TRANSGENIC PLANTS EXPRESSING MUTANT GEMINIVIRUS AC1 OR C1 GENES
The invention involves production of transgenic plants containing DNA encoding AC1/C1 wildtype and mutant sequences that negatively interfere in trans with geminiviral replication during infection. The transgenic plants produced by the invention are resistant to viral infection.
[0001] A variety of geminivirus genes and mutant derivatives were generated and transferred to plant cells. Transgenic plants containing these genes were produced. Transgenic plants containing trans-dominant mutations developed resistance to geminivirus infection.
BACKGROUND[0002] Geminiviruses present the most serious disease problem in many vegetable crops in tropical and subtropical regions. For example, major epidemics of geminivirus infections of beans and tomatoes have occurred in Florida, the Caribbean Basin, Mexico, and Central America. In the past, traditional breeding methods failed to produce cultivars with significant levels of resistance to geminiviruses. An alternative approach lies in producing virus-resistant transgenic plants according to the present invention.
[0003] The geminivirus group are single stranded DNA viruses that infect both monocotyledonous (monocot) and dicotyledonous (dicot) plants. A common feature among all gemini viruses is the mode of genomic replication, which involves a rolling circle mechanism.
[0004] Tomato mottle virus (ToMoV) is one example of a geminivirus. It has a two component (bipartite) genome, an ability to infect dicot plants and is transmitted by whitefly. The DNA of its two genomic components, DNA-A and DNA-B, has previously been cloned and sequenced. Isolated clones of DNA-A and DNA-B of ToMoV are themselves infectious when mechanically inoculated into tomato and N. benthamiana, or when delivered to either host by agroinoculation. An invariant geminiviral DNA sequence required for replication is present in an intergenic, common region (CR) in each genomic component.
[0005] The ToMoV DNA-A genomic component has four ORF, one of which, AC1, must be expressed for efficient replication of both A and B components. The AC1 ORF encodes a protein having several functional activities: a DNA binding site specific to the DNA-A CR; a DNA nicking activity; and a NTP binding activity. The DNA binding region mediates an initiator protein function during rolling circle replication.
[0006] AC3 protein is a second ToMoV-coded function involved in DNA replication and production of single-stranded circular DNA.
[0007] Tomato yellow leaf curl virus (TYLCV) is another example of a geminivirus. TYLCV has a monopartite genome organization, infects monocot plants, and is leaf-hopper transmitted. The TYLCV C1 protein is required for replication, encoded by the C1 ORF.
[0008] Being DNA viruses, geminiviruses offer advantages for antiviral strategies. Several geminiviruses have been cloned and sequenced. Transgenic plants having mutant viral genes can be produced, e.g., by introducing expression cassettes comprising mututated virus genes directly into plants with a particle gun, or into plant suspension cells or protoplasts by electroporation, or by Agrobacterium transfection.
SUMMARY OF THE INVENTION[0009] The invention involves production of transgenic plants containing DNA encoding AC1/C1 wildtype and mutant sequences that negatively interfere in trans with geminiviral replication during infection. The resulting transgenic plants are resistant to viral infection.
DESCRIPTION OF THE FIGURE[0010] FIG. 1 shows the results of a transient assay for trans-dominance done with BGMV-GA in NT-1 cells.
DETAILED DESCRIPTION OF THE INVENTION[0011] A. Production of infectious clones
[0012] Infectious clones of geminiviruses are produced by methods known to the skilled worker. Geminivirus DNA is extracted from tissue as follows. Young tissue is collected from infected plants, frozen in liquid nitrogen and ground in a mortar in the presence of extraction buffer (10 mM Tris-Cl, pH 7.5, 10 mM EDTA, and 1% SDS, 1:4 wt/vol ratio) and centrifuged for about 105 g minutes. The supernatant is adjusted to about 1 M NaCl and stored at about 4° C. for about 12 hr, then centrifuged for about 107 g minutes. After phenol extraction, the solution is adjusted to 0.3 M sodium acetate, and the DNA is precipitated in alcohol. Viral nucleic acids are isolated by agarose gel electrophoresis.
[0013] These viral nucleic acid fractions are digested with restriction enzymes and isolated by agarose gel electrophoresis. The DNA is cloned in a suitable cloning vector, e.g., pBluescript KS+, and its identity is confirmed by sequencing.
[0014] Full-length clones of the geminivirus genome are constructed, e.g., by a PCR-based cloning strategy. Primers are synthesized that will amplify the entire ORF plus about ten nucleotides on each side of the ORF. The primers should include mismatched bases to create restriction sites before and after the C1 or AC1 ORF which will allow convenient cloning without altering initiation and termination codons of C1 or AC1 ORFs.
[0015] Primer 1 is complementary to and anneals with the viral sense strand of the geminiviral genome. The 5′ end of the primer is located 40-50 base pairs 3′ of the translation start, and the 3′ end is located 10-20 base pairs 3′ of the translation start site. Translation start is defined by CAT on the viral sense strand; AC1 or C1 ORFs are located on the complementary strand of the viral genome and sequence coordinates are given for the viral sense polarity strands.
[0016] Primer 2 is complementary to and anneals with the strand (complementary sense polarity) of the geminiviral genome. The 5′ end of the primer is located 40-50 base pairs 3′ of the AC1 or C1 termination condon, and the 3′ end of the primer is located 10-20 base pairs 3′ of the translation stop as determined on the complementary sense polarity strand.
[0017] The primers are used in a PCR reaction to amplify the C1 or AC1 ORF from cloned viral DNA or purified geminivirus DNA. The amplified DNA is digested with appropriate restriction enzymes to cut sites engineered in the ends of the PCR fragment and the resulting fragment is cloned into a suitable vector. C1- or AC1-containing clones are identified and sequenced to confirm the presence and integrity of the cloned C1 or AC1 ORF.
[0018] The sequence of the AC1/C1 ORF is used for designing the primers for amplification of the PCR fragment of AC1/C1 ORF. For example, these primers are designed so that this ORF is cloned into the BamHI and HindIII sites of pBluescript KS+. The BamHI site is located at the 5′ end of the complementary sense primer, which amplifies the amino terminal end of the ORF. A HindIII site is located at the 5′ end of the viral sense primer which anneals to the carboxy end of the ORF.
[0019] Infectious clones preferably are selected. The infectivity of the clones are determined by construction of Agrobacterium having greater-than-full-length viral genes with at least two common regions of DNA-A and DNA-B. Infectivity is determined by microparticle inoculation. Seeds are germinated on moist filter paper to produce 1-3 cm long radicles of a host, and this tissue is bombarded by DNA-coated particles with a particle gun. Inoculated plants are placed in a growth chamber at about 26° C. with about 14 hour photoperiods. Infectivity is confirmed by PCR with primers specific for geminiviruses or Southern blot analysis. For example, 1.3-kb PCR products are expected when primers PAL1v1978 and PAV1c715 are used.
[0020] Cloned viral DNA is digested with restriction enzymes and analyzed on agarose gels to produce a unique 2.5 to 2.7-kb fragment. The DNA bands are removed from the gel and cloned into an appropriate vector. For monopartite geminiviruses, the insert preferably includes the entire genome. For bipartite geminiviruses, entire inserts of both genomic components are preferable. The single insert of the monopartite geminivirus or both cloned components of bipartite geminiviruses are introduced into a host plant and tested for infectivity by biolistic delivery or agroinoculation.
[0021] The cloned C1 (monopartite viruses) or AC1 (bipartite viruses) ORF are isolated by selecting for the following characteristics:
[0022] A. The AC1 or C1 ORF encodes a protein product of about 42 Kd.
[0023] B. The nucleotide sequence of the C1 or AC1 ORF is at least 60% homologous to the AC1 ORF of a previously identified geminiviruses (e.g., BDMV, ToMoV, or TYLCV). The deduced amino acid sequence of the ORF will contain several characteristic sequences which are similar in sequence and relative position within the ORF i.e., motifs within the C1 or AC1 sequences.
[0024] B. Introducing Mutations
[0025] Mutations are introduced by site-directed mutagenesis of cloned C1 or AC1 ORF by methods known in the art, e.g., using the method of Kunkel et al. (Recombinant DNA Methodology, 1989, pp. 587-601) (herein, “Kunkel mutagenesis”).
[0026] In particular, mutations are introduced into amino acid sequence motifs in C1 or AC1 ORF that are highly conserved among all gemini viruses. Four motifs are preferred in the DNA-nicking domain of the protein. These include (capital letters denote high conservation of amino acid, lower case denotes some conservation, and “x” denotes a variable position in the motif):
[0027] (1) FLTYpxC
[0028] (2) HlHvliQ
[0029] (3) vKxYxdKd; and
[0030] (4) FHPNIQxak.
[0031] Additionally two motifs are preferred in the NTP-binding domain of the protein. These include:
[0032] (5) EGx2RTGKt; and
[0033] (6) NviDDi.
[0034] The individual codons specifying the most highly conserved amino acids within these motifs are mututated. For example, one or more of the following mutations introduced to the C1 or AC1 ORF:
[0035] (1) vKxYxdKd to
[0036] (a) vKxFxdKd;
[0037] (b) vKxAxdKd;
[0038] (c) vKxYxdRd;
[0039] (2) EGx2RTGKt to
[0040] (a) EGx2RTGHt;
[0041] (b) EGx2RTGAt;
[0042] (c) RGx2RTGKht;
[0043] (3) NviDDi to
[0044] (a) NviRDi;
[0045] (b) NviKDi; or
[0046] (c) NviDYi,
[0047] (herein mutations 1(a), 1(b), 1(c), 2(a), 2(b), 2(c), and 3(a), 3(b), 3(c), respectively). Acidic or basic amino acids are changed to the opposite charge, to alanine (alanine scanning) or to other neutral amino acids. Combinations of mutants are also made. For example, a single C1 or AC1 ORF containing codon changes corresponding to vKxFxdKd and EGx2RTGHt (double mutations 1(a) and 2(a), above) are constructed and tested. Other mutants in motifs within AC1/C1 are possible and are used. The presence of the codon change is confirmed by DNA sequencing. Agrobacterium-mediated transfer of the plant expressible mutated AC1/C1 ORF is done using procedures known to those skilled in the art.
[0048] If an infectious clone of the geminivirus is available, effects of mutations on replication can be tested. The mutation is introduced into the C1 or AC1 ORF of an infectious clone. Mutant DNA is transferred to plant cells. Replication of wild type viruses is tested for infection as a positive control. Mutations which create transdominant molecules generally abolish replication when engineered into infectious clones. A number of mutations which change codons for conserved amino acids within these motifs will be lethal and potentially transdominant. Other mutations in C1 or AC1 which abolish replication should also be considered potentially transdominant. Any non-functional C1 or AC1 molecule has the potential to be transdominant.
[0049] Mutated C1 or AC1 ORFs are installed into a suitable plant transformation vector in the sense orientation and under the control of a strong constitutive promoter sequence and suitable terminator for high level expression in the target plant species. This step is performed for each of the C1/AC1 mutants created.
[0050] C. Assays
[0051] A transient assay is useful to screen candidate constructs for transdominant interference activity. This is done by first coinoculating protoplasts or a plant cell suspension culture with the infectious geminivirus clone and a plasmid containing mutant C1 or AC1 ORF under control of a strong constitutive plant promoter. Control treatments are inoculated with an infectious clone. Total DNA is harvested from inoculated cells, and is assayed for viral replication. Transominant C1 or AC1 mutants are identified as those which suppress geminiviral replication relative to control treatments after coinoculation.
