Whole-genome duplication in an algal symbiont bolsters coral heat tolerance | Science Advances
Abstract
The algal endosymbiont
Durusdinium trenchii
enhances the resilience of coral reefs under thermal stress.
D. trenchii
can live freely or in endosymbiosis, and the analysis of genetic markers suggests that this species has undergone whole-genome duplication (WGD). However, the evolutionary mechanisms that underpin the thermotolerance of this species are largely unknown. Here, we present genome assemblies for two
D. trenchii
isolates, confirm WGD in these taxa, and examine how selection has shaped the duplicated genome regions using gene expression data. We assess how the free-living versus endosymbiotic lifestyles have contributed to the retention and divergence of duplicated genes, and how these processes have enhanced the thermotolerance of
D. trenchii
. Our combined results suggest that lifestyle is the driver of post-WGD evolution in
D. trenchii
, with the free-living phase being the most important, followed by endosymbiosis. Adaptations to both lifestyles likely enabled
D. trenchii
to provide enhanced thermal stress protection to the host coral.