Plant and Cell Physiology Supplement
Supplement to Plant and Cell Physiology Vol. 44
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Functional analysis of ABA-activated SnRK2 protein kinase in Arabidopsis
*Riichiro YoshidaTokunori HoboKazuya IchimuraTsuyoshi MizoguchiFuminori TakahashiTaishi UmezawaJose AronsoJoseph R. EckerKazuo Shinozaki
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Pages 399

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Abstract
Protein phosphorylation has pivotal roles in ABA and osmotic stress signaling in higher plants. Two protein phosphatase genes, ABI1 and ABI2, are known to regulate these signaling pathways in Arabidopsis. Here we demonstrate that two protein kinases, p44 and p42, are activated by ABA in Arabidopsis T87 cultured cells, and at least one protein kinase, p44, is activated not only by ABA but also by low-humidity in Arabidopsis plants. Analysis of T-DNA knockout mutants and biochemical analysis using a specific antibody revealed that the p44 is encoded by a SnRK2-type protein kinase gene, SRK2E. The srk2e mutation resulted in a wilty phenotype mainly due to loss of stomatal closure in response to a rapid humidity decrease. ABA-inducible gene expression was suppressed in srk2e. These results show that SRK2E plays an important role in ABA signaling in response to water stress.
Yoshida et al. (2002) Plant Cell Physiol. 43(12) in press
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© 2003 by The Japanese Society of Plant Physiologists
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