Transgenic resistance to tobacco ringspot virus.

The coat protein (CP) gene including the 3'-untranslated region (UTR) of RNA2 of a cherry isolate of Tobacco ringspot virus (TRSV) was utilized in a CP-mediated resistance (CP-MR) strategy. To facilitate construction of plant expression vectors the sequence context of the CP gene translation initiation codon was modified at the 5'-end of the coding sequence by including an initiation codon. The gene was ligated to a version of the Cauliflower mosaic virus (CaMV) 35S promoter with a duplicated enhancer. The cloned CP gene was used to transform Nicotiana tabacum cv. Xanthi, as a systemic and local lesion host. The transgenic plants showed different level of resistance ranging from complete resistance to reduction in symptom severity post inoculation with the cherry isolate of TRSV. A CP gene transcript was detected in different tissue of transgenic lines, but translation product was undetectable by Western blot analysis or enzyme-linked immunosorbent assay (ELISA). Interestingly, 100% of seed transmission was blocked in a resistant line, which offers important prospects for engineering TRSV into economically important crops as soybean with 100% seed transmission.