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Kapuy O, Vinod PK, Bánhegyi G, Novák B. Systems-level feedback regulation of cell cycle transitions in Ostreococcus tauri. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2018; 126:39-46. [PMID: 29499434 DOI: 10.1016/j.plaphy.2018.02.010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2017] [Revised: 02/08/2018] [Accepted: 02/10/2018] [Indexed: 06/08/2023]
Abstract
Ostreococcus tauri is the smallest free-living unicellular organism with one copy of each core cell cycle genes in its genome. There is a growing interest in this green algae due to its evolutionary origin. Since O. tauri is diverged early in the green lineage, relatively close to the ancestral eukaryotic cell, it might hold a key phylogenetic position in the eukaryotic tree of life. In this study, we focus on the regulatory network of its cell division cycle. We propose a mathematical modelling framework to integrate the existing knowledge of cell cycle network of O. tauri. We observe that feedback loop regulation of both G1/S and G2/M transitions in O. tauri is conserved, which can make the transition bistable. This is essential to make the transition irreversible as shown in other eukaryotic organisms. By performing sequence analysis, we also predict the presence of the Greatwall/PP2A pathway in the cell cycle of O. tauri. Since O. tauri cell cycle machinery is conserved, the exploration of the dynamical characteristic of the cell division cycle will help in further understanding the regulation of cell cycle in higher eukaryotes.
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Affiliation(s)
- Orsolya Kapuy
- Semmelweis University, Department of Medical Chemistry, Molecular Biology and Pathobiochemistry, Budapest, Hungary.
| | - P K Vinod
- Centre for Computational Natural Sciences and Bioinformatics, International Institute of Information Technology, Hyderabad, India
| | - Gábor Bánhegyi
- Semmelweis University, Department of Medical Chemistry, Molecular Biology and Pathobiochemistry, Budapest, Hungary
| | - Béla Novák
- University of Oxford, Oxford Centre for Integrative Systems Biology, Oxford, United Kingdom
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2
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Huysman MJJ, Tanaka A, Bowler C, Vyverman W, De Veylder L. Functional characterization of the diatom cyclin-dependent kinase A2 as a mitotic regulator reveals plant-like properties in a non-green lineage. BMC PLANT BIOLOGY 2015; 15:86. [PMID: 25887918 PMCID: PMC4392632 DOI: 10.1186/s12870-015-0469-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2015] [Accepted: 02/26/2015] [Indexed: 06/01/2023]
Abstract
BACKGROUND Cyclin-dependent kinases (CDKs) are crucial regulators of cell cycle progression in eukaryotes. The diatom CDKA2 was originally assigned to the classical A-type CDKs, but its cell cycle phase-specific transcription at the G2-to-M phase transition is typical for plant-specific B-type CDKs. RESULTS Here, we report the functional characterization of CDKA2 from the diatom Phaeodactylum tricornutum. Through a yeast two-hybrid library screen, CDKA2 was found to interact with the G2/M-specific CDK scaffolding factor CKS1. Localization of CDKA2 was found to be nuclear in interphase cells, while in cells undergoing cytokinesis, the signal extended to the cell division plane. In addition, overexpression of CDKA2 induced an overall reduction in the cell growth rate. Expression analysis of cell cycle marker genes in the overexpression lines indicates that this growth reduction is primarily due to a prolongation of the mitotic phase. CONCLUSIONS Our study indicates a role for CDKA2 during cell division in diatoms. The functional characterization of a CDK with clear CDKB properties in a non-green organism questions whether the current definition of B-type CDKs being plant-specific might need revision.
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Affiliation(s)
- Marie J J Huysman
- Department of Plant Systems Biology, Flanders Institute for Biotechnology (VIB), 9052, Ghent, Belgium.
- Department of Plant Systems Biology, VIB, and Bioinformatics, Ghent University, 9052, Ghent, Belgium.
- Protistology and Aquatic Ecology, Department of Biology, Ghent University, 9000, Ghent, Belgium.
- Environmental and Evolutionary Genomics Section, Institut de Biologie de l'Ecole Normale Supérieure, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 8186, Institut National de la Santé et de la Recherche Médicale U1024, Ecole Normale Supérieure, 75230, Paris, Cedex 05, France.
| | - Atsuko Tanaka
- Environmental and Evolutionary Genomics Section, Institut de Biologie de l'Ecole Normale Supérieure, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 8186, Institut National de la Santé et de la Recherche Médicale U1024, Ecole Normale Supérieure, 75230, Paris, Cedex 05, France.
