Elucidating gene expression adaptation of phylogenetically divergent coral holobionts under heat stress

As coral reefs struggle to survive under climate change, it is crucial to
know whether they have the capacity to withstand changing conditions,
particularly increasing seawater temperatures. Thermal tolerance requires
the integrative response of the different components of the coral
holobiont (coral host, algal photosymbiont, and associated microbiome).
Here, using a controlled thermal stress experiment across three divergent
Caribbean coral species, we attempt to dissect holobiont member
metatranscriptome responses from coral taxa with different sensitivities
to heat stress and use phylogenetic ANOVA to study the evolution of gene
expression adaptation. We show that coral response to heat stress is a
complex trait derived from multiple interactions among holobiont members.
We identify host and photosymbiont genes that exhibit lineage-specific
expression level adaptation and uncover potential roles for bacterial
associates in supplementing the metabolic needs of the coral-photosymbiont
duo during heat stress. Our results stress the importance of integrative
and comparative approaches across a wide range of species to better
understand coral survival under the predicted rise in sea surface
temperatures.