Recent progress on gene silencing/suppression by virus-derived small interfering RNAs in rice viruses especially Rice grassy stunt virus

Abstract

Noncoding RNAs play essential functions during epigenetic regulation of gene expression and development in numerous organisms. Three type of small noncoding RNAs found in eukaryotes, which are small interfering RNAs (siRNAs), microRNAs (miRNAs) and piwi-interacting RNAs (piRNAs). Small RNAs (sRNAs) originated from infecting viruses are known as virus-derived small interfering RNAs (vsiRNAs), are responsible for RNA silencing in plants. However, Virus-induced gene silencing (VIGS) is mainly dependent on RNA silencing (RNAi). Interestingly, RNA silencing happens in plants and insects during viral infections. VsiRNAs originate from dsRNA molecules which further require hosts Dicer-like (DCL) proteins, RNA dependent RNA polymerase (RdRP) proteins, and Argonaute (AGO) proteins. RdRP uses ssRNA for complete RNA amplification process as well as DCL dependent secondary vsiRNA formation. Viral Suppressors of RNA silencing (VSRs) interfere with the movement of signals during silencing mechanism. Moreover, intercellular movement of viruses is facilitated by virus-encoded movement proteins. Proteomic and Transcriptomic mechanisms regulated by specific factors like microRNAs, which has become an essential factor of gene regulation. RNAi is also involved in gene suppression by regulating the transcriptional and post-transcriptional gene expression in many eukaryotes. Rice grassy stunt virus (RGSV) is a member of genus Tenuivirus. Although, there is no much work done on RGSV, but this virus has become very potent and destructive, and effects rice crop in many Asian countries, particularly in China. In this review, we have highlighted the rice viruses’ biology and silencing suppressors. This work will be helpful for plant virologists in understanding the role of vsiRNAs mechanism in rice viruses especially RGSV.