part of the cells thereof is able to be produced introducing a foreign gene in a rose callus in the manner described above.
Examples of genes of enzymes involved in flavonoid synthesis include flavonoid 3′,5′-hydroxylase gene and aromatic acyl group transferase gene. Although there are no particular limitations on the sources thereof, flavonoid 3′,5′-hydroxylase gene derived from a pansy or other plant of the violet family, or aromatic acyl group transferase gene derived from torenia or other plant belonging to the snapdragon family, which have been confirmed to function in roses, is preferable.
The carnation used in the present invention is preferably a commercially useful standard type or spray type. There are no particular limitations on the varieties thereof. Any of varieties such as Feeling White, Precross Doozy, Starzarl or Kortina Chanel may be used.
With respect to carnation, flavonoid 3′,5′-hydroxylase gene cDNA derived from salvia under the control of a chalcone synthase gene derived from common snapdragon, petunia dihydroflavanol 4-reductase genomic gene, and anthocyanin synthase derived from carnation, SURB gene were introduced under prescribed conditions mediated by Agrobacterium. Since the resulting transformant underwent a color change due to the action of the introduced genes, the introduced genes were suggested to be present in petal cells, and particularly in cells of the L1 layer of petals engaged in pigment synthesis. The resulting transformant was determined to be a chimeric plant in which the introduced genes were only present in the L1 layer based on PCR using as a template genomic DNA extracted from various carnation organs.
EXAMPLESThe following provides a more detailed explanation of the present invention through examples thereof.
Example 1 Method for Introducing Genes into RoseNumerous methods have already been reported relating to rose transformation (such as Firoozababy et al., Bio/Technology, 12: 883-888, 1994, U.S. Pat. No. 5,480,789 and WO 2005/017147), and a foreign gene can be introduced into a rose in accordance with these methods.
More specifically, a rose callus derived from the leaf of a sterile seedling was immersed for 5 minutes in a broth containing Agrobacterium tumefaciens strain Ag10 (Lazo et al., Bio/Technology, 9: 963-967, 1991) followed by wiping off excess broth with sterile filter paper, transplanting to a subculturing medium and co-cultivating in a dark location for 2 days.
Subsequently, after washing with MS liquid medium containing 400 mg/l of carbenicillin, the rose callus was transplanted to a selection/disinfection medium in which 50 mg/l of kanamycin and 200 mg/l of carbenicillin were added to subculturing medium. Transplantation and culturing were repeated on the portion that grew normally without being inhibited in the selection medium to select a kanamycin-resistant callus.
The transformed callus that exhibited kanamycin resistance was cultured in redifferentiation medium containing 50 mg/l kanamycin and 200 mg/l of carbenicillin to obtain kanamycin-resistant shoots. The resulting shoots were acclimated after causing to form roots in ½ MS medium (not containing kanamycin). After potting the acclimated individuals, the acclimated individuals were cultivated in a closed system greenhouse and allowed to bloom. Subsequently, the individuals were maintained and allowed to grow by ordinary vegitative propagation (grafting).
Example 2 Construction of Binary Vector pSPB130Anthocyanin can be stabilized and its blue color can be made more intense by modifying the anthocyanin with an aromatic acyl group (see, for example, PCT/JP96/00348). The following experiment was conducted for the purpose of producing an acylated delphinidine-type anthocyanin.
Total RNA was obtained from the petals of torenia (trade name: Summer Wave (trademark)) after which polyA+RNA was prepared there from. A cDNA library using λZAPII (Stratagene) as a vector was prepared from this polyA+RNA using a directional cDNA library production kit (Stratagene) according to the method recommended by the manufacturer.
Since the major anthocyanin of torenia has the glucose at position 5 modified by an aromatic acyl group (Suzuki et al., Molecular Breeding, 6, 239-246, 2000), anthocyanin acyl group transferase is expressed in torenia petals. Anthocyanin acyl group transferase retains the amino acid sequence of Asp-Phe-Gly-Trp-Gly-Lys, and anthocyanin acyl group transferase gene can be acquired by using a synthetic DNA corresponding thereto as a primer (PCT/JP96/00348).
More specifically, PCR was carried out using Taq polymerase (Takara, Japan) under conditions recommended by the manufacturer using 10 ng of single-strand DNA synthesized during production of the torenia cDNA library as a template, and using 100 ng of ATC primer (5′-GA(TC)TT(TC)GGITGGGGIAA-3′, wherein I represents inosine and (TC) represents either represents T or C) (SEQ ID NO. 1) and 100 ng of oligo dT primer (5′-TTTTTTTTTTTTTTTTTCTCGAG-3′) (SEQ ID NO. 2) as primers. PCR was carried out for 25 cycles of reactions consisting of 1 minute at 95° C., 1 minute at 55° C. and 1 minute at 72° C. The resulting approximately 400 bp DNA fragment was recovered by Gene Clean II (BIO 101 Inc.) according to the method recommended by the manufacturer and sub-cloned to pCR-TOPO.