- Current address: Muroran Marine Station, Field Science Center for Northern Biosphere, Hokkaido University, Muroran, Hokkaido, 051-0013, Japan.
| | - Chris Bowler
- Environmental and Evolutionary Genomics Section, Institut de Biologie de l'Ecole Normale Supérieure, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 8186, Institut National de la Santé et de la Recherche Médicale U1024, Ecole Normale Supérieure, 75230, Paris, Cedex 05, France.
| | - Wim Vyverman
- Protistology and Aquatic Ecology, Department of Biology, Ghent University, 9000, Ghent, Belgium.
| | - Lieven De Veylder
- Department of Plant Systems Biology, Flanders Institute for Biotechnology (VIB), 9052, Ghent, Belgium.
- Department of Plant Systems Biology, VIB, and Bioinformatics, Ghent University, 9052, Ghent, Belgium.
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3
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Hindle MM, Martin SF, Noordally ZB, van Ooijen G, Barrios-Llerena ME, Simpson TI, Le Bihan T, Millar AJ. The reduced kinome of Ostreococcus tauri: core eukaryotic signalling components in a tractable model species. BMC Genomics 2014; 15:640. [PMID: 25085202 PMCID: PMC4143559 DOI: 10.1186/1471-2164-15-640] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2014] [Accepted: 07/08/2014] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND The current knowledge of eukaryote signalling originates from phenotypically diverse organisms. There is a pressing need to identify conserved signalling components among eukaryotes, which will lead to the transfer of knowledge across kingdoms. Two useful properties of a eukaryote model for signalling are (1) reduced signalling complexity, and (2) conservation of signalling components. The alga Ostreococcus tauri is described as the smallest free-living eukaryote. With less than 8,000 genes, it represents a highly constrained genomic palette. RESULTS Our survey revealed 133 protein kinases and 34 protein phosphatases (1.7% and 0.4% of the proteome). We conducted phosphoproteomic experiments and constructed domain structures and phylogenies for the catalytic protein-kinases. For each of the major kinases families we review the completeness and divergence of O. tauri representatives in comparison to the well-studied kinomes of the laboratory models Arabidopsis thaliana and Saccharomyces cerevisiae, and of Homo sapiens. Many kinase clades in O. tauri were reduced to a single member, in preference to the loss of family diversity, whereas TKL and ABC1 clades were expanded. We also identified kinases that have been lost in A. thaliana but retained in O. tauri. For three, contrasting eukaryotic pathways - TOR, MAPK, and the circadian clock - we established the subset of conserved components and demonstrate conserved sites of substrate phosphorylation and kinase motifs. CONCLUSIONS We conclude that O. tauri satisfies our two central requirements. Several of its kinases are more closely related to H. sapiens orthologs than S. cerevisiae is to H. sapiens. The greatly reduced kinome of O. tauri is therefore a suitable model for signalling in free-living eukaryotes.
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Affiliation(s)
| | | | | | | | | | | | | | - Andrew J Millar
- SynthSys and School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JD, UK.
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Frazer C, Young PG. Carboxy-terminal phosphorylation sites in Cdc25 contribute to enforcement of the DNA damage and replication checkpoints in fission yeast. Curr Genet 2012; 58:217-34. [PMID: 22806395 DOI: 10.1007/s00294-012-0379-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Revised: 06/14/2012] [Accepted: 07/06/2012] [Indexed: 11/27/2022]
Abstract
In fission yeast and vertebrate cells, Cdc25 phosphatase is the target of checkpoint-mediated response to DNA replication blocks, DNA damage, and extracellular stress. As such, it is a key regulator of cell cycle progress and genomic stability. In fission yeast, phosphorylation of Cdc25 by the checkpoint kinases Cds1 and Chk1 and also Srk1 during stress creates a binding site for the 14-3-3 homolog Rad24; the complex is then exported from the nucleus. Cdc25 contains 12 potential serine/threonine phosphorylation sites that are phosphorylated in vitro by Cds1; 9 reside in the amino terminal half of the protein with the remaining sites are located in the extreme C-terminus. We have previously shown that deletion of the nine amino terminal sites results in degradation of the mutant protein while the checkpoint is enforced by the Mik1 kinase acting on Cdc2 tyrosine-15. Here, we examine the influence of the three C-terminal sites on the negative regulation of Cdc25. These sites are conserved in vertebrates and have been shown to be phosphorylated following DNA damage and replication blocks. We show that these three sites have a role in the negative regulation of Cdc25 following replication arrest, but perhaps more importantly they appear to particularly contribute to regulating the duration, and thus the effectiveness of the arrested state.
