Plant and Cell Physiology Advance Access originally published online on June 18, 2009
Plant and Cell Physiology 2009 50(7):1345-1363; doi:10.1093/pcp/pcp083
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This article appears in the following Plant and Cell Physiology issue: Special Issue Articles: Omics and Bioinformatics [View the issue table of contents]
Three Arabidopsis SnRK2 Protein Kinases, SRK2D/SnRK2.2, SRK2E/SnRK2.6/OST1 and SRK2I/SnRK2.3, Involved in ABA Signaling are Essential for the Control of Seed Development and Dormancy
1Biological Resources Division, Japan International Research Center for Agricultural Sciences (JIRCAS), Ibaraki, 305-8686 Japan
2Plant Science Center, RIKEN Yokohama Institute, Kanagawa, 230-0045 Japan
3Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, 113-8657 Japan
4Experimental Plant Division, Bioresource Center, RIKEN Tsukuba Institute, Ibaraki, 305-0074 Japan
*Corresponding author: E-mail, kazukoys{at}jircas.affrc.go.jp; Fax, +81-29-838-6643.
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Abstract |
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ABA is an important phytohormone regulating various plant processes, including stress tolerance, seed development and germination. SRK2D/SnRK2.2, SRK2E/SnRK2.6/OST1 and SRK2I/SnRK2.3 are redundant ABA-activated SNF1-related protein kinases 2 (SnRK2s) in Arabidopsis thaliana. We examined the role of these protein kinases in seed development and germination. These SnRK2 proteins were mainly expressed in the nucleus during seed development and germination. The triple mutant (srk2d srk2e srk2i) was sensitive to desiccation and showed severe growth defects during seed development. It exhibited a loss of dormancy and elevated seed ABA content relative to wild-type plants. The severity of these phenotypes was far stronger than that of any single or double SRK2D, SRK2E and SRK2I mutants, including the srk2d srk2i mutant. The triple mutant had greatly reduced phosphorylation activity in in-gel kinase experiments using basic leucine zipper (bZIP) transcription factors including ABI5. Microarray experiments revealed that 48 and 30% of the down-regulated genes in abi5 and abi3 seeds were suppressed in the triple mutant seeds, respectively. Moreover, disruption of the three protein kinases induced global changes in the up-regulation of ABA-repressive gene expression, as well as the down-regulation of ABA-inducible gene expression. These alterations in gene expression result in a loss of dormancy and severe growth defects during seed development. Collectively, these results indicate that SRK2D, SRK2E and SRK2I protein kinases involved in ABA signaling are essential for the control of seed development and dormancy through the extensive control of gene expression.
Keywords: ABA signaling • ABI5 • Arabidopsis thaliana • Dormancy • Seed maturation • SnRK2 protein kinase
Abbreviations: ABI3, ABA-INSENSITIVE3; ABI5, ABA-INSENSITIVE5; ABRE, ABA-responsive element; AREB, ABRE-binding protein; bZIP, basic leucine zipper; DAF, days after flowering; DAI, days after imbibition; GFP, green fluorescent protein; GST, glutathione S-transferase; HSP, heat shock protein; LEA, late embryogenesis abundant; PP2C, protein phosphatase 2C; qRT-PCR, quantitative real-time PCR; SnRK2, SNF1-related protein kinase 2.
(Received May 18, 2009; Accepted June 4, 2009)
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