[0052] In vitro assays for transdominance correlate lethal mutations and transdominant activity in transient assays. This is exemplified in a BGMV-GA model system. These results are readily applicable to produce a transdominant C1 or AC1 ORFs from other geminiviruses. Transgenic plants resistant to ToMoV were created by transforming them with an AC1 ORF derived from ToMoV and engineered to contain similar mutations.
[0053] Expression cassettes constructed above are installed into binary plasmids and transformed into Agrobacterium strains for plant transformation protocols. Plants are transformed by methods tailored to the specific variety or line.
[0054] Transgenic status of R0 and later generation plants and their segregating progeny is verified by routine methods, including: ELISA assays for NPTII protein detection; DNA assays such as PCR amplification with the AC1/C1 primers of plants and Southern blot hybridization for detection of transgenes using AC1/C1 as viral probes; and Southern blot hybridization to detect AC1 or C1 transgenes. Demonstration that R1 plants transformed with geminivirus gene constructions express NPTII protein is done by ELISA. Protein in leaf tissue samples taken from R1 transgenic plant seedlings is extracted and analyzed for NPTII protein by ELISA.
[0055] Geminivirus transgene expression is also measured by Northern blot analysis. Transgene expression in a number of R0 and R1 plants was done by Northern blot hybridization. Total RNA extracted from leaves of transgenic plants is separated by agarose gel electrophoresis. After electrophoresis, RNA is pressure blotted onto membrane. Membranes are hybridized with radiolabeled probes, washed, and autoradiographed.
[0056] D. Identification of gemini-resistant transgenic plants
[0057] Geminivirus-resistant transgenic plants are identified by challenging transgenic plants and progeny. R1 plants from self pollinated R0 primary regenerants are agroinoculated about 3 weeks after sowing. Alternative methods include biolistic inoculation, sap transmission from infected tissue (if the isolate is mechanically transmissible), insect transmission, or grafting. For bipartite geminiviruses, agroinoculation preferably involves delivery of greater-that-full-length (i.e., at least 2 common regions) DNA-A and DNA-B components into the seedlings using Agrobacterium strains, e.g., containing a binary vector having in its T-DNA a partial or full tandem duplication of infectious geminivirus DNA. Geminivirus-resistant plants are incorporated into traditional breeding programs to develop elite breeding lines that include the resistance-conferring transgene. These changes produce C1 or AC1 molecules when made alone or in combination with a mutant.
[0058] Plants showing the highest steady state levels of transgene RNA are challenged by Agrobacterium-mediated inoculation. Resistance is determined by lack or delay of symptom expression and low levels of viral DNA in plants as determined by squash blot hybridization tests with viral probes (Gilbertson et al., 1991. Plant Disease 75:336-342.). Resistance is also determined by inoculation with viruliferous Bemisia tabaci as described. It is expected that plants with low levels of mRNA accumulation for the mutated AC1/C1 ORF have symptoms and those with high levels have no symptoms.
[0059] Since the AC1/C1 proteins have domains required for DNA-nicking and NTP-binding that are conserved among all geminiviruses, an antiviral strategy involving mutated AC1/C1 protein is applicable to plant-geminivirus systems in general.
[0060] Other viruses include: 1 Virus Genes/Regions SEQ ID NO. TGV-GA1 AC1 ORF DNA-A (complementary seq) 57 TGV-GA1 Common & Intergenic Region (viral) 58 TLCV-IND Full Length Seguence (stemloop begin) 59 “Chino” Partial AC1, Common region, AV1 60 PHV AC1, Common region, Intergenic, AV1 61 PHV BV1 ORF 62 PHV BC1, Hypervar., Common, & Interg. Reg 63
[0061] The following examples are offered by way of illustration and not by way of limitation.
EXAMPLE 1[0062] Gene Expression Vectors
[0063] All E. coli culture and plasmid DNA isolation methods were carried out according to standard methods. Restriction digestions, filling in of 5′ end overhangs, calf intestinal alkaline phosphatase treatments of DNA and ligation of DNA fragments and gel electrophoretic separation of DNA fragments and their isolation from gels were done according to manufacturers' recommendations and methods. Agrobacterium large plasmid DNA was isolated. Agrobacterium transformation and culture is performed according to general methods known to those skilled in the art.
[0064] Tables 1A and 1B list geminiviral transcribed sequences, expression vectors, binary plasmids, and Agrobacterium strains described in the Examples. 2 TABLE 1A Constructs used to Create Transgenic Plants Transcribed Seq. Expression Binary Agrobacterium (open reading frame Vector Vector tumefaciens or antisense seq.) Used Used designation ToMoV-AC1as pRT101e pJTS246&Dgr; RTAC ToMoV-AC1 pRT101e pJTS246&Dgr; RTSC ToMoV-AC1as DH51 pJTS235 DHAC ToMoV-AC1 DH51 pJTS235 DHSC ToMoV-AC1-AC2-AC3as pRT101e pJTS246&Dgr; RT3AA ToMoV-AC1as pRT101e pJTS246&Dgr; RTFS ToMoV-AC1 pLAT pJTS246&Dgr; LASD, LASU ToMoV-AC1d1m pRT101e pJTS246&Dgr; MEU ToMoV-AC1d1m pRT101e pJTS246&Dgr; MEU2 ToMoV-AC1d1m1 pRT101e pJTS246&Dgr;- MUA ToMoV-AC1d1m23 pRT101e pJTS246&Dgr; MUB ToMoV-AC1 p&Dgr;1CO35 pJTS246&Dgr; COALS ToMoV-AC1d1m p&Dgr;1CO35 pJTS246&Dgr; CODLM ToMoV-AC1d1m1 pRTIN pJTS246&Dgr; MUAIN ToMoV-AC1d1m23 pRTIN pJTS246&Dgr; MUBIN TYLCV-C1as pRT101e pJTS246&Dgr; LCA TYLCV-&Dgr;C2as pRT101e pJTS246&Dgr; LCR′ TYLCV-C1as TYLCV-V1as pRT101e pJTS246&Dgr; LCR″ TYLCV-C1-&Dgr;C2-&Dgr;C3as pRT101e pJTS246&Dgr; RT3CA TYLCV-C1-&Dgr;C2-&Dgr;C3as p&Dgr;1CO35 pJTS246&Dgr; CO3CA TYLCV-C104 ePmax-Tplus pGA482&Dgr; + C104 HYGR TYLCV-C225 ePmax-Tplus pGA482&Dgr; + C225 HYGR TYLCV-C259 ePmax-Tplus pGA482&Dgr; + C259 HYGR TYLCV-C1-&Dgr;C2-&Dgr;C3 pRT101e pJTS246&Dgr; RT3CS
[0065] 3 TABLE 1B Constructs for Agrobacterium Inoculation Geminivirus strain and Binary Vector Agrobacterium Sequence Used Designation ToMaV-A dimer pJTS222 A.t. ToMoV-A ToMoV-B 1.67mer pJTS222 A.t. ToMoV-B TYLCV-EG dimer pJTS222 A.t. TYLC-EG
EXAMPLE 1.1[0066] Synthesis of expression vector pRT101e
[0067] The pRT101e expression vector listed in Table 1A was made by removing a 325-bp HindIII-EcoRV fragment from pUC8-CaMVCAT (Pharmacia) and inserting it into HincII-HindIII-digested pRT101 (Dr. Topfer, Max Planck-Institut fur Zuchtungsforschung, 5000 Koln 30, Germany), thereby adding a segment of the 35S promoter containing the upstream enhancer (Kay et al., Science, 1987, 236:1299-1302) to the 5′ end of the 35S promoter sequence of PRT101.
EXAMPLE 1.2[0068] Expression vector pDH51
[0069] The pDH51 expression vector of Table 1A (T. Hohn, Friedrich Miescher Institute, P.O. Box 2543, CH-4002, Basel, Switzerland) is comprised of a CaMV 35S promoter-35S terminator expression cassette.
EXAMPLE 1.3[0070] Synthesis of expression vector p&Dgr;1CO35
[0071] The p&Dgr;1CO35 expression vector of Table 1A was derived from pCO1bam (Dr. Neil Olszewski, University of Minnesota-Twin Cities, College of Biological Sciences). The 1.0-kb EcoR1-SalI fragment of pCO1bam, containing the promoter controlling expression of the commelina yellow mottle virus (CoYMV) transcript (Medberry et al., Plant Cell, 1992, 4:185-92), was inserted into EcoR1-SalI-digested pSL1180 (Pharmacia). A 1.1-kb EcoRI-DraI fragment of the resulting construct was inserted into EcoRI-HincII-digested pRT101, thereby replacing the CaMV 35S promoter of pRT101 with the CoYMV promoter. Some restriction sites, including BamHI and BglII, were removed by partially digesting this plasmid with HindIII and recircularizing it with T4 DNA ligase to produce p&Dgr;1CO35.
EXAMPLE 1.4[0072] Synthesis of expression vector pRTIN
[0073] The pRTIN expression vector of Table 1A is a derivative of pRT101e and pCOIN, in which the 35S terminator of pRT101e was replaced with the protease inhibitor gene terminator/polyadenylation site (TINH) of pCOIN. To produce pCOIN, the 760-bp HindIII-XbaI fragment of pTPI-1 (Dr. C. Ryan, Washington State University, Pullman, Wash.) containing TINH was inserted into HindIII-XbaI-digested Bluescript II KS+(Stratagene). The 770-bp XbaI-KpnI fragment of the resulting construct was inserted into XbaI-KpnI-digested pUC19. The 800-bp PstI-KpnI terminator fragment of the resulting plasmid was ligated with the KpnI-PstI fragment of p&Dgr;1CO35 to produce pCOIN. The 805-bp SphI-SspI fragment of pCOIN was inserted into SphI-SmaI-digested pRT101e, thereby replacing the 35S terminator of pRT101e with TINH. The resulting plasmid was further modified by inserting into a EcoRI site a DNA fragment with EcoRI ends and internal restriction sites including BamHI to produce pRTIN.
EXAMPLE 1.5[0074] Synthesis of expression vector ePmas-Tphas
[0075] The expression vector ePmas-Tphas of Table 1A was assembled by combining an octopine synthase upstream activating sequence (ocs UAS) and a mannopine synthase promoter (mas2′).
[0076] The ocs UAS was excised from pAL1050 (Dr. Paul J. J. Hooykaas, State Univ. of Leiden, 2333 AL Leiden, The Netherlands), which was isolated from Agrobacterium tumefaciens strain LBA4404 (Dr. P. J. J. Hooykaas). A 2.8-kb EcoRI fragment of pAL1050, containing nt 13362-16202 of ocs UAS was inserted into the EcoRI site of pSL1180 (Pharmacia). A 311-bp SacI-BamHI fragment of the resulting plasmid, containing nt 13774-14085 of the ocs UAS, was ligated into SacI-BamHI-digested pBluescript II KS+. A 285-bp XhoI-MfeI fragment containing the ocs UAS was ligated with the EcoRI-XhoI fragment of pBluescript II KS+ with ocs UAS to produce a plasmids having tandemly repeated ocs UAS element structure. A EcoRI-XhoI fragment of the recombinant plasmid was ligated with another MfeI-XhoI fragment to produce a recombinant plasmid, pBluescript+UAS3, having three tandemly repeated ocs UAS elements.
