title: Photosynthetic circadian rhythmicity patterns of Symbiodinium, [corrected] the coral endosymbiotic algae.
abstract: Biological clocks are self-sustained endogenous timers that enable organisms (from cyanobacteria to humans) to anticipate daily environmental rhythms, and adjust their physiology and behaviour accordingly. Symbiotic corals play a central role in the creation of biologically rich ecosystems based on mutualistic symbioses between the invertebrate coral and dinoflagellate protists from the genus Symbiodinium. In this study, we experimentally establish that Symbiodinium photosynthesis, both as a free-living unicellular algae and as part of the symbiotic association with the coral Stylophora pistillata, is 'wired' to the circadian clock mechanism with a 'free-run' cycle close to 24 h. Associated photosynthetic pigments also showed rhythmicity under light/dark conditions and under constant light conditions, while the expression of the oxygen-evolving enhancer 1 gene (within photosystem II) coincided with photosynthetically evolved oxygen in Symbiodinium cultures. Thus, circadian regulation of the Symbiodinium photosynthesis is, however, complicated as being linked to the coral/host that have probably profound physiochemical influence on the intracellular environment. The temporal patterns of photosynthesis demonstrated here highlight the physiological complexity and interdependence of the algae circadian clock associated in this symbiosis and the plasticity of algae regulatory mechanisms downstream of the circadian clock.
authors.affiliation: The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 52900, Israel. sorekm@gmail.com
authors.forename: Michal
authors.initials: M
authors.lastname: Sorek
authors.forename: Yosef Z
authors.initials: YZ
authors.lastname: Yacobi
authors.forename: Modi
authors.initials: M
authors.lastname: Roopin
authors.forename: Ilana
authors.initials: I
authors.lastname: Berman-Frank
authors.forename: Oren
authors.initials: O
authors.lastname: Levy
mesh_terms: D020418:Algal Proteins / Q000235:genetics / Q000378:metabolism; D000818:Animals; D037421:Anthozoa / Q000502:physiology*; D002338:Carotenoids / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D002940:Circadian Rhythm; D018076:DNA, Complementary / Q000235:genetics / Q000378:metabolism; D004141:Dinoflagellida / Q000502:physiology*; D008969:Molecular Sequence Data; D010100:Oxygen / Q000378:metabolism; D017440:Photoperiod; D010788:Photosynthesis; D045332:Photosystem II Protein Complex / Q000378:metabolism; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017422:Sequence Analysis, DNA; D013559:Symbiosis
chemical_list: D020418:Algal Proteins; D018076:DNA, Complementary; D045332:Photosystem II Protein Complex; D012333:RNA, Messenger; D002734:Chlorophyll; D002338:Carotenoids; D010100:Oxygen
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