title: Metabolite profiling of symbiont and host during thermal stress and bleaching in a model cnidarian-dinoflagellate symbiosis.
abstract: Bleaching (dinoflagellate symbiont loss) is one of the greatest threats facing coral reefs. The functional cnidarian-dinoflagellate symbiosis, which forms coral reefs, is based on the bi-directional exchange of nutrients. During thermal stress this exchange breaks down; however, major gaps remain in our understanding of the roles of free metabolite pools in symbiosis and homeostasis. In this study we applied gas chromatography-mass spectrometry (GC-MS) to explore thermally induced changes in intracellular pools of amino and non-amino organic acids in each partner of the model sea anemone Aiptasia sp. and its dinoflagellate symbiont. Elevated temperatures (32 °C for 6 days) resulted in symbiont photoinhibition and bleaching. Thermal stress induced distinct changes in the metabolite profiles of both partners, associated with alterations to central metabolism, oxidative state, cell structure, biosynthesis and signalling. Principally, we detected elevated pools of polyunsaturated fatty acids (PUFAs) in the symbiont, indicative of modifications to lipogenesis/lysis, membrane structure and nitrogen assimilation. In contrast, reductions of multiple PUFAs were detected in host pools, indicative of increased metabolism, peroxidation and/or reduced translocation of these groups. Accumulations of glycolysis intermediates were also observed in both partners, associated with photoinhibition and downstream reductions in carbohydrate metabolism. Correspondingly, we detected accumulations of amino acids and intermediate groups in both partners, with roles in gluconeogenesis and acclimation responses to oxidative stress. These data further our understanding of cellular responses to thermal stress in the symbiosis and generate hypotheses relating to the secondary roles of a number of compounds in homeostasis and heat-stress resistance.
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: Beatson Institute for Cancer Research, Garscube Estate, Switchback Road, Bearsden, Glasgow G61 1BD, UK.
authors.forename: Sergey
authors.initials: S
authors.lastname: Tumanov
authors.affiliation: Metabolomics Laboratory, School of Biological Sciences, The University of Auckland, Private Bag 92019 Auckland Mail Centre, Auckland 1142, New Zealand.
authors.forename: Silas
authors.initials: S
authors.lastname: Villas-Bôas
authors.affiliation: School of Biological Sciences, Victoria University of Wellington, PO Box 600, Wellington 6140, New Zealand simon.davy@vuw.ac.nz.
authors.forename: Simon K
authors.initials: SK
authors.lastname: Davy
mesh_terms: D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D004141:Dinoflagellida / Q000378:metabolism*; D005231:Fatty Acids, Unsaturated / Q000378:metabolism; D008401:Gas Chromatography-Mass Spectrometry; D006019:Glycolysis; D006358:Hot Temperature; D050155:Lipogenesis; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D010788:Photosynthesis; D012615:Sea Anemones / Q000378:metabolism*; D013312:Stress, Physiological; D013559:Symbiosis
chemical_list: D000596:Amino Acids; D005231:Fatty Acids, Unsaturated
keywords: Aiptasia; Coral; GC-MS; Photoinhibition; Symbiodinium