Parental thermal environment controls the offspring phenotype in Brook charr (Salvelinus fontinalis): insights from a transcriptomic study.

Brook charr is a cold-water species which is highly sensitive to increased water temperatures, such as those associated with climate change. Environmental variation can potentially induce phenotypic changes that are inherited across generations, for instance, via epigenetic mechanisms. Here, we tested whether parental thermal regimes (intergenerational plasticity) and offspring-rearing temperatures (within-generational plasticity) modify the brain transcriptome of Brook charr progeny (fry stage). Parents were exposed to either cold or warm temperatures during final gonad maturation and their progeny were reared at 5°C or 8°C during the first stages of development. Illumina Novaseq6000 was used to sequence the brain transcriptome at the yolk sac resorption stage. The number of differentially expressed genes (DEGs) was very low when comparing fry reared at different temperatures (79 DEGs). In contrast, 9050 DEGs were significantly differentially expressed between fry issued from parents exposed to either cold or warm temperatures. There was a significant down-regulation of processes related to neural and synaptic activity in fry originating from the warm parental group vs. fry from the cold parental one. We also observed significant up-regulation of DNA methylation genes and of the most salient processes associated with compensation to warming, such as metabolism, cellular response to stress, and adaptive immunity.