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1: EMBO J. 2005 Sep 7;24(17):3147-57. Epub 2005 Aug 11.
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A plant RNA virus suppresses RNA silencing through viral RNA replication.

Takeda A, Tsukuda M, Mizumoto H, Okamoto K, Kaido M, Mise K, Okuno T.

Laboratory of Plant Pathology, Graduate School of Agriculture, Kyoto University, Kyoto, Japan.

RNA interference (RNAi) is a post-transcriptional gene-regulatory mechanism that operates in many eukaryotes. RNAi is induced by double-stranded RNA (dsRNA) and is mainly involved in defence against transposons and viruses. To counteract RNAi, viruses have RNAi suppressors. Here we show a novel mechanism of RNAi suppression by a plant virus Red clover necrotic mosaic virus (RCNMV). To suppress RNAi, RCNMV needs multiple viral components, which include viral RNAs and putative RNA replicase proteins. A close relationship between the RNA elements required for negative-strand RNA synthesis and RNAi suppression suggests a strong link between the viral RNA replication machinery and the RNAi machinery. In a transient assay, RCNMV interferes with the accumulation of small-interfering RNA (siRNAs) in RNAi induced by a hairpin dsRNA and it also interferes with microRNA (miRNA) biogenesis. An Arabidopsis dcl1 mutant showed reduced susceptibility to RCNMV infection. Based on these results, we propose a model in which, to replicate, RCNMV deprives the RNAi machinery of Dicer-like enzymes that are involved in both siRNA and miRNA biogenesis.

Publication Types:
PMID: 16096641 [PubMed - indexed for MEDLINE]

PMCID: PMC1201356