title: ABA-activated SnRK2 protein kinase is required for dehydration stress signaling in Arabidopsis.
abstract: Protein phosphorylation has pivotal roles in ABA and osmotic stress signaling in higher plants. Two protein phosphatase genes, ABI1 and ABI2, are known to regulate these signaling pathways in Arabidopsis: The identity of ABA-activated protein kinases required for the ABA signaling, however, remains to be elucidated. Here we demonstrate that two protein kinases, p44 and p42, were activated by ABA in Arabidopsis T87 cultured cells, and at least one protein kinase, p44, was activated not only by ABA but also by low humidity in Arabidopsis plants. Analysis of T-DNA knockout mutants and biochemical analysis using a specific antibody revealed that the p44 is encoded by a SnRK2-type protein kinase gene, SRK2E. The srk2e mutation resulted in a wilty phenotype mainly due to loss of stomatal closure in response to a rapid humidity decrease. ABA-inducible gene expression of rd22 and rd29B was suppressed in srk2e. These results show that SRK2E plays an important role in ABA signaling in response to water stress.
authors.affiliation: Laboratory of Plant Molecular Biology, RIKEN Tsukuba Institute, 3-1-1, Koyadai, Tsukuba, Ibaraki, 305-0074 Japan.
authors.forename: Riichiro
authors.initials: R
authors.lastname: Yoshida
authors.forename: Tokunori
authors.initials: T
authors.lastname: Hobo
authors.forename: Kazuya
authors.initials: K
authors.lastname: Ichimura
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Mizoguchi
authors.forename: Fuminori
authors.initials: F
authors.lastname: Takahashi
authors.forename: Jose
authors.initials: J
authors.lastname: Aronso
authors.forename: Joseph R
authors.initials: JR
authors.lastname: Ecker
authors.forename: Kazuo
authors.initials: K
authors.lastname: Shinozaki
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology*; D017360:Arabidopsis / Q000201:enzymology* / Q000502:physiology; D029681:Arabidopsis Proteins; D002460:Cell Line; D002478:Cells, Cultured; D004789:Enzyme Activation / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D019950:Mitogen-Activated Protein Kinase 1 / Q000187:drug effects / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000187:drug effects / Q000378:metabolism; D009154:Mutation; D009997:Osmotic Pressure / Q000187:drug effects; D010641:Phenotype; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism; D019441:Plant Epidermis / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D010937:Plant Growth Regulators / Q000494:pharmacology*; D017346:Protein Serine-Threonine Kinases / Q000187:drug effects / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects* / Q000502:physiology; D014867:Water / Q000494:pharmacology
chemical_list: D000040:Abscisic Acid; D029681:Arabidopsis Proteins; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D010749:Phosphoprotein Phosphatases; D010937:Plant Growth Regulators; D017346:Protein Serine-Threonine Kinases; D014867:Water; C490996:At5g01820 protein, Arabidopsis; C087434:ABI1 protein, Arabidopsis; C106443:ABI2 protein, Arabidopsis