When the base sequence thereof was determined, a sequence was observed that was homologous to gentian acyl group transferase gene (Fujiwara et al., Plant J., 16, 421-431, 1998). Furthermore, the base sequence was determined using the Sequencer 310 or 377 (Applied Biosystems) according to the Diprimer Method (Applied Biosystems).
This DNA fragment was then labeled with DIG using a DIG labeling and detection kit (Nippon Roche), and the torenia cDNA library was screened by plaque hybridization according to the method recommended by the manufacturer. Twelve of the resulting clones yielding a positive signal were randomly selected and plasmids were recovered there from followed by determination of base sequences. These sequences demonstrated good homology with anthocyanin acyl group transferase. The entire base sequence was determined for cDNA contained in the clone designated pTAT7 (SEQ ID NO. 3).
After digesting pBE2113-GUS (Mitsuhara et al., Plant Cell. Physiol., 37, 45-59, 1996) with SacI, the ends were smoothened followed by insertion of an 8 bp XhoI linker (Takara). An approximately 1.7 kb DNA fragment obtained by digesting pTAT7 with BamHI and XhoI was inserted into the BamHI and XhoI sites of this plasmid to obtain pSPB120. After digesting pSPB120 with SnaBI and BamHI, the ends were smoothened followed by ligation to obtain pSPB120′. On the other hand, a plasmid pCGP1961, containing F3′,5′ H#40 cDNA derived from pansy, was completely digested with BamHI followed by partial digestion with XhoI and recovery of the resulting approximately 1.8 kb DNA fragment which was then ligated with pUE5H digested with BamHI and XhoI. The resulting plasmid was designated pUEBP40.
After digesting pUEBP40 with SnaBI and BamHI, the ends were smoothened followed by ligation to obtain pUEBP40′. An approximately 2.7 kb DNA fragment obtained by partially digesting pUEBP40 with HindIII was recovered and ligated with a DNA fragment partially digested with HindIII. Among the resulting plasmids, the binary vector in which neomycin phosphotransferase gene, pansy F3′5′H #40 and torenia 5AT gene were respectively ligated in the same direction in order starting from the right border of the binary vector was designated as pSPB130 (
The pSPB130 was introduced into a light violet-colored rose “WKS82”, and 89 transformants were obtained. Accumulation of delphinidin was confirmed in all 44 transformants that underwent pigment analysis. The delphinidin content was a maximum of 91% (mean: 49%). Flower color changed from 186d of the RHS color chart (greyed-purple group) to 80c (purple-violet group). The analysis values of representative transformants are shown in the following tables.
Genomic DNA was extracted from petals, leaves, stems, roots and pollen of “WKS82” (to be referred to as the “host”) and recombinants nos. 5 and 24 produced in Example 3 (WKS82/130-4-1 and WKS82/130-9-1, to be referred to as “recombinants”) using DNeasy Plant Mini Kit (Qiagen) in accordance with the method recommended by the manufacturer. Introduced genes (pansy F3′S′H gene (SEQ ID NO. 4), torenia 5AT gene (SEQ ID NO. 3) and E. coli NPTII gene) were amplified by PCR with Takara Ex Taq (Takara) using the extracted DNA as templates.
Moreover, rose anthocyanin synthase (ANS) gene was amplified as an endogenous control. The PCR reaction conditions consisted of repeating 25 cycles consisting thermal denaturation for 5 minutes at 94° C., for 30 seconds at 94° C., for 30 seconds at 55° C. and for 1 minute at 72° C., followed by an elongation reaction for 7 minutes at 72° C. The resulting amplification products were eletrophoresed in agarose gel and amplified fragments were detected by ethidium bromide staining.
Furthermore, BP40-F2 and BP40-R3 were used as primers for amplification of pansy F3′5′H gene, TAT7-50F and TAT7-R1 were used for amplification of torenia 5AT, NPTII-F and NPTII-R were used for amplification of NTPII gene, and RhANS69-r1 and RhANS69-m1 were used for amplification of ANS gene.
As a result of analyzing by PCR, although the introduced genes were detected in the petals, leaves and stems of the recombinants, these introduced genes were not detected in the genomes of the roots or pollen. The results are shown in Table 3 and
In addition, petals, epidermal systems of the leaves and stems, sepal, stamen and pistil are known to be derived from the L1 layer and L2 layer, pollen and oocytes from the L2 layer, and the internal tissue of leaves and stems along with roots from the L3 layer. Since introduced genes were not detected in the genomes of the roots and pollen, these recombinants were suggested to be chimeric plants in which introduced genes were only present in the L1 layer.
