Limited stress and tissue-specific transcriptional and translational activity of transposable elements in mosquitoes

The mobilization of transposable elements (TEs) can either negatively impact the host's fitness or contribute to the species evolution. TE protein expression is the first stage for transposition, but organisms developed defenses to control it. The intensity of regulatory mechanisms can vary among tissues, and in response to stress, it may facilitate TE activation across different species. Using hundreds of RNA-Seq and mass spectrometry experiments we calculated TE expression on twelve mosquito species. Most mosquito TE families exhibit constitutive RNA expression with abundant lncRNA production, yet only a limited number of proteins are effectively produced, in a tissue-specific manner. Under natural conditions, TEs exhibit distinct expression in somatic and germinal tissues, notably with pronounced repression in ovaries, associated with increased PIWI and AGO3 expression. Following exposure to abiotic stress and viral infection, certain TE families undergo altered expression. However, some stressors have no effects on TEs, or cause opposite effects in different species. Furthermore, repression predominates over induction in most cases. These data suggest that while some proteins are synthesized, the majority of TE transcripts function in a regulatory capacity. We also propose that the conventional notion of TEs being more expressed under stress conditions may not be universally valid.