Ph.D. Dissertation Defense - Xin Wang

Sep 13 2018 03:00 PM - Sep 13 2018 04:00 PM

 TITLE:  Molecular How corals got bones - Comparative genomics reveals the evolution of coral calcification

 ADVISOR:  Professor Manuel Aranda

 DATE:  September 13

 TIME:  3 pm

 LOCATION: Auditorium (level 0) between buildings 4 and 5

BIO: Xin earned his BSc in the agricultural facility of science & Engineering at China Agricultural University, and acquired his Master degree in genomics at Beijing Institute of Genomics, Chinese Academy of Science. Then he firstly joined KAUST as an intern in 2014 and subsequently pursued his Ph.D. in comparative genomics research with Dr. Aranda. His research at KAUST mainly focused on evolutionary mechanisms of coral calcification and adaptations to climate changes using comparative genomics.

ABSTRACT:  Scleractinian corals represent the foundation species of one of the most diverse and productive ecosystem on earth, coral reefs. Corals not only constitute the trophic basis of these ecosystems but also provide essential habitats and shelter for a wide variety of marine species, many of which are commercially relevant. Despite the ecological importance of corals, very little is known about how their soft-bodied ancestor evolved the ability to form a calcified skeleton and became the ecosystem builders they are today.
Corallimorpharia is closely related to reef-building corals but lack the ability to form calcified skeletons. Here we assembled and annotated two draft genomes of the corallimorpharians, Amplexidiscus fenestrafer, and Discosoma sp., and further provided an online interface to facilitate the use of these resources, closing the current evolutionary gap between Actiniaria and Scleractinia. Corallimorpharia has been proposed to be “naked corals” that supposedly lost the ability to calcify in response to increasing ocean acidification during the Cretaceous period around 110 - 132 MYA. However, our broad phylogenomic approach using whole genome data, including phylogenetic analyses of nuclear encoding genes as well as genome-wide presence/absence information and synteny conservation from six hexacorallian species, provides robust evidence that corallimorpharians are a monophyletic sister group of scleractinians, therefore rejecting the “naked coral” hypothesis. Being the closest non-calcifying relative of scleractinian corals, corallimorpharians appear to be the best candidates to understand the evolutionary origin of coral calcification. Molecular divergence analysis of scleractinian coral and Corallimorpharia genes suggests that the soft-bodied ancestor of corals evolved the ability to calcify within approximately 80 million years after the divergence of these two orders. To uncover the molecular basis of coral skeletal formation and growth, we integrate genomic and transcriptomic data as well as skeletal proteomic data and show that gene and domain duplications have been the main evolutionary mechanisms underlying the evolution of calcification in scleractinian corals.