Journal Article

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

Kazuo Nakashima, Yasunari Fujita, Norihito Kanamori, Takeshi Katagiri, Taishi Umezawa, Satoshi Kidokoro, Kyonoshin Maruyama, Takuya Yoshida, Kanako Ishiyama, Masatomo Kobayashi, Kazuo Shinozaki and Kazuko Yamaguchi-Shinozaki

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 50, issue 7, pages 1345-1363
Published in print July 2009 | ISSN: 0032-0781
Published online June 2009 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcp083
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

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  • Molecular and Cell Biology
  • Plant Sciences and Forestry

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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

Journal Article.  10751 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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