A novel chloride channel in Vicia faba guard cell vacuoles activated by the serine/threonine kinase, CDPK

Zhen Ming Pei, John M. Ward, Jeffrey F. Harper, Julian I. Schroeder

Research output: Contribution to journalArticlepeer-review

140 Scopus citations

Abstract

Calcium-Dependent Protein Kinases (CDPKs) in higher plants contain a C-terminal calmodulin-like regulatory domain. Little is known regarding physiological CDPK targets. Both kinase activity and multiple Ca2+-dependent signaling pathways have been implicated in the control of stomatal guard cell movements. To determine whether CDPK or other protein kinases could have a role in guard cell signaling, purified and recombinant kinases were applied to Vicia faba guard cell vacuoles during patch-clamp experiments. CDPK activated novel vacuolar chloride (VCL) and malate conductances in guard cells. Activation was dependent on both Ca2+ and ATP. Furthermore, VCL activation occurred in the absence of Ca2+ using a Ca2+-independent, constitutively active, CDPK* mutant. Protein kinase A showed weaker activation (22% as compared with CDPK). Current reversals in whole vacuole recordings shifted with the Nernst potential for Cl- and vanished in glutamate. Single channel recordings showed a CDPK-activated 34 ± 5 pS Cl- channel. VCL channels were activated at physiological potentials enabling Cl- uptake into vacuoles. VCL channels may provide a previously unidentified, but necessary, pathway for anion uptake into vacuoles required for stomatal opening. CDPK-activated VCL currents were also observed in red beet vacuoles suggesting that these channels may provide a more general mechanism for kinase-dependent anion uptake.

Original languageEnglish (US)
Pages (from-to)6564-6574
Number of pages11
JournalEMBO Journal
Volume15
Issue number23
DOIs
StatePublished - Dec 2 1996

Keywords

  • Cl channel
  • Cytosolic Ca
  • Protein kinase
  • Signal transduction
  • Stomata

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