Porites astreoides RNA-Seq data - Global Search PGAFF

Rising ocean temperature threatens coral reefs, yet thermal tolerance varies among coral species and populations. Using the Coral Bleaching Automated Stress System (CBASS), we examined thermal thresholds and transcriptomic dynamics in two wild Porites astreoides populations from thermally contrasting habitats with documented differences in bleaching susceptibility: a more tolerant Inshore population vs. a more sensitive Offshore population. RNA-sequencing at six timepoints during a 19-hour acute heat stress assay, coupled with photosynthetic efficiency measurements (Fv/Fm), revealed a higher standardized thermal tolerance threshold, i.e. effective dose (ED50), in Inshore corals (37.77C) compared to Offshore corals (36.94C), supporting previous observed differences from a longer-term heat stress experiment. Importantly, at 34C, the lowest heat stress applied, the Offshore population consistently exhibited more differentially expressed genes (DEGs) than the Inshore population. For example, during peak stress, Offshore corals expressed 1,285 DEGs compared to just 238 Inshore. Principal component analysis (PCA) revealed temperature as the primary driver of transcriptional variation (explaining 30% of the variance along PC1), while population origin accounted for a smaller but significant proportion (21% along PC2). Inshore corals displayed a muted transcriptomic response and rapid recovery, whereas Offshore corals exhibited larger, delayed responses. We interpret these response differences as transcriptomic resilience and acclimation; two emerging mechanistic patterns associated with increased coral thermal tolerance. No evidence of gene expression frontloading was detected, suggesting epigenetic or post-transcriptional regulation underlies the observed resilience differences. Our results demonstrate long-term, fine-scale population differences in resilience mechanisms, suggesting stable thermal tolerance strategies that can inform future conservation efforts.