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Affiliation(s)
- Corey Frazer
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON, K7L 3N6, Canada
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5
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Spadafora ND, Parfitt D, Marchbank A, Li S, Bruno L, Vaughan R, Nieuwland J, Buchanan-Wollaston V, Herbert RJ, Bitonti MB, Doonan J, Albani D, Prinsen E, Francis D, Rogers HJ. Perturbation of cytokinin and ethylene-signalling pathways explain the strong rooting phenotype exhibited by Arabidopsis expressing the Schizosaccharomyces pombe mitotic inducer, cdc25. BMC PLANT BIOLOGY 2012; 12:45. [PMID: 22452972 PMCID: PMC3362767 DOI: 10.1186/1471-2229-12-45] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2011] [Accepted: 03/27/2012] [Indexed: 05/29/2023]
Abstract
BACKGROUND Entry into mitosis is regulated by cyclin dependent kinases that in turn are phosphoregulated. In most eukaryotes, phosphoregulation is through WEE1 kinase and CDC25 phosphatase. In higher plants a homologous CDC25 gene is unconfirmed and hence the mitotic inducer Schizosaccharomyces pombe (Sp) cdc25 has been used as a tool in transgenic plants to probe cell cycle function. Expression of Spcdc25 in tobacco BY-2 cells accelerates entry into mitosis and depletes cytokinins; in whole plants it stimulates lateral root production. Here we show, for the first time, that alterations to cytokinin and ethylene signaling explain the rooting phenotype elicited by Spcdc25 expression in Arabidopsis. RESULTS Expressing Spcdc25 in Arabidopsis results in increased formation of lateral and adventitious roots, a reduction of primary root width and more isodiametric cells in the root apical meristem (RAM) compared with wild type. Furthermore it stimulates root morphogenesis from hypocotyls when cultured on two way grids of increasing auxin and cytokinin concentrations. Microarray analysis of seedling roots expressing Spcdc25 reveals that expression of 167 genes is changed by > 2-fold. As well as genes related to stress responses and defence, these include 19 genes related to transcriptional regulation and signaling. Amongst these was the up-regulation of genes associated with ethylene synthesis and signaling. Seedlings expressing Spcdc25 produced 2-fold more ethylene than WT and exhibited a significant reduction in hypocotyl length both in darkness or when exposed to 10 ppm ethylene. Furthermore in Spcdc25 expressing plants, the cytokinin receptor AHK3 was down-regulated, and endogenous levels of iPA were reduced whereas endogeous IAA concentrations in the roots increased. CONCLUSIONS We suggest that the reduction in root width and change to a more isodiametric cell phenotype in the RAM in Spcdc25 expressing plants is a response to ethylene over-production. The increased rooting phenotype in Spcdc25 expressing plants is due to an increase in the ratio of endogenous auxin to cytokinin that is known to stimulate an increased rate of lateral root production. Overall, our data reveal important cross talk between cell division and plant growth regulators leading to developmental changes.
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Affiliation(s)
- Natasha D Spadafora
- School of Biosciences, Cardiff University, Cardiff CF10 3AT, UK
- Dipartimento di Ecologia, Università della Calabria, Arcavacata di Rende, Cosenza I-87030, Italy
| | - David Parfitt
- School of Biosciences, Cardiff University, Cardiff CF10 3AT, UK
| | | | - Sherong Li
- School of Biosciences, Cardiff University, Cardiff CF10 3AT, UK
| | - Leonardo Bruno
- Dipartimento di Ecologia, Università della Calabria, Arcavacata di Rende, Cosenza I-87030, Italy
| | - Rhys Vaughan
- School of Biosciences, Cardiff University, Cardiff CF10 3AT, UK
| | | | | | - Robert J Herbert
- Institute of Science and the Environment, University of Worcester, Henwick Grove, Worcester WR2 6AJ, UK
| | - Maria Beatrice Bitonti
- Dipartimento di Ecologia, Università della Calabria, Arcavacata di Rende, Cosenza I-87030, Italy
| | - John Doonan
- Plant Phenomics Centre, Institute of Biological, Environmental and Rural Sciences, Penglais, Aberystwyth University, Ceredigion SY23 3DA, Aberystwyth, UK
| | - Diego Albani
- Department of Botanical, Ecological and Geological Sciences, University of Sassari, Via Piandanna 4, Sassari 07100, Italy
| | - Els Prinsen
