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

EMBO J. 1996 Dec 2;15(23):6564-74.


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.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adenosine Triphosphate / metabolism
  • Calcium / metabolism*
  • Cell Movement
  • Chloride Channels / physiology*
  • Cytosol / metabolism
  • Fabaceae / cytology*
  • Fabaceae / physiology*
  • Kinetics
  • Membrane Potentials
  • Patch-Clamp Techniques
  • Plants, Medicinal*
  • Protein-Serine-Threonine Kinases / metabolism*
  • Species Specificity
  • Vacuoles / physiology
  • Vacuoles / ultrastructure
  • Vegetables


  • Chloride Channels
  • Adenosine Triphosphate
  • Protein-Serine-Threonine Kinases
  • Calcium