title: Identification of two protein kinases required for abscisic acid regulation of seed germination, root growth, and gene expression in Arabidopsis.
abstract: Abscisic acid (ABA) is an important phytohormone regulating various plant processes, including seed germination. Although phosphorylation has been suggested to be important, the protein kinases required for ABA signaling during seed germination and seedling growth remain elusive. Here, we show that two protein kinases, SNF1-RELATED PROTEIN KINASE2.2 (SnRK2.2) and SnRK2.3, control responses to ABA in seed germination, dormancy, and seedling growth in Arabidopsis thaliana. A snrk2.2 snrk2.3 double mutant, but not snrk2.2 or snrk2.3 single mutants, showed strong ABA-insensitive phenotypes in seed germination and root growth inhibition. Changes in seed dormancy and ABA-induced Pro accumulation consistent with ABA insensitivity were also observed. The snrk2.2 snrk2.3 double mutant had a greatly reduced level of a 42-kD kinase activity capable of phosphorylating peptides from ABF (for ABA Response Element Binding Factor) transcription factors. ABA-induced expression of several genes whose promoters contain an ABA response element (ABRE) was reduced in snrk2.2 snrk2.3, suggesting that the mechanism of SnRK2.2 and SnRK2.3 action in ABA signaling involves the activation of ABRE-driven gene expression through the phosphorylation of ABFs. Together, these results demonstrate that SnRK2.2 and SnRK2.3 are redundant but key protein kinases that mediate a major part of ABA signaling in Arabidopsis.
authors.affiliation: Center for Plant Cell Biology, Institute for Integrative Genome Biology and Department of Botany and Plant Sciences, University of California, Riverside, California 92521, USA.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Fujii
authors.forename: Paul E
authors.initials: PE
authors.lastname: Verslues
authors.forename: Jian-Kang
authors.initials: JK
authors.lastname: Zhu
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism*; D017360:Arabidopsis / Q000033:anatomy & histology / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D018525:Germination; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D010766:Phosphorylation; D010937:Plant Growth Regulators / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism; D018517:Plant Roots / Q000033:anatomy & histology / Q000254:growth & development*; D030821:Plants, Genetically Modified; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012639:Seeds / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014867:Water / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D007527:Isoenzymes; D010937:Plant Growth Regulators; D011993:Recombinant Fusion Proteins; C492978:SnRK2 protein, Arabidopsis; D014157:Transcription Factors; D014867:Water; D000040:Abscisic Acid; D017346:Protein Serine-Threonine Kinases