Influence of ocean acidification on eastern (Crassostrea virginica) and Pacific oyster (Crassostrea gigas) DNA methylation

Epigenetic modification, specifically DNA methylation, is one possible mechanism for transgenerational plasticity. Before inheritance of methylation patterns can be characterized we need a better understanding of how environmental change modifies the parental epigenome. The influence of experimental ocean acidification on DNA methylation was examined in gonad tissue two congeneric species: eastern (Crassostrea virginica) and Pacific oysters (Crassostrea gigas). Methylation islands were characterized in both species, and were found primarily in gene bodies. There were no conserved genes in methylation islands between species. Differentially methylated loci (DML) were found in gene bodies, with 598 in C. virginica and 628 in C. gigas. A total of 81 genes with DML were common between species. Genes with DML were involved in various biological process, with no process significantly enriched. These results demonstrate a role for DNA methylation in gene activity and transcriptional control, although the functional role of methylation is still unclear. Understanding how experimental ocean acidification conditions modify the oyster epigenome, and if these modifications are inherited, will allow for a better understanding of how ecosystems will response to environmental change.