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Cloning and electrophysiological analysis of KST1, an inward rectifying K+ channel expressed in potato guard cells.
Author(s) -
MüllerRöber B.,
Ellenberg J.,
Provart N.,
Willmitzer L.,
Busch H.,
Becker D.,
Dietrich P.,
Hoth S.,
Hedrich R.
Publication year - 1995
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1002/j.1460-2075.1995.tb07238.x
Subject(s) - guard cell , biology , biophysics , patch clamp , heterologous expression , ion channel , membrane potential , electrophysiology , potassium channel , voltage clamp , xenopus , microbiology and biotechnology , biochemistry , gene , recombinant dna , neuroscience , receptor
Potassium uptake by guard cells represents part of the osmotic motor which drives stomatal opening. Patch‐clamp measurements have identified inward rectifying K+ channels capable of mediating K+ uptake in guard cells and various other plant cell types. Here we report the molecular cloning and characterization of a voltage‐dependent K+ channel (KST1) from potato (Solanum tuberosum L.) guard cells. In situ hybridization shows expression of kst1 in guard cells. Two‐electrode voltage‐clamp and patch‐clamp studies of the gene product after cRNA injection into Xenopus oocytes identified KST1 as a slowly activating, voltage‐dependent, inward rectifying K+ channel. The single channel current voltage curve was linear in the range ‐160 to +20 mV, with a deduced single channel conductance of 7 pS in symmetrical 100 mM K+. This channel type, modulated by pH changes within the physiological range, required ATP for activation. In line with the properties of a K(+)‐selective channel, KST1 was permeable to K+, Rb+ and NH4+ and excluded Na+ and Li+. Cs+ at submillimolar concentrations blocked the channel in a voltage‐dependent manner. Related studies on potato guard cell protoplasts confirmed the biophysical characteristics of the kst1 gene product (KST1) in the heterologous expression system. Therefore, KST1 represents a major K+ uptake channel in potato guard cells.