The p22 RNA Silencing Suppressor of the Crinivirus Tomato chlorosis virus is Dispensable for Local Viral Replication but Important for Counteracting an Antiviral RDR6-Mediated Response during Systemic Infection

Abstract

Among the components of the RNA silencing pathway in plants, RNA-dependent RNA polymerases (RDRs) play fundamental roles in antiviral defence. Here, we demonstrate that the <i>Nicotiana benthamiana</i> RDR6 is involved in defence against the bipartite crinivirus (genus <i>Crinivirus</i>, family <i>Closteroviridae</i>) <i>Tomato chlorosis virus</i> (ToCV). Additionally, by producing a p22-deficient ToCV infectious mutant clone (ToCVΔp22), we studied the role of this viral suppressor of RNA silencing in viral infection in both wild-type and RDR6-silenced <i>N. benthamiana</i> (NbRDR6i) plants. We demonstrate that p22 is dispensable for the replication of ToCV, where RDR6 appears not to have any effect. Furthermore, the finding that ToCV∆p22 systemic accumulation was impaired in wild-type <i>N. benthamiana</i> but not in NbRDR6i plants suggests a role for p22 in counteracting an RDR6-mediated antiviral response of the plant during systemic infection.