[0077] The mas2′ promoter element was isolated as follows. Plasmid pE93 (Dr. Stan Gelvin, Purdue University) is derived from pRK290 (Ditta et al., 1980). EcoRI fragment #13 of pE93 contains nt 16202-21634 of the octopine Ti plasmid, and lacks an internal ClaI fragment at nt 8672-20128 (Eco13&Dgr;Cla). A 4-kb EcoRI-XhoI fragment was ligated with the SalI-EcoRI fragment of pBR322, to produce pJTS213. This plasmid was introduced into E. coli GM119 (Dr. Gurnam Gill, Pharmacia & Upjohn, Kalamazoo, Mich.), which is deficient in DNA adenine methylation. Thus, normally undigestible ClaI site beginning at nt 20128 in Eco13&Dgr;Cla is cleavable by ClaI. A 951-bp ClaI-NcoI fragment of pJTS213 containing nt 21079-20128 was isolated and ligated with the ClaI-NcoI fragment of pSL1180 to produce pSL1180+Pmas.
[0078] A ocs UAS-enhanced mannopine synthase promoter cassette (Epmas) was assembled as follows. A 365-bp ClaI-FspI mas2′ fragment from pSL1180+Pmas was ligated with the ClaI-EcoRV fragment of pBluescript +VAS3. Clones in which the mas2′ was inserted downstream of the ocs UAS repeat were identified by restriction digestion. To facilitate the addition of the phaseolin transcription terminator, a 250-bp multiple cloning site (mcs) XhoI-SalI fragment from pSL1180 was ligated into the XhoI-digested recombinant plasmid. Two plasmids, pBluescript+UAS3+Pmas+mcs (orientations I and II), containing a construct with the mcs inserted in the two possible orientations were isolated.
[0079] The phaseolin terminator was added to pBluescript+UAS3+Pmas+mcs, completing the assembly of Epmas-mcs-Tphas, as follows. A 1.1-kb PstI-EcoRI fragment of pUC19-hph-Tphas (described below in the assembly of pGA482&Dgr;+HYGR), which contains the phaseolin transcription terminator (Tag), was ligated with PstI-EcoRI-digested pBluescript II KS+. A 1.2-kb SacII-ClaI fragment of the resulting plasmid was ligated with the SacII-ClaI fragment of pBluescript+UAS3+Pmas+mcs (orientation I) to produce a plasmid having the ePmas-Tphas insert.
EXAMPLE 1.6[0080] Synthesis of expression vector pLAT
[0081] The expression vector pLAT of Table 1A was produced as follows. The promoter of the LAT52 gene (Twell et al., Development, 1990, 109:705-13) was used to construct an AC1 gene construct in sense orientation that does not express in vegetative tissue. A 600-bp NcoI-SalI fragment of pLAT52-7a (Dr. S. McCormick, Plant Gene Expression Center, USDA ARS, Albany, Calif.), which contains the LAT52 promoter, was ligated with NcoI-SalI-digested pSL1180 to produce pLAT.
EXAMPLE 2.1[0082] Synthesis of binary vector pJTS246&Dgr;
[0083] The binary vector pJTS246&Dgr; of Table 1A was produced as as a derivative of pGA482 (Dr. G. An, Washington State University, Pullman, WN), by replacing the nopaline synthase controlled NPTII sequence with a CaMV 35S promoter-NPTII-phaseolin terminator selectable marker. The selectable marker was situated at the left T-DNA border to insure that the passenger gene, inserted at the right T-DNA border, would be transferred into the plant cell.
[0084] A BamHI fragment of pUC8-CaMVCAT was ligated with a 2.2-kb BamHI fragment of pDOB513ro4.6K (J. L. Slightom, Pharmacia & Upjohn), containing the NPTII coding region and octopine Ti plasmid T-DNA ORF No. 26 transcription terminator, to produce pJTS228. The pJTS228 construct has the 2.2-kb fragment, inserted as a transcription fusion unit immediately downstream of the CaMV 35S promoter of pUC8-CaMVCAT. Most of the CAT gene of pUC8-CaMVCAT was deleted from pJTS228 by digesting with EcoRI to produce pJTS228&Dgr;. A 4.0-kb BamHI-NcoI fragment from pJTS228 was ligated with a 1.55 kb BamHI-NcoI fragment from pkanPhas (J. L. SLightom, Pharmacia & Upjohn) containing the NPTII coding sequences 5′ distal to the NcoI site and the phaseolin terminator. A resulting plasmid, in which the T-DNA transcription terminator fused to the NPTII ORF was replaced with the phaseolin storage protein terminator from Phaseolus vulgaris, was designated pJTS233.
[0085] pJTS233 was digested with HindIII and flush ended. A 2.8-kb EcoRI fragment containing the 35S promoter, NPTII coding region and phaseolin terminator was isolated and ligated in a 3-part reaction with SmaI-BamHI fragment of pUC9 and an 8.0-kb BamHI-EcoRI fragment of pGA482 containing the broad host range replicon, left and right nopaline Ti T-DNA borders and nopaline synthase promoter. The desired construct, pJTS246, was cloned and isolated. pJTS246 was modified to eliminate the ampicillin drug resistance contributed by pUC9. The plasmid was digested with ScaI and HindIII, and treated with HindIII linkers followed by HindIII digestion. The resulting plasmid, pJTS246&Dgr;, had 1730-bp of pUC sequence deleted from pJTS246.
EXAMPLE 2.2[0086] Synthesis of binary vector pJTL222
[0087] pJTS222 is pGA492 (Dr. G. An) in which a 2.2-kb BamHI-HindIII fragment replaced by the 430 bp BamHI-HindIII fragment of pUC8-CamVCAT containing the CaMV 35S promoter.
EXAMPLE 2.3[0088] Synthesis of binary vector pJTS235
[0089] pJTS235 was a binary plasmid derived from pGA492 in which the NPTII coding sequence and its transcription terminator were removed and replaced with a CaMV 35S promoter-NPTII coding sequence-phaseolin terminator selectable marker. pJTS235 was constructed by ligating a 2.1-kb BamHI fragment of pJTS233 containing the NPTII coding sequence and phaseolin terminator into the BamHI fragment of pJTS222. The resulting plasmid, pJTS235 had the NPTII structural gene under the control of 35S promoter.
EXAMPLE 2.4[0090] Synthesis of binary vector pJTS250
[0091] pJTS250 was assembled as follows. A 353-bp PstI-BamHI fragment of pLG90 (provided by Dr. L. Gritz, Biogen, S.A., 46 Route des Acacias, Geneva, Switzerland), which includes the entire hygromycin phosphotransferase gene (hph) coding region from the ATG translation start codon to 15 bp distal to the translation terminator, was ligated with the PstI-BamHI digest of pUC9 to produce pUC9+hph-a. Another aliquot of AvaI-digested pLG90 with AvaI flush ended. The 670-bp PstI fragment was cloned into the SmaI-PstI fragment of pUC9 to produce pUC9+hph-b, creating a 670-bp fragment PstI-EcoRI fragment. A 1.18-kb NaeI-BamHI fragment containing the phaseolin terminator (J. L. Slightom) was cloned into the BamHI-SmaI fragment of pUC9 to create pUC9+Tphas. The above three fragments (353-, 670- and 1180-bp) were ligated with the BamHI digest of pJTS222. The resulting binary plasmid, pJTS250, was produced comprised of a P35S-hph-Tphas plant selectable marker, and the capability to transform plant tissue to hygromycin resistance via Agrobacterium-mediated gene transfer.
EXAMPLE 2.5[0092] Synthesis of binary vector pGA482&Dgr;+HYGR
[0093] pGA482&Dgr;+HYGR was produced from the following plasmids: pGA470 (Dr. G. An); pJTS262, including the entire T-DNA of pGA470 and a broad host range replicon; pJTS222; pJTS250, a binary plasmid that includes HYGR constructed by ligation of four fragments, including 353-bp PstI-BamHI fragment encoding part of the hph coding region, 670-bp PstI fragment encoding the remainder of the hph coding region, 1180-bp NaeI-BamHI fragment constituting Tphas and pJTS222 digested with BamHI; pUC19B2-Pnos; pUC19B2+hph-Tphas; pnos-hph-Tphas expression cassette; and pGA482G (Dr. G. An).
[0094] The pGA482A+HYGR was constructed as follows: SalI fragments of pGA470 were ligated into SalI-digested pBR322. The resulting construct, pJTS262, is comprised of the entire T-DNA of pGA470 (from right to left border) and a second fragment containing part of the broad host range replicon. The 345-bp BclI-BamHI fragment of the resulting plasmid, having the nopaline synthase promoter (Pnos) fused to the 5′ 42-bp of nopaline synthase (14 N-terminal amino acids), was inserted into the BamHI site of pUC19B2, having the SmaI site of pUC19 converted to a BglII site. The resultant recombinant plasmid, pUC19B2+Pnos, had the Pnos segment within the BamHI-BglII fragment.
[0095] A 2.2-kb BamHI fragment containing the hph coding region from bacterial transposon Tn5 and the phaseolin transcription terminator (hph-Tphas) was isolated from pJTS250. The 2.2-kb hph-Tphas fragment was inserted into the BamHI site of pUC19B2. The pUC19B2-Pnos was digested with BamHI and HindIII. pUC19B2+hph-Tphas was partially digested with BamHI and completely with HindIII to produce a 2.2-kb fragment with BamHI-HindIII ends. The fragment was ligated with BamHI-HindIII digested pUC19B2-Pnos plasmid. The resulting construct, a Pnos-hph-Tphas expression cassette, pUC19B2+HYGR, was partially digested with BamHI; a resulting 5.3-kb fragment was digested with BglII to produce a 2.6-kb fragment. Separately, HindIII-EcoRI-digested pGA482 was ligated with HindIII-EcoRI-digested pSL1180, lacking a mcs. The resulting construct was further restricted to delete 2.5-kb of the original T-DNA containing the mcs. This binary was digested with BglII and ligated with the BamHI-BglII-ended 2.6-kb Pnos-hph-Tphas fragment to produce pGA482&Dgr;+HYGR.
EXAMPLE 3[0096] Geminivirus DNA Insertion into Expression Vector Constructs
EXAMPLE 3.1[0097] Synthesis of Wild-Type ToMoV-FL AC1 ORF
[0098] ToMoV was collected from infected tomato plants in Bradenton, Fla. and inoculated into Nicotiana benthamiana and tomato. DNA was isolated from infected plants and viral DNA was isolated by preparative agarose gels. Viral DNA was digested with BglII, inserted into BglII-digested pSP72 to produce a full-length A-component clone (Seq ID 17). Similarly, a full-length DNA-B clone was produced from viral DNA digested with BamHI and inserted into BamHI-digested pBluescript II KS+ (Seq ID 18). DNA of either clone inoculated into N. benthamiana produced symptoms similar to the original virus.
[0099] A dimer clone in which DNA-A was inserted as a direct, tandem duplicate into the cloning vector was made by removing the single insert from its original vector with BglII and reinserting it into BglII-digested pSP72. The ApaI fragment of the resulting plasmid comprising the cloned DNA-A was inserted into the ApaI site of pBluescript II KS+.
EXAMPLE 3.3[0100] Synthesis of ToMoV-AC1
[0101] Wild type AC1 sense ORF and antisense (as) ORF of Table 1A were constructed from the AC1 ORF (SEQ ID 1 and 2) and part of the intergenic region was amplified by PCR from ToMoV-infected N. benthamiana DNA using primers PFL-2549B (SEQ ID 9) (5′-GGATCCGAGTAACTCATCTGGAGTACC-3′) and PFL-1108B (SEQ ID 10) (5′-GGATCCGGAAGTAGATGGAGCACCCGC-3′). The 1.1-kb PCR product was BamHI-digested and inserted into the BamHI site pBluescript II KS+ to produce pTFAC1.
