Identification of features regulating OST1 kinase activity and OST1 function in guard cells

被引:203
作者
Belin, Christophe [1 ]
de Franco, Pierre-Olivier
Bourbousse, Clara
Chaignepain, Stephane
Schmitter, Jean-Marie
Vavasseur, Alain
Giraudat, Jerome
Barbier-Brygoo, Helene
Thomine, Sebastien
机构
[1] CNRS, Inst Sci Vegetal, F-91198 Gif Sur Yvette, France
[2] Inst Europeen Chim & Biol, F-33607 Pessac, France
[3] Lab Echanges Membranaires & Signalisat, Direct Sci Vivant, Commiss Energie Atom, F-13108 St Paul Les Durance, France
关键词
D O I
10.1104/pp.106.079327
中图分类号
Q94 [植物学];
学科分类号
071001 ;
摘要
The phytohormone abscisic acid (ABA) mediates drought responses in plants and, in particular, triggers stomatal closure. Snf1-related kinase 2 (SnRK2) proteins from several plant species have been implicated in ABA-signaling pathways. In Arabidopsis ( Arabidopsis thaliana) guard cells, OPEN STOMATA 1 (OST1)/SRK2E/SnRK2-6 is a critical positive regulator of ABA signal transduction. A better understanding of the mechanisms responsible for SnRK2 protein kinase activation is thus a major goal toward understanding ABA signal transduction. Here, we report successful purification of OST1 produced in Escherichia coli: The protein is active and autophosphorylates. Using mass spectrometry, we identified five target residues of autophosphorylation in recombinant OST1. Sequence analysis delineates two conserved boxes located in the carboxy-terminal moiety of OST1 after the catalytic domain: the SnRK2-specific box (glutamine-303 to proline-318) and the ABA-specific box (leucine-333 to methionine-362). Site-directed mutagenesis and serial deletions reveal that serine (Ser)-175 in the activation loop and the SnRK2-specific box are critical for the activity of recombinant OST1 kinase. Targeted expression of variants of OST1 kinase in guard cells uncovered additional features that are critical for OST1 function in ABA signaling, although not required for OST1 kinase activity: Ser-7, Ser-18, and Ser-29 and the ABA-specific box. Ser-7, Ser-18, Ser-29, and Ser-43 represent putative targets for regulatory phosphorylation and the ABA-specific box may be a target for the binding of signaling partners in guard cells.
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收藏
页码:1316 / 1327
页数:12
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