Biogenesis And Function Of Virus-Derived Small Interfering Rnas In Plants

RNA silencing is a deeply conserved mechanism that operates in most eukaryotes. A hallmark of RNA silencing is the processing of double-stranded RNA (dsRNA) precursors into 21-24-nucleotide (nt) small RNAs that function as sequence-specific cellular regulators. One of the well-established roles of RNA silencing is antiviral defense in plants. The virus-derived small RNAs found in the infected host cells serve as a manifestation that viral RNAs are targeted by the host RNA silencing machinery. On the other hand, many viruses encode proteins that suppress the activities of host silencing machinery, reflecting a viral counterdefense strategy evolved during the long-standing virus host arms race. In many cases, viral disease symptoms are attributable, at least in part, to the interference of the host endogenous small RNA pathways by the virus-encoded silencing suppressors. During the last few years, significant advances have been made in our understanding of the host RNA silencing machinery involved in antiviral defense in plants, mainly through genetic analysis in Arabidopsis. Application of the next-generation DNA sequencing technology has enabled high-resolution profiling of the virus-derived small RNAs in the infected hosts. This review covers the most recent advances in our understanding of the biogenesis and cellular activity of virus-derived small interfering RNAs (siRNAs) in plants.