EXAMPLE 3.4[0102] Synthesis of ToMoV-AC1dlm
[0103] For the production of the mutated ORF, the AC1 ORF and part of the intergenic region was PCR amplified from ToMoV-infected N. benthamiana DNA by PCR using primers PFL-2549H (SEQ ID 16) (5′-TATCA+E,uns AAGCTTGAGTAACTCATCTGGAGTACC-3′) and PFL-1108B (SEQ ID 10) (5′-TATC+E,uns GGATCCGGAAGTAGATGGAGCACCCGC-3′) to produce a HindIII site near the translation start codon and a BamHI site near the translation terminator codon. The HindIII-BamHI-digested product was ligated with HindIII-BamHI-digested pBluescript II KS+ in a sense orientation relative to the f1 origin of replication. Mutations were generated in the NTP binding motifs of AC1 of this clone.
[0104] Trans-dominant lethal mutants (dlm) of AC1 protein (SEQ ID 3 and 4) were created by Kunkel mutagenesis. The above pBluescript plasmid was transformed into CJ236 (Invitrogen Co.), a dut-, ung-strain, so that the amplified plasmid DNA contains uracil. Single-stranded DNA was produced by transfecting the above transformed cells with helper phage M13-K07. The complementary sense strand of the ssDNA was synthesized in vitro using deoxynucleotides, including dTTP, and two mutagenic primers: PFAC1-680c (SEQ ID 11) (5′-CAAGAACAGGGcAcACGATGTGGG-3′) and PFAC1-781c (SEQ ID 12) (5′-GTATAACGTCATTaAatACATCGCACCGC-3′). The lower case letters indicate altered nucleotides. The product was treated with T4 DNA ligase and transformed into XL1 Blue E. coli (Stratagene) to amplify plasmids containing the mutations produced by the mutagenic primers, which resulted in the mutations 2(a), 3(b) and 3(c), described above.
EXAMPLE 3.5[0105] Synthesis of ToMoV-AC1dlm1
[0106] The 1.1-kb BamHI fragment of pTFAC1, containing wild type AC1 ORF, was inserted to the BamHI site of pRT101e to produce a sense (pRTAC1-S) construct. The AC1 triple mutant (AC1 dlm) ORF was removed as a 1.1-kb XhoI-BamHI fragment from its vector and inserted in the sense orientation into XhoI-BamHI-digested pRT101e to produce pRT101e+AC1dlm. Plasmids pRTAC1-S and pRT101e+AC1dlm were cleaved at the unique PmlI site. After an additional digestion with ScaI, 1.6- and 3.2-kb fragments were isolated from each digest. The 1.6-kb fragment from pRTAC1-S was ligated with the 3.2-kb fragment from pRT101e+AC1dlm to produce a construct comprising the sequence designated as ToMoV-AC1dlm1 (SEQ ID 5 and 6) in Table 1A, mutation 2a described above.
EXAMPLE 3.6[0107] Synthesis of ToMoV-AC1dlm23
[0108] Plasmids PRTAC1-S and pRT101e+AC1dlm were cleaved at the unique PmlI site. After an additional digestion with ScaI, 1.6- and 3.2-kb fragments were isolated from each digest. The 3.2-kb fragment from pRTAC1-S was ligated with the 1.6-kb fragment from pRT101e+AC1dlm to produce a construct comprising the sequence designated as ToMoV-AC1dlm23 (SEQ ID 7 and 8) in Table 1A, double mutations 3(b) and 3(c) described above.
EXAMPLE 3.7[0109] Synthesis of ToMoV-AC1-AC2-AC3
[0110] A construct containing the AC1-AC2-AC3 fragments was produced by ligating a BamHI-HindIII fragment of a binary plasmid comprised of a dimer of the full-length, infectious ToMoV A-component with BamHI-HindIII-digested pJTS222. The BamHI-HindIII fragment from this construct was inserted into BamHI-HindIII-digested pBluescript II KS+. A 1.24 kb BglII-SphI fragment of the resulting plasmid, containing the complete AC2 and AC3 coding sequences and the C-terminal two-thirds of the AC1 ORF (SEQ ID 15), was ligated into BglII-SphI-digested pSL1180. The resulting plasmid contained the &Dgr;AC1-AC2-AC3 fragment from ToMoV-A.
EXAMPLE 4[0111] TYLCV-IS-EG Wild Type and Mutant Sequences.
EXAMPLE 4.1[0112] Synthesis of TYLCV-C1
[0113] Tomato leaves with TYLCV symptoms were collected in Fayoum, Giza and Ismailia, Egypt. They were grafted to Geneva 80 tomatoes and N. benthamiana. The tomatoes and tobacco developed symptoms typical of TYLCV. Infectious TYLCV (TYLCV-IS-EG1) DNA was isolated from the infected N. benthamiana. The C1 ORF of TYLCV-IS-EG1 (SEQ ID 19 and 20) was produced as a 1.1-kb fragment by PCR amplification of infected plant DNA. The primers used were pTYIRc4 (SEQ ID 21) (5′-GGCCATAGAGCTTTGAGGGATCC CGATTCATTTC-3′) and PTYC2v1679 (SEQ ID 22) (5′-GGTAGTAT GAGGATCCACAGTCTAGGTCT-3′). After BamHI-digesting the PCR products, they were ligated with BamHI-digested pBluescript II KS+ to produce pEGAL1-AS1, which contained the C1 ORF, as TYLCV-C1.
EXAMPLE 4.2[0114] Synthesis of TYLCV-&Dgr;C2as
[0115] A truncated C2 ORF (&Dgr;C2) was produced as a 365 bp fragment by PCR amplification of TYLCV-IS-EG1-infected N. benthamiana DNA. The primers PTYC2v1499 (SEQ ID 32) (5′-ATTTGTGGATCCTGATTACCTTCCTGATGTTGTGG-3,) and PTYC2c1814 (SEQ ID 35) (5′-AAACGGATCCTTGAAAAATTGGGC-3′) were used. The primers were BamHI-digested and ligated into BamHI-digested pBluescript II KS+ to produce pTYC2-25-1, which contained the &Dgr;C2 ORF in antisense orientation.
EXAMPLE 4.3[0116] Synthesis of TYLCV-V1
[0117] A truncated V1 ORF was produced as a 625-bp fragment by PCR amplification of TYLCV-IS-EG1 infected N. benthamiana DNA. The primers used were PTYAR1v466 (SEQ ID 33) (5′-TTAGGATCCTATATCTGTTGTAAGGGC-3′) and PTYAR1c1046 (SEQ ID 34) (5′-TTAACTAATGCAGGATCCTACATTCCAGAGGGC-3′).
[0118] The primers were BamHI-digested and ligated into BamHI-digested pBluescript II KS+ to produce pTYV1-6-1, which contains the V1 ORF.
EXAMPLE 4.4[0119] Synthesis of TYLCV-C1-&Dgr;C2-&Dgr;C3
[0120] A 1.3-kb fragment of the TYLCV-IS-EG1 genome from nt 1471 to nt 20 via nt 2787 (Navot et al 1991) was produced by PCR amplification of infected N. benthamiana DNA. The primers used were PTYIRc4 and PTYC2v1499. The primers were BamHI-digested and inserted into BamHI-digested pBluescript II KS+ to produce pTYEGC4.
EXAMPLE 4.5[0121] Synthesis of TYLCV ORF Mutations
[0122] A full-length infectious clone of TYLCV-IS-EG1 (pTYEG14) was created to serve as the basis for TYLCV ORF constructs and for agroinoculation (see below). DNA from a tomato infected with TYLCV-IS-EG1 was used as template in two PCR amplification reactions. The first used primers PTYC1c2196 (SEQ ID 37) (5′-AAATCTGCAGATGAACTAGAAGAGTGGG-3′) and PTYV1v1164 (SEQ ID 36) (5′-GTACGAGAACCATACTGAAAACGCCT-3′) to amplify a fragment. The PstI-SphI-digested fragment was ligated with PstI-SphI-digested pGEM-5zf+ (Promega) to produce plasmid pEGI1A.
[0123] The second amplification reaction employed primers PTYC1v2182 (SEQ ID 39) (5′-TAGGCCATGGCCGCGCAGCGGAATACACG-3′) and PTYC3c1320 (SEQ ID 38) (5′-GGTTCTGCAGCAGAGCAGTTGATCATGTATTG-3′). The PstI-NcoI-digested fragment was ligated with PstI-NcoI-digested pGEM-5zf+to produce pEGI1-7B.
[0124] To assemble the full-length virus, the PstI-NcoI fragment of pEGI1-7B was ligated with the PstI-NcoI fragment of pEGI1A to produce a construct comprising full-length 2.7-kb viral DNA. The full-length construct was tested for infectivity by biolistic delivery into tobacco cells and found to create symptoms identical to the original disease. This clone was called pTYEG14. Orientation of insertion with respect to the f1 origin of replication was confirmed by DNA sequencing. Three mutant C1 ORFs were constructed, each having one or two base changes altering the amino acid specificity of one codon by Kunkel mutagenesis using the plasmid representing the full-length infectious clone of TYLCV-IS-EG1 (pTYEG14) as template. The mutagenic primers (all viral sense) were: PC1v2467 (SEQ ID 25) (5′-GTTTCCGTCTcgCTCCACGTAGG-3′); PC1v2101 (SEQ ID 28) (5′-GGCCCACATTGTTgCGCCTGTTCTGC-3′); and PC1v2000 (SEQ ID 31) (5′-GGGTCTACGTCTctAATGACGTTGTACC-3′). (Lower case letters indicate altered nucleotides.) The resulting DNA was treated with T4 DNA ligase and transformed into XLI Blue E. coli cells to produce the following constructs: pTYK104R #1 (SEQ ID 23 and 24), mutation 1(c); pTYK225A #4 (SEQ ID 26 and 27), mutation 2(b); and pTYD259R #5 (SEQ ID 29 and 30), mutation 3(a), described above.
[0125] The three mutant C1 ORFs were cloned into pCRII (Invitrogen). The C1 ORF for each mutant was PCR amplified using primers PTYIRc4 (SEQ ID 21) (5′-GGCCATAGAGCTTTGAGGATCCCGATTCATTTC-3′) and PTYCv1707 (SEQ ID 42) (5′-GGTAGTATGAGGATCCACAGTCTAGGTCT-3′). The amplified fragments were ligated with pCRII to produce: pC1K104R #2, mutation 1(c); pC1K225A #4, mutation 2(b); and pC1D29R #2, mutation 3(a), described above.
[0126] These three ORF in BamHI fragments of their respective vectors provided the mutant C1 ORFs for expression cassettes for Agrobacterium mediated transformation.
EXAMPLE 5[0127] BGMV Constructions
[0128] Wild-type and mutated versions of BGMV C1 (replication protein) ORF have been prepared. The wild-type sequence (SEQ ID 43 and 44) was mutated by Kunkel mutagenesis. Mutations in BGMV-C1 disclosed here include: 4 ORF Mutant SEQ ID Mutagenic Primer BGAC190 control 45 47 BGAC221 mutation 2(c) 48 50 BGAC228 mutation 2(a) 51 53 BGAC262 mutation 3(a) 54 56
[0129] SEQ ID NOS. 45, 48, 51, and 54, refer to mutagenized BGMV-C1 ORF DNA sequences presented in the Sequence Listing. These encode protein sequences 46, 49, 52, and 55, respectively. The mutant sequences were derived from wildtype DNA by Kunkel mutagenesis with mutagenic primers 47, 50, 53, and 56, respectively.
