title: Gene expression signatures of energetic acclimatisation in the reef building coral Acropora millepora.
abstract: BACKGROUND
  Understanding the mechanisms by which natural populations cope with environmental stress is paramount to predict their persistence in the face of escalating anthropogenic impacts. Reef-building corals are increasingly exposed to local and global stressors that alter nutritional status causing reduced fitness and mortality, however, these responses can vary considerably across species and populations.
  
  
  RESULTS
  We compare the expression of 22 coral host genes in individuals from an inshore and an offshore reef location using quantitative Reverse Transcription-PCR (qRT-PCR) over the course of 26 days following translocation into a shaded, filtered seawater environment. Declines in lipid content and PSII activity of the algal endosymbionts (Symbiodinium ITS-1 type C2) over the course of the experiment indicated that heterotrophic uptake and photosynthesis were limited, creating nutritional deprivation conditions. Regulation of coral host genes involved in metabolism, CO2 transport and oxidative stress could be detected already after five days, whereas PSII activity took twice as long to respond. Opposing expression trajectories of Tgl, which releases fatty acids from the triacylglycerol storage, and Dgat1, which catalyses the formation of triglycerides, indicate that the decline in lipid content can be attributed, at least in part, by mobilisation of triacylglycerol stores. Corals from the inshore location had initially higher lipid content and showed consistently elevated expression levels of two genes involved in metabolism (aldehyde dehydrogenase) and calcification (carbonic anhydrase).
  
  
  CONCLUSIONS
  Coral host gene expression adjusts rapidly upon change in nutritional conditions, and therefore can serve as an early signature of imminent coral stress. Consistent gene expression differences between populations indicate that corals acclimatize and/or adapt to local environments. Our results set the stage for analysis of these processes in natural coral populations, to better understand the responses of coral communities to global climate change and to develop more efficient management strategies.
authors.affiliation: Climate Change and Ocean Acidification Team, Australian Institute of Marine Science, Townsville, Queensland, Australia. l.bay@aims.gov.au
authors.forename: Line K
authors.initials: LK
authors.lastname: Bay
authors.forename: Aurélie
authors.initials: A
authors.lastname: Guérécheau
authors.forename: Nikos
authors.initials: N
authors.lastname: Andreakis
authors.forename: Karin E
authors.initials: KE
authors.lastname: Ulstrup
authors.forename: Mikhail V
authors.initials: MV
authors.lastname: Matz
mesh_terms: D000064:Acclimatization / Q000235:genetics* / Q000502:physiology; D000444:Aldehyde Dehydrogenase / Q000235:genetics / Q000378:metabolism; D000818:Animals; D037421:Anthozoa / Q000235:genetics* / Q000469:parasitology / Q000502:physiology; D002256:Carbonic Anhydrases / Q000235:genetics / Q000378:metabolism; D016000:Cluster Analysis; D057894:Coral Reefs; D051048:Diacylglycerol O-Acyltransferase / Q000235:genetics / Q000378:metabolism; D004141:Dinoflagellida / Q000378:metabolism / Q000502:physiology; D017753:Ecosystem; D006790:Host-Parasite Interactions; D008055:Lipids / Q000096:biosynthesis; D045332:Photosystem II Protein Complex / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012623:Seawater; D013559:Symbiosis; D059467:Transcriptome
chemical_list: D008055:Lipids; D045332:Photosystem II Protein Complex; D000444:Aldehyde Dehydrogenase; D051048:Diacylglycerol O-Acyltransferase; D002256:Carbonic Anhydrases