Suppression of Antiviral Silencing by Cucumber Mosaic Virus 2b Protein in Arabidopsis Is Associated with Drastically Reduced Accumulation of Three Classes of Viral Small Interfering RNAs

摘要: We investigated the genetic pathway in Arabidopsis thaliana targeted during infection by cucumber mosaic virus (CMV) 2b protein, known to suppress non-cell-autonomous transgene silencing and salicylic acid (SA)–mediated resistance. show that expressed from CMV genome drastically reduced accumulation of 21-, 22-, 24-nucleotide classes viral small interfering RNAs (siRNAs) produced Dicer-like4 (DCL4), DCL2, DCL3, respectively. The defect a 2b–deletion mutant (CMV-Δ2b) plant was efficiently rescued mutants producing neither 21- nor 22-nucleotide siRNAs. Since analysis further identifies unique antiviral role for DCL3 upstream DCL4, our data indicate inhibition distinct siRNAs plays key suppression silencing. Strikingly, disease symptoms caused CMV-Δ2b defective were as severe those CMV, demonstrating an indirect suppressor activity virulence. found production without interference depended largely on RNA-dependent RNA polymerase 1 (RDR1) inducible SA. Given RDR6-dependent silencing, results suggest model which inhibits RDR1-dependent confer SA-dependent resistance directing