Figure 4 Preconditioned (PC) corals treated with Bcl-2 inhibitor venetoclax lost the more thermal-resilient phenotype and bleached at the same rate as non-preconditioned (NPC) corals. A) Fluorescence confocal microscopy pictures of coral fragments that underwent 5-day long heat stress without or with venetoclax. Host cells are visualized in green, algal cells in red. B) Bleaching rate of PC and NPC corals based on calculating the symbiont: host cells signal ratio. A set of control experiments was designed to rule out the effect of venetoclax itself to coral symbiont density. Multiway ANOVA analysis with Tukey’s post hoc test (microscopy_signal ~ time * conditioning * treatment) was used to test the similarity of bleaching rate. The analysis showed a significant difference in bleaching rate between PC and NPC corals not treated with venetoclax (p = 0.000) but no difference in corals treated with venetoclax (p = 0.464) pointing to the crucial role of pBcl-2 in acclimatization and coral bleaching. Graphs show mean values with standard error bars, n = 5.
Figure 5