Enchytraeus albidus Transcriptome or Gene expression

Enchytraeus albidus (Clitellata; Enchytraeidae) is a terrestrial earthworm widespread along the coasts of northern Europe and the Arctic. This species tolerates freezing of body fluids and survives winters in a frozen state. The acclimatory physiological mechanisms behind freeze tolerance of this species involve increased fluidity of membrane lipids during cold exposure and accumulation of cryoprotectants (glucose) during the freezing process. The regulatory processes of these physiological responses have not been studied, partly because no gene expression tools were developed yet. The main aim of this study was to understand if the freeze tolerance mechanisms have a transcriptomic basis in E. albidus. For that purpose, first the transcriptome of E. albidus was developed using RNAseq (miseq) for de novo assembly. Second, two populations from contrasting thermal environments (Germany and Greenland) were compared using RNAseq with barcoding (Illumina). Both of these populations are freeze tolerant, but the population from Germany is not particularly cold tolerant whereas the one from Greenland is extremely cold tolerant, . Results showed much more plastic responses from the Greenland strain as well as constitutive overexpression. These altered transcriptional networks are associated with an adapted homeostasis coping with prolonged freezing conditions. Previously identified physiological alterations in cold tolerant enchytraeids are underpinned/confirmed at the transcriptome level. These processes involve the fatty acids metabolism, sugar metabolism and transport and oxidative stress . As such, this tolerant phenotype is the consequence of genetic adaptation to cold stress and may have driven evolutionary divergence of the two populations. This could eventually lead to speciation?