PCD pathways consist of a complex protein network of interacting genes, so we calculated the expression ratio of pro-survival vs. pro-death genes to better express the prevalent signaling in the cell. After preconditioning, the pa-BI-1/pa-BAK, pa-BI-1/pa-BAX, pa-Bcl/pa-BAK, and pa-Bcl/pa-BAX ratios shift towards the pro-survival partners during the early heat-stress response (Fig. 2B). In PC corals, the pa-BI-1 to pa-BAK ratio increases at 3h (p=0.0102) , pa-BI-1 to pa-BAX ratio increases at the first hour after stress beginning (p = 0.0010), pa-Bcl-2 to pa-BAK increases at 3 hours (p = 0.001), while compared to pa-BAX, it’s the basal expression in non-stressed PC corals and the expression around 1h of the thermal stress that shifts towards the pro-life partner (p(0h) <0.001, p(1h) < 0.001). These results suggest that during thermal preconditioning, the coral PCD pathway is modulated to favor the pro-survival genes.