After removal of anther and bagging horticultural varieties immediately prior to blooming in accordance with ordinary methods, pollen of the host or recombinant no. 24 produced in Example 3 (WKS82/130-9-1, to be referred to as the recombinant) cultivated in a greenhouse in the morning on a sunny day was adhered at the time the stamen had adequately matured. Subsequently, the plants were again bagged to prevent adhesion of other pollen and then investigated for the presence of seed formation. Furthermore, the pollen was fresh pollen obtained by recovering the anther prior to dehiscence and then allowing to stand at room temperature for 1 day in a desiccator containing silica gel followed by recovering from the anther that underwent dehiscence on the following day. The female parents consisted of a Grandiflora perpetual rose variety known as “Queen Elizabeth” and a Floribunda perpetual rose variety known as “Gold Bunny”.
The presence of seed formation was confirmed one month or more after crossing for fruit that had not dropped physiologically and in which seed setting was observed. Moreover, in order to confirm the passing on of introduced genes to the next generation for seeds obtained by crossing with the recombinant, genomic DNA was extracted from the resulting seeds using Nucleon Phytopure for Plant DNA Extraction Kit (Amersham Biosciences), and after further amplifying with the REPLI-g Kit (Qiagen), the introduced gene (pansy F3′5′H gene) was detected by PCR.
The results are shown in Table 4. There were hardly any differences observed in the seed-set rates between the host and the recombinant. Moreover, as a result of analyzing seeds obtained by crossing with the recombinant, there were no introduced genes detected in the seeds. On the basis of these findings, although there were no differences in pollen fertilizing ability between the host and recombinant, for reasons such as introduced gene not being contained in pollen cells of the recombinant, the introduced gene was suggested to not be passed to the next generation.
After removal of anthers and bagging horticultural varieties immediately prior to blooming in accordance with ordinary methods, pollen of the host or recombinant no. 24 produced in Example 3 (WKS82/130-9-1, to be referred to as the recombinant) cultivated outdoors in the morning on a sunny day was adhered at the time the stamen had adequately matured. Subsequently, the plants were again bagged to prevent adhesion of other pollen and then investigated for the presence of seed formation. Furthermore, the pollen was fresh pollen obtained by recovering the anther prior to dehiscence and then allowing to stand at room temperature for 1 day in a desiccator containing silica gel followed by recovering from the anther that underwent dehiscence on the following day.
The female parents consisted of a Grandiflora perpetual rose variety known as “Queen Elizabeth” and a Floribunda perpetual rose variety known as “Gold Bunny”.
The presence of seed formation was confirmed three months or more after crossing for fruit that had not dropped physiologically and in which seed setting was observed. Moreover, seeds recovered from crossing with the recombinant were recovered and treated at a low temperature of 40° C. for 3 months follows by seeding. In order to confirm the passing on of introduced genes to the next generation for these seeds, genomic DNA was extracted from leaves of the resulting seedlings using the DNeasy Plant Mini Kit (Qiagen) followed by detection of the introduced gene (pansy F3′5′H gene) by PCR. Furthermore, rose glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene was detected as the intrinsic control gene.
In addition, although germination is normally observed in about one month in the case of treating the seeds at low temperatures, germination was only observed in a portion of the seeds even after three months. Therefore, a portion of the seeded seeds that did not germinate were re-recovered, and a similar analysis was carried out using those seeds. Genomic DNA was extracted from the re-recovered seeds using Nucleon Phytopure for Plant DNA Extraction Kit (Amersham Biosciences), and after amplifying the genomic DNA with the REPLI-g Kit (Qiagen), the introduced gene (pansy F3′5′H gene) was detected by PCR.
The results are shown in Tables 5 and 6. There were hardly any differences observed in the seed-set rates between the host and the recombinant. Moreover, although seedlings obtained by crossing with the recombinant were analyzed by PCR, introduced genes derived from the recombinant were not detected in the seedlings. Moreover, there were also no introduced genes derived from the recombinant detected in the seeds. On the basis of these findings, although there were no differences in pollen fertilizing ability between the host and recombinant, for reasons such as introduced gene not being contained in pollen cells of the recombinant, the introduced gene was suggested to not be passed to the next generation.
After removal of anther and bagging horticultural varieties immediately prior to blooming in accordance with ordinary methods, pollen of the host or recombinant no. 24 produced in Example 3 (WKS82/130-9-1, to be referred to as the recombinant) cultivated outdoors in the morning on a sunny day was adhered at the time the stamen had adequately matured.
Subsequently, the plants were again bagged to prevent adhesion of other pollen and then investigated for the presence of seed formation. Furthermore, the pollen was fresh pollen obtained by recovering the anther prior to dehiscence and then allowing to stand at room temperature for 1 day in a desiccator containing silica gel followed by recovering from the anther that underwent dehiscence on the following day.
