Tissue-specific response of transposable elements to temperature stress in the Antarctic fish Trematomus bernacchii

Abstract

Genome architecture is deeply influenced by Transposable elements (TEs) activity. Through their ability to migrate from one location to another, TEs are one of the main drivers of genomic plasticity. This distinctive feature contributes to biological evolution and adaptation to environmental changes. Climate changes affect the whole world, as in Antarctica, where the suborder Notothenioidei dominate the fish fauna in terms of number of species and biomass. Trematomus, due to its peculiar characteristics, is one of the most studied genera belonging to Notothenioidei, and it is a good model to investigate the effects that the increase in temperature can cause in transposable elements. We analyzed the available RNA-Seq data obtained from specimens of Trematomus bernacchii exposed at two different temperatures, -0.9 °C and 0.6 °C for three different periods of exposition (six hours, seven days, and twenty days). The aim was to investigate the transcriptional activity of TEs and that of genes encoding for proteins involved in their silencing mechanisms in two different tissues (gill and brain). Our findings highlighted a variation in TE transcriptional activity in the two analysed tissues as a consequence of the temperature stress. A remarkable upregulation of TEs in the six hours and seven days periods was observed. On the contrary, a stabilization of the TE transcriptional values was observed for the twenty days of exposition. Moreover, the transcriptional analysis of genes encoding proteins involved in TE silencing such as those responsible for heterochromatin formation, of the NuRD complex, and the argonaute family highlighted their activity in both tissues with a prompter response in the brain than in the gill. Overall, our findings suggested that T. bernacchii can adapt to temperature changes in less than twenty days corroborating the idea that TEs might represent a promising molecular tool for species adaptation.