- Department of Biology, University of Antwerp, Groenenborgerlaan 171, Antwerp B-2020, Belgium
| | - Dennis Francis
- School of Biosciences, Cardiff University, Cardiff CF10 3AT, UK
| | - Hilary J Rogers
- School of Biosciences, Cardiff University, Cardiff CF10 3AT, UK
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Shotgun proteomic analysis of the unicellular alga Ostreococcus tauri. J Proteomics 2011; 74:2060-70. [DOI: 10.1016/j.jprot.2011.05.028] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2011] [Revised: 05/03/2011] [Accepted: 05/17/2011] [Indexed: 01/02/2023]
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Spadafora ND, Doonan JH, Herbert RJ, Bitonti MB, Wallace E, Rogers HJ, Francis D. Arabidopsis T-DNA insertional lines for CDC25 are hypersensitive to hydroxyurea but not to zeocin or salt stress. ANNALS OF BOTANY 2011; 107:1183-92. [PMID: 20647223 PMCID: PMC3091795 DOI: 10.1093/aob/mcq142] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2010] [Revised: 06/08/2010] [Accepted: 06/09/2010] [Indexed: 05/21/2023]
Abstract
BACKGROUND AND AIMS In yeasts and animals, cyclin-dependent kinases are key regulators of cell cycle progression and are negatively and positively regulated by WEE1 kinase and CDC25 phosphatase, respectively. In higher plants a full-length orthologue of CDC25 has not been isolated but a shorter gene with homology only to the C-terminal catalytic domain is present. The Arabidopis thaliana;CDC25 can act as a phosphatase in vitro. Since in arabidopsis, WEE1 plays an important role in the DNA damage/DNA replication checkpoints, the role of Arath;CDC25 in conditions that induce these checkpoints or induce abiotic stress was tested. Methods arath;cdc25 T-DNA insertion lines, Arath;CDC25 over-expressing lines and wild type were challenged with hydroxyurea (HU) and zeocin, substances that stall DNA replication and damage DNA, respectively, together with an abiotic stressor, NaCl. A molecular and phenotypic assessment was made of all genotypes Key RESULTS There was a null phenotypic response to perturbation of Arath;CDC25 expression under control conditions. However, compared with wild type, the arath;cdc25 T-DNA insertion lines were hypersensitive to HU, whereas the Arath;CDC25 over-expressing lines were relatively insensitive. In particular, the over-expressing lines consistently outgrew the T-DNA insertion lines and wild type when challenged with HU. All genotypes were equally sensitive to zeocin and NaCl. CONCLUSIONS Arath;CDC25 plays a role in overcoming stress imposed by HU, an agent know to induce the DNA replication checkpoint in arabidopsis. However, it could not enhance tolerance to either a zeocin treatment, known to induce DNA damage, or salinity stress.
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Affiliation(s)
- Natasha D. Spadafora
- School of Biosciences, Cardiff University, Main College, Cardiff CF10 3AT, UK
- Institute of Science and the Environment, University of Worcester, Henwick Grove, Worcester WR2 6AJ, UK
| | - John H. Doonan
- Department of Cell Biology, John Innes Centre, Colney Lane, Norwich NR4 7UH, UK
| | - Robert J. Herbert
- Institute of Science and the Environment, University of Worcester, Henwick Grove, Worcester WR2 6AJ, UK
| | - M. Beatrice Bitonti
- Dipartimento di Ecologia, Università della Calabria, Arcavacata di Rende, I-87030 Cosenza, Italy
| | - Emily Wallace
- School of Biosciences, Cardiff University, Main College, Cardiff CF10 3AT, UK
| | - Hilary J. Rogers
- School of Biosciences, Cardiff University, Main College, Cardiff CF10 3AT, UK
| | - Dennis Francis
- School of Biosciences, Cardiff University, Main College, Cardiff CF10 3AT, UK
- For correspondence. E-mail
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8
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Lipavská H, Masková P, Vojvodová P. Regulatory dephosphorylation of CDK at G₂/M in plants: yeast mitotic phosphatase cdc25 induces cytokinin-like effects in transgenic tobacco morphogenesis. ANNALS OF BOTANY 2011; 107:1071-86. [PMID: 21339187 PMCID: PMC3091802 DOI: 10.1093/aob/mcr016] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2010] [Revised: 11/02/2010] [Accepted: 12/03/2010] [Indexed: 05/07/2023]
Abstract
