title: AUREOCHROME1a-mediated induction of the diatom-specific cyclin dsCYC2 controls the onset of cell division in diatoms (Phaeodactylum tricornutum).
abstract: Cell division in photosynthetic organisms is tightly regulated by light. Although the light dependency of the onset of the cell cycle has been well characterized in various phototrophs, little is known about the cellular signaling cascades connecting light perception to cell cycle activation and progression. Here, we demonstrate that diatom-specific cyclin 2 (dsCYC2) in Phaeodactylum tricornutum displays a transcriptional peak within 15 min after light exposure, long before the onset of cell division. The product of dsCYC2 binds to the cyclin-dependent kinase CDKA1 and can complement G1 cyclin-deficient yeast. Consistent with the role of dsCYC2 in controlling a G1-to-S light-dependent cell cycle checkpoint, dsCYC2 silencing decreases the rate of cell division in diatoms exposed to light-dark cycles but not to constant light. Transcriptional induction of dsCYC2 is triggered by blue light in a fluence rate-dependent manner. Consistent with this, dsCYC2 is a transcriptional target of the blue light sensor AUREOCHROME1a, which functions synergistically with the basic leucine zipper (bZIP) transcription factor bZIP10 to induce dsCYC2 transcription. The functional characterization of a cyclin whose transcription is controlled by light and whose activity connects light signaling to cell cycle progression contributes significantly to our understanding of the molecular mechanisms underlying light-dependent cell cycle onset in diatoms.
authors.affiliation: Protistology and Aquatic Ecology, Department of Biology, Ghent University, B-9000 Gent, Belgium.
authors.forename: Marie J J
authors.initials: MJ
authors.lastname: Huysman
authors.forename: Antonio E
authors.initials: AE
authors.lastname: Fortunato
authors.forename: Michiel
authors.initials: M
authors.lastname: Matthijs
authors.forename: Benjamin Schellenberger
authors.initials: BS
authors.lastname: Costa
authors.forename: Rudy
authors.initials: R
authors.lastname: Vanderhaeghen
authors.forename: Hilde
authors.initials: H
authors.lastname: Van den Daele
authors.forename: Matthias
authors.initials: M
authors.lastname: Sachse
authors.forename: Dirk
authors.initials: D
authors.lastname: Inzé
authors.forename: Chris
authors.initials: C
authors.lastname: Bowler
authors.forename: Peter G
authors.initials: PG
authors.lastname: Kroth
authors.forename: Christian
authors.initials: C
authors.lastname: Wilhelm
authors.forename: Angela
authors.initials: A
authors.lastname: Falciatore
authors.forename: Wim
authors.initials: W
authors.lastname: Vyverman
authors.forename: Lieven
authors.initials: L
authors.lastname: De Veylder
mesh_terms: D020418:Algal Proteins / Q000235:genetics / Q000378:metabolism; D002455:Cell Division; D016213:Cyclins / Q000235:genetics* / Q000378:metabolism; D003624:Darkness; D017377:Diatoms / Q000166:cytology / Q000235:genetics* / Q000502:physiology / Q000528:radiation effects; D005786:Gene Expression Regulation; D005816:Genetic Complementation Test; D008027:Light; D008954:Models, Biological; D009154:Mutation; D010788:Photosynthesis; D011401:Promoter Regions, Genetic; D014176:Protein Biosynthesis; D015398:Signal Transduction; D014158:Transcription, Genetic
chemical_list: D020418:Algal Proteins; D016213:Cyclins