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Article

  • The EMBO Journal (2005) 24, 3147 - 3157
  • doi:10.1038/sj.emboj.7600776

Published online: 11 August 2005

A plant RNA virus suppresses RNA silencing through viral RNA replication

Atsushi Takeda1,a, Misato Tsukuda1,a, Hiroyuki Mizumoto1, Kimiyuki Okamoto1, Masanori Kaido1, Kazuyuki Mise1 and Tetsuro Okuno1

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

Correspondence to:

Tetsuro Okuno, Laboratory of Plant Pathology, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan. Tel.: +81 75 753 6131; Fax: +81 75 753 6131; E-mail: okuno@kais.kyoto-u.ac.jp

aThese authors contributed equally to this work

Received 12 January 2005; Accepted 18 July 2005

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.

  • Keywords:

    • Dicer,
    • plant virus,
    • RNAi,
    • suppressor,
    • virus replication