title: A cyclin-dependent kinase-activating kinase regulates differentiation of root initial cells in Arabidopsis.
abstract: Cell division and differentiation continue throughout the plant life cycle without significant loss of control. However, little is known about the mechanisms that allow the continuous development of meristems. Cell division is controlled by a family of cyclin-dependent kinases (CDKs). CDK-activating kinases (CAKs) are known to phosphorylate and activate almost all CDKs and thus may have a crucial role in controlling CDK activities in each cell of the meristems. Here, we show that overexpression of sense or antisense gene for Cak1At in Arabidopsis by using the glucocorticoid-mediated transcriptional induction system resulted in a reduction of CDK activities. After 14-24 h of glucocorticoid treatment, starch granules appeared in columellar initials in the root meristem, and cortical initials were periclinally divided into cortical and endodermal cells. Accumulation of the cyclin beta-glucuronidase fusion protein ceased after 72 h of glucocorticoid treatment. Our results indicate that a change of Cak1At activity leads to differentiation of initial cells, followed by cessation of cell division. Therefore, we propose that differentiation of initial cells is controlled by Cak1At but is maintained independent of cell division.
authors.affiliation: Institute of Molecular and Cellular Biosciences, University of Tokyo, Tokyo 113-0032, Japan. mumede@imcbns.iam.u-tokyo.ac.jp
authors.forename: M
authors.initials: M
authors.lastname: Umeda
authors.forename: C
authors.initials: C
authors.lastname: Umeda-Hara
authors.forename: H
authors.initials: H
authors.lastname: Uchimiya
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000235:genetics / Q000502:physiology*; D029681:Arabidopsis Proteins; D002454:Cell Differentiation; D002455:Cell Division; D003001:Cloning, Molecular; D016213:Cyclins / Q000235:genetics; D016373:DNA, Antisense / Q000235:genetics; D003907:Dexamethasone / Q000494:pharmacology; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D005822:Genetic Vectors; D005938:Glucocorticoids / Q000494:pharmacology; D005966:Glucuronidase / Q000235:genetics; D018519:Meristem / Q000166:cytology; D010766:Phosphorylation; D018517:Plant Roots / Q000166:cytology* / Q000187:drug effects / Q000502:physiology; D030821:Plants, Genetically Modified; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D012231:Rhizobium / Q000235:genetics
chemical_list: D029681:Arabidopsis Proteins; D016213:Cyclins; D016373:DNA, Antisense; D005938:Glucocorticoids; D011993:Recombinant Fusion Proteins; D003907:Dexamethasone; C112244:Cak1at protein, Arabidopsis; D017346:Protein Serine-Threonine Kinases; D005966:Glucuronidase