BACKGROUND During the last three decades, the cell cycle and its control by cyclin-dependent kinases (CDKs) have been extensively studied in eukaryotes. This endeavour has produced an overall picture that basic mechanisms seem to be largely conserved among all eukaryotes. The intricate regulation of CDK activities includes, among others, CDK activation by CDC25 phosphatase at G₂/M. In plants, however, studies of this regulation have lagged behind as a plant Cdc25 homologue or other unrelated phosphatase active at G₂/M have not yet been identified. SCOPE Failure to identify a plant mitotic CDK activatory phosphatase led to characterization of the effects of alien cdc25 gene expression in plants. Tobacco, expressing the Schizosaccharomyces pombe mitotic activator gene, Spcdc25, exhibited morphological, developmental and biochemical changes when compared with wild type (WT) and, importantly, increased CDK dephosphorylation at G₂/M. Besides changes in leaf shape, internode length and root development, in day-neutral tobacco there was dramatically earlier onset of flowering with a disturbed acropetal floral capacity gradient typical of WT. In vitro, de novo organ formation revealed substantially earlier and more abundant formation of shoot primordia on Spcdc25 tobacco stem segments grown on shoot-inducing media when compared with WT. Moreover, in contrast to WT, stem segments from transgenic plants formed shoots even without application of exogenous growth regulator. Spcdc25-expressing BY-2 cells exhibited a reduced mitotic cell size due to a shortening of the G₂ phase together with high activity of cyclin-dependent kinase, NtCDKB1, in early S-phase, S/G₂ and early M-phase. Spcdc25-expressing tobacco ('Samsun') cell suspension cultures showed a clustered, more circular, cell phenotype compared with chains of elongated WT cells, and increased content of starch and soluble sugars. Taken together, Spcdc25 expression had cytokinin-like effects on the characteristics studied, although determination of endogenous cytokinin levels revealed a dramatic decrease in Spcdc25 transgenics. CONCLUSIONS The data gained using the plants expressing yeast mitotic activator, Spcdc25, clearly argue for the existence and importance of activatory dephosphorylation at G₂/M transition and its interaction with cytokinin signalling in plants. The observed cytokinin-like effects of Spcdc25 expression are consistent with the concept of interaction between cell cycle regulators and phytohormones during plant development. The G₂/M control of the plant cell cycle, however, remains an elusive issue as doubts persist about the mode of activatory dephosphorylation, which in other eukaryotes is provided by Cdc25 phosphatase serving as a final all-or-nothing mitosis regulator.
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Affiliation(s)
- Helena Lipavská
- Department of Experimental Plant Biology, Faculty of Science, Charles University in Prague, Viničná 5, Prague 2, Czech Republic.
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9
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Abstract
BACKGROUND The complex events of mitosis rely on precise timing and on immaculate preparation for their success, but the G₂/M transition in the plant cell cycle is currently steeped in controversy and alternative models. SCOPE In this brief review, the regulation of the G₂/M transition in plants is commented on. The extent to which the G₂/M transition is phosphoregulated by WEE1 kinase and CDC25 phosphatase, as exemplified in yeasts and animals, is discussed together with an alternative model that excludes these proteins from this transition. Arabidopsis T-DNA insertional lines for WEE1 and CDC25 that develop normally prompted the latter model. An argument is then presented that environmental stress is the norm for higher plants in temperate conditions. If so, the repressive role that WEE1 has under checkpoint conditions might be part of the normal cell cycle for many proliferative plant cells. Arabidopsis CDC25 can function as either a phosphatase or an arsenate reductase and recent evidence suggests that cdc25 knockouts are hypersensitive to hydroxyurea, a drug that induces the DNA-replication checkpoint. That other data show a null response of these knockouts to hydroxyurea leads to an airing of the controversy surrounding the enigmatic plant CDC25 at the G₂/M transition.
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Affiliation(s)
- Dennis Francis
- School of Biosciences, Cardiff University, Main Building, Cardiff, UK.