The female parents consisted of wild varieties known as R. multiflora Thunb. ex Murray, R. wichuraiana Crep. and R. rugosa Thunb. ex Murray).
The presence of seed formation was confirmed two months or more after crossing for fruit that had not dropped physiologically and in which seed setting was observed. Moreover, the resulting seeds were recovered and subjected to treatment at a low temperature of 4° C. for 3 months followed by seeding. In order to confirm the presence of crossing with the host or recombinant and the passing on of introduced genes to the next generation, genomic DNA was extracted from leaves of the resulting seedlings using the DNeasy Plant Mini Kit (Qiagen) followed and analyzed by PCR. A gene involved in perpetuality (KSN gene) was used as an indicator for the presence of crossing with the host or recombinant, while an introduced gene derived from the recombinant in the form of pansy F3′5′H gene was used as an indicator for the presence of passing on the introduced gene. Furthermore, rose GAPDH gene was used as an intrinsic control gene.
The KSN gene is formed as a result of an approximately 9 kb transposon being inserted into the ksn gene (having a function that maintains the shoot meristem) of seasonal roses, and since expression of this gene is inhibited as a result thereof causing inhibition of the formation of flower buds on the shoot meristem to be cancelled, flower bud formation is promoted which is reported to cause the flower to become perpetual1). Horticultural varieties are homozygous for the KSN gene. On the other hand, seasonal wild varieties are homozygous for the ksn gene. Thus, in wild varieties (seasonal varieties), the KSN gene is thought to only be detected in the case it has been crossed with a horticultural variety.
In addition, although germination is normally observed in about one month in the case of treating the seeds at low temperatures, germination was only observed in a portion of the seeds even after three months. Therefore, a portion of the seeded seeds that did not germinate were re-recovered, and a similar analysis was carried out using those seeds. Genomic DNA was extracted from the re-recovered seeds using Nucleon Phytopure for Plant DNA Extraction Kit (Amersham Biosciences), and after amplifying the genomic DNA with the REPLI-g Kit (Qiagen), the presence of crossing with the host or recombinant and the presence of passing on of the introduced gene was detected by PCR.
The results are shown in Tables 7 and 8. Seed-set rates were extremely low in the case of using either the recombinant for each of the pollen parents. Although the resulting seedlings were analyzed by PCR, pollination between the host or recombinant and the wild varieties was observed, but the introduced gene derived from the recombinant was not detected. Moreover, seeded seeds that did not germinate were re-recovered, and when the seeds were observed for development, nearly all the seeds were empty, and normal embryos were only able to be confirmed in an extremely small number of the seeds. Although these were also similarly analyzed by PCR, pollination was confirmed between the host or recombinant and the wild varieties even though an introduced gene derived from the recombinant was not detected. On the basis of these findings, for reasons such as introduced gene not being contained in pollen cells of the recombinant, the introduced gene was thought to not be passed to the next generation.
Accordingly, since an introduced gene is not contained in pollen cells of the recombinant even in the case of pollination between the recombinant and wild varieties (R. multiflora Thunb. ex Murray, R. wichuraiana Crep. and R. rugosa Thunb. ex Murray), the introduced gene was suggested to not have the possibility of being passed to the next generation.
Furthermore, normal embryos were unable to be confirmed for any of the seeds of R. wichuraiana Crep.
In situ hybridization was carried out in order to investigate the localization of an introduced gene in more detail. After severing a bud measuring about 5 mm in size in the vertical direction, the severed portions were fixed by immersing in a formaldehyde fixing solution. Next, the fixing solution was sequentially replaced with ethanol solutions ranging from 50% to 100% to dehydrate the severed portions followed by replacement (clarification) with 25% lemozol. The sections were subsequently gradually immersed in paraffin and embedded therein. The embedded samples were sliced with a microtome and adhered to slide glasses. After hydrating the slide glasses, treating with Proteinase K and carrying out pretreatment in the form of acetylation and the like, the samples were dehydrated and dried. DIG-labeled probes (antisense and sense probes of BP40, TAT, NPTII and each gene) were dissolved in a hybridization solution, placed on the dried slide glasses and allowed to react. Following hybridization, the slide glasses were washed followed by detection of DIG.
As shown in the photographs of
A carnation was produced in which an introduced gene was present only in the L1 layer.