[0130] A 1.8 Kb BamHI-XhoI fragment containing the 35S promoter transcriptionally fused to a mutated AC1 ORF from BGMV-GA followed by the nopaline synthase transcription terminator was removed from WRG2398 (Dr. D. R. Russell, Agracetus Corp., Middleton, Wis.). The AC1 coding sequence was mutated in vitro using Kunkel mutagenesis to produce double mutations 2(c) and 2(a). This fragment was ligated with pRT101e digested with the same enzymes and the ligation mix used to transform E. coli DH5 cells. Some transformants yielded desired recombinant plasmids that had the entire expression cassette from WRG2398 inserted into PRT101e (pJTS364). The new expression cassette was removed as a 2.9-Kb fragment from one of the recombinant plasmids by partial digestion with HindIII. It was ligated with pJTS246&Dgr; that has been digested with HindIII and treated with CIAP. After transformation of DH5 cells, one recombinant among the transformants was identified that had the expression cassette inserted in the binary vector. DNA of this binary vector was transformed into A. tumefaciens LBA4404 and one transformant containing the binary was called strain At364.
[0131] Plasmid pJTS364 was digested with EcoRV to eliminate the duplicated 35S promoters (P355) and the cleaved DNA ligated. A fraction of the rejoined molecules have a deletion for the fragment between the EcoRV sites which contains the 35S enhancer (e35S) from WRG2398 and P35S from pRT101e. The ligation mix was used to transform DH5 cells. Among the transformants, the desired deleted plasmid was found and called pJTS365. The 2.5-Kb expression cassette was removed and ligated with HindIII-digested, CIAP treated pJTS246&Dgr;. The ligation mix was used to transform DH5 cells. Recombinant binary plasmids were identified among the transformants and one of these was used as a source of DNA which was transformed into A. tumefaciens LBA4404. The transformed agrobacterium having the recombinant binary was called At365.
[0132] The listed BGMV ORF are installed into appropriate promoter vectors and then into binary plasmids for Agrobacterium-mediated transformation into Phaseolus plants. Additionally, expression vectors are delivered into plants by biolistic acceleration or other methods by which plants can be transformed. Regenerated transformed plants are evaluated for levels of transgene RNA accumulation by RNA blot analysis to verify activity of the transgene. Subsequently, progeny are evaluated for ability to resist BGMV infection.
EXAMPLE 6[0133] Expression Cassettes and Agrobacterium strains.
[0134] The following ToMoV constructs were produced.
EXAMPLE 6.1[0135] RTSC and RTAC
[0136] The 1.1-kb BamHI fragment of pTFAC1, containing wild type AC1 ORF was inserted to the BamHI site of pRT101e. Antisense (pRTAC1-A) and sense (pRTAC1-S) constructs were produced. HindIII fragments of each plasmid were each inserted into the HindIII site of pJTS246&Dgr; in the same transcriptional direction as the NPTII selectable marker. The binary vectors were transformed into LBA4404 to produce RTAC (antisense) and RTSC (sense).
EXAMPLE 6.2[0137] DHSC and DHAC
[0138] The wild type AC1 ORF was also inserted as a. BamHI fragment into BamHI-digested pDH51 in both orientations creating pDHAC1-S (sense) and pDHAC1-AS (antisense). The expression cassette of each recombinant was removed with EcoRI and inserted into EcoRI-digested pJTS235. Recombinant binary plasmids were selected that had the expression cassette inserted such that the directions of transcription as the selectable marker. These binary plasmids were introduced into LBA4404 by transformation to produce DHSC (sense) and DHAC (antisense).
EXAMPLE 6.3[0139] RTSFS
[0140] pRTAC1-S was digested with BglII and flush ended by filling out. The resulting plasmid, pRTAC1-S&Dgr;BglII, lacked a BglII site but retained a core 4-base Sau3A site. This mutation shifted the translation reading frame by adding four nucleotides thereby producing a translation stop codon, and truncating the polypeptide (SEQ ID 13 and 14). A 2.1-kb HindIII fragment of pRTAC1-S&Dgr;BglII, which contains the expression cassette, was inserted in both orientations into the HindIII site of pJTS246&Dgr;, unidirectional or divergent respecting the sense of selectable marker. A plasmid having an unidirectional orientation was introduced into LBA4404 by transformation to produce RTSFS.
EXAMPLE 6.4[0141] RT3AA
[0142] The 1.24-kb BglII-KpnI fragment of pSL1180+&Dgr;AC1-AC2-AC3 was ligated into BglII-KpnI-digested pRTAC1-A to produce, pRT3AA, a pRT101e-like construct with the AC1, AC2 and AC3 ORFs inserted in antisense orientation. The 2.7 kb HindIII fragment of the pRT3AA was inserted into the HindIII site of pJTS246&Dgr; in unidirectional orientation. The construct was introduced into LBA4404 by transformation to produce RT3AA.
EXAMPLE 6.5[0143] LASD and LASU
[0144] The 600-bp EcoRI-HincII fragment of pSL1180+PLAT52 was ligated with EcoRI-HincII-digested pRTAC1-S to replace the 800-bp 35S EcoRI-HincII promoter fragment by the 600-bp LAT52 EcoRI-HincII promoter fragment. After linearizing the plasmid with NcoI, the ATG start codon was destroyed by mung bean nuclease. The resulting plasmid contained an EcoRI and HindIII, but lacked a NcoI site. Accordingly, the sequences flanking the mutated NcoI site were the same as in the original LAT52 promoter untranslated 5′ leader. The 5′ untransformed leader was lengthened to 181 bp and included 68% A/T nucleotides. HindIII cut plasmid fragment containing the expression cassette was inserted into the HindIII site of pJTS246&Dgr; in both unidirectional and divergent orientations respecting the sense of the selectable marker. One binary of each type was transformed into LBA4404 creating strains LASU and LASD, respectively.
EXAMPLE 6.6[0145] MEU and MEU2
[0146] The AC1 triple mutant (dlmAC1) ORF was removed as a 1.1-kb Xho I-BamHI fragment from its vector and inserted in the sense orientation into Xho I-Bam HI-digested pRT101e. A 2.1-kb expression cassette thus created was removed from pRT101e+AC1dlm by incompletely digesting the recombinant vector with HindIII and isolating a 2.1-kb fragment. This fragment was inserted into the HindIII site of pJTS246&Dgr; to produce a mutated enhanced unidirectional (MEU) vector. A second binary involving the same expression cassette which was tandemly duplicated in the unidirectional orientation was called MEU2. Both of the above binary vectors were transformed into LBA4404 to produce MEU and MEU2, respectively.
EXAMPLE 6.7[0147] MUA and MUB
[0148] ToMoV-AC1dlm1 was partially digested with HindIII and the 2.1-kb expression cassette was isolated. ToMoV-AC1dlm3 was completely digested with HindIII and the 2.1-kb cassette isolated. Each cassette was inserted into the HindIII site of pJTS246&Dgr;. The recombinants were transformed into LBA4404 creating the Agrobacterium strains MUA and MUB, respectively.
EXAMPLE 6.8[0149] MUAIN and MUBIN
[0150] The 1.2 kb XhoI-BamHI-fragment of pRT101e+AC1 dlm1 containing the AC1dlm1 ORF was ligated with the XhoI-BamHI-fragment of pRTIN+Geneblock in a sense orientation. This construct was incompletely digested with HindIII followed by complete digestion with ScaI to produce a 2.6-kb fragment comprising the expression cassette. They were ligated with HindIII-digested pJTS246&Dgr; in a divergent orientation respecting the selectable marker. The resulting Agrobacterium strain was called MUAIN.
[0151] The 2.1 kb BamHI fragment of pRT101e+AC1dlm23, containing the AC1dlm23, was ligated with BamHI-digested OpRTIN+Geneblock plasmid in the sense orientation. This plasmid was digested with HindIII and ScaI producing a 2.6-kb expression cassette fragment which inserted into HindIII-digested pJTS246&Dgr; in an unidirectional direction. Plasmid DNA from this clone was transformed into LBA4404 to produce MUBIN.
EXAMPLE 6.9[0152] CODLM
[0153] The 1.1 kb BamHI fragment containing the wild type AC1 ORF was inserted into the BamHI site of p&Dgr;1CO35 in a sense orientation to produce p&Dgr;1CO35+AC1S. The 4.5 kb ApaI-BglII fragment of p&Dgr;1CO35+AC1S was restricted to delete a 475-bp comprising wild-type AC1 ORF and ligated to the ApaI-BglII fragment of pRT101e+AC1 dlm1 to replace the wild type internal fragment by the mutated fragment. The recombinant (p&Dgr;1CO35+AC1 dlm) was incompletely digested with HindIII, the 2.4-kb fragment containing the expression cassette isolated and inserted into the HindIII site of pJTS246&Dgr; in an unidirectional orientation. The plasmid was transformed into LBA4404 cells to produce CODLM.
EXAMPLE 7[0154] Constructs Containing TYLCV-IS-EG1
EXAMPLE 7.1[0155] LCA
[0156] The 1.1 kb BamHI fragment of pEGAL1-AS1 containing the C1 ORF was inserted in the BamHI site of pRT101e in an antisense orientation to produce pRTLCA1-A. A 2.1 kb HindIII fragment of pRTLCA1-A was inserted into the HindIII of pJTS246&Dgr; in the unidirectional (U) orientation with regard to directions of transcription. LBA4404 cells were transformed with the resulting plasmid to produce LCA.
EXAMPLE 7.2[0157] LCR′
[0158] A 350-bp BamHI fragment encoding part of the C2 ORF of TYLCV-IS-EG1 was removed from pTYC2-25-1 and ligated into the BamHI site of pRT101e. The resulting construct contained the truncated C2 ORF inserted in an antisense orientation with respect to P35S. The 1.3-kb expression cassette removed by HindIII digestion was inserted into the HindIII site of pJTS246&Dgr;. Plasmid DNA of the resulting recombinant was partially digested with HindIII and ligated with the C1 antisense expression cassette. The desired plasmid had one copy of each the expression cassette inserted such that the directions of transcription of all cassettes was unidirectional. DNA of this binary plasmid was transformed into L3A4404 to produce a strain, LCR′, comprising the two-cassette recombinant binary plasmid.
EXAMPLE 7.3[0159] LCR″
[0160] A 620-bp BamHI fragment of pTYV1-6-1 encoding part of the V1 ORF of TYLCV-IS-EG1 was ligated into the BamHI site of pRT101e in an antisense orientation with respect to the 35S promoter. A HindIII fragment of the resulting plasmid was ligated into the HindIII site of pJTS246&Dgr; in an unidirectional direction respecting the selectable marker. Plasmid DNA of this recombinant was transformed into LBA4404 to produce LCR″.
EXAMPLE 7.4[0161] RT3CA
[0162] The 1.3 kb BamHI fragment of pTYEGC4 containing the C1+AC2+AC3C structure was inserted into the BamHI site of pRT101e in an antisense manner with respect to the direction of transcription of the 35S promoter. The 2.3-kb HindIII fragment of pTYEGC4 the resulting plasmid containing the expression cassette was inserted into the HindIII site of pJTS24GA in an unidirectional transcription directions. LBA4404 transformed with this plasmid to produce strain RT3CA.
