Transcriptome and proteins reveal mechanisms of Phaeocystis globosa adaptation to long-term ocean warming

In recent years, Phaeocystis globosa has become one of the major causes of harmful algal blooms in the coastal areas of China, relying on the competitive advantage gained by its heterotypic life cycle. Accompanied by increasing global CO2 emissions, ocean warming will change the structure of marine ecosystems and directly affect marine organisms. However, the long-term adaptive response of P. globosa to ocean warming remains unknown. Here, we investigated the physiological, transcriptomic, and proteomic differences in P. globosa under short-term and long-term warming conditions. The results of the study showed that in short-term warming, the life cycle of the P. globosa was transformed by an increase in the number of solitary cells, a decrease in the number of colonies, a constant diameter of the colonies, a decrease in the content of extracellular polysaccharides, and a stress on photosynthesis. Transcriptomic data showed significant downregulation of genes related to photosynthesis, polysaccharide synthesis, and amino acid synthesis, while genes related to polysaccharide degradation and DNA replication were significantly upregulated. In the long-term warming group, the number of solitary cells continued to increase, the number of colonies increased dramatically but the diameter was significantly reduced, the extracellular polysaccharide content was restored, and photosynthesis resumed. Transcriptomic and proteomic combined analysis revealed that cells allocated more energy to amino acid and fatty acid synthesis rather than extracellular polysaccharide synthesis. The study results indicate that P. globosa changes in energy metabolism as a crucial strategy to adapt to warming conditions.