title: A genome-wide survey of photoreceptor and circadian genes in the coral, Acropora digitifera.
abstract: Corals exhibit circadian behaviors, but little is known about the molecular mechanisms underlying the regulation of these behaviors. We surveyed the recently decoded genome of the coral, Acropora digitifera, for photoreceptor and circadian genes, using molecular phylogenetic analyses. Our search for photoreceptor genes yielded seven opsin and three cryptochrome genes. Two genes from each family likely underwent tandem duplication in the coral lineage. We also found the following A. digitifera orthologs to Drosophila and mammalian circadian clock genes: four clock, one bmal/cycle, three pdp1-like, one creb/atf, one sgg/zw3, two ck2alpha, one dco (csnk1d/cnsk1e), one slim/BTRC, and one grinl. No vrille, rev-ervα/nr1d1, bhlh2, vpac2, adcyap1, or adcyaplr1 orthologs were found. Intriguingly, in spite of an extensive survey, we also failed to find homologs of period and timeless, although we did find one timeout gene. In addition, the coral genes were compared to orthologous genes in the sea anemone, Nematostella vectensis. Thus, the coral and sea anemone genomes share a similar repertoire of circadian clock genes, although A. digitifera contains more clock genes and fewer photoreceptor genes than N. vectensis. This suggests that the circadian clock system was established in a common ancestor of corals and sea anemones, and was diversified by tandem gene duplications and the loss of paralogous genes in each lineage. It will be interesting to determine how the coral circadian clock functions without period.
authors.affiliation: Marine Genomics Unit, Okinawa Institute of Science and Technology, Onna, Okinawa 904-0495, Japan. eiichi@oist.jp
authors.forename: Eiichi
authors.initials: E
authors.lastname: Shoguchi
authors.forename: Makiko
authors.initials: M
authors.lastname: Tanaka
authors.forename: Chuya
authors.initials: C
authors.lastname: Shinzato
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kawashima
authors.forename: Nori
authors.initials: N
authors.lastname: Satoh
mesh_terms: D000818:Animals; D037421:Anthozoa / Q000235:genetics*; D002874:Chromosome Mapping; D056925:Circadian Rhythm Signaling Peptides and Proteins / Q000235:genetics*; D056931:Cryptochromes / Q000235:genetics*; D005786:Gene Expression Regulation; D016678:Genome; D055355:Opsins / Q000235:genetics*; D010802:Phylogeny; D012689:Sequence Homology, Nucleic Acid
chemical_list: D056925:Circadian Rhythm Signaling Peptides and Proteins; D056931:Cryptochromes; D055355:Opsins