Résumé
Long non-coding RNAs (lncRNAs) are a new class of RNA regulators, defined as transcripts longer than 200 nucleotides, lacking protein coding capacity and characterized by a high degree of tissue-specific expression. They act as essential regulators of many normal biological processes. Several studies also demonstrate their implication in the immune response, often as essential regulators of the expression of genes coding for proteins associated with immune system. LncRNAs are increasingly being studied in mammalian. However, their potential importance in insects is still poorly considered. The objective of this work was to identify lncRNAs, whose expression is associated with viral infection in the fall armyworm Spodoptera frugiperda by using high-throughput sequencing (RNA-Seq). In particular, we compared lncRNA expression in S. frugiperda larvae infected with viruses displaying different virulence strategies.We injected the entomopathogenic densovirus JcDV and the polydnavirus HdIV into fifth-instar (less than 1-day-old) S. frugiperda larvae. Larvae injected with PBS buffer served as negative controls. Expression of lncRNAs and protein-coding mRNA in hemocytes were analyzed 72h after infection. Then we identified lncRNAs which were specifically regulated upon viral infection and those which were differentially regulated by only one virus. A total of 1190 lncRNAs were identified in all hemocytes samples. To validate the effect of viral infection on the expression of several differentially expressed lncRNAs, their levels were evaluated by qRT-PCR. To further test whether these lncRNAs are tissue specific, we also measured their expression in fat body from PBS-, HdIV- or JcDV-infected larvae, 72h post-infection by qRT-PCR.Our study provides a list of lncRNAs potentially involved in the antiviral response of S. frugiperda. This is a starting point for further investigations on the biological importance of these new class of molecules in a main crop pest.