SGS3 Cooperates with RDR6 in Triggering Geminivirus-Induced Gene Silencing and in Suppressing Geminivirus Infection in Nicotiana Benthamiana.

Fangfang Li,Xueping Zhou,Yaqin Wang

doi:10.3390/v9090247

Abstract

RNA silencing has an important role in defending against virus infection in plants. Plants with the deficiency of RNA silencing components often show enhanced susceptibility to viral infections. RNA-dependent RNA polymerase (RDRs) mediated-antiviral defense has a pivotal role in resistance to many plant viruses. In RDR6-mediated defense against viral infection, a plant-specific RNA binding protein, Suppressor of Gene Silencing 3 (SGS3), was also found to fight against some viruses in Arabidopsis. In this study, we showed that SGS3 from Nicotiana benthamiana (NbSGS3) is required for sense-RNA induced post-transcriptional gene silencing (S-PTGS) and initiating sense-RNA-triggered systemic silencing. Further, the deficiency of NbSGS3 inhibited geminivirus-induced endogenous gene silencing (GIEGS) and promoted geminivirus infection. During TRV-mediated NbSGS3 or N. benthamiana RDR6 (NbRDR6) silencing process, we found that their expression can be effectively fine-tuned. Plants with the knock-down of both NbSGS3 and NbRDR6 almost totally blocked GIEGS, and were more susceptible to geminivirus infection. These data suggest that NbSGS3 cooperates with NbRDR6 against GIEGS and geminivirus infection in N. benthamiana, which provides valuable information for breeding geminivirus-resistant plants.

Highlights

RNA silencing is a surveillance system in eukaryotic organisms induced by double-strandedRNA that is subsequently processed by a double-stranded RNA (dsRNA)-specific RNase III enzyme (Dicer) into21–25-nucleotide long, small interfering RNA
We show that NbSGS3 cooperates with N. benthamiana RDR6 (NbRDR6) in triggering geminivirus-induced endogenous gene silencing (GIEGS) and in suppressing several geminivirus infections
RNA and protein gel blot analyses revealed that suppression of local silencing by dsSGS3 and dsRDR6 was accompanied by an accumulation of both green fluorescent protein (GFP) mRNA and protein, and loss of GFP-specific siRNAs in the infiltrated leaves (Figure 1B)

Summary

Introduction

RNA silencing is a surveillance system in eukaryotic organisms induced by double-strandedRNA (dsRNA) that is subsequently processed by a dsRNA-specific RNase III enzyme (Dicer) into21–25-nucleotide (nt) long, small interfering RNA (siRNAs). RNA silencing is a surveillance system in eukaryotic organisms induced by double-stranded. The siRNAs are loaded into the RNA-induced silencing complex (RISC), including ARGONAUTE (AGO) proteins, to guide the sequence-specific degradation of complementary RNAs [1,2,3]. In RDRs-mediated RNA silencing process, Suppressor of. Gene Silencing 3 (SGS3), which accompanies with RDR6, is required to convert single-stranded to double-stranded RNA (dsRNA) to produce both exogenous and endogenous siRNAs [5,6,7]. Several recent reports have shown that the knock-out or knock-down of RDR6 in plants did display more susceptibility to viruses, and to bacterial and fungal pathogens, suggesting RDR6-mediated RNA silencing has a defense role against a wide range of pathogens including viral, bacterial and fungal

Methods

Results

Conclusion