LAUSR

Significance Transposable elements (TEs) are genomic parasites that are found in all genomes. Here, we show that viral infections impact TE transcript amounts in Drosophila somatic tissues. This is of major importance in the understanding of the tempo and mode of genetic diversification, suggesting that viral infections act as a significant factor determining TE activity. In addition, our results also suggest that the amounts of the maternally transmitted small RNAs that control TEs in the progeny may also be altered, which could have long-term, evolutionary impacts. Transposable elements (TEs) are genomic parasites that are found in all genomes, some of which display sequence similarity to certain viruses. In insects, TEs are controlled by the Piwi-interacting small interfering RNA (piRNA) pathway in gonads, while the small interfering RNA (siRNA) pathway is dedicated to TE somatic control and defense against viruses. So far, these two small interfering RNA pathways are considered to involve distinct molecular effectors and are described as independent. Using Sindbis virus (SINV) in Drosophila, here we show that viral infections affect TE transcript amounts via modulations of the piRNA and siRNA repertoires, with the clearest effects in somatic tissues. These results suggest that viral acute or chronic infections may impact TE activity and, thus, the tempo of genetic diversification. In addition, these results deserve further evolutionary considerations regarding potential benefits to the host, the virus, or the TEs.