[0163] The 1.3 kb BamHI fragment of pTYEGC4 comprising C1+AC2+AC3 DNA was ligated into the BamHI site of p&Dgr;1Co35 in an antisense orientation with respect to the Commelina yellow mottle virus promoter. The 2.8 kb HindIII fragment of the resulting plasmid containing the expression cassette was inserted into the HindIII site of pJTS246&Dgr; in an unidirectional orientation respecting the selectable marker. Plasmid DNA transformed into LBA4404 produced CO3CA.
[0164] The mutated 1.2 kb fragments containing C1 ORF were removed from their pCRII vectors and directionally ligated into the EcoRV-HindIII fragment of ePmas-mcs-Tphas.
[0165] The resulting constructs were digested with XhoI and NaeI. HindIII fragments of pGA482&Dgr;+HYGR were flush ended by filling out, and digested with XhoI. The XhoI-NaeI expression cassettes were ligated into the binary vector that had an XhoI cohesive end and a blunt end to produce three constructs, C104, C225 and C259. DNA of each of the constructs were transformed into LBA4404 to produce the strains LC104, LC225 and LC259 and into Agrobacterium strain EHA105 (Mogen International, N.V.) to produce strains EC104, EC225 and EC259.
EXAMPLE 7.5[0166] RT3CS
[0167] The 1.3 kb BamHI fragment of pTYEGC4 containing the C1+&Dgr;C2+&Dgr;C3C structure was inserted into the BamHI site of pRT101e in an sense manner with respect to the direction of transcription of the 35S promoter. The 2.3-kb HindIII fragment of pTYEGC4 the resulting plasmid containing the expression cassette was inserted into the HindIII site of pJTS246&Dgr; in an unidirectional transcription directions. LBA4404 transformed with this plasmid to produce strain RT3CS.
EXAMPLE 8[0168] Production of Transgenic Plants Containing Disclosed Constructions and Analysis of Transgene expression
[0169] Transgenic plant were produced by Agrobacterium-co-cultivation procedures well known to those skilled in the art.
[0170] The media of compositions used are here defined, for 1 liter:
[0171] ½× basal: ½× MS salts (Gibco), 10 g sucrose, 7 g agar, pH 5.8;
[0172] TCM: 1× MS salts, 30 g sucrose, 0.2 g KH2PO4, 1× N&N vitamins (Gibco), 0.1 mg 2,4-D, 0.05 mg kinetin, 20 mg acetosyringone, 7 g agar, pH 5.8
[0173] 1Z: 1× MS salts, 30 g sucrose, 1× N&N vitamins, 1 mg zeatin, 100 mg kanamycine sulfate, 500 mg carbenicillin, 7 g agar, pH 5.8;
[0174] TR1: 1× MS salts, 30 g sucrose, 1× N&N vitamins, 3 mg glycine, 0.17 g NaH2PO4.H2O, 40 mg acetosyringone, pH 5.8;
[0175] MK5: ½× MS salts, 10 g sucrose, 1× N&N vitamins, 3 mg glycine, 0.17 g NaH2PO4.H2O, 50 mg kanamycin sulfate, 500 mg carbenicillin, 7 g agar, pH 5.8;
[0176] C: 1× MS salts, 30 g sucrose, 1× N&N vitamins, 3 mg glycine, 0.8 g NH4NO3, 2 mg BAP, 0.5 mg IAA, 100 mg kanamycine sulfate, 250 mg carbenicillin, 7 g agar, pH 5.8.
[0177] Seeds were sterilized by briefly rinsing in 70% EtOH and then in a solution of 20% chlorox plus Tween-20. The seeds were dried in vacuo and then rinsed several times with sterile water. Washed seeds were transferred into ½× basal media and incubated in a Magenta box for about 7 days in 16 hour photoperiods daily.
[0178] Fully expanded cotyledons were cut aseptically under water. Two cuts were made at the end, and the tip of the cotyledon piece and the center piece was retained and used. A culture of Agrobacterium containing the appropriate binary plasmid was initiated 24 hours before co-cultivation. Bacteria in 4-5 ml of the culture were collected by centrifugation and resuspended in TR1-liquid media. The suspension was poured onto cut cotyledon pieces and incubated for about 25 min. The cotyledon pieces were placed on sterile filter papers and placed compactly on TCM medium. The plates were kept in the dark at room temperature for about 48 hours, after which they were placed on plates containing 1Z medium. The plates were incubated in 16 hours light daily at about 24° C. for about 21 days.
[0179] Calli that formed on cotyledon pieces were transferred to fresh 1Z plates and shoots were removed as they formed to ½-X MK-5 tubes for rooting. A 4-mm piece of leaf from the shoot was also placed on C medium for callus formation. Twelve to fourteen days after the plating on C medium, calli were scored as “−” or “+”. About 60 to 70% of shoots with +callus root in MK5 media. Those that have +callus but did not root were trimmed off at the end and re-rooted on fresh MK5 tubes. About 80% of these will root on the second attempt.
[0180] Rooted shoots were removed to potting soil when a strong root system has developed, usually about 3 weeks after rooting. The plants were kept in a closed plastic bags for about 3 days, the bags were opened slowly after that to acclimatize the young plant. A 6- to 8-mm piece of leaf tissue was collected for the NPTII ELISA assay. The NPTII positive plants were transferred to the greenhouse for seed production. About 4 to 5 weeks in the greenhouse leaf tissues were collected for RNA isolation and Northern blots were done for these plants.
EXAMPLE 9[0181] Analysis of Transgenic Plants
[0182] Transgene RNA expression in transgenic tomato lines was accomplished by estimating steady state transcription levels using Northern blot hybridization. The level of transgene expression was used to select lines for agroinoculation. Total RNA was isolated from leaves and stems of young plants and electrophoresed on agarose gels.
[0183] The appropriate ORF DNA probe was radio-labeled and hybridized to RNA blotted on paper. After washing the RNA was visualized by autoradiography on X-ray film.
[0184] The following Tables 2, 3, and 4 summarize results showing plants produced with geminivirus constructs described above. The following symbols are used:
[0185] No+ or No−, Northern blot positive or negative;
[0186] So+ or So−, Southern blot positive or negative;
[0187] *, no data;
[0188] R0 and R1, primary and progeny lines.
[0189] Table 2 summarizes the transgenic tomato plants produced by transfer of wildtype ToMoV ORF DNA into the plant by Agrobacterium infection. For example, several tomato plants (TGM-1 to -17, -20, -24, -28, -29, -33 to -41, -47 to -49, -53, -54, -59 to -67, -70 to -131; TTGV92-1 to -5, -10, -13 to -20) were produced by Agrobacterium containing the RTAC construct. As shown in Table 1A, this construct is comprised of the ToMoV AC1 OFR in an antisense configuration. The predominant characteristic of these RTAC-containing plants is the presence of ToMoV DNA in the plant tissue (i.e., So+), transcribed RNA (i.e., No+), and transmitted these traits to their progeny (R1 RNA). Table 2 also described transgenic plants with DHAC and RT3AA constructs, comprised of ToMoV AC1 and AC1-AC2-AC3 antisense ORF, respectively (Table 1A).
[0190] Table 3 describes transgenic tomato plant containing mutant ToMoV ORF. These include the meu, meu2, Codlm, mub, mua, mubin, mauin, rtsfs, lasu, and lasd constructs described in Table 1A.
[0191] Table 4 describes transgenic tomato plant containing TYLCV ORF. These include LCA, LCR, RT3CA, RT3CS and Co3CA constructs of Table 1A, comprising TYLCV C1, C2 and C3 ORF.
[0192] These results establish that the methods described herein produce transgenic plants using DNA constructs containing gemini virus ORF. 5 TABLE 2 TOMATO PLANTS TRANSFORMED WITH ToMoV R0 R1 R0 Product Gene RNA RNA DNA Tgm-1, 10, 12, 14, 20, 29, 39, 53, 54, 64, RTAC No+ No+ So+ 66, 70, 71, 80, 81, 82, 127 Tgm-3, 8, 13, 16, 17, 24, 28, 33, 34, 36, RTAC * * So+ 40, 41, 47, 48, 49, 65, 114 Tgm-35 RTAC * * So− Tgm-59, 79, 102, 88, 116 RTAC No− No− So+ Tgm-67 RTAC No+ No− So+ Tgm-84, 90, 93, 94, 97, 98, 99, 100, 101, RTAC No+ * So+ 103, 106, 107, 108, 112, 113, 115, 117, 120, 121, 122, 123, 125, 129, 131 Tgm-18, 19, 26, 42, 55, 58, 68 DHAC * * So+ Tgm-23, 31, 44, 51 DHAC No+ No+ So+ Tgm-27 DHAC No− No+ So+ 3AA-3, 7, 9, 12, 13, 18, 21, 22, 23, RT3AA No+ * * 26, 27, 30 3AA-4, 11, 16 RT3AA No− * * TTGV92-1 RTAC No+ No− So+ TTGV92-2, 5, 15, 17 RTAC No− * So+ TTGV92-3, 13, 19 RTAC No− * So− TTGV92-4, 20 RTAC No+ No+ So+ TTGV92-6, 20 DHAC No+ No+ So+ TTGV92-7 DHAC * No+ So+ TTGV92-10 RTAC No+ No+ * TTGV92-11 DHAC No+ * So+ TTGV92-14 RTAC No− * * TTGV92-16 RTAC * * So−
[0193] 6 TABLE 3 TOMATO PLANTS TRANSFORMED WITH ToMoV REP ORF DOMINANT LETHAL MUTANT CONSTRUCTS Con- R0 R1 Product struct RNA RNA TTGV92-26, 28, 36 meu2 * * TTGV92-27 meu2 No− * TTGV92-42 meu2 * No+ DLM2, 39, 42, 46, 47, 48, 49, 51, 52, 55, 58, meu No+ * 60, 62, 64, 66, 68, 70, 72, 74, 76, 79, 80, 81, 82, 83, 85, 88, 89, 90, 91, 93, 95, 96, 97, 98, 99, 100, 101, 102, 104, 106, 107, 108, 109, 110, 112, 116, 117, 118, 119, 120, 122, 124, 126, 127, 130, 133, 135, 136, 137, 139, 144, 148, 149, 151, 180, 155, 159, 162, 167, 170, 172, 173, 177, 192, 198, 200, 201, 204, 206, 211, 215, 217, 219, 220 DLM3, 5, 7, 9, 10, 12, 14, 15, 18, 21, 26, 30, meu No+ No+ 31 DLM16 meu2 No− No− DLM17, 29 meu * * DLM22 meu No− No− DLM24 meu No− No− DLM25 meu2 No+ No+ DLM27, 28 meu No− No− DLM32 meu2 No+ No+ DLM37, 38, 44, 57, 59, 61, 75, 115, 129, 131, meu No− * 138, 150, 166, 174, 179, 189, 208 DLM143 meu No− * CODLM2, 4, 5, 6, 8, 9, 10, 13, 14, 15, 16, 18, Cod1m No+ * 21, 24, 26, 28 CODLM3, 7, 19, 27 Cod1m No− * MU-2, 3, 4, 5, 6, 7, 14, 15, 19, 20, 26, 27, 30, mub No+ * 31, 32, 33, 34, 36, 37 MU-8, 9, 12, 16, 18, 22, 28, 39, 41 mua No+ * MU-11 mua No− * MU-13, 47 mub No− * MUIN-3, 6, 7 mubin No+ * MUIN-4, 5 muain No+ * MUIN-8, 10, 11, 14, 17, 18 mubin * * MUIN-9, 15, 16, 19 muain * RTSFS-1, 3, 4, 6, 9, 10 rtsfs No+ * RTSFS-7, 8 rtsfs No− * LAS-1 1asu No+ * LAS-6, 10 1asd No+ * LAS-11 1asd No− *
[0194] 7 TABLE 4 TRANSGENIC TOMATO PLANTS TRANSFORMED WITH TYLCV GENE CONSTRUCTS R0 R0 R1 Product Construct DNA RNA RNA Lca-1, 2, 37, 39, 43 1ca So− * * Lca-5, 14, 21, 24, 29 1ca So+ * No+ Lca-6, 35, 36, 46 1ca So+ * * Lca-8, 12, 18, 19, 20, 26, 28 1ca So+ * No− Lca-25 1ca * * No− Lca-45 1ca So+ No+ * Lcr-1, 5, 6, 22 1cr So+ No+ * Lcr-3, 4, 17, 18, 20, 24 1cr So− No− * Lcr-12 1cr So− No+ * Lcr-16, 31 1cr So+ No− * Lcr-25 1cr So+ * * Lcr-26, 27, 29, 32 1cr So− * * 3CA-2, 3, −4, −6, −12, −15, −17, RT3CA * No+ * −18, −19, −21, −22 CO3CA-1, −2, −4, −5, −7, −8, −9, Co3CA * No+ * −11, −12, −13, −14, −17, −18, −19 CO3CA-6, −10 Co3CA * No− * RT3CS-1 RT3CS * No− *
EXAMPLE 10[0195] Viral Challenge of Transgenic Plants
EXAMPLE 10.1[0196] ToMoV Agroinoculation Vector
[0197] A 5.6-kb fragment composed of a dimer of full-length infectious DNA-A was ligated with BamHI-HindIII digested binary plasmid pJTS222 to produce construct comprising the ToMoV-A dimer. The resulting plasmid produced transformed LBA4404 cells, uses as the A-component in agroinoculation experiments.
