Genetic Analysis of the Monopartite Tomato Yellow Leaf Curl Geminivirus: Roles of V1, V2, and C2 ORFs in Viral Pathogenesis

AbstractTomato yellow leaf curl virus (TYLCV) is a whitefly-transmitted geminivirus with a monopartite genome. We have investigated the functions of the V1, V2, and C2 ORFs by mutational analysis. We analyzed the ability of TYLCV mutants containing disrupted ORFs V1, V2, or C2 to replicate, spread, and cause symptoms inNicotiana benthamianaand tomato plants. All the mutants retained the capability of autonomous replication in protoplast-derived cells of tomato and leaf discs ofN. benthamiana,although both V1 and V2 gene products appeared to play a role in the accumulation of viral single-stranded DNA. In contrast, none of the mutants was able to systemically infect tomato plants, demonstrating that the V1, V2, and C2 gene products are all required for a successful infection process in this host. The effect of the mutation in ORF C2 appeared to be host-specific, sinceN. benthamianaplants were systemically infected, although symptom development was attenuated