10th International Virology Summit
Amity University, India
Title: Velvet bean severe mosaic begomovirus DNA-A encoded RNA silencing suppressor proteins
Biography: Narayan Rishi
Geminiviruses (family Geminiviridae) are classified into nine genera and unassigned viruses on the basis of host range, insect vector and genome organization. These genera are: Becurtovirus, Begomovirus, Capulavirus, Curtovirus, Eragrovirus, Grablovirus, Mastrevirus, Topocuvirus and Turncurtovirus. Begomoviruses are divided into two categories i.e. bipartite or monopartite (old world) bipartite (new world). Viruses have evolved to encode unique proteins to counter RNA silencing known as RNA silencing suppressors (RSS). Several begomovirus and their associated betasatellite-encoded viral proteins have been identified as RSSs. A large number of structural such as coat protein (CP) and non-structural viral proteins possessing suppressor activity have been involved in crucial viral functions, including viral movement, viral replication etc. Mucuna pruriens (L) DC (Velvet bean/“magic bean”) of family Fabaceae is used in Ayurvedic medicines for Parkinson’s disease, liver dysfunction, blood-related diseases, snake bite, endocrine and male reproductive disorders. Velvet bean severe mosaic virus (VbSMV) is a bipartite DNA virus infecting Mucuna pruriens (Velvet bean) belongs to the genus Begomovirus, family Geminiviridae. In this study VbSMV was identified from velvet bean. For the identification of suppressor proteins, primers were designed for all genes of VbSMV by adding appropriate site for restriction enzymes for inframe cloning in the vector. Out of the two assays reported for the identification of suppressor genes we used Agrobacterium co-infiltration assay. It was delineated that proteins encoded by VbSMV viz. AV2 (pre-coat protein), AC2 (TrAP), AV1 (coat protein) are suppressors of RNA silencing as identified through Agrobacterium co-infiltration assay using Nicotiana benthamiana as a host plant. AV2 showed strong suppressor activity whereas AC2 and AV1 were found to be weak suppressors. This is the first report on identification of suppressor of RNA silencing encoded by VbSMV infecting a medicinal plant. Identified suppressor proteins are being used to develop virus resistant transgenic plants and understanding RNA silencing pathway.