title: A eukaryotic LOV-histidine kinase with circadian clock function in the picoalga Ostreococcus.
abstract: The marine environment has unique properties of light transmission, with an attenuation of long wavelengths within the first meters of the water column. Marine organisms have therefore evolved specific blue-light receptors such as aureochromes to absorb shorter-wavelength light. Here, we identify and characterize a light, oxygen, or voltage sensing (LOV) containing histidine kinase (LOV-HK) that functions as a new class of eukaryotic blue-light receptor in the pico-phytoplanktonic cell Ostreococcus tauri. This LOV-HK is related to the large family of LOV-HKs found in prokaryotes. Phylogenetic analysis indicates that the LOV domains from LOV-HKs, including O. tauri LOV-HK, and phototropins (phot; plant and green algal LOV serine/threonine kinases) have different evolutionary histories. Photochemical analysis shows that the LOV domain of LOV-HK binds a flavin cofactor and absorbs blue light with a fast photocycle compared with its prokaryotic counterparts. Ostreococcus tauri LOV-HK expression is induced by blue light and is under circadian control. Further, both overexpression and downregulation of LOV-HK result in arrhythmia of the circadian reporter CCA1:Luc under constant blue light. In contrast, photochemical inactivation of O. tauri LOV-HK is without effect, demonstrating its importance for function of the circadian clock under blue light. Overexpression/downregulation of O. tauriLOV-HK alters CCA1 rhythmicity under constant red light, irrespective of LOV-HK's photochemical reactivity, suggesting that O. tauri LOV-HK also participates in regulation of the circadian clock independent of its blue-light-sensing property. Molecular characterization of O. tauri LOV-HK demonstrates that this type of photoreceptor family is not limited to prokaryotes.
authors.affiliation: UPMC Univ Paris 06, CNRS, UMR7621 Laboratoire d'Océanographie Microbienne, Observatoire Océanologique, F-66651, Banyuls-sur-Mer, France.
authors.forename: El-Batoul
authors.initials: el-B
authors.lastname: Djouani-Tahri
authors.forename: John M
authors.initials: JM
authors.lastname: Christie
authors.forename: Sophie
authors.initials: S
authors.lastname: Sanchez-Ferandin
authors.forename: Frédéric
authors.initials: F
authors.lastname: Sanchez
authors.forename: François-Yves
authors.initials: FY
authors.lastname: Bouget
authors.forename: Florence
authors.initials: F
authors.lastname: Corellou
mesh_terms: D000595:Amino Acid Sequence; D000460:Chlorophyta / Q000201:enzymology* / Q000528:radiation effects; D057906:Circadian Clocks; D003001:Cloning, Molecular; D018506:Gene Expression Regulation, Plant; D000071677:Histidine Kinase; D008027:Light; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D055519:Photoreceptors, Plant / Q000378:metabolism*; D010802:Phylogeny; D010839:Phytoplankton / Q000201:enzymology* / Q000235:genetics / Q000528:radiation effects; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism*; D018749:RNA, Plant / Q000235:genetics; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
chemical_list: D055519:Photoreceptors, Plant; D010940:Plant Proteins; D018749:RNA, Plant; D011494:Protein Kinases; D000071677:Histidine Kinase