Journal Article

Phosphorylation of the Inward-Rectifying Potassium Channel KAT1 by ABR Kinase in <i>Vicia </i>Guard Cells

Izumi C. Mori, Nobuyuki Uozumi and Shoshi Muto

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 41, issue 7, pages 850-856
Published in print July 2000 | ISSN: 0032-0781
Published online July 2000 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcd003
Phosphorylation of the Inward-Rectifying Potassium Channel KAT1 by ABR Kinase in Vicia Guard Cells

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  • Biochemistry
  • Molecular and Cell Biology
  • Plant Sciences and Forestry

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A 48-kDa protein kinase was detected in Vicia faba guard cell protoplasts by an in-gel protein kinase assay using a recombinant peptide (KAT1C) of the carboxyl-terminus of an inward-rectifying voltage-dependent K+ channel cloned from Arabidopsis thaliana, KAT1. This protein kinase (ABR* kinase) was activated by pretreatment of guard cell protoplasts with ABA, but not by pretreatment with IAA, 2,4-D, kinetin or GA3. The activation of ABR* kinase was dependent on the time and concentration of ABA. The kinase activity was sensitive to staurosporine and K-252a, protein kinase inhibitors, and insensitive to Ca2+. No ABR* kinase activity was detected in mesophyll cell protoplasts. These characteristics of ABR* kinase are consistent with those of an ABA-responsive protein kinase (ABR kinase) reported previously [Mori and Muto (1997), Plant Physiol. 113: 833]. These results indicate that ABR* kinase phosphorylates the inward-rectifying K+ channel in response to treatment of stomatal guard cells with ABA. The data reported here provide evidence that this ABA-responsive protein kinase may promote ABA signaling by directly phosphorylating guard cell ion channels.

Keywords: Key words: ABA — Phosphorylation — Potassium channel — Protein kinase — Stomata — Vicia faba.; Abbreviations: AAPK, ABA-activated protein kinase; ABR kinase, ABA-responsive protein kinase; CDPK, calmodulin-domain-like protein kinase; GCPs, guard cell protoplasts; IK,in, inward-rectifying K+ current; IPTG, β-d-thiogalactopyranoside; K+in channel, inward-rectifying K+ channel; K+out channel, outward-rectifying K+ channel; MCPs, mesophyll cell protoplasts.

Journal Article.  4649 words.  Illustrated.

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

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