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Study of RNA interference based antiviral immunity in insects by means of an integrated approach in Schistocerca gregaria and Drosophila melanogaster.

RNA(i) interference is a post-transcriptional gene silencing mechanism mediated by small (s)RNA molecules. In short, sRNAs are incorporated into an RNA-induced silencing complex (RISC), which is then directed to a messenger RNA target via Watson-Crick base pairing. Subsequently, the effector protein of RISC, namely an Argonaute protein, acts to inhibit or degrade the specific transcript, resulting in suppressed gene expression. According to the Argonaute with which the sRNAs interact in the RISC, three main groups of sRNAs can be classified in insects: micro (mi)RNAs, which interact with Ago1; small interfering (si)RNAs, which interact with Ago2; and PIWI-interacting (pi)RNAs. This classification is further supported by the main biological processes in which these sRNAs are involved: miRNAs mainly control the expression of endogenous genes, being potentially implicated in the regulation of any biological process; siRNAs are important antiviral effectors; and piRNAs protect genomic integrity, by controlling the activity of mobile genetic agents, such as transposons. 

This study provides insights into the RNAi-based antiviral immunity in lepidopteran and orthopteran insects, specifically in Bombyx mori and Trichoplusia ni –derived cell lines; and in the locusts, Schistocerca gregaria and Locusta migratoria. First, an important role of the siRNA pathway in the immunity against persistent and acute viral infections in two lepidopteran cell lines is demonstrated. In this context, it is shown that overexpression of key effectors of this pathway leads to an improved defense against an acute viral infection. Second, the piRNA pathway is demonstrated to also play an antiviral role in the investigated lepidopteran cells, which strongly supports a functional diversification of this mechanism in insects. At last, a general overview of the components of the main sRNA pathways is provided in the desert locust S. gregaria. In this scope, evidence for an antiviral role of the siRNA pathway is also found in the migratory locust, L. migratoria, as well as a role of the piRNA pathway in the control of transposons.

Taken together, this doctoral thesis provides an overview of the sRNA mechanisms in lepidopteran and orthopteran insects, as well as new insights into the antiviral and anti-transposon roles of some of these pathways in these animals. 

Date:1 Oct 2013 →  27 Jun 2018
Keywords:Drosophila melanogaster, Schistocerca gregaria, RNA
Disciplines:Animal biology, Genetics
Project type:PhD project