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

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.

• Authors: Yasunari Fujita, Kazuo Nakashima, Takuya Yoshida, Takeshi Katagiri, Satoshi Kidokoro, Norihito Kanamori, Taishi Umezawa, Miki Fujita, Kyonoshin Maruyama, Kanako Ishiyama, Masatomo Kobayashi, Shoko Nakasone, Kohji Yamada, Takuya Ito, Kazuo Shinozaki, Kazuko Yamaguchi-Shinozaki
• Journal: Plant & cell physiology (Plant Cell Physiol) Vol. 50 Issue 12 Pg. 2123-32 (Dec 2009) ISSN: 1471-9053 [Electronic] Japan
• PMID: 19880399 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• 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

Topics

• Abscisic Acid (metabolism)
• Arabidopsis (enzymology, genetics, growth & development)
• Arabidopsis Proteins (genetics, 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, genetics)
• Protein Phosphatase 2C
• Protein Serine-Threonine Kinases (genetics, metabolism)
• Water (metabolism)