Journal Article

Co-Expression of Calcium-Dependent Protein Kinase with the Inward Rectified Guard Cell K<sup>+</sup> Channel KAT1 Alters Current Parameters in <i>Xenopus laevis</i> Oocytes

Gerald Berkowitz, Xiao Zhang, Richard Mercier, Qiang Leng and Michael Lawton

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 41, issue 6, pages 785-790
Published in print June 2000 | ISSN: 0032-0781
Published online June 2000 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/41.6.785
Co-Expression of Calcium-Dependent Protein Kinase with the Inward Rectified Guard Cell K+ Channel KAT1 Alters Current Parameters in Xenopus laevis Oocytes

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Increased guard cell cytosolic [Ca2+] is known to be involved in signal transduction pathways leading to stomatal closure, and inhibit the inward rectifying guard cell K+ channel KAT1. Guard cell calcium-dependent protein kinase (CDPK) has been shown to phosphorylate KAT1; such phosphorylation is known to modulate other K+ channels involved in signal transduction cascades. The work reported here focused on demonstrating CDPK-dependent inhibition of KAT1 currents. A cDNA encoding soybean CDPK was generated and it's translation product was shown to be functional; demonstrating Ca2+-dependent autophosphorylation and phosphorylation of a target protein. Ion currents were monitored using voltage clamp techniques upon expression of KAT1 in Xenopus laevis oocytes. Coexpression of recombinant CDPK with KAT1 in oocytes altered the kinetics and magnitude of induced K+ currents; at a given hyperpolarizing command voltage, the magnitude of KAT1 currents was reduced and the half-time for channel activation was increased. This finding supports a model of Ca2+-dependent ABA inhibition of inward K+ currents in guard cells as being mediated by CDPK phosphorylation of KAT1.

Keywords: Calcium dependent protein kinase; K+ channel; Signal transduction; Stomatal physiology

Journal Article.  0 words. 

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

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