Wolbachia-mediated protection of Drosophila melanogaster against systemic infection with its natural viral pathogen Drosophila C virus does not involve changes in levels of highly abundant miRNAs.

The presence of Wolbachia confers virus protection to insects. The molecular mechanism underlying Wolbachia-mediated protection in this tripartite host-endosymbiont-virus interaction is not yet fully understood. In the bipartite association between Drosophila melanogaster and Drosophila C virus (DCV), changes in the expression of microRNAs (miRNAs) influence the outcome of viral pathogenesis. Here we examined whether changes in miRNA expression are similarly involved in the Drosophila-Wolbachia-DCV association. The levels of highly abundant miRNAs in D. melanogaster, Wolbachia-mono-infected D. melanogaster, and DCV- and Wolbachia-bi-infected D. melanogaster were quantified using RT-qPCR and compared. The results show that the abundance of the 17 tested D. melanogaster miRNAs is not affected by Wolbachia endosymbiosis or by bi-infection of Wolbachia and DCV. These results suggest that the in vivo protection conferred by Wolbachia to its native host against D. melanogaster's natural pathogen DCV is not likely to be dependent on or associated with changes in the levels of highly expressed miRNAs.