[0198] A 6.9-kb XbaI fragment that includes a full length infectious clone of DNA-B and the complete pBluescript II KS+ plasmid was inserted into the XbaI site of pJTS222. The resulting plasmid produced transformed LBA4404 cells used as the B-component in agroinoculation experiments.
EXAMPLE 10.2[0199] TYLC-IS-EG1 Agroinoculation Vector
[0200] The full length TYLCV-IS-EG1 DNA from infectious clone pTYEG14 was removed from the plasmid by SphI digestion and inserted at high molar excess into the SphI site of pGEM5Zf+(Promega). The resulting plasmid, pTYEG7, contained a dimer of infectious TYLCV-IS-EG1 DNA. The 6.7-kb fragment of ScaI-PstI fragment of pTYEG7 comprised the dimer and part of pGEMZAf+. The 1.9-kb PstI-ScaI fragment of pSL1180 was ligated with the 6.7-kb fragment from pTYEG to produce a 8.7-kb construct with a single BglII site.
[0201] The 7.0 kb ScaI-BamHI fragment of the resulting recombinant plasmid was ligated with HpaI-BamHI-digested pJTS222. A resulting construct was used to transform LBA4404 cells to produce AtLC1, which was used in the TYLCV agroinoculation experiments.
10.3[0202] Agroinoculation Procedure
[0203] R1 plants from self pollinated R0 primary regenerants were agroinoculated 3 weeks after sowing. For bipartite geminiviruses, agroinoculation involves delivery of greater-than-full-length (must contain 2 common regions) ToMoV DNA-A and DNA-B into the seedlings using Agrobacterium. A small amount of a mixture of two Agrobacterium strains each containing a binary vector having in its T-DNA a partial or full tandem duplication of infectious geminivirus DNA was injected into the plant. For monopartite geminiviruses, only one agrobacterial strain is required if it carries a binary vector comprising a full or partial duplication of a full length infectious DNA.
[0204] Overnight cultures of Agrobacteria were diluted, and injected into stems of one month old tomato seedlings. About 100 hours later, a second inoculation identical to the first is performed.
[0205] Detection of NPTII by ELISA was taken as an indicium of the presence of the transgene. Agroinoculation experiments, summarized in Tables 5 to 10, show an array of resistance phenotypes. The data show several transgenic tomatoes resistant to ToMoV infection, including DLM12, TTGV92-42, CODLM6, CODLM8, CODLM13, CODLM14, MUA9, MUB20, MUA8, MUA18, MUA28, and MUA41. 8 TABLE 5 ToMoV Agroinoculations - DLM Transgenics Fraction of symptom-free Days Part and virus-free plants Line Inoculation NPTII positives NPTII negatives (Generation) observation visual blot visual blot TTGV92-36 20 2/16 2/16 0/2 0/2 (R1) TTGV92-42 20 9/11 8/11 3/7 3/7 (R1) untransformed 20 * * 0/17 0/17 DLM3 (R1) 26 * 5/16 * 0/2 DLM7 (R1) 26 * 4/15 * 1/3 DLM9 (R1) 26 * 0/14 * 1/2 DLM10 (R1) 26 * 2/16 * 0/2 DLM12 (R1) 26 * 10/17 * 0/1 untransformed 26 * * * 0/20 DLM12 (R1) 23 8/11 6/11 * * TTGV92-42-(R2) 23 * * 3/18 2/18 TTGV92-42-(R2) 23 6/13 4/13 0/5 0/5 TTGV92-42 23 13/15 10/15 0/3 0/3 (R1) untransformed 23 * * 1/24 1/24 DLM12 (R1) 21 12/20 13/20 1/5 1/5 DLM14 (R1) 21 6/18 4/18 * * DLM15 (R1) 21 0/14 0/14 0/4 0/4 DLM27 (R1) 21 0/15 0/15 0/3 0/3 DLM28 (R1) 21 1/16 1/16 0/1 0/1 untransformed 21 * * 0/15 0/15 DLM5 (R1) 18 0/13 1/13 0/5 0/5 DLM17 (R1) 18 1/5 1/5 3/9 3/9 DLM22 (R1) 18 0/15 0/15 0/3 0/3 DLM26 (R1) 18 2/3 2/3 1/5 1/5 DLM29 (R1) 18 0/13 0/13 1/3 1/3 DLM30 (R1) 18 3/14 3/14 1/4 1/4 DLM31 (R1) 18 4/12 4/12 0/6 0/6 TTGV92-42-17(R2) 18 7/13 6/13 1/4 1/4 TTGV92-42(R2) 18 17/18 17/18 * * untransformed 18 * * 0/20 0/20 DLM16 (R1) 18 0/13 0/13 0/5 0/5 DLM18 (R1) 18 2/16 2/16 0/2 0/2 DLM21 (R1) 18 0/18 0/18 * * DLM24 (R1) 18 1/11 1/11 0/7 0/7 DLM25 (R1) 18 7/16 6/16 0/2 0/2 DLM32 (R1) 18 1/16 1/16 0/2 0/2 untransformed 18 * * 0/13 0/13 DLM39 (R1) 30 0/15 1/15 1/4 1/4 DLM46 (R1) 18 0/15 0/15 0/5 0/5 DLM47 (R1) 18 5/17 4/17 0/3 0/3 DLM48 (R1) 18 0/15 0/15 0/5 0/5 DLM49 (R1) 18 1/16 9/16 0/4 0/4 DLM55 (R1) 18 0/14 0/14 0/6 0/6 DLM58 (R1) 18 0/14 1/14 0/6 0/6 untransformed 30 * * 0/9 0/9
[0206] 9 TABLE 6 ToMoV Agroinocu1ations: 3AA Transgenics Fraction of symptoms and virus free plants Line DPI NPTII positives NPTII negatives (Generation) observation visual blot visual blot 3AA3 (R1) 25 1/14 1/14 0/6 0/6 3AA7 (R1) 25 3/18 3/18 0/2 0/2 3AA9 (R1) 25 1/19 1/19 0/1 0/1 3AA12 (R1) 25 0/14 0/14 0/6 0/6 3AA13 (R1) 25 1/4 0/4 0/4 0/4 3AA16 (R1) 25 1/11 1/11 0/9 0/9 3AA18 (R1) 25 0/4 0/4 2/20 2/20 untransformed 25 * * 0/15 0/15 3AA13 (R1) 22 2/19 2/19 0/1 0/1 3AA21 (R1) 25 3/13 3/13 0/7 0/7 3AA22 (R1) 22 6/16 9/16 0/4 0/4 3AA23 (R1) 25 3/9 4/9 0/1 0/1 3AA26 (R1) 25 0/16 0/16 0/4 0/4 3AA27 (R1) 25 0/10 0/10 0/4 0/4 3AA30 (R1) 25 2/18 5/18 0/2 0/2 untransformed 25 * * 0/15 0/15
[0207] 10 TABLE 7 ToMoV Agroinoculations: LAS Transgenics Fraction of symptoms and virus free plants Line DPI NPTII positives NPTII negatives (Generation) observation visual blot visual blot LAS6 (R1) 25 8/11 8/11 0/9 0/9 LAS1 (R1) 25 0/10 0/10 0/10 0/10 LAS10 (R1) 25 1/14 1/14 1/6 1/6 LAS11 (R1) 25 * * 0/20 0/20 untransformed 25 * * 0/14 0/14
[0208] 11 TABLE 8 ToMoV Agroinoculations: CODLM Transgenics Fraction of symptom- and virus-free plants Line DPI NPTII positives NPTII negatives (Generation) observation visual blot visual blot CODLM2 20 0/14 0/14 0/6 0/6 (R1) CODLM5 ″ 0/15 0/15 0/5 0/5 (R1) CODLM6 ″ 9/14 3/14 0/6 0/6 (R1) CODLM8 ″ 8/20 1/20 No NPTII- * (R1) plants CODLM9 ″ 0/18 0/18 0/2 0/2 (R1) CODLM10 ″ 0/17 0/17 0/3 0/3 (R1) CODLM13 ″ 11/20 0/20 No NPTII- * (R1) plants CODLM14 ″ 7/16 0/16 0/4 0/4 (R1) untransformed ″ * * 1/9 1/9
[0209] 12 TABLE 9 ToMoV Agroinoculations: MUA and MUB Transgenics Fraction of symptom- and virus-free plants Line DPI NPTII positives NPTII negatives (Generation) observation visual blot visual blot MUA9 22 8/14 10/14 0/6 0/6 MU820 ″ 10/20 1/20 No * NPTII− MUB37 ″ 1/14 0/14 0/6 0/6 MUB3 20 0/14 0/14 0/6 0/6 MUB5 ″ 1/7 0/17 0/3 0/3 MUB7 ″ 1/18 1/18 0/2 0/2 MUA8 ″ 6/6 5/6 0/14 0/14 MUA12 ″ No * 0/20 0/20 NPTII+ MUB14 ″ 2/15 1/15 0/5 0/5 MUB15 ″ 5/20 3/20 No * NPTII− MUA16 ″ 5/14 4/14 0/6 0/6 MUA18 22 * 6/6 * 0/14 MUB19 ″ * 1/11 * No NPTII− MUB26 ″ * 0/15 * 0/5 MUA22 21 * 11/11 * 0/9 MUB33 ″ * 0/15 * 0/5 MUB30 ″ * 4/12 * 0/8 MUA28 ″ * 12/12 * 0/7 MUA41 ″ * 6/9 * 0/11 MUB36 ″ * 1/15 * 0/5 MUA39 ″ * 5/14 * 4/6 MUB31 ″ * 2/16 * 0/4 MUB34 ″ * No * 0/20 NPTII+ MUB32 ″ * 3/16 * 0/4 untransformed ″ * * 0/10 0/10
[0210] 13 TABLE 10 ToMoV Agroinoculations: RTFS Transgenics Fraction of symptom- and virus-free plants Line DPI NPTII positives NPTII negatives (Generation) observation visual blot visual blot RTFS1 20 5/12 2/12 0/8 0/8 RTFS3 ″ 0/15 0/15 0/5 0/5 RTFS4 ″ 5/16 1/16 0/4 0/4 RTFS6 ″ 10/12 10/12 0/8 0/8 RTFS9 ″ 5/13 3/13 0/7 0/7 RTFS10 ″ No NPTII+ * 0/20 0/20 untransformed ″ * * 0/10 0/10
EXAMPLE 10.4[0211] Squash Blot Assay of Geminivirus
[0212] Approximately 3 weeks after agroinoculation, visible symptoms were monitored and compared to untransformed tomato lines. At the same time, two samples per plant of leaf extract were applied to a hybridization membrane. This was done by squashing a leaf disc about ⅛ inch diameter on the membrane such that leaf sap thoroughly impregnated the membrane. After the membrane was treated to denature the DNA in the extract, it was hybridized according to the same protocol as used for Northern blots with a radioactive probe that would detect the DNA-B component of ToMoV or the C1 ORF of TYLCV. The presence of viral DNA in the plant sap could be detected by autoradiography.
