Journal Article

Characterization of Silencing Suppressor 2b of Cucumber Mosaic Virus Based on Examination of its Small RNA-Binding Abilities

Kazunori Goto, Takashi Kobori, Yoshitaka Kosaka, Tomohide Natsuaki and Chikara Masuta

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 48, issue 7, pages 1050-1060
Published in print July 2007 | ISSN: 0032-0781
Published online July 2007 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcm074
Characterization of Silencing Suppressor 2b of Cucumber Mosaic Virus Based on Examination of its Small RNA-Binding Abilities

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  • Biochemistry
  • Molecular and Cell Biology
  • Plant Sciences and Forestry

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Double-stranded (ds) RNAs and imperfect hairpin RNAs of endogenous genes trigger post-transcriptional gene silencing (PTGS) and are cleaved by a Dicer-like nuclease into small interfering RNAs (siRNAs) and microRNs (miRNAs), respectively. Such small RNAs (siRNAs and miRNAs) then guide an RNA-induced silencing complex (RISC) for sequence-specific RNA degradation. While PTGS serves as an antiviral defense in plants, many plant viruses encode suppressors as a counter defense. Here we demonstrate that the PTGS suppressor (2b) of a severe strain (CM95R) of cucumber mosaic virus (CMV) can bind to in vitro synthesized siRNAs and even to long dsRNAs to a lesser extent. However, the 2b suppressor weakly bound to a miRNA (miR171) duplex in contrast to another small RNA-binding suppressor, p19 of tombusvirus that can effectively bind miRNAs. Because the 2b suppressor of an attenuated strain of CMV (CM95), which differs in a single amino acid from the 2b of CM95R, could barely bind siRNAs, we hypothesized that the weak suppressor activity of the attenuated strain resulted from a loss of the siRNA-binding property of 2b via a single amino acid change. Here we consider that 2b interferes with the PTGS pathway by directly binding siRNAs (or long dsRNA).

Keywords: Cucumber mosaic virus; PTGS; siRNA; Viral suppressor

Journal Article.  6827 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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