title: Transcriptomic differences between day and night in Acropora millepora provide new insights into metabolite exchange and light-enhanced calcification in corals.
abstract: The evolutionary success of reef-building corals is often attributed to their symbiotic relationship with photosynthetic dinoflagellates of the genus Symbiodinium, but metabolic interactions between the partners and the molecular bases of light-enhanced calcification (LEC) are not well understood. Here, the metabolic bases of the interaction between the coral Acropora millepora and its dinoflagellate symbiont were investigated by comparing gene expression levels under light and dark conditions at the whole transcriptome level. Among the 497 differentially expressed genes identified, a suite of genes involved in cholesterol transport was found to be upregulated under light conditions, confirming the significance of this compound in the coral symbiosis. Although ion transporters likely to have roles in calcification were not differentially expressed in this study, expression levels of many genes associated with skeletal organic matrix composition and organization were higher in light conditions. This implies that the rate of organic matrix synthesis is one factor limiting calcification at night. Thus, LEC during the day is likely to be a consequence of increases in both matrix synthesis and the supply of precursor molecules as a result of photosynthetic activity.
authors.affiliation: ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Qld, 4811, Australia.
authors.forename: A
authors.initials: A
authors.lastname: Bertucci
authors.affiliation: ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Qld, 4811, Australia.|Evolution, Ecology and Genetics, Research School of Biology, Australian National University, Bldg. 46, Canberra, ACT, 0200, Australia.
authors.forename: S
authors.initials: S
authors.lastname: Forêt
authors.affiliation: ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Qld, 4811, Australia.|Evolution, Ecology and Genetics, Research School of Biology, Australian National University, Bldg. 46, Canberra, ACT, 0200, Australia.
authors.forename: E E
authors.initials: EE
authors.lastname: Ball
authors.affiliation: ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Qld, 4811, Australia.|Comparative Genomics Centre and Department of Molecular and Cell Biology, James Cook University, Townsville, Qld, 4811, Australia.
authors.forename: D J
authors.initials: DJ
authors.lastname: Miller
mesh_terms: D000818:Animals; D037421:Anthozoa / Q000235:genetics* / Q000528:radiation effects; D001315:Australia; D002113:Calcification, Physiologic; D002940:Circadian Rhythm; D004141:Dinoflagellida / Q000502:physiology; D020869:Gene Expression Profiling; D008027:Light; D008969:Molecular Sequence Data; D010788:Photosynthesis; D017423:Sequence Analysis, RNA; D013559:Symbiosis; D059467:Transcriptome
keywords: biomineralization; cholesterol; coral; light-enhanced calcification; organic matrix; symbiosis