Cloning and electrophysiological analysis of KST1, an inward rectifying K+ channel expressed in potato guard cells

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 charac...

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Bibliographic Details
Published in:The EMBO journal 1995-06, Vol.14 (11), p.2409-2416
Main Authors: Müller‐Röber, B., Ellenberg, J., Provart, N., Willmitzer, L., Busch, H., Becker, D., Dietrich, P., Hoth, S., Hedrich, R.
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Animals
Base Sequence
Cations
Cloning, Molecular
DNA, Complementary - genetics
DNA, Plant - genetics
Electrophysiology
Female
Gene Expression
Genes, Plant
Hydrogen-Ion Concentration
In Vitro Techniques
Molecular Sequence Data
Oocytes - metabolism
Plants - genetics
Plants - metabolism
Potassium Channels - genetics
Potassium Channels - metabolism
Sequence Homology, Amino Acid
Solanum tuberosum - genetics
Solanum tuberosum - metabolism
Xenopus
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Summary: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.
ISSN:0261-4189
1460-2075
DOI:10.1002/j.1460-2075.1995.tb07238.x