title: Transcriptional versus non-transcriptional clocks: a case study in Ostreococcus.
abstract: Circadian rhythms are ubiquitous on earth from cyanobacteria to land plants and animals. Circadian clocks are synchronized to the day/night cycle by environmental factors such as light and temperature. In eukaryotes, clocks rely on complex gene regulatory networks involving transcriptional regulation but also post-transcriptional and post-translational regulations. In multicellular organisms clocks are found at multiple levels from cells to organs and whole organisms, making the study of clock mechanisms more complex. In recent years the picoalga Ostreococcus has emerged as a new circadian model organism thanks to its reduced gene redundancy and its minimalist cellular organization. A simplified version of the "green" plant clock, involving the master clock genes TOC1 and CCA1, has been revealed when the functional genomics and mathematical model approaches were combined. Specific photoreceptors such as a blue light sensing LOV histidine kinase mediate light input to the Ostreococcus clock. Non-transcriptional redox rhythms have also been identified recently in Ostreococcus and human red blood cells. This review highlights the progress made recently in the understanding of circadian clock architecture and function in Ostreococcus in the context of the marine environment.
authors: Sorbonne Universités, Université Pierre et Marie Curie (Paris 06), Observatoire Océanologique, F-66651 Banyuls/Mer, France; Centre National de la Recherche Scientifique, Unité Mixte de Recherche, UMR7621, LOMIC, Laboratoire d'Océanographie Microbienne, F-66651 Banyuls/Mer, France. Electronic address: fy.bouget@obs-banyuls.fr.
authors: François-Yves
authors: FY
authors: Bouget
authors: Laboratoire de Physique des Lasers, Atomes et Molécules, Université Lille 1, CNRS, Unité Mixte de Recherche 8523, Unité de Formation et de Recherche de Physique, Villeneuve d'Ascq, France.
authors: Marc
authors: M
authors: Lefranc
authors: Laboratoire de Physique des Lasers, Atomes et Molécules, Université Lille 1, CNRS, Unité Mixte de Recherche 8523, Unité de Formation et de Recherche de Physique, Villeneuve d'Ascq, France.
authors: Quentin
authors: Q
authors: Thommen
authors: Laboratoire de Physique des Lasers, Atomes et Molécules, Université Lille 1, CNRS, Unité Mixte de Recherche 8523, Unité de Formation et de Recherche de Physique, Villeneuve d'Ascq, France.
authors: Benjamin
authors: B
authors: Pfeuty
authors: Sorbonne Universités, Université Pierre et Marie Curie (Paris 06), Observatoire Océanologique, F-66651 Banyuls/Mer, France; Centre National de la Recherche Scientifique, Unité Mixte de Recherche, UMR7621, LOMIC, Laboratoire d'Océanographie Microbienne, F-66651 Banyuls/Mer, France.
authors: Jean-Claude
authors: JC
authors: Lozano
authors: Sorbonne Universités, Université Pierre et Marie Curie (Paris 06), Observatoire Océanologique, F-66651 Banyuls/Mer, France; Centre National de la Recherche Scientifique, Unité Mixte de Recherche, UMR7621, LOMIC, Laboratoire d'Océanographie Microbienne, F-66651 Banyuls/Mer, France.
authors: Philippe
authors: P
authors: Schatt
authors: Sorbonne Universités, Université Pierre et Marie Curie (Paris 06), Observatoire Océanologique, F-66651 Banyuls/Mer, France; Centre National de la Recherche Scientifique, Unité Mixte de Recherche, UMR7621, LOMIC, Laboratoire d'Océanographie Microbienne, F-66651 Banyuls/Mer, France.
authors: Hugo
authors: H
authors: Botebol
authors: Sorbonne Universités, Université Pierre et Marie Curie (Paris 06), Observatoire Océanologique, F-66651 Banyuls/Mer, France; Centre National de la Recherche Scientifique Unité Mixte de Service, UMS2348, F-66651 Banyuls/Mer, France.
authors: Valérie
authors: V
authors: Vergé
mesh_terms: D001683:Biological Clocks / Q000235:genetics*; D000460:Chlorophyta / Q000235:genetics*; D002940:Circadian Rhythm / Q000235:genetics / Q000502:physiology*; D023281:Genomics / Q000379:methods; D000071677:Histidine Kinase; D008386:Marine Biology; D008954:Models, Biological; D055519:Photoreceptors, Plant / Q000235:genetics*; D011494:Protein Kinases / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics*
chemical_list: D055519:Photoreceptors, Plant; D014157:Transcription Factors; D011494:Protein Kinases; D000071677:Histidine Kinase
keywords: Circadian clock; Marine phytoplankton; Ostreococcus; Photoreceptor; Systems biology