Phosphorylation of the inward rectifying potassium channel KAT1 by ABR kinase in Vicia guard cells

Izumi C. Mori, Nobuyuki Uozumi, Shoshi Muto

Research output: Contribution to journalArticlepeer-review

46 Citations (Scopus)


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.

Original languageEnglish
Pages (from-to)850-856
Number of pages7
JournalPlant and Cell Physiology
Issue number7
Publication statusPublished - 2000
Externally publishedYes


  • ABA
  • Phosphorylation
  • Potassium Channel
  • Protein Kinase
  • Stomata
  • Vicia faba

ASJC Scopus subject areas

  • Physiology
  • Plant Science
  • Cell Biology


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