title: Phosphorylation of Serine 186 of bHLH Transcription Factor SPEECHLESS Promotes Stomatal Development in Arabidopsis.
abstract: The initiation of stomatal lineage and subsequent asymmetric divisions in Arabidopsis require the activity of the basic helix-loop-helix transcription factor SPEECHLESS (SPCH). It has been shown that SPCH controls entry into the stomatal lineage as a substrate either of the MITOGEN-ACTIVATED PROTEIN KINASE (MAPK) cascade or GSK3-like kinase BRASSINOSTEROID INSENSITIVE 2 (BIN2). Here we show that three serine residues of SPCH appear to be the primary phosphorylation targets of Cyclin-Dependent Kinases A;1 (CDKA;1) in vitro, and among them Serine 186 plays a crucial role in stomatal formation. Expression of an SPCH construct harboring a mutation that results in phosphorylation deficiencies on Serine 186 residue failed to rescue stomatal defects in spch null mutants. Expression of a phosphorylation-mimic mutant SPCH(S186D) complemented stomatal production defects in the transgenic lines harboring the targeted expression of dominant-negative CDKA;1.N146. Therefore, in addition to MAPK- and BIN2-mediated phosphorylation on SPCH, phosphorylation at Serine 186 is positively required for SPCH function in regulating stomatal development.
authors: Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, 20 Nanxincun, Beijing 100093, China.
authors: Ke-Zhen
authors: KZ
authors: Yang
authors: Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, 20 Nanxincun, Beijing 100093, China.
authors: Min
authors: M
authors: Jiang
authors: Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, 20 Nanxincun, Beijing 100093, China.
authors: Ming
authors: M
authors: Wang
authors: Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, 20 Nanxincun, Beijing 100093, China.
authors: Shan
authors: S
authors: Xue
authors: Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, 20 Nanxincun, Beijing 100093, China.
authors: Ling-Ling
authors: LL
authors: Zhu
authors: Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, 20 Nanxincun, Beijing 100093, China.
authors: Hong-Zhe
authors: HZ
authors: Wang
authors: Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, 20 Nanxincun, Beijing 100093, China.
authors: Jun-Jie
authors: JJ
authors: Zou
authors: Department of Botany, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada.
authors: Eun-Kyoung
authors: EK
authors: Lee
authors: Department of Botany, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada.
authors: Fred
authors: F
authors: Sack
authors: Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, 20 Nanxincun, Beijing 100093, China. Electronic address: lejie@ibcas.ac.cn.
authors: Jie
authors: J
authors: Le
mesh_terms: D020816:Amino Acid Motifs; D017360:Arabidopsis / Q000737:chemistry / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D051792:Basic Helix-Loop-Helix Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D010766:Phosphorylation; D054046:Plant Stomata / Q000737:chemistry / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D012694:Serine / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; D012694:Serine; C517480:SPEECHLESS protein, Arabidopsis
keywords: Arabidopsis; development; phosphorylation; stomata; transcription factor