The transgenic carnation was produced in the manner described below by gene introduction mediated by Agrobacterium. A plasmid pCGP2442 (described in U.S. Pat. No. US/988,293 filed on Nov. 15, 2007) contained in the T-DNA region thereof flavonoid 3′,5′-hydroxylase gene cDNA under the control of a promoter of a chalcone synthase gene derived from common snapdragon, a genomic gene of petunia dihydroflavonol 4-reductase, an anthocyanin synthase gene derived from carnation, and a transformation selectable marker in the form of tobacco acetolactate synthase gene SURB cDNA under the control of cauliflower mosaic virus 35S promoter. This plasmid was introduced into Agrobacterium using the method described in Japanese Unexamined International Patent Publication No. H11-505116 followed by further introducing into Carnation variety Cortina Chanel. Delphinidin was detected in petals of the resulting transgenic carnation that is not contained in natural carnations. This indicates that the introduced gene at least functions in the epidermal cells of the petals. A detailed analysis was conducted on one strain thereof (strain 19907). In addition, as a result of extracting chromosomal DNA from this strain 19907 and analyzing by southern hybridization using a gene of the aforementioned pCGP2442 T-DNA as a probe, the introduced gene was confirmed have been inserted into a chromosome.
A tissue culture was produced by planting shoots of strain 19907 and strain 26898 in hormone-free MS solid medium containing 5 μg/L of Glean. When the shoots were observed for the presence of root formation for 4 to 5 weeks, although strain 26898 formed roots, strain 19907 did not.
Next, leaf sections obtained from strain 19907, strain 26898 and the Kortina Chanel variety were cultured for 5 weeks in half-strength MS solid medium with 0.5 mg/L IAA and containing 5 μg/L of Glean, and half-strength MS solid medium with 0.5 mg/L IAA not containing Glean. The leaf sections of strain 19907 and the Kortina Chanel variety that were cultured in medium containing 5 μg/L of Glean became brown. The leaf section obtained from strain 26898 was green and was observed to have formed roots.
Chromosomal DNA was extracted from the leaves and roots of strain 19907 using the DNeasy Plant Mini Kit (Qiagen). PCR was then carried out using 100 ng of this DNA as a template and using synthetic primers for amplifying SuRB gene (#960: 5′-ATT TCC GCC TCA TTA GAA GG-3′, #1468: 5′-GCC TCA TGT TTC CAT TTG TCG-3′). After carrying out the reaction for 15 minutes at 95° C. at reaction volume of 25 μl using Hot Star Taq, the reaction was further carried out for 35 cycles with one cycle consisting of 1 minute at 96° C., 30 seconds at 52° C. and 2 minutes at 72° C., followed by finally carrying out the reaction for 7 minutes at 72° C. When the reaction product was analyzed by agarose gel electrophoresis, although the band for SURB was observed in the case of using leaf DNA as a template, the SURB band was not observed in the case of using root DNA.
Leaves are known to be composed of L1, L2 and L3 cells, while roots are known to be composed of L2 and L3 cells. On the basis of the above results, in the case of strain 19907, the introduced gene was present in L1 cells, but not present in L2 and L3 cells, or in other words, strain 19970 was determined to be a chimeric plant in which the introduced gene is only present in the L1 layer.
Example 10 Study of Potential for Application of the Technology of the Present Invention to Various Plants(1) Example of Infection into Petunia
Using petunia for the floricultural plant, a gene involved in flavonoid synthesis was introduced as a foreign gene.
A DNA fragment (approx. 2.0 kb), linking butterfly pea F3′5′H cDNA and an nos terminator, was recovered from an El235S promoter sequence, having two repeating enhancer sequences upstream from a cauliflower mosaic virus (CaMV) 35S promoter (Plant Cell Physiol., 37, 49-59 (1996)), and pSPB748 (Plant Cell Physiol., 43, s277 (2002)), obtained by introducing a butterfly pea F3′5′H cDNA sequence (described in Patent Application No. WO 2004/020637) and a nopaline synthase (nos) terminator sequence into a binary vector pBinPlus (Transgenic Research, 4, 288-290 (1995)), by digesting with BamHI and partially digesting with EcoRI, followed by introducing into a BamHI/EcoRI site of pBluescriptII (sk-) (Stratagene) to obtain a plasmid pB-Bn. A gene cassette consisting of a GUS gene and an nos terminator was extracted with XbaI and KpnI from a 6xXRE promoter sequence having six repetitions of mouse xenobiotic responsive element (XRE), and pBlueSXXREGUS (Kodama (2003), Molecular mechanisms of chemical-inducible gene expression in higher plants for monitoring and remediation of environmental contaminants, Diss.), obtained by introducing a GUS gene and an nos terminator into pBluescriptII (ks+) (Stratagene), followed by introducing to the same site a DNA fragment (approx. 2.0 kb) linking butterfly pea F3′5′H and nos terminator excised from pB-Bn by digesting with XbaI and KpnI to obtain pB-X6Bn. A gene cassette (2.2 kb) consisting of 6xXRE promoter sequence, butterfly pea F3′,5′H cDNA and an nos terminator sequence, excised by digesting pB-X6Bn with XhoI, was then introduced into the SalI site of a vector pSKAVAt (Kodama (2003)), in which AhRV and Arnt, to which a 5′ untranslated (UTR) sequence of alfalfa mosaic virus was respectively added, were inserted in the forward direction into two sets of expression units consisting of a CamV35S promoter and an nos terminator in a binary vector pBin19, to construct pSBP1459.
pSPB1459 was then introduced into Agrobacterium tumefaciens strain Ag10 (BioTechnology, 9, 963-967 (1991)) to transform petunia (variety PL, Skr4 xSw63 (same as in Nature, 366, 276-279) according to the Agrobacterium method using a leaf disc. Introduction of plasmid into Agrobacterium and transformation were carried out in accordance with a known method (Plant J., 5, p. 81-82 (1994)). Although flower color of variety PL is white to light pink since it lacks flavonoid 3′,5′-hydroxylase gene and flavonoid 3′-hydroxylase gene, the petunia variety used for the purpose of this experiment is not limited to PL. 38 independent strains of transformed petunia PAB were acquired.
(2) Example of Infection to Torenia—Part 1Using torenia for the floricultural plant, a selectable marker gene in the form of GFP gene was introduced as a foreign gene.
CaMV35S-sGFP(S65T)-NOS3′ (Curr. Biol., 6, 325-330 (1996)) was digested with BamHI and EcoRI, and DNA (1.0 kb) linking sGFP gene and nos terminator gene was introduced into the BamHI/EcoRI site of pBluescriptII (sk-) to construct a plasmid pB-Gn. A gene cassette consisting of GUS gene and nos terminator was excised from pBlueSXXREGUS-last with XbaI and KpnI, and a gene cassette (1.0 kb) consisting of sGFP and nos terminator excised from pB-Gn with XbaI and KpnI was introduced into the same site to construct pB-X6Gn. A gene cassette (1.2 kb) consisting of 6xXRE promoter, sGFP and nos terminator excised from pB-X6Gn by digesting with XhoI was then introduced into the SalI site of pSKAVAt to construct pSPB1458.
pSPB1458 was then introduced into Agrobacterium tumefaciens strain Ag10 followed by transforming torenia (variety Summer Wave Blue: SWB (Suntory Flowers) to a leaf disc according to the Agrobacterium method using a leaf disc. Transformation of torenia was carried out in accordance with a known method (Mol. Breeding, 6, 239-246 (2000)). Although the flower color of the SWB variety is blue, the variety of torenia used for the purpose of this experiment is not limited to SWB. 40 independent strains of transformed torenia TAG were acquired.
(3) Example of Infection into Torenia—Part 2
Using torenia for the horticultural plant, a gene involved in flavonoid synthesis was introduced as a foreign gene.
A construct (pSFL307 or pSFL308), having an expression cassette of a gene involved in aurone synthesis and a cassette for inhibiting expression of anthocyanin synthesis-related genes by RNAi, was introduced using torenia variety Summer Wave Blue as the host plant according to a method using Agrobacterium in the same manner as described above. The flower color of the resulting torenia changed from blue to yellow.
(4) Example of Infection into Tobacco, Verbena or Nierembergia
Using tobacco, verbena or nierembergia for the floricultural plant, a transcription factor gene was introduced as a foreign gene.
Thale cress PHR1 gene (Genes & Development, 15: 2122-2133 (2001)), which is expressed under phosphate starvation conditions, was subcloned in a pCR2.1 vector using a TOPO-TA Cloning Kit (Invitrogen) in accordance with the manual. A product amplified by a PCR reaction using primers PHRf (5′-ATGGAGGCTCGTCCAGTTCAT-3′) and PHRr (5′-TCAATTATCGATTTTGGGACGC-3′) was subcloned and designated as pSPB1892. A binary vector pSPB2311, having an (Mac) promoter linking an enhancer sequence of a 35S promoter and a mannopine synthase promoter, and a mannopine synthase (mas) terminator, was excised with SmaI to obtain pSPB2311A. A fragment smoothened by excising pSBP1892 with EcoRI was then inserted into pSBP2311A to obtain pSBP2314.
Continuing, Agrobacterium (strain Ag10) was then transformed using pSBP1898 based on a known method (Plant J., 5, 81, 1994), and tobacco, verbena and Nierembergia were transformed using the transformant Agrobacterium having pSPB1898. Transformation of tobacco, verbena and Nierembergia was respectively carried out based on known methods (Science, 227, 1229, 1985; Plant Cell Rep., 21, 459, 2003; and, Plant Biotech., 23, 19, 2006). Gene introduction in the resulting plant bodies was confirmed by extracting DNA from a leaf of each plant body followed by PCR using PHR1 gene as a template. 11 PHR1 transgenic plants were acquired from tobacco, 16 from verbena and 1 from Nierembergia.
(5) Example of Infection into Impatiens and Begonia
Using impatiens or begonia for the floricultural plant, a transcription factor gene was introduced as a foreign gene.
Transformation of impatiens (Impatiens walleriana) was basically carried out using the varieties Glitter Red (Sakata Seed) and Tempo Pink (Takii & Co.) in accordance with U.S. Pat. No. 6,121,511. After pre-culturing shoot apices, nodes, leaf stalks and leaf sections cut from an in vitro seedlings for 5 days in a preculturing liquid medium (MS medium containing 1 mg/L of TDZ), the samples were allowed to stand undisturbed for 48 hours in a preculturing solid medium (MS medium containing 0.05 mg/L of NAA, 6 mg/L of zeatin and 0.3% gellan gum). Subsequently, the samples were infected with Agrobacterium (strain Ag10) containing pSPB2314 followed by culturing for 4 to 8 weeks on a selective medium (MS medium containing 0.05 mg/L of NAA, 6 mg/L of zeatin, 100 mg/L of kanamycin, 500 mg/L of carbenicillin, 100 mg/L of cefotaxime and 3% gellan gum) to obtain shoots (Table 9). Shoots were unable to be obtained from the leaf sections since they browned easily. Although numerous shoots were obtained from a single explant in the case of shoot apices and nodes, these were thought to contain a large number of false positives. Expression took a considerable amount of time in shoots obtained from leaf stalks, and although they were few in number, they appeared to be the most reliable.
Transformation of begonia (Begonia semperflorens) was carried out using the varieties Ambassador White and Ambassador Scarlet (Sakata Seed). Leaf sections and leaf stalks were cut out from in vitro seedlings and infected with Agrobacterium (strain Ag10) containing pSPB2314, followed by culturing for 3 days in the dark on co-cultivation medium (MS medium containing 0.5 mg/L of IAA, 0.1 mg/L of TDZ, 0.5% PVP, 2 mg/L of AgNO3, 200 μM acetosyringone and 0.3% gellan gum). Subsequently, the samples were cultured for 3 to 5 days in pre-selective medium (MS medium containing 1 mg/L of BAP, 1 mg/L of zeatin, 0.1 mg/L of IAA, 500 mg/L of timentin, 50 μM acetosyringone and 0.25% gellan gum), followed by consecutively culturing for 2 weeks in selective medium 1 (MS medium containing 2 mg/L TDZ, 0.1 mg/L NAA, 100 mg/L of kanamycin, 500 mg/L of timentin and 0.4% agar), culturing for 2 weeks in selective medium 2 (MS medium containing 0.2 mg/L of BAP, 0.1 mg/L of NAA, 100 mg/L of kanamycin, 500 mg/L of timentin and 0.4% agar), and 3 weeks in selective medium 3 (MS medium containing 100 mg/L kanamycin, 500 mg/L of timentin and 0.4% agar). Surrounding tissue was cut away from the shoots that formed during that time when they grew to a diameter of 5 mm or more, the shoots were transferred to a selective medium 4 (MS medium containing 150 mg/L of kanamycin, 500 mg/L of timentin and 0.4% agar), and after further culturing for 2 to 3 weeks, the shoots were transferred to root initiation medium (MS medium containing 100 mg/L of kanamycin, 500 mg/L of timentin and 0.4% agar) to obtain root forming shoots (Table 10).
As is indicated above, a foreign gene was determined to be able to be introduced using Agrobacterium in floricultural plants other than roses and carnations such as petunias, torenia, tobacco, verbena, nierembergia, impatiens or begonias. The introduced foreign gene is not limited to the specific genes exemplified here, but rather any gene is considered to be able to be introduced into these floricultural plants using similar methods provided it is a gene that functions in L1 cells following introduction. Since the technology of the present invention can be applied to floricultural plants into which a foreign gene can be introduced using Agrobacterium, with respect to these plants, it is possible to produce a floricultural plant of the present invention, namely a floricultural plant in which a foreign gene is only present in a part of the cells of the transgenic plant but not present in other cells.
INDUSTRIAL APPLICABILITYA transgenic plant produced according to the method disclosed by the present invention is a chimeric plant that does not have an introduced gene in the L2 cell layer that includes germ cells and the like, but rather only has the introduced gene in cells of the L1 layer. Since this type of transformant does not have an introduced gene in germ cells, the possibility of the transgenic plant being freely used as a crossing parent by an unauthorized third party can be prevented.
In addition, since there is concern regarding transgenic plants over dispersal of an introduced gene into the natural world, the possibility of introduced gene dispersal can be completely negated by producing a transgenic plant does not have an introduced gene in the germ cells thereof. Accordingly, the burden placed on persons attempting to use a transgenic plant industrially with respect to application for approval for commercial use of a transgenic plant (in Japan, the “Law Concerning the Conservation and Sustainable Use of Biological Diversity through Regulations on the Use of Living Modified Organisms” (Cartagena protocol)) can be reduced.
