Transgenic plants expressing geminivirus movement proteins: Abnormal phenotypes and delayed infection by Tomato mottle virus in transgenic tomatoes expressing the Bean dwarf mosaic virus BV1 or BC1 proteins

Transgenic tomato plants expressing wild-type or mutated BV1 or BC1 movemen t proteins from Bean dwarf mosaic virus (BDMV) were generated and examined for phenotypic effects and resistance to Tomato mottle virus (ToMoV), Fewer transgenic plants were recovered with the wild-type or mutated BC1 genes, compared with the wild-type or mutated BV1 genes. Transgenic tomato plants expressing the wild-type or mutated BV1 proteins appeared normal. Interesti ngly, although BDMV induces only a symptomless infection in tomato (i,e., B DMV is not well adapted to tomato), transgenic tomato plants expressing the BDMV BC1 protein showed a viral disease-like phenotype (i,e,, stunted grow th, and leaf mottling, (curling, and distortion), This suggests that the sy mptomless phenotype of BDMV in tomato is not due to a host-specific defect in the BC1 protein. One transgenic line expressing the BC1 gene did not sho w the viral disease-like phenotype, This was associated with a deletion in the 3' region of the gene, which resulted in expression of a truncated BC1 protein, Several Ro plants, expressing either wild-type or mutated BV1 or B C1 proteins, showed a significant delay in ToMoV infection, compared with n ontransformed plants, R-1 progeny plants also showed a significant delay in ToMoV infection, but this delay was less than that in the R-0 parents. The se results also demonstrate that expression of viral movement proteins, in transgenic plants, can have deleterious effects on various aspects of plant development.