DNA methylation patterns of redband trout from desert and montane environments

Epigenetic variation is a potential pathway for rapid response to environmental change and has been shown to influence local adaptation at the population level through population-environment interactions. The most well-understood mechanism of epigenetic variation is DNA-methylation, a form of gene regulation that acts in response to environmental stress. Previous studies have shown ecotypic variation in DNA-methylation, but few have attempted to quantify epigenetic variation in natural populations. As such, we developed a study to compare levels of DNA-methylation in Rainbow Trout (Oncorhynchus mykiss) from contrasting environments. For this study we sampled populations from cold montane and warm desert streams on repeated intervals and tissue samples were collected for epigenetic analysis. Levels of DNA-methylation (percent methylation) will be quantified using targeted bisulfite sequencing of promotor regions of three candidate genes (Heat Shock Protein 70, 90, and 47) that have previously been shown to be important to thermal stress response in coldwater fishes. Subsequent transcriptomic analyses will also be performed to evaluate the potential relationship between methylation level and gene expression in these regions. We hypothesize that percent methylation will be different between desert and montane populations, with desert populations expressing lower overall methylation patterns resulting in upregulation of genes favorable to survival. Since the fitness cost of maladaptive epigenetic variation is relatively low when compared to the cost of maladaptive genetic variation, we predict that epigenetic variation may be favored in environments where thermal regimes are less stable.