Role of gene body methylation in coral acclimatization and adaptation

Gene body methylation (GBM) has been hypothesized to modulate responses to environmental change, including transgenerational plasticity, but the evidence thus far has been lacking. Here we show that coral fragments reciprocally transplanted between two distant reefs respond with genome-wide increase or decrease in GBM disparity among genes. Surprisingly, this simple genome-wide adjustment predicted broad-scale gene expression changes and fragments’ fitness in the new environment. This supports GBM’s role in acclimatization, which may consist in modulating the expression balance between environmentally-responsive and housekeeping genes. At the same time, constitutive differences in GBM between populations did not align with plastic GBM changes upon transplantation and were mostly observed among F ST outliers, indicating that they arose through genetic divergence rather than through transgenerational inheritance of acquired GBM states. One-sentence summary Genome-wide shifts in gene body methylation predict gene expression and fitness during acclimatization but do not contribute to epigenetic divergence between populations.