Unraveling the Molecular Arms Race: Grapevine Fanleaf Virus Proteins as Suppressors of Plant Antiviral Silencing Pathways

There exists a constant evolutionary combat between hosts and their invading pathogens. The plant-virus pathosystem is no exception. Plants have evolved multiple defense mechanisms to combat viral invasion. One of these mechanisms involves the viral RNA-induced silencing complex that targets and cleaves viral RNAs, thereby preventing viral RNA translation and replication. The RNA silencing pathway starts with the host RNA III-type Dicer-like (DCL) endoribonuclease cleavage of double-stranded RNA into virus-derived short interfering RNAs. This guide strand combines with Argonaute (AGO) protein to form the RNA-induced silencing complex used to cleave viral transcripts (Gaffar and Koch 2019; Jin et al. 2022). On the other hand, viruses have evolved counteracting strategies to overcome this antiviral mechanism by encoding viral suppressors of RNA silencing (VSR) proteins, which inhibit one or more steps of host RNA silencing pathways (Lopez-Gomollon and Baulcombe 2022). For instance, the polerovirus protein P0 destabilizes AGO, and the helper component protease of potyvirus sequester short interfering RNAs (Li and Wang 2019). Understanding this complex molecular arms race is important for gaining insights into the various strategies viruses deploy to overcome host defense and to develop effective tools to inhibit viral anti-silencing methods.