Acts as 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. Forms a homodimer to measure siRNA duplex in a length-preference mode. Binds to both siRNA duplexes (19bp) and long siRNA duplexes (30bp). Homodimer. Homotetramer (dimer of dimers). Belongs to the cucumovirus/ilarvirus protein 2b family.