3 research outputs found

    Super-induction of Dicer-2 expression by alien double-stranded RNAs: An evolutionary ancient response to viral infection?

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    Dicer-2 is a ribonuclease involved in the insect RNAi pathway. On attempting to knockdown Dicer-2 expression in the insect Blattella germanica by RNAi, we found that treatment with Dicer-2 dsRNA upregulated the targeted mRNA. This unexpected result was also observed after treating with a nucleopolyhedrovirus dsRNA. Experiments with this alien dsRNA showed an all-or-none response with a threshold for inducing Dicer-2 upregulation between 0.4 and 0.04 μg in terms of dsRNA concentration and between 50 and 20 bp in terms of dsRNA length. The response seems specific of dsRNA given that equivalent experiments carried out with dsDNA did not affect Dicer-2 expression. In insects, Dicer-2 is postulated to be a sensor of viral infections and a key antiviral defense element. The upregulation of Dicer-2 expression after dsRNA administration fits well with this sensor role, and the occurrence of this mechanism in B. germanica, a phylogenetically basal insect, suggests that sensing alien RNAs might be an ancestral function of Dicer-2 proteins. © 2012 Springer-Verlag.Support for this research was provided by the Spanish MICINN (grant CGL2008-03517/BOS to X.B. and predoctoral fellowship to J.L.), by the CSIC (grant 2010TW0019, from the Formosa program to X.B.), and by the National Science Council of Taiwan (NSC 97-2313-B-002-031 and NSC 100-2923-B-002-002 to H.-J.L.).N
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