RNA silencing suppressors encoded by viruses of the family Tombusviridae

Abstract

RNA silencing is a sequence-specific gene-inactivation mechanism conserved among eukaryotes that functions as an antiviral defense in plants and animals. To counteract this defense, viruses encode RNA silencing suppressors. Over 30 RNA silencing suppressors have been identified, but the mechanisms by which they suppress RNA silencing is unclear for most of them. The best-characterized suppressor is P19, encoded by viruses of the genus Tombusvirus, which belongs to the family Tombusviridae. Three suppressors have also been identified in the genera Carmovirus, Aureusvirus, and Dianthovirus in the family Tombusviridae. In this review, we summarize recent findings regarding these four RNA silencing suppressors, focusing on their modes of action in RNA silencing suppression and their roles in virus infection.