GORK, a delayed outward rectifier expressed in guard cells of Arabidopsis thaliana, is a K+-selective, K+-sensing ion channel

Here we report on the molecular identification, guard cell expression and f unctional characterization of AtGORK, an Arabidopsis thaliana guard cell ou tward rectifying K+-channel. GORK represents a new member of the plant Shak er K+ channel superfamily.When heterologously expressed in Xenopus oocytes the gene product of GORK mediated depolarization-activated K+ currents. In agreement with the delayed outward rectifier in intact guard cells and prot oplasts thereof, GORK is activated in a voltage- and potassium-dependent ma nner. Furthermore, the single channel conductance and regulation of GORK in response to pH changes resembles the biophysical properties of the guard c ell delayed outward rectifier. Thus GORK very likely represents the molecul ar entity for depolarization-induced potassium release from guard cells. (C ) 2000 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.