EXPRESSION OF THE COAT PROTEIN GENES OF GRAPEVINE VIRUS A AND B IN NICOTIANA SPECIES AND EVALUATION OF THE RESISTANCE CONFERRED ON TRANSGENIC PLANTS
A. Minafra, R. Gölles, A. da Camara Machado, P. Saldarelli, N. Buzkan, V. Savino, G.P. Martelli, H. Katinger, M. Laimer da Camara Machado
Agrobacterium-mediated transformation of leaf discs of N. benthamiana and N. occidentalis with constructs containing the coat protein (CP) genes of grapevine virus A (GVA) or grapevine virus B (GVB), produced several lines of transgenic plants. Some of the transformant lines (GVAcp+ and GVBcp+) growing on a selective kanamycin-containing medium were assayed in R1 generation for the expression of transgenic mRNAs and coat proteins. Some of the plants that hybridized specific digoxigenin-labeled riboprobes to both viruses, contained detectable amounts of viral CP as shown by Western blot analysis, whereas others did not. The behaviour of R1 seedlings following challenge inoculation with homologous viruses at a concentration of 1 µg ml-1 was monitored by TAS-ELISA up to 18 days post inoculation Various levels of resistance to both viruses were observed, as expressed by reduction of virus accumulation. Some of the GVAcp+ lines also showed a 3-4 day delay in symptom appearance.