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10
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Suchomelová-Mašková P, Novák O, Lipavská H. Tobacco cells transformed with the fission yeast Spcdc25 mitotic inducer display growth and morphological characteristics as well as starch and sugar status evocable by cytokinin application. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2008; 46:673-684. [PMID: 18550380 DOI: 10.1016/j.plaphy.2008.04.017] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2007] [Indexed: 05/26/2023]
Abstract
In plants, the G2/M control of cell cycle remains an elusive issue as doubts persist about activatory dephosphorylation--in other eukaryotes provided by CDC25 phosphatase and serving as a final all-or-nothing mitosis regulator. We report on the effects of tobacco (Nicotiana tabacum L., cv. Samsun) transformation with fission yeast (Schizosaccharomyces pombe) cdc25 (Spcdc25) on cell characteristics. Transformed cell suspension cultures showed higher dry mass accumulation during the exponential phase and clustered more circular cell phenotypes compared to chains of elongated WT cells. Similar cell parameters, as in the transformants, can be induced in WT by cytokinins. Spcdc25 cells, after cytokinin treatment, showed giant cell clusters and growth inhibition. In addition, Spcdc25 expression led to altered carbohydrate status: increased starch and soluble sugars with higher sucrose:hexoses ratio, inducible in WT by cytokinin treatment. Taken together, the Spcdc25 transformation had a cytokinin-like effect on studied characteristics. However, endogenous cytokinin determination revealed markedly lower cytokinin levels in Spcdc25 transformants. This indicates that the cells sense Spcdc25 expression as an increased cytokinin availability, manifested by changed cell morphology, and in consequence decrease endogenous cytokinin levels. Clearly, the results on cell growth and morphology are consistent with the model of G2/M control including cytokinin-regulated activatory dephosphorylation. Nevertheless, no clear link is obvious between Spcdc25 transformation and carbohydrate status and thus the observed cytokinin-like effect on carbohydrate levels poses a problem. Hence, we propose that Spcdc25-induced higher CDK(s) activity at G2/M generates a signal-modifying carbohydrate metabolism to meet high energy and C demands of forthcoming cell division.
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Affiliation(s)
- Petra Suchomelová-Mašková
- Department of Plant Physiology, Faculty of Science, Charles University in Prague, Viničná 5, 128 44 Prague 2, Czech Republic
| | - Ondřej Novák
- Laboratory of Growth Regulators, Palacký University & Institute of Experimental Botany, Academy of Sciences of the Czech Republic, Šlechtitelů 11, Olomouc, Czech Republic
| | - Helena Lipavská
- Department of Plant Physiology, Faculty of Science, Charles University in Prague, Viničná 5, 128 44 Prague 2, Czech Republic
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11
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Abstract
The basic components of the plant cell cycle are G1 (postmitotic interphase), S-phase (DNA synthesis phase), G2 (premitotic interphase) and mitosis/cytokinesis. Proliferating cells are phosphoregulated by cyclin-dependent protein kinases (CDKs). Plant D-type cyclins are sensors of the G0 to G1 transition, and are also important for G2/M. At G1/S, the S-phase transcription factor, E2F, is released from inhibitory retinoblastoma protein. Negative regulation of G1 events is through KRPs (Kip-related proteins). Plant S-phase genes are similar to animal ones, but timing of expression can be different (e.g. CDC6 at the start of S-phase) and functional evidence is limited. At G2/M, A-type and the unique B-type CDKs when bound to A, B and D cyclins, drive cells into division; they are negatively regulated by ICK1/2 and perhaps also by WEE1 kinase. In Arabidopsis, a putative CDC25 lacks a regulatory domain. Mitosis depends on correct temporal activity of CDKs, Aurora kinases and anaphase promotion complex; CDK-cyclin B activity beyond metaphase is catastrophic. Endoreduplication (re-replication of DNA in the absence of mitosis) is characterized by E2F expression and down-regulation of mitotic cyclins. Some cell size data support, whilst others negate, the idea of cell size having an impact on development.
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Affiliation(s)
- Dennis Francis
- School of Biosciences, Cardiff University, PO Box 915, Cardiff CF10 3TL, UK
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12
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Polit JT, Kazmierczak A. Okadaic acid (1 microM) accelerates S phase and mitosis but inhibits heterochromatin replication and metaphase anaphase transition in Vicia faba meristem cells. JOURNAL OF EXPERIMENTAL BOTANY 2007; 58:2785-97. [PMID: 17609530 DOI: 10.1093/jxb/erm148] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Protein kinases and phosphatases are the foremost agents which take part in cell cycle regulation in both plants and other eukaryotes. Protein kinases are a very well examined group of proteins with respect to chemical structure and function. Nowadays protein phosphatases, including PP1 and PP2A belonging to the PSP family, are the focus of interest. Okadaic acid (OA) which is a specific inhibitor of protein phosphatase activity is widely used to study them. In the present research, the involvement of OA-sensitive phosphatases in the regulation of progression of the plant cell cycle was analysed (in planta) using Vicia faba root meristems synchronized with hydroxyurea and divided into five series. Each series was treated with 1 muM OA for 3 h for different time periods corresponding to the consecutive cell cycle phases. The results showed that in the OA-treated cells DNA replication and mitosis began earlier than in the control cells, since G(1) and G(2) phases were significantly shorter and the H1 histone kinases activity was higher. Moreover, autoradiography and morphological analyses of mitotic figures revealed that the OA-treated cells entered mitosis before the end of heterochromatin replication. An immunocytochemical search showed that earlier initiation of S phase in the OA-treated cells correlated with more abundant phosphorylation of Rb-like protein in comparison with the control cells. OA also induced significant condensation of metaphase chromosomes and blocked metaphase-anaphase transition.
