Phosphorylation of the inward-rectifying potassium channel KAT1 by ABR kinase in Vicia guard cells.
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.
Mori
I C
IC
Nagoya University Bioscience Center, Nagoya University, Chikusa, Japan.
Uozumi
N
N
Muto
S
S
D000040:Abscisic Acid / Q000378:metabolism; D029681:Arabidopsis Proteins; D001483:Base Sequence; D002118:Calcium / Q000378:metabolism; D017931:DNA Primers; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D010766:Phosphorylation; D010940:Plant Proteins; D015221:Potassium Channels / Q000378:metabolism*; D024661:Potassium Channels, Inwardly Rectifying; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D019685:Rosales / Q000166:cytology / Q000378:metabolism*
D029681:Arabidopsis Proteins; D017931:DNA Primers; D004791:Enzyme Inhibitors; C501210:KAT1 protein, Arabidopsis; D010940:Plant Proteins; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D047428:Protein Kinase Inhibitors; D011994:Recombinant Proteins; D000040:Abscisic Acid; D011494:Protein Kinases; D002118:Calcium