Three SnRK2 protein kinases are the main positive regulators of abscisic acid signaling in response to water stress in Arabidopsis

Plant Cell Physiol. 2009 Dec;50(12):2123-32. doi: 10.1093/pcp/pcp147.

Abstract

Responses to water stress are thought to be mediated by transcriptional regulation of gene expression via reversible protein phosphorylation events. Previously, we reported that bZIP (basic-domain leucine zipper)-type AREB/ABF (ABA-responsive element-binding protein/factor) transcription factors are involved in ABA signaling under water stress conditions in Arabidopsis. The AREB1 protein is phosphorylated in vitro by ABA-activated SNF1-related protein kinase 2s (SnRK2s) such as SRK2D/SnRK2.2, SRK2E/SnRK2.6 and SRK2I/SnRK2.3 (SRK2D/E/I). Consistent with this, we now show that SRK2D/E/I and AREB1 co-localize and interact in nuclei in planta. Our results show that unlike srk2d, srk2e and srk2i single and double mutants, srk2d srk2e srk2i (srk2d/e/i) triple mutants exhibit greatly reduced tolerance to drought stress and highly enhanced insensitivity to ABA. Under water stress conditions, ABA- and water stress-dependent gene expression, including that of transcription factors, is globally and drastically impaired, and jasmonic acid (JA)-responsive and flowering genes are up-regulated in srk2d/e/i triple mutants, but not in other single and double mutants. The down-regulated genes in srk2d/e/i and areb/abf triple mutants largely overlap in ABA-dependent expression, supporting the view that SRK2D/E/I regulate AREB/ABFs in ABA signaling in response to water stress. Almost all dehydration-responsive LEA (late embryogenesis abundant) protein genes and group-A PP2C (protein phosphatase 2C) genes are strongly down-regulated in the srk2d/e/i triple mutants. Further, our data show that these group-A PP2Cs, such as HAI1 and ABI1, interact with SRK2D. Together, our results indicate that SRK2D/E/I function as main positive regulators, and suggest that ABA signaling is controlled by the dual modulation of SRK2D/E/I and group-A PP2Cs.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Abscisic Acid / metabolism*
  • Arabidopsis / enzymology*
  • Arabidopsis / genetics
  • Arabidopsis / growth & development
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism*
  • Basic-Leucine Zipper Transcription Factors / metabolism
  • Cyclopentanes / metabolism
  • Dehydration / metabolism*
  • Gene Expression Profiling
  • Gene Expression Regulation, Plant
  • Mutagenesis, Insertional
  • Mutation
  • Oligonucleotide Array Sequence Analysis
  • Oxylipins / metabolism
  • Phosphoprotein Phosphatases / metabolism
  • Plants, Genetically Modified / enzymology
  • Plants, Genetically Modified / genetics
  • Protein Phosphatase 2C
  • Protein-Serine-Threonine Kinases / genetics
  • Protein-Serine-Threonine Kinases / metabolism*
  • Water / metabolism

Substances

  • AREB1 protein, Arabidopsis
  • Arabidopsis Proteins
  • Basic-Leucine Zipper Transcription Factors
  • Cyclopentanes
  • Oxylipins
  • SnRK2 protein, Arabidopsis
  • Water
  • jasmonic acid
  • Abscisic Acid
  • Protein-Serine-Threonine Kinases
  • Phosphoprotein Phosphatases
  • Protein Phosphatase 2C