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Affiliation(s)
- Justyna Teresa Polit
- Department of Cytophysiology, University of Łódź, 90-231 Łódź, ul. Pilarskiego 14, Poland.
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13
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Abstract
Cell cycle regulation is of pivotal importance for plant growth and development. Although plant cell division shares basic mechanisms with all eukaryotes, plants have evolved novel molecules orchestrating the cell cycle. Some regulatory proteins, such as cyclins and inhibitors of cyclin-dependent kinases, are particularly numerous in plants, possibly reflecting the remarkable ability of plants to modulate their postembryonic development. Many plant cells also can continue DNA replication in the absence of mitosis, a process known as endoreduplication, causing polyploidy. Here, we review the molecular mechanisms that regulate cell division and endoreduplication and we discuss our understanding, albeit very limited, on how the cell cycle is integrated with plant development.
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Affiliation(s)
- Dirk Inzé
- Department of Plant Systems Biology, Flanders Interuniversity Institute for Biotechnology (VIB), Ghent University, Technologiepark 927, B-9052 Gent, Belgium.
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Corellou F, Camasses A, Ligat L, Peaucellier G, Bouget FY. Atypical regulation of a green lineage-specific B-type cyclin-dependent kinase. PLANT PHYSIOLOGY 2005; 138:1627-36. [PMID: 15965018 PMCID: PMC1176432 DOI: 10.1104/pp.105.059626] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
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.
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Affiliation(s)
- Florence Corellou
- 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
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15
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Bothwell JHF, Ng CKY. The evolution of Ca2+ signalling in photosynthetic eukaryotes. THE NEW PHYTOLOGIST 2005; 166:21-38. [PMID: 15760348 DOI: 10.1111/j.1469-8137.2004.01312.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
It is likely that cytosolic Ca2+ elevations have played a part in eukaryotic signal transduction for about the last 2 Gyr, being mediated by a group of molecules which are collectively known as the [Ca2+]cyt signalling toolkit. Different eukaryotes often display strikingly similar [Ca2+]cyt signalling elevations, which may reflect conservation of toolkit components (homology) or similar constraints acting on different toolkits (homoplasy). Certain toolkit components, which are presumably ancestral, are shared by plants and animals, but some components are unique to photosynthetic organisms. We propose that the structure of modern plant [Ca2+]cyt signalling toolkits may be explained by their modular adaptation from earlier pathways.
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Affiliation(s)
- John H F Bothwell
- Marine Biological Association of the UK, The Laboratory, Citadel Hill, Plymouth, PL1 2PB, UK.
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16
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Affiliation(s)
- Arthur R Grossman
- The Carnegie Institution, Department of Plant Biology, Stanford, California 94305, USA.
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17
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Bisova K, Krylov DM, Umen JG. Genome-wide annotation and expression profiling of cell cycle regulatory genes in Chlamydomonas reinhardtii. PLANT PHYSIOLOGY 2005; 137:475-91. [PMID: 15710686 PMCID: PMC1065349 DOI: 10.1104/pp.104.054155] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2004] [Revised: 11/23/2004] [Accepted: 11/25/2004] [Indexed: 05/17/2023]
Abstract
Eukaryotic cell cycles are driven by a set of regulators that have undergone lineage-specific gene loss, duplication, or divergence in different taxa. It is not known to what extent these genomic processes contribute to differences in cell cycle regulatory programs and cell division mechanisms among different taxonomic groups. We have undertaken a genome-wide characterization of the cell cycle genes encoded by Chlamydomonas reinhardtii, a unicellular eukaryote that is part of the green algal/land plant clade. Although Chlamydomonas cells divide by a noncanonical mechanism termed multiple fission, the cell cycle regulatory proteins from Chlamydomonas are remarkably similar to those found in higher plants and metazoans, including the proteins of the RB-E2F pathway that are absent in the fungal kingdom. Unlike in higher plants and vertebrates where cell cycle regulatory genes have undergone extensive duplication, most of the cell cycle regulators in Chlamydomonas have not. The relatively small number of cell cycle genes and growing molecular genetic toolkit position Chlamydomonas to become an important model for higher plant and metazoan cell cycles.