[0213] The presence of viral DNA was highly correlated with appearance of symptoms, an indicia of susceptibility to infection. The virus-free phenotype was correlated with the presence of the marker in families of transgenic tomatoes segregating the NPTII marker.
[0214] FIG. 1 shows that expression of the ToMoV AC1dlm transgene is required for resistance to ToMoV infection mediated by agroinoculation. High expression is necessary but in itself does not ensure resistance.
EXAMPLE 10.4[0215] Viruliferous Whitefly Inoculations
[0216] Ten whiteflies carrying ToMoV were put on each eight-day old seedling. Twenty-five seedlings were used per family. In those families of seedlings which were not homozygous for the transgene, NPTII assays were correlated with squash blot results. Twenty-one to thirty-one days after inoculation, samples of each plant were taken for biochemical and molecular hybridization assays. The results are-summarized in Table 11. The Visual Rating gives the average of are plants, in which “0” is no symptoms and “4” is with most marked symptoms. The squash blot results give the fraction of the plants that were virus free. 14 TABLE 11 Florida Greenhouse Whitefly ToMoV Inoculations Fraction of symptom- and virus-free plants NPTII NPTII DPI Positives Negatives Squash Line obser- Blot Blot Visual Blot (Generation) vation Blot Blot Ratings Results TGM44 (R2) 21 7/20 0/6 2.2 13/26 TGM44 (R2) 21 6/17 0/9 1.6 10/26 untransformed 21 * 7/25 3.6 7/25 DLM12 (R2) 31 10/26 * 1.0 20/26 DLM12 (R2) 31 8/26 * 2.0 18/26 untransformed 31 * 1/19 3,7 3/19 DLM12 (R2) 31 8/20 * 0.8 8/20 DLM14 (R2) 31 3/11 * 1.7 3/11 DLM14 (R2) 31 9/23 * 3.0 12/23 untransformed 31 * 0/16 2.9 0/16 TTGV92-42 (R2) 32 7/21 1/5 2.5 23/26 TTGV92-42 (R3) 32 22/26 * 0 26/26 untransf. 32 * * 3.8 6/15 XPH5978 32 * 10/26 2.9 No Data XPH5979 32 * 7/26 2.7 No Data
EXAMPLE 11[0217] Transdominance in plant cell lines
[0218] A mutated form of AC1 protein of BGMV inhibits replication of DNA-A in a tobacco suspension cell system. To evaluate AC1 protein mutants for their potential to interfere with viral replication, a transient assay was used to detect trans-dominant interference activity of the mutant viral ORF. (Table 12 and FIG. 2.). 15 TABLE 12 Effects of BGMV AC1 Mutations on Replication and Transdominance Mutation Replication Trans-dominance WT AC1 + 0% mutation 1(a) − 90% mutation 1(c) − 90% I190R + 0% mutation 2(c) + 0%* mutation 2(a) − 50-80% mutation 3(a) − >95% mutations 2(a) and (c) − 50-80%
[0219] NT-1 cells were inoculated with wildtype DNA-A or a lethal mutant of DNA-A of BGMV-GA (ADM; double mutations 2(a) and (c) in combination with carrier DNA (PBS) or AC1 transexpression vectors containing mutated forms of AC1 ORF. Total DNA was harvested from the NT-1 tobacco cells at 72 hours after inoculation, electrophoresed in an agarose gel, blotted onto paper and probed with a radiolabeled DNA probe corresponding to the coat protein of BGMV-GA DNA-A. The results demonstrate that wildtype AC1 protein produced in trans can replicate a lethal AC1 mutant of DNA-A. More importantly, the results show that codon changes in the nicking motif of the AC1 ORF abolished infectivity and replication. In the transient assay for trans-dominance interference, double mutations 1(a) and 1(c) showed trans-dominance interference (Table 12).
[0220] Additional experimental treatments included:
[0221] A+PBS: wildtype BGMV-DNA-A was introduced into NT-1 cells with PBS at DNA weight ratios of 1:100 and 5:95 wildtype:PBS;
[0222] A+TDM: BGMV-DNA-A was introduced into NT-1 cells with transexpression vector coding for double mutations 2(a) and 2(c) at ratios of 1:100 and 5:95;
[0223] A+TD262R: BGMV-DNA-A was introduced with transexpression vector coding for mutation 3(a) at ratios of 1:100 and 5:95;
[0224] ADM+PBS: DNA-A containing double mutations 2(a) and 2(c) with PBS at 5:95;
[0225] ADM+TAC1: DNA-A containing double mutations 2(a) and 2(c) with transexpression vector coding for wildtype AC1 at a ratio of 5:95.
[0226] The transexpression vectors used in these experiments express AC1 in the proper context for replication.
[0227] FIG. 1 represents the results of these experiments. The mutations created in the 35S promoter driven AC1 ORF are listed in the first column. These ORF are used in trans with wild-type DNA-A of BGMV-GA to determine transdominance interference. Replication was tested in an NT-1 cell system. Replication is presented as the amount of reduction in replication in comparison to wild-type replication level. Trans-dominance was determined by engineering each mutation into a AC1 transexpression vectors which contained the AC1 ORF under control of the CaMV 35S promoter. Mutant AC1 expression vectors were coinoculated into NT-1 cells along with WT DNA-A and reductions in DNA-A replication were estimated from autoradiograms. Trans-dominance data are expressed as the observed reduction in DNA-A replication when co-inoculated with each AC1 mutant. Mutation 2(c) confers a temperature sensitive phenotype for replication, supporting replication at 23° C. but not at 28° C.
[0228] Replication was observed in inoculations with wildtype BGMV-DNA-A plus carrier DNA (A+PBS) (FIG. 1). No replication was observed in inoculations with a mutant of DNA-A containing double mutations 2(a) and 2(c) coinoculated with carrier DNA (ADM+PBS). Replication of double mutations 2(a) and 2(c) was, however, complemented by transexpression of wildtype AC1 in the transient expression vector (ADM+TAC1). Replication of BGMV-DNA-A in the presence of two different AC1 mutants, treatments A+TDM and A+TD262R reduced replication of virus DNA-A compared to the A+PBS treatments. Accordingly, transexpression of AC1 mutants can inhibit replication of BGMV-DNA-A. Further lethal mutants of AC1 inhibit replication when expressed in trans to DNA-A.
[0229] The results show that non-lethal mutants do not exhibit detectable transdominant activity. While levels of transdominance varied among different AC1 mutants, only replication-lethal mutants exhibited transdominant interference. Levels of AC1 expression directly relate to levels of trans-dominance and replication (FIG. 1). Thus, AC1 expression, results in production of a protein that mediates the “trans”-effective suppression. That is, this protein likely binds to the CR region which mediates its suppressive effect by inhibiting the binding of the wildtype AC1 protein.
Claims
1. A transgenic plant comprising chromosomal DNA, the plant harboring geminivirus DNA integrated into the chromosomal DNA, the geminivirus DNA encoding a protein required for geminivirus replication, and the geminivirus DNA conferring resistance to viral infection.
2. Transgenic plants according to
- claim 1 in which the geminivirus DNA is wild type DNA.
3. The transgenic plant according to
- claim 1 in which the geminivirus DNA comprises an ORF selected from the group consisting of AC1 and C1.
4. The transgenic plant according to
- claim 3 in which the geminivirus DNA comprises DNA encoding an amino acid sequence selected from the group consisting of FLTYpxC; pHlHvliQ; vKxYxdKd; FHPNlQxak; EGx2RTGKt; and NviDDi.
5. The transgenic plant according to
- claim 1 in which the geminivirus DNA is a transdominant interference mutant of a geminivirus gene.
6. The transgenic plant according to
- claim 5 in which the geminivirus DNA comprises an ORF selected from the group consisting of AC1 and C1.
7. The transgenic plant according to
- claim 5 in which the geminivirus DNA encodes a sequence motif selected from the group consisting of a DNA-nicking domain and a NTP-binding domain.
8. The transgenic plant according to
- claim 7 in which at least one mutation region of the transdominant interference mutant of the geminivirus DNA encodes an amino acid sequence comprising FLTYpxC; pHlHvliQ; vKxYxdKd; FHPNlQxak; EGx2RTGKt; and NviDDi.
9. The transgenic plant according to claims 7 or 8 in which the geminivirus DNA consists of at least one mutation of FLTYpxC; pHlHvliQ; vKxYxdKd; FHPNlQxak; EGx2RTGKt; and NviDDi in the AC1 ORF.
10. The transgenic plant according to claims 7 or 8 in which the geminivirus DNA consists of at least one mutation of FLTYpxC; pHlHvliQ; vKxYxdKd; FHPNlQxak; EGx2RTGKt; and NviDDi.
11. A transgenic plant according to
- claim 8 in which the geminivirus DNA is a ToMoV AC1 mutant selected from the group consisting of Sequence ID Nos. 3, 5, 7, 13, 14 and 15.
12. A transgenic plant according to
- claim 8 in which the geminivirus DNA is a TYLCV C1 mutant selected from the group consisting of Sequence ID Nos. 23, 26, and 29.
13. A transgenic plant according to
- claim 8 in which the geminivirus DNA is a BGMV AC1 mutant selected from the group consisting of Sequence ID Nos. 45, 48, 51, and 54.
14. A method of interfering with geminivirus infection of a transgenic plant comprising:
- selecting a transgenic plant according to
- claim 1; and
- growing said transgenic plant.
Type: Application
Filed: Apr 15, 1997
Publication Date: Aug 2, 2001
Inventors: JOHN T. STOUT (KALAMAZOO, MI), HANG T. LUU (KALAMAZOO, MI), STEVEN F. HANSON (MADISON, WI), DOUGLAS P. MAXWELL (VERONA, WI), PAUL G. AHLQUIST (MADISON, WI), ROBERT L. GILBERTSON (DAVIS, CA)
Application Number: 08838151
International Classification: A01H005/00;