Claims
1: A floricultural plant that contains a foreign gene only in a part of the cells thereof, but not in other cells.
2: The floricultural plant according to claim 1, wherein the part of the cells comprise a part of a cell layer.
3: The floricultural plant according to claim 1, wherein the other cells are pollen cells or ovule cells.
4: The floricultural plant according to claim 1, wherein the other cells are cells comprising the L2 layer.
5: The floricultural plant according to claim 2, wherein the part of the cell layer is either the L1 layer or the L1 layer and the L3 layer.
6: The floricultural plant according to claim 2, wherein the floricultural plant is a floricultural plant into which a foreign gene is able to be introduced mediated by Agrobacterium.
7: The floricultural plant according to claim 6, wherein the floricultural plant is any of rose, carnation, petunia, torenia, tobacco, verbena, nierembergia, chrysanthemum, lily, morning glory, common snapdragon, cyclamen, orchid, prairie gentian, freesia, gerbera, gladiola, baby's breath, kalanchoe, pelargonium, geranium, tulip, rapeseed, potato, tomato, poplar, banana, eucalyptus, sweet potato, soybean, alfalfa, lupine and cauliflower.
8: The floricultural plant according to claim 1, wherein the foreign gene is a gene that functions in L1 layer cells following introduction.
9: The floricultural plant according to claim 8, wherein the foreign gene is a gene relating to flower color.
10: The floricultural plant according to claim 9, wherein the foreign gene is a gene involved in flavonoid synthesis.
11: The floricultural plant according to claim 10, wherein the foreign gene is one or a plurality of flavonoid hydroxylase gene derived from a plant belonging to the violet family, aromatic acyl group transferase gene derived from a plant belonging to the snapdragon family, flavonoid 3′,5′-hydroxylase gene cDNA derived from salvia, genomic gene of petunia dihydroflavonol 4-reductase, and anthocyanin synthase gene derived from carnation.
12: The floricultural plant according to claim 8, wherein the foreign gene is a selectable marker gene or a gene encoding a transcription factor.
13: The floricultural plant according to claim 7, wherein the floricultural plant is a rose.
14: The floricultural plant according to claim 13, wherein the rose is Rosa hybrida.
15: The floricultural plant according to claim 14, wherein the rose is hybrid tea rose, floribunda or miniature rose.
16: The floricultural plant according to claim 13, wherein the foreign gene is a gene relating to flower color.
17. The floricultural plant according to claim 13, wherein the foreign gene is a gene involved in flavonoid synthesis.
18: The floricultural plant according to claim 17, wherein the foreign gene is flavonoid 3′,5′-hydroxylase gene derived from a plant belonging to the violet family and/or aromatic acyl group transferase gene derived from a plant belonging to the snapdragon family.
19: The floricultural plant according to claim 18, wherein the plant belonging to the violet family is a pansy.
20: The floricultural plant according to claim 18, wherein the plant belonging to the snapdragon family is a torenia.
21: The floricultural plant according to claim 13, wherein flower color changes to a bluish color as compared with a rose prior to gene introduction.
22: The floricultural plant according to claim 7, wherein the floricultural plant is a carnation.
23: The floricultural plant according to claim 22, wherein the carnation is of the spray type or standard type.
24: The floricultural plant according to claim 23, wherein the foreign gene is a gene relating to flower color.
25: The floricultural plant according to claim 24, wherein the foreign gene is a gene of an enzyme involved in flavonoid synthesis.
26: The floricultural plant according to claim 25, wherein the foreign gene is one or a plurality of flavonoid 3′,5′-hydroxylase gene cDNA derived from salvia, genomic gene of petunia dihydroflavonol 4-reductase, and anthocyanin synthase gene derived from carnation.
27: The floricultural plant according to claim 22, wherein flower color changes to a bluish color as compared with a carnation prior to gene introduction.
28: A tissue having the same properties as the floricultural plant according to claim 1, or a vegitative propagation product thereof.
29: A method for producing the floricultural plant according to claim 1, comprising a step for introducing a foreign gene into a plant mediated by Agrobacterium, and selecting a plant in which the foreign gene is only present in a part of the cells thereof.
30: A method for preventing dispersal of an introduced gene into the natural world by producing the floricultural plant not having a foreign gene in the germ cells thereof according to claim 3.
Type: Application
Filed: Apr 13, 2012
Publication Date: Aug 2, 2012
Applicant: SUNTORY HOLDINGS LIMITED (OSAKA)
Inventors: JUNICHI TOGAMI (MISHIMA-GUN), EKATERINA MOURADOVA (MILL PARK)
Application Number: 13/446,591
International Classification: A01H 5/00 (20060101); A01H 1/06 (20060101); C12N 5/04 (20060101);
