GENETIC-ENGINEERING OF POTYVIRUS RESISTANCE USING CONSTRUCTS DERIVED FROM THE ZUCCHINI YELLOW MOSAIC-VIRUS COAT PROTEIN GENE

Three versions of the zucchini yellow mosaic virus (ZYMV) coat protein gene were engineered for expression in plants: the full-length coat protein sequence, the conserved core portion of the gene, and an antisense version. These constructs were introduced into muskmelon (Cucumis melo) and tobacco plants (Nicotiana tabacum) via Agrobacterium tumefaciens-mediated transformation; gene expression was verified by Northern and Western analysis. Transgenic R(0) and R(1) muskmelon plants expressing the full length coat protein gene exhibited apparent immunity to ZYMV infection: There was a lack of symptom development during a 3-mo observation period and no measurable virus accumulation as determined by ELISA. Melon plants expressing the core or antisense constructs showed a several-day delay of systemic symptom development and reduction in virus titer. Furthermore, transgenic R(1) tobacco plants expressing the full-length coat protein, core, or antisense constructs of ZYMV, a nonpathogen of tobacco, showed a short delay in symptom development and reduced virus titer when inoculated with the heterologous potyviruses, potato virus Y, and tobacco etch virus. The transgenic tobacco plants were not protected against the non-potyvirus, tobacco mosaic virus.