title: Brassinosteroid-regulated GSK3/Shaggy-like kinases phosphorylate mitogen-activated protein (MAP) kinase kinases, which control stomata development in Arabidopsis thaliana.
abstract: Brassinosteroids (BRs) are steroid hormones that coordinate fundamental developmental programs in plants. In this study we show that in addition to the well established roles of BRs in regulating cell elongation and cell division events, BRs also govern cell fate decisions during stomata development in Arabidopsis thaliana. In wild-type A. thaliana, stomatal distribution follows the one-cell spacing rule; that is, adjacent stomata are spaced by at least one intervening pavement cell. This rule is interrupted in BR-deficient and BR signaling-deficient A. thaliana mutants, resulting in clustered stomata. We demonstrate that BIN2 and its homologues, GSK3/Shaggy-like kinases involved in BR signaling, can phosphorylate the MAPK kinases MKK4 and MKK5, which are members of the MAPK module YODA-MKK4/5-MPK3/6 that controls stomata development and patterning. BIN2 phosphorylates a GSK3/Shaggy-like kinase recognition motif in MKK4, which reduces MKK4 activity against its substrate MPK6 in vitro. In vivo we show that MKK4 and MKK5 act downstream of BR signaling because their overexpression rescued stomata patterning defects in BR-deficient plants. A model is proposed in which GSK3-mediated phosphorylation of MKK4 and MKK5 enables for a dynamic integration of endogenous or environmental cues signaled by BRs into cell fate decisions governed by the YODA-MKK4/5-MPK3/6 module.
authors: Institute Biotechnology of Horticultural Crops, Center for Life and Food Sciences Weihenstephan, Technische Universität München, D-85354 Freising, Germany; Max F. Perutz Laboratories, University of Vienna, A-1030 Vienna, Austria.
authors: Mamoona
authors: M
authors: Khan
authors: Institute Biotechnology of Horticultural Crops, Center for Life and Food Sciences Weihenstephan, Technische Universität München, D-85354 Freising, Germany; Max F. Perutz Laboratories, University of Vienna, A-1030 Vienna, Austria.
authors: Wilfried
authors: W
authors: Rozhon
authors: Unité de Recherche en Génomique Végétale Plant Genomics 2, rue Gaston Cremieux, 91057 Evry, France.
authors: Jean
authors: J
authors: Bigeard
authors: Laboratoire Analyse et Modélisation pour la Biologie et l'Environnement, CNRS, University of Evry, Boulevard François Mitterrand, 91025 Evry, France.
authors: Delphine
authors: D
authors: Pflieger
authors: Max F. Perutz Laboratories, University of Vienna, A-1030 Vienna, Austria.
authors: Sigrid
authors: S
authors: Husar
authors: Department for Applied Genetics and Cell Biology, University of Natural Resources and Applied Life Sciences, A-1190 Vienna, Austria.
authors: Andrea
authors: A
authors: Pitzschke
authors: Department of Molecular Systems Biology, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria.
authors: Markus
authors: M
authors: Teige
authors: Gregor Mendel Institute of Molecular Plant Biology, Austrian Academy of Sciences, A-1030 Vienna, Austria.
authors: Claudia
authors: C
authors: Jonak
authors: Unité de Recherche en Génomique Végétale Plant Genomics 2, rue Gaston Cremieux, 91057 Evry, France; College of Science, King Saud University, P. O. Box 2455, Riyadh 11451, Saudi Arabia.
authors: Heribert
authors: H
authors: Hirt
authors: Institute Biotechnology of Horticultural Crops, Center for Life and Food Sciences Weihenstephan, Technische Universität München, D-85354 Freising, Germany; Max F. Perutz Laboratories, University of Vienna, A-1030 Vienna, Austria. Electronic address: brigitte.poppenberger@wzw.tum.de.
authors: Brigitte
authors: B
authors: Poppenberger
mesh_terms: D017360:Arabidopsis / Q000378:metabolism*; D060406:Brassinosteroids / Q000378:metabolism*; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D005982:Glutathione Transferase / Q000378:metabolism; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism*; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism*; D008954:Models, Biological; D008957:Models, Genetic; D010766:Phosphorylation; D054046:Plant Stomata / Q000378:metabolism*; D030821:Plants, Genetically Modified; D011994:Recombinant Proteins / Q000378:metabolism; D015398:Signal Transduction; D013256:Steroids / Q000378:metabolism
chemical_list: D060406:Brassinosteroids; D011994:Recombinant Proteins; D013256:Steroids; D005982:Glutathione Transferase; D038362:Glycogen Synthase Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases