Intracellular K+ sensing of SKOR, a Shaker-type K+ channel from Arabidopsis

Plant J. 2006 Apr;46(2):260-8. doi: 10.1111/j.1365-313X.2006.02689.x.

Abstract

Most K+ channels in plants are structurally classified into the Shaker family named after the shaker K+ channel in Drosophila. Plant K+ channels function in many physiological processes including osmotic regulation and K+ nutrition. An outwardly rectifying K+ channel, SKOR, mediates the delivery of K+ from stelar cells to the xylem in the roots, a critical step in the long-distance distribution of K+ from roots to the upper parts of the plant. Here we report that SKOR channel activity is strictly dependent on intracellular K+ concentrations. Activation by K+ did not affect the kinetics of voltage dependence in SKOR, indicating that a voltage-independent gating mechanism underlies the K+ sensing process. Further analysis showed that the C-terminal non-transmembrane region of the SKOR protein was required for this sensing process. The intracellular K+ sensing mechanism couples SKOR activity to K+ nutrition status in the 'source cells', thereby establishing a supply-based unloading system for the regulation of K+ distribution.

MeSH terms

  • Animals
  • Arabidopsis / physiology*
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / physiology*
  • Cloning, Molecular
  • Electrophysiology
  • Male
  • Membrane Potentials
  • Oocytes / physiology
  • Patch-Clamp Techniques
  • Potassium / physiology
  • Shaker Superfamily of Potassium Channels / genetics
  • Shaker Superfamily of Potassium Channels / physiology*
  • Xenopus / physiology

Substances

  • Arabidopsis Proteins
  • SKOR protein, Arabidopsis
  • Shaker Superfamily of Potassium Channels
  • Potassium