Expression of full-length and truncated Rep genes from Mungbean yellow mosaic virus-Vigna inhibits viral replication in transgenic tobacco.

Mungbean yellow mosaic virus-Vigna (MYMV-Vig) is a bipartite geminivirus that causes a severe yellow mosaic disease in blackgram. An assay was developed to study MYMV-Vig replication by agroinoculation of tobacco leaf discs with partial dimers of the virus. This assay, in a non-host model plant, was used to evaluate pathogen-derived resistance contributed by MYMV-Vig genes in transgenic plants. Viral DNA accumulation was optimum in tobacco leaf discs cultured for 10 days after infection with Agrobacterium tumefaciens strain Ach5 containing partial dimers of both DNA A and DNA B of MYMV-Vig. Transgenic tobacco plants with MYMV-Vig genes for coat protein (CP), replication-associated protein (Rep)-sense, Rep-antisense, truncated Rep (T-Rep), nuclear shuttle protein (NSP) and movement protein (MP) were generated. Leaf discs from transgenic tobacco plants, harbouring MYMV-Vig genes, were agroinoculated with partial dimers of MYMV-Vig and analyzed for viral DNA accumulation. The leaf discs from transgenic tobacco plants harbouring CP and MP genes supported the accumulation of higher levels of MYMV-Vig DNA. However, MYMV-Vig accumulation was inhibited in one transgenic plant harbouring the Rep-sense gene and in two plants harbouring the T-Rep gene. Northern analysis of these plants revealed a good correlation between expression of Rep or T-Rep genes and inhibition of MYMV-Vig accumulation.