Cucumber mosaic virus -encoded 2b suppressor inhibits Arabidopsis Argonaute1 cleavage activity to counter plant defense

RNA silencing refers to small regulatory RNA-mediated processes that repress endogenous gene expression and defend hosts from offending viruses. As an anti-host defense mechanism, viruses encode suppressors that can block RNA silencing pathways. Cucumber mosaic virus (CMV)-encoded 2b protein was among the first suppressors identified that could inhibit post-transcriptional gene silencing (PTGS), but with little or no effect on miRNA functions. The mechanisms underlying 2b suppression of RNA silencing are unknown. Here, we demonstrate that the CMV 2b protein also interferes with miRNA pathways, eliciting developmental anomalies partially phenocopying ago1 mutant alleles. In contrast to most characterized…