title: Atypical regulation of a green lineage-specific B-type cyclin-dependent kinase.
abstract: Cyclin-dependent kinases (CDKs) are the main regulators of cell cycle progression in eukaryotes. The role and regulation of canonical CDKs, such as the yeast (Saccharomyces cerevisiae) Cdc2 or plant CDKA, have been extensively characterized. However, the function of the plant-specific CDKB is not as well understood. Besides being involved in cell cycle control, Arabidopsis (Arabidopsis thaliana) CDKB would integrate developmental processes to cell cycle progression. We investigated the role of CDKB in Ostreococcus (Ostreococcus tauri), a unicellular green algae with a minimal set of cell cycle genes. In this primitive alga, at the basis of the green lineage, CDKB has integrated two levels of regulations: It is regulated by Tyr phosphorylation like cdc2/CDKA and at the level of synthesis-like B-type CDKs. Furthermore, Ostreococcus CDKB/cyclin B accounts for the main peak of mitotic activity, and CDKB is able to rescue a yeast cdc28(ts) mutant. By contrast, Ostreococcus CDKA is not regulated by Tyr phosphorylation, and it exhibits a low and steady-state activity from DNA replication to exit of mitosis. This suggests that from a major role in the control of mitosis in green algae, CDKB has evolved in higher plants to assume other functions outside the cell cycle.
authors.affiliation: Unité Mixte de Recherche 7628 Centre National de la Recherche Scientifique, Université Paris VI, Laboratoire Arago, Modèles en Biologie Cellulaire et Evolutive, BP44, 66651 Banyuls sur Mer, France.
authors.forename: Florence
authors.initials: F
authors.lastname: Corellou
authors.forename: Alain
authors.initials: A
authors.lastname: Camasses
authors.forename: Laetitia
authors.initials: L
authors.lastname: Ligat
authors.forename: Gérard
authors.initials: G
authors.lastname: Peaucellier
authors.forename: François-Yves
authors.initials: FY
authors.lastname: Bouget
mesh_terms: D002453:Cell Cycle; D018844:Cyclin-Dependent Kinases / Q000096:biosynthesis / Q000378:metabolism*; D016213:Cyclins / Q000378:metabolism; D007700:Kinetics; D008938:Mitosis; D019000:Phosphotyrosine / Q000378:metabolism; D059828:Plant Cells; D010944:Plants / Q000201:enzymology*; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000201:enzymology*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism
chemical_list: D016213:Cyclins; D029701:Saccharomyces cerevisiae Proteins; D019000:Phosphotyrosine; D018844:Cyclin-Dependent Kinases