Multi-omics reveals the adaptation of a marine diatom to ocean acidification and warming

Although ocean acidification and warming could act interactively on marine phytoplankton, little is known about the molecular basis for this interaction on an evolutionary scale. Here we explored the adaptation to ocean acidification in combination with warming in a model marine diatom Phaeodactylum tricornutum. Whole-genome re-sequencing identifies a larger genetic diversity loss and a higher genetic differentiation in the populations adapted for two years to warming than that to acidification. However, this diversity loss was less under acidification combined with warming, suggesting that the evolution driven by warming was constrained by acidification. By integrating genomics, transcriptomics and physiological data, we found that the underlying molecular basis for this constraint is associated with the expression of genes involved in some key metabolic pathways or biological processes, such as the glyoxylate pathway, amino acid and fatty acid metabolism, and circadian rhythms. Our results shed new light on the evolutionary responses of marine phytoplankton to multiple environmental changes in the context of global change and provide new insights into the molecular basis underpinning interactions among those multiple drivers.