Strong activator of the late viral genes promoters. Enhances the expression of the capsid protein and nuclear shuttle protein. Acts as a suppressor of RNA-mediated gene silencing, also known as post-transcriptional gene silencing (PTGS), a mechanism of plant viral defense that limits the accumulation of viral RNAs. Suppresses the host RNA silencing by inhibiting adenosine kinase (ADK), a kinase involved in a general methylation pathway. Also suppresses the host basal defense by interacting with and inhibiting SNF1 kinase, a key regulator of cell metabolism implicated in innate antiviral defense. Determines pathogenicity