The Xiamen Symposium on Marine Environmental Sciences (XMAS 2025)

Elevated seawater temperature has been considered as the major stressor causing the expulsion of Symbiodiniaceae in coral holobiont, known as “coral bleaching”. The thermal resilience of Symbiodiniaceae has shown to be species specific, further exploration of the underlying cell metabolic response should be examined individually. In this study, comparative metabolomics and proteomic analyses were combined to investigate the difference metabolic responses to heat stress between symbiont coral reef isolated Fugacium kawagutii (formerly Clade F) and non-symbiont Effrenium sp. (formerly Clade E). In this 24-h time course experiment, F. kawagutii and Effrenium sp. were cultured under heat shock stress condition respectively. Comparative metabolomics were conducted between two species using reversed phase liquid chromatography coupled to high-resolution mass spectrometry (LC-QTOF MS). Our pairwise metabolomics comparisons revealed that F. kawagutii was more thermal stable than Effrenium sp. metabolically, showing limited quantity of identified differential metabolites in heat stress group compared to control group. Moreover, KEGG enrichment analysis shows that arachidonic acid metabolic pathway and the synthetic pathway of terpenoids express change remarkably in Effrenium sp., indicating the membrane structure has been destroyed and dissociated. Comparative proteomics were then carried out to elucidate the cell mechanism. Results show that the proteins involved with photosynthesis and antioxidant system maintained relative stable in F. kawagutii than those in Effrenium sp., consistent with the metabolomic profiling. Taken together, our results confirm that antioxidant activity and membrane integrity plays important roles in the species-specific thermal resilience of Symbiodiniaceae.

Symbiodiniaceae,thermal resilience,metabolomics,iTRAQ proteomics,arachidonic acid,terpenoid synthesis