Co-expression of calcium-dependent protein kinase with the inward rectified guard cell K+ channel KAT1 alters current parameters in Xenopus laevis oocytes

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

Research output: Contribution to journalArticlepeer-review

45 Scopus citations

Abstract

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.

Original languageEnglish (US)
Pages (from-to)785-790
Number of pages6
JournalPlant and Cell Physiology
Volume41
Issue number6
DOIs
StatePublished - 2000

All Science Journal Classification (ASJC) codes

  • Physiology
  • Plant Science
  • Cell Biology

Keywords

  • Calcium dependent protein kinase
  • K channel
  • Signal transduction
  • Stomatal physiology

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