An ancient genome duplication in the speciose reef-building coral genus, Acropora
Whole-genome duplication (WGD) has been recognized as a significant evolutionary force in the origin and diversification of vertebrates, plants, and other organisms. Acropora, one of the most speciose reef-building coral genera, responsible for creating spectacular but increasingly threatened marine ecosystems, is suspected to have originated by polyploidy, yet there is no genetic evidence to support this hypothesis. Using comprehensive phylogenomic and comparative genomic approaches, we analyzed five Acropora genomes and an Astreopora genome (Scleractinia: Acroporidae) to show that a WGD event likely occurred between 27.9 and 35.7 Million years ago (Mya) in the most recent common ancestor of Acropora, concurrent with a massive worldwide coral extinction. We found that duplicated genes became highly enriched in gene regulation functions, some of which are involved in stress responses. The different functional clusters of duplicated genes are related to the divergence of gene expression patterns during development. Some gene duplications of proteinaceous toxins were generated by WGD in Acropora compared with other Cnidarian species. Collectively, this study provides evidence for an ancient WGD event in corals and it helps to explain the origin and diversification of Acropora.