Abstract
BackgroundIn plants and insects, RNA interference (RNAi) is the main responder against viruses and shapes the basis of antiviral immunity. Viruses counter this defense by expressing viral suppressors of RNAi (VSRs). While VSRs in Drosophila melanogaster were shown to inhibit RNAi through different modes of action, whether they act on other silencing pathways remained unexplored.Methodology/Principal FindingsHere we show that expression of various plant and insect VSRs in transgenic flies does not perturb the Drosophila microRNA (miRNA) pathway; but in contrast, inhibits antiviral RNAi and the RNA silencing response triggered by inverted repeat transcripts, and injection of dsRNA or siRNA. Strikingly, these VSRs also suppressed transposon silencing by endogenous siRNAs (endo-siRNAs).Conclusions/SignificanceOur findings identify VSRs as tools to unravel small RNA pathways in insects and suggest a cosuppression of antiviral RNAi and endo-siRNA silencing by viruses during fly infections.
Highlights
RNA silencing is a eukaryotic gene regulation mechanism by which RNA expression is shut down in a sequence specific manner through the intervention of homologous small non coding RNAs [1]
These results indicate that the viral suppressors of RNAi (VSRs) here tested do not appreciably perturb the miRNA pathway in Drosophila
We analyzed the ability of 9 VSRs to interfere with small RNA silencing pathways in adult flies
Summary
RNA silencing is a eukaryotic gene regulation mechanism by which RNA expression is shut down in a sequence specific manner through the intervention of homologous small non coding RNAs [1]. They are restricted to the gonads where they silence Transposable Elements (TEs) [4]. The ,21 nt siRNAs originate from the processing by Dicer-2 (Dcr2) of long dsRNA precursors, such as those produced by inverted-repeat (IR) transgenes. They load into Argonaute-2 (Ago2) and guide the cleavage of target mRNAs with perfect complementary sequence matches [5]. RNA interference (RNAi) is the main responder against viruses and shapes the basis of antiviral immunity Viruses counter this defense by expressing viral suppressors of RNAi (VSRs). While VSRs in Drosophila melanogaster were shown to inhibit RNAi through different modes of action, whether they act on other silencing pathways remained unexplored
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