title: A plant RNA virus suppresses RNA silencing through viral RNA replication.
abstract: 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.
authors.affiliation: Laboratory of Plant Pathology, Graduate School of Agriculture, Kyoto University, Kyoto, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Takeda
authors.forename: Misato
authors.initials: M
authors.lastname: Tsukuda
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Mizumoto
authors.forename: Kimiyuki
authors.initials: K
authors.lastname: Okamoto
authors.forename: Masanori
authors.initials: M
authors.lastname: Kaido
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Mise
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Okuno
mesh_terms: D020413:3' Untranslated Regions; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism / Q000821:virology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D035683:MicroRNAs / Q000096:biosynthesis; D009154:Mutation; D010942:Plant Viruses / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference / Q000502:physiology*; D012328:RNA Viruses / Q000235:genetics* / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics* / Q000378:metabolism; D034741:RNA, Small Interfering / Q000096:biosynthesis / Q000235:genetics; D012367:RNA, Viral / Q000235:genetics* / Q000378:metabolism; D012324:RNA-Dependent RNA Polymerase / Q000235:genetics / Q000378:metabolism; D043244:Ribonuclease III / Q000235:genetics / Q000378:metabolism
chemical_list: D020413:3' Untranslated Regions; D029681:Arabidopsis Proteins; D018797:Cell Cycle Proteins; D035683:MicroRNAs; D018749:RNA, Plant; D034741:RNA, Small Interfering; D012367:RNA, Viral; D012324:RNA-Dependent RNA Polymerase; C402383:DCL1 protein, Arabidopsis; D043244:Ribonuclease III