title: Assessment of metabolic modulation in free-living versus endosymbiotic Symbiodinium using synchrotron radiation-based infrared microspectroscopy.
abstract: The endosymbiotic relationship between coral hosts and dinoflagellates of the genus Symbiodinium is critical for the growth and productivity of coral reef ecosystems. Here, synchrotron radiation-based infrared microspectroscopy was applied to examine metabolite concentration differences between endosymbiotic (within the anemone Aiptasia pulchella) and free-living Symbiodinium over the light-dark cycle. Significant differences in levels of lipids, nitrogenous compounds, polysaccharides and putative cell wall components were documented. Compared with free-living Symbiodinium, total lipids, unsaturated lipids and polysaccharides were relatively enriched in endosymbiotic Symbiodinium during both light and dark photoperiods. Concentrations of cell wall-related metabolites did not vary temporally in endosymbiotic samples; in contrast, the concentrations of these metabolites increased dramatically during the dark photoperiod in free-living samples, possibly reflecting rhythmic cell-wall synthesis related to light-driven cell proliferation. The level of nitrogenous compounds in endosymbiotic cells did not vary greatly across the light-dark cycle and in general was significantly lower than that observed in free-living samples collected during the light. Collectively, these data suggest that nitrogen limitation is a factor that the host cell exploits to induce the biosynthesis of lipids and polysaccharides in endosymbiotic Symbiodinium.
authors.affiliation: Institute of Marine Biotechnology, National Dong Hwa University, Pingtung, Taiwan, Republic of China. pengse@nmmba.gov.tw
authors.forename: Shao-En
authors.initials: SE
authors.lastname: Peng
authors.forename: Chii-Shiarng
authors.initials: CS
authors.lastname: Chen
authors.forename: Yen-Fang
authors.initials: YF
authors.lastname: Song
authors.forename: Huai-Ting
authors.initials: HT
authors.lastname: Huang
authors.forename: Pei-Luen
authors.initials: PL
authors.lastname: Jiang
authors.forename: Wan-Nan U
authors.initials: WN
authors.lastname: Chen
authors.forename: Lee-Shing
authors.initials: LS
authors.lastname: Fang
authors.forename: Yao-Chang
authors.initials: YC
authors.lastname: Lee
mesh_terms: D000818:Animals; D004141:Dinoflagellida / Q000145:classification / Q000502:physiology*; D015591:Microspectrophotometry; D017440:Photoperiod; D012615:Sea Anemones / Q000166:cytology / Q000502:physiology*; D017550:Spectroscopy, Fourier Transform Infrared; D013559:Symbiosis; D017356:Synchrotrons; D013997:Time Factors
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