title: Mapping carbon fate during bleaching in a model cnidarian symbiosis: the application of13C metabolomics.
abstract: Coral bleaching is a major threat to the persistence of coral reefs. Yet we lack detailed knowledge of the metabolic interactions that determine symbiosis function and bleaching-induced change. We mapped autotrophic carbon fate within the free metabolite pools of both partners of a model cnidarian-dinoflagellate symbiosis (Aiptasia-Symbiodinium) during exposure to thermal stress via the stable isotope tracer (13C bicarbonate), coupled to GC-MS. Symbiont photodamage and pronounced bleaching coincided with substantial increases in the turnover of non13C-labelled pools in the dinoflagellate (lipid and starch store catabolism). However,13C enrichment of multiple compounds associated with ongoing carbon fixation and de novo biosynthesis pathways was maintained (glucose, fatty acid and lipogenesis intermediates). Minimal change was also observed in host pools of13C-enriched glucose (a major symbiont-derived mobile product). However, host pathways downstream showed altered carbon fate and/or pool composition, with accumulation of compatible solutes and nonenzymic antioxidant precursors. In hospite symbionts continue to provide mobile products to the host, but at a significant cost to themselves, necessitating the mobilization of energy stores. These data highlight the need to further elucidate the role of metabolic interactions between symbiotic partners, during the process of thermal acclimation and coral bleaching.
authors.affiliation: School of Biological Sciences, Victoria University of Wellington, PO Box 600, Wellington, 6140, New Zealand.
authors.forename: Katie E
authors.initials: KE
authors.lastname: Hillyer
authors.affiliation: School of Health and Biomedical Sciences, RMIT University, PO Box 71, Bundoora, 3083, Vic, Australia.
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Dias
authors.affiliation: Metabolomics Australia, School of BioSciences, The University of Melbourne, Parkville, Vic, 3010, Australia.
authors.forename: Adrian
authors.initials: A
authors.lastname: Lutz
authors.affiliation: Metabolomics Australia, School of BioSciences, The University of Melbourne, Parkville, Vic, 3010, Australia.
authors.forename: Ute
authors.initials: U
authors.lastname: Roessner
authors.affiliation: School of Biological Sciences, Victoria University of Wellington, PO Box 600, Wellington, 6140, New Zealand.
authors.forename: Simon K
authors.initials: SK
authors.lastname: Davy
mesh_terms: D000818:Animals; D002244:Carbon / Q000378:metabolism*; D002247:Carbon Isotopes / Q000032:analysis; D004141:Dinoflagellida / Q000378:metabolism* / Q000502:physiology; D008401:Gas Chromatography-Mass Spectrometry; D006358:Hot Temperature; D007553:Isotope Labeling; D055432:Metabolomics / Q000379:methods*; D012615:Sea Anemones / Q000378:metabolism* / Q000502:physiology; D013312:Stress, Physiological; D013559:Symbiosis / Q000502:physiology
chemical_list: D002247:Carbon Isotopes; D002244:Carbon
keywords: 
  Aiptasia
  ; 
  Symbiodinium
  ; GC-MS; coral bleaching; metabolomics; photodamage; stable isotope tracer; translocation