The two-pore channel TPK1 gene encodes the vacuolar K+ conductance and plays a role in K+ homeostasis.
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.
Gobert
Anthony
A
Department of Biology Area 9, University of York, York YO10 5DD, United Kingdom.
Isayenkov
Stanislav
S
Voelker
Camilla
C
Czempinski
Katrin
K
Maathuis
Frans J M
FJ
D017360:Arabidopsis / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism*; D004553:Electric Conductivity; D004594:Electrophysiology; D017343:Genes, Plant; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006706:Homeostasis; D009154:Mutation; D011188:Potassium / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D014617:Vacuoles / Q000378:metabolism*
D029681:Arabidopsis Proteins; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D011188:Potassium