Effects of arboviral infections on transposable element transcript levels in Aedes aegypti.

Transposable elements (TEs) are mobile repeated sequences found in all genomes. TEs are controlled by RNA interference pathways in most organisms, and this control involves the piRNA pathway and the siRNA pathway, which is also known to be the first line of antiviral defense in invertebrates. Using Drosophila, we recently showed that viral infections result in the modulation of TE transcript levels through modulation of the small RNA repertoire. The Aedes aegypti mosquito is of particular interest because almost half of its genome is made of TEs, and it is described as a major vector of viruses (such as the dengue (DENV), Zika (ZIKV) and chikungunya (CHIKV) arboviruses). Moreover, Aedes mosquitoes are unique among insects in that the piRNA pathway is also involved in the somatic antiviral response, in addition to the TE control and piRNA pathway genes expanded in the mosquito genome. For these reasons, we studied the impacts of viral infections on TE transcript levels in Ae. aegypti samples. We retrieved public datasets corresponding to RNA-seq data obtained from viral infections by DENV, ZIKV and CHIKV in various tissues. We found that TE transcripts are moderately modulated following viral infection and that the direction of the modulation varies greatly across tissues and viruses. These results highlight the need for an in-depth investigation of the tightly intertwined interactions between TEs and viruses.