Intracellular K+ sensing of SKOR, a Shaker-type K+ channel from Arabidopsis.
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.
Liu
Kun
K
Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720, USA.
Li
Legong
L
Luan
Sheng
S
D000818:Animals; D017360:Arabidopsis / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000502:physiology*; D003001:Cloning, Molecular; D004594:Electrophysiology; D008297:Male; D008564:Membrane Potentials; D009865:Oocytes / Q000502:physiology; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000502:physiology; D051637:Shaker Superfamily of Potassium Channels / Q000235:genetics / Q000502:physiology*; D014981:Xenopus / Q000502:physiology
D029681:Arabidopsis Proteins; C114544:SKOR protein, Arabidopsis; D051637:Shaker Superfamily of Potassium Channels; D011188:Potassium