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First published online May 25, 2007; 10.1104/pp.107.096149 Plant Physiology 144:1360-1369 (2007) © 2007 American Society of Plant Biologists Light-Dependent Regulation of Cell Division in Ostreococcus: Evidence for a Major Transcriptional Input1,[W]Unité Mixte de Recherche 7628 Centre National de la Recherche Scientifique, Université Paris VI, Laboratoire Arago, 66650 Banyuls sur Mer, France (M.M., C.S., L.G., F.C., F.Y.-B.); Faculté de Médecine, OUEST-genopole Transcriptome Platform, IFR 140 GFAS, CS 34317, 35043 Rennes cedex, France (A.M., B.J., R.B., J.M.); Medical Genomics Unit, Molecular Genetics and Biochemistry Department, Hospital Center, 35043 Rennes, France (R.B., J.M.); and Faculté de Médecine, Centre National de la Recherche Scientifique Unité Mixte de Recherche 6061 "Génétique et Développement," Régulation transcriptionnelle et Oncogenèse, Université de Rennes 1, IFR 140 GFAS, CS 34317, 35043 Rennes cedex, France (J.M.)
Cell division often occurs at specific times of the day in animal and photosynthetic organisms. Studies in unicellular photosynthetic algae, such as Chlamydomonas or Euglena, have shown that the photoperiodic control of cell division is mediated through the circadian clock. However, the underlying mechanisms remain unknown. We have studied the molecular basis of light-dependent control of cell division in the unicellular green alga Ostreococcus. We found that cell division obeys a circadian oscillator in Ostreococcus. We provide evidence suggesting that the clock may, at least in part, regulate directly cell division independently of the metabolism. Combined microarray and quantitative real-time reverse transcription-polymerase chain reaction analysis of the main core cell cycle gene expression revealed an extensive transcriptional regulation of cell division by the photoperiod in Ostreococcus. Finally, transcription of the main core cell cycle genes, including cyclins and cyclin-dependent kinases, was shown to be under circadian control in Ostreococcus, suggesting that these genes are potential targets of the circadian clock in the control of cell division.
1 This work was supported by a Centre National de la Recherche Scientifique "Action Thématique d'Intérêt Prioritaire" young investigator fellowship, the "Marine Genomics" European Network of Excellence, and the Groupement d'Intérêt Scientifique "Génomique Marine" programs (to F.-Y.B.), and by grants from the Conseil Régional de Bretagne to OUEST-génopole. The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: François-Yves Bouget (fy.bouget{at}obs-banyuls.fr). [W] The online version of this article contains Web-only data. www.plantphysiol.org/cgi/doi/10.1104/pp.107.096149 * Corresponding author; e-mail fy.bouget{at}obs-banyuls.fr; fax 33468887398. Received January 22, 2007; accepted May 13, 2007; published May 25, 2007.
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