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(Journal Article) |
Proceedings of the National Academy of Sciences of the United States of America 104 (25): 10726-31 (2007)
The two-pore channel TPK1 gene encodes the vacuolar K+ conductance and plays a role in K+ homeostasis.
Anthony Gobert
,
Stanislav Isayenkov
,
Camilla Voelker
,
Katrin Czempinski
,
Frans J M Maathuis
ABSTRACT
The Arabidopsis thaliana genome contains five genes that encode two pore K+ (TPK) channels. The most abundantly expressed isoform of this family, TPK1, is expressed at the tonoplast where it mediates K+ -selective currents between cytoplasmic and vacuolar compartments. TPK1 open probability depends on both cytoplasmic Ca2+ and cytoplasmic pH but not on the tonoplast membrane voltage. The channel shows intrinsic rectification and can be blocked by Ba2+, tetraethylammonium, and quinine. TPK1 current was found in all shoot cell types and shows all of the hallmarks of the previously described vacuolar K (VK) tonoplast channel characterized in guard cells. Characterization of TPK1 loss-of-function mutants and TPK1-overexpressing plants shows that TPK1 has a role in intracellular K+ homeostasis affecting seedling growth at high and low ambient K+ levels. In stomata, TPK1 function is consistent with vacuolar K+ release, and removal of this channel leads to slower stomatal closure kinetics. During germination, TPK1 contributes to the radicle development through vacuolar K+ deposition to provide expansion growth or in the redistribution of essential minerals.