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Affiliation(s)
- Katerina Bisova
- The Salk Institute for Biological Studies, La Jolla, California 92037, USA
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18
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Abstract
In recent years, considerable progress has been made in unraveling the control mechanisms operating on the plant cell cycle and most of the key regulators have now been identified, including cyclin-dependent kinases (CDKs), cyclins, CDK-inhibitory proteins, the WEE kinase and proteins of the retinoblastoma-related protein (RBR)/E2F/DP pathway. The review discusses recent developments in our understanding of the plant cell cycle machinery and highlights the role of the cell cycle in plant development.
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Affiliation(s)
- Dirk Inzé
- Department of Plant Systems Biology, Flanders Interuniversity Institute for Biotechnology (VIB), Ghent University, Gent, Belgium.
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Robbens S, Khadaroo B, Camasses A, Derelle E, Ferraz C, Inzé D, Van de Peer Y, Moreau H. Genome-wide analysis of core cell cycle genes in the unicellular green alga Ostreococcus tauri. Mol Biol Evol 2004; 22:589-97. [PMID: 15537805 DOI: 10.1093/molbev/msi044] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The cell cycle has been extensively studied in various organisms, and the recent access to an overwhelming amount of genomic data has given birth to a new integrated approach called comparative genomics. Comparing the cell cycle across species shows that its regulation is evolutionarily conserved; the best-known example is the pivotal role of cyclin-dependent kinases in all the eukaryotic lineages hitherto investigated. Interestingly, the molecular network associated with the activity of the CDK-cyclin complexes is also evolutionarily conserved, thus, defining a core cell cycle set of genes together with lineage-specific adaptations. In this paper, we describe the core cell cycle genes of Ostreococcus tauri, the smallest free-living eukaryotic cell having a minimal cellular organization with a nucleus, a single chloroplast, and only one mitochondrion. This unicellular marine green alga, which has diverged at the base of the green lineage, shows the minimal yet complete set of core cell cycle genes described to date. It has only one homolog of CDKA, CDKB, CDKD, cyclin A, cyclin B, cyclin D, cyclin H, Cks, Rb, E2F, DP, DEL, Cdc25, and Wee1. We have also added the APC and SCF E3 ligases to the core cell cycle gene set. We discuss the potential of genome-wide analysis in the identification of divergent orthologs of cell cycle genes in different lineages by mining the genomes of evolutionarily important and strategic organisms.
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Affiliation(s)
- Steven Robbens
- Université Paris VI, Laboratoire Arago, Modèles en Biologie Cellulaire et Evolutive, Banyuls sur Mer, France
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20
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Ral JP, Derelle E, Ferraz C, Wattebled F, Farinas B, Corellou F, Buléon A, Slomianny MC, Delvalle D, d'Hulst C, Rombauts S, Moreau H, Ball S. Starch division and partitioning. A mechanism for granule propagation and maintenance in the picophytoplanktonic green alga Ostreococcus tauri. PLANT PHYSIOLOGY 2004; 136:3333-40. [PMID: 15448195 PMCID: PMC523392 DOI: 10.1104/pp.104.044131] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2004] [Revised: 05/11/2004] [Accepted: 05/11/2004] [Indexed: 05/20/2023]
Abstract
Whereas Glc is stored in small-sized hydrosoluble glycogen particles in archaea, eubacteria, fungi, and animal cells, photosynthetic eukaryotes have resorted to building starch, which is composed of several distinct polysaccharide fractions packed into a highly organized semicrystalline granule. In plants, both the initiation of polysaccharide synthesis and the nucleation mechanism leading to formation of new starch granules are currently not understood. Ostreococcus tauri, a unicellular green alga of the Prasinophyceae family, defines the tiniest eukaryote with one of the smallest genomes. We show that it accumulates a single starch granule at the chloroplast center by using the same pathway as higher plants. At the time of plastid division, we observe elongation of the starch and division into two daughter structures that are partitioned in each newly formed chloroplast. These observations suggest that in this system the information required to initiate crystalline polysaccharide growth of a new granule is contained within the preexisting polysaccharide structure and the design of the plastid division machinery.
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Affiliation(s)
- Jean-Philippe Ral
- Laboratoire de Chimie Biologique Unité Mixte de Recherche 8576 du Centre National de la Recherche Scientifique, Université des Sciences et Technologies de Lille, 59655 Villeneuve d'Ascq cedex, France
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