Transcriptional responses of reef-building coral Leptoria phrygia to localized thermal anomalies: a seasonal and experimental approach.

Coral resilience depends on the ability to withstand and adapt to environmental fluctuations. As reefs increasingly face both global and local thermal stress, understanding the molecular basis for this resilience is critical. In southern Taiwan, corals near a nuclear power plant outlet (NPPOL) experience elevated and variable seawater temperatures compared to a nearby stable reef (WLT). In this study, we generated a high-quality genome assembly for the common coral Leptoria phrygia and combined it with seasonal transcriptomic and population genetic analyses. Despite high connectivity and low genetic differentiation between sites, L. phrygia exhibited distinct, seasonally dynamic transcriptional responses. Stress- and metabolism-related pathways, including apoptosis, cytoskeletal remodeling, and tricarboxylic acid (TCA) cycle regulation, were enriched in summer and winter, whereas lipid metabolism and biosynthesis dominated in transitional seasons. Comparative field and tank experiments identified core differentially expressed genes, including vitellogenins and Ca²⁺-homeostasis genes, as biomarkers of resilience. These findings reflect transcriptional variation rather than direct physiological mechanisms. Overall, our findings provide a genomic resource for L. phrygia and describe gene expression variation across contrasting thermal environments.