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