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Cyclin‐dependent kinase activity maintains the shoot apical meristem cells in an undifferentiated state
Authors:Tarik Gaamouche  Carmem‐Lara de O Manes  Dorota Kwiatkowska  Barbara Berckmans  Rachel Koumproglou  Sara Maes  Tom Beeckman  Teva Vernoux  John H Doonan  Jan Traas  Dirk Inzé  Lieven De Veylder
Institution:1. Department of Plant Systems Biology, VIB, 9052 Gent, Belgium;2. Department of Plant Biotechnology and Genetics, Ghent University, 9052 Gent, Belgium;3. Present address: Université Pierre et Marie Curie, Unité Mixte de Recherche 7621, Océanographie Microbienne, Observatoire Océanologique, 66651 Banyuls sur Mer, France.;4. Department of Biophysics and Morphogenesis of Plants, University of Silesia, 40‐032 Katowice, Poland;5. John Innes Centre, Norwich Research Park, Colney, Norwich, NR4 7UH, UK;6. Laboratoire de Reproduction et Dévelopement des Plantes, Institut National de la Recherche Agronomique, 69364 Lyon Cedex 07, France
Abstract:As the shoot apex produces most of the cells that comprise the aerial part of the plant, perfect orchestration between cell division rates and fate specification is essential for normal organ formation and plant development. However, the inter‐dependence of cell‐cycle machinery and meristem‐organizing genes is still poorly understood. To investigate this mechanism, we specifically inhibited the cell‐cycle machinery in the shoot apex by expression of a dominant negative allele of the A‐type cyclin‐dependent kinase (CDK) CDKA;1 in meristematic cells. A decrease in the cell division rate within the SHOOT MERISTEMLESS domain of the shoot apex dramatically affected plant growth and development. Within the meristem, a subset of cells was driven into the differentiation pathway, as indicated by premature cell expansion and onset of endo‐reduplication. Although the meristem structure and expression patterns of the meristem identity genes were maintained in most plants, the reduced CDK activity caused splitting of the meristem in some plants. This phenotype correlated with the level of expression of the dominant negative CDKA;1 allele. Therefore, we propose a threshold model in which the effect of the cell‐cycle machinery on meristem organization is determined by the level of CDK activity.
Keywords:Arabidopsis thaliana  cell cycle  CDK  endo‐reduplication  organogenesis  shoot apical meristem
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