Abstract
The control of viral infections in insects is a current issue of major concern and RNA interference (RNAi) is considered the main antiviral immune response in this group of animals. Here we demonstrate that overexpression of key RNAi factors can help to protect insect cells against viral infections. In particular, we show that overexpression of Dicer2 and Argonaute2 in lepidopteran cells leads to improved defense against the acute infection of the Cricket Paralysis Virus (CrPV). We also demonstrate an important role of RNAi in the control of persistent viral infections, as the one caused by the Macula-like Latent Virus (MLV). Specifically, a direct interaction between Argonaute2 and virus-specific small RNAs is shown. Yet, while knocking down Dicer2 and Argonaute2 resulted in higher transcript levels of the persistently infecting MLV in the lepidopteran cells under investigation, overexpression of these proteins could not further reduce these levels. Taken together, our data provide deep insight into the RNAi-based interactions between insects and their viruses. In addition, our results suggest the potential use of an RNAi gain-of-function approach as an alternative strategy to obtain reduced viral-induced mortality in Lepidoptera, an insect order that encompasses multiple species of relevant economic value.
Highlights
RNA interference (RNAi) is a post-transcriptional gene-silencing mechanism directed by small RNA molecules
We worked with two important lepidopteran cell lines, namely the Trichoplusia ni High Five cells and the B. mori Bm5 cells, and with the well-characterized Cricket Paralysis Virus (CrPV)
Since we have demonstrated the presence of virus-specific Ago2-bound siRNAs corresponding to the genomes of three different known persistent viruses in BmN cells (Fig. 4), we further investigated the importance of key siRNA-directed RNAi (siRNAi) pathway players in the control of mlv transcript levels in lepidopteran cells
Summary
RNA interference (RNAi) is a post-transcriptional gene-silencing mechanism directed by small RNA molecules. The guide strand available to direct target RNA recognition by Watson-Crick base pairing At this point, the catalytic component of RISC, Argonaute[2] (Ago2), mediates the degradation of complementary viral RNA, combating the viral infection[1]. Due to the advance of genomic and transcriptomic tools, identification of persistent viruses has become more recurring, with several reported cases both in vivo and in cultured cells[15,16,17,18,19,20] In this context, it is noteworthy that, most insect RNAi-based antiviral immunity research has been performed in models of acute infection, it has been demonstrated that the siRNAi machinery is involved in the defence against persistent infections in Drosophila cells[21]. A clear example of this refers to the economically important order of Lepidoptera, with several persistent viral infections well reported[5,19,20,22]
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