Expression of pro-survival genes pa-BI-1 and pa-Bcl-2 and pro-death genes pa-BAK and pa-BAX showed a dynamic stress response during the first 24 hours of the hyperthermal treatment (Fig. 2A). After preconditioning, the expression of pro-survival pa-BI-1 and pa-Bcl-2 was ~ 1.6x higher in PC corals than in NPC corals at 3h (p(BI-1,3h) <0.001, p(Bcl-2, 3h)p=0.0011). The expression of the pro-death pa-BAK first increased in both PC and NPC corals at 3 hours (p(NPC-C) = 0.0026, p(PC-C) = 0.0680) before declining to almost control levels in PC corals at 6 hours (~ 2-fold difference between PC and NPC corals, p = 0.0018). At 12 hours, the expression in NPC corals was already decreasing but slightly higher than in PC corals (p=0.0798), and the expression levels equalized at time 24h. The expression profiles of pa-BAXsignificantly differed between PC and NPC corals. In NPC corals there was a gradual increase during the first 6 hours, but the expression in PC corals sharply peaked at 3 hours and then rapidly decreased towards 6 hours (p(1h) = 0.0282, p(3h)<0.001, p(6h) =0.0861).