Dissection of RNAi-based antiviral immunity in plants.

RNA interference (RNAi)-based antiviral defense is a small RNA-dependent repression mechanism of plants to against viruses. Although the core components of antiviral RNAi are well known, it is unclear whether additional factors exist that regulate RNAi. Recently, a forward genetic screen identified two novel components of antiviral RNAi, providing important insights into the antiviral RNAi mechanism. Meanwhile, it was discovered that microRNAs make important contributions to host antiviral RNAi. On the other hand, to counteract host antiviral RNAi, most viruses encode viral suppressors of RNA silencing (VSRs). Recent studies have revealed the multiple functions of VSRs and the intricate interactions between plant hosts and viruses. These findings add to our knowledge of the sophisticated host antiviral defense mechanism in plants. Ongoing molecular functional studies will improve our understanding of the co-evolutionary arms race between viruses and plants, and thereby provide key information for the development of plant antiviral strategies.