Figure 5 Analyses of programmed cell death pathway point to the prevalent role of symbiophagy (autophagy) in P. acuta thermally induced bleaching. A) Caspase-3 activity in NPC and PC corals under different conditions. i) Caspase-3 activity in NPC and PC corals at day 3 of the heat stress. ii) Caspase-3 activity in NPC and PC corals without (dashed lines) and with (black) venetoclax after 5-days long thermal stress compared to control (dotted) corals. iii) Caspase-3 activity in corals treated with apoptosis activator colchicine compared to controls. Error bars represent standard deviations (n = 4). B) Expression of genes related to programmed cell death pathways, relative to control at time 0h. Control samples are depicted with dark grey dotted line, non-preconditioned (NPC) with light grey dashed line and preconditioned (PC) with black solid line. ΔΔCt method was used to calculate the relative expression and the ratios. Graph shows mean values with standard error bars. * marks significant (p ≦ 0.05) difference between PC and NPC calculated using one-way ANOVA with Tukey’s post hoc test for each timepoint individually, n = 10.