Full-length transcriptome maps of reef-building coral illuminate the molecular basis of calcification, symbiosis, and circadian genes

We sequenced the full-length transcriptomes
of four common and frequently dominant reef-building corals, including
two Robusta clade species, Pocillopora damicornis and Pocillopora verrucosa, and two Complexa
clade species, Acropora muricata and Montipora foliosa, using
the PacBio Sequel II platform. We obtained information on gene
functions, structures and expression profiles.
Among them, a comparative analysis of biomineralization-related genes provided
insights into the molecular basis of coral skeletal density. The
gene expression profiles of the symbiote Symbiodiniaceae were also isolated and
annotated from the holobiont sequence data; these profiles showed more highly
convergent traits related to gene structure and expression level than
those of coral hosts. Interestingly,
we observed that intracellular algal cells share some evolutionary convergence
between intracellular symbiosis in corals and intracellular digestion in
amphioxus. Finally, a phylogenetic
analysis of key circadian clock genes among
27 evolutionarily representative species indicated that there are four key
members in early metazoans, including cry genes; Clock or Npas2; cyc or Arntl; and tim, while per, as the fifth member, occurs in Bilateria.