The 21-Nucleotide, but Not 22-Nucleotide, Viral Secondary Small Interfering RNAs Direct Potent Antiviral Defense by Two Cooperative Argonautes inArabidopsis thaliana
Open Access
- 1 April 2011
- journal article
- Published by Oxford University Press (OUP) in THE PLANT CELL ONLINE
- Vol. 23 (4), 1625-1638
- https://doi.org/10.1105/tpc.110.082305
Abstract
Arabidopsis thaliana defense against distinct positive-strand RNA viruses requires production of virus-derived secondary small interfering RNAs (siRNAs) by multiple RNA-dependent RNA polymerases. However, little is known about the biogenesis pathway and effector mechanism of viral secondary siRNAs. Here, we describe a mutant of Cucumber mosaic virus (CMV-Δ2b) that is silenced predominantly by the RNA-DEPENDENT RNA POLYMERASE6 (RDR6)-dependent viral secondary siRNA pathway. We show that production of the viral secondary siRNAs targeting CMV-Δ2b requires SUPPRESSOR OF GENE SILENCING3 and DICER-LIKE4 (DCL4) in addition to RDR6. Examination of 25 single, double, and triple mutants impaired in nine ARGONAUTE (AGO) genes combined with coimmunoprecipitation and deep sequencing identifies an essential function for AGO1 and AGO2 in defense against CMV-Δ2b, which act downstream the biogenesis of viral secondary siRNAs in a nonredundant and cooperative manner. Our findings also illustrate that dicing of the viral RNA precursors of primary and secondary siRNA is insufficient to confer virus resistance. Notably, although DCL2 is able to produce abundant viral secondary siRNAs in the absence of DCL4, the resultant 22-nucleotide viral siRNAs alone do not guide efficient silencing of CMV-Δ2b. Possible mechanisms for the observed qualitative difference in RNA silencing between 21- and 22-nucleotide secondary siRNAs are discussed.Keywords
This publication has 88 references indexed in Scilit:
- Virus-derived small interfering RNAs at the core of plant–virus interactionsTrends in Plant Science, 2010
- Plant virus-mediated induction of miR168 is associated with repression of ARGONAUTE1 accumulationThe EMBO Journal, 2010
- ARGONAUTE 1 homeostasis invokes the coordinate action of the microRNA and siRNA pathwaysEMBO Reports, 2009
- Mechanism of Induction and Suppression of Antiviral Immunity Directed by Virus-Derived Small RNAs in DrosophilaCell Host & Microbe, 2008
- Sorting of Small RNAs into Arabidopsis Argonaute Complexes Is Directed by the 5′ Terminal NucleotideCell, 2008
- Specificity of ARGONAUTE7-miR390 Interaction and Dual Functionality in TAS3 Trans-Acting siRNA FormationCell, 2008
- Antiviral Immunity Directed by Small RNAsCell, 2007
- Analysis of the C. elegans Argonaute Family Reveals that Distinct Argonautes Act Sequentially during RNAiCell, 2006
- Animal virus replication and RNAi-mediated antiviral silencing in Caenorhabditis elegansNature, 2005
- Analysis of Relative Gene Expression Data Using Real-Time Quantitative PCR and the 2−ΔΔCT MethodMethods, 2001