Open AccessAtTPK4, an Arabidopsis tandem-pore K + channel, poised to control the pollen membrane voltage in a pH- and Ca 2+ -dependent manner
Author(s) -
Dirk Becker,
Dietmar Geiger,
Marcel Dunkel,
Anja Roller,
Adam Bertl,
Andreas Latz,
Armando Carpaneto,
Petra Dietrich,
M. Rob G. Roelfsema,
Camilla Voelker,
Diana Schmidt,
Bernd MuellerRoeber,
Katrin Czempinski,
Rainer Hedrich
Publication year - 2004
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.0401502101
Subject(s) - arabidopsis , biophysics , depolarization , transmembrane protein , membrane potential , biology , voltage gated ion channel , potassium channel , ion channel , biochemistry , chemistry , mutant , gene , receptor
TheArabidopsis tandem-pore K+ (TPK) channels displaying four transmembrane domains and two pore regions share structural homologies with their animal counterparts of the KCNK family. In contrast to theShaker -likeArabidopsis channels (six transmembrane domains/one pore region), the functional properties and the biological role of plant TPK channels have not been elucidated yet. Here, we show that AtTPK4 (KCO4) localizes to the plasma membrane and is predominantly expressed in pollen. AtTPK4 (KCO4) resembles the electrical properties of a voltage-independent K+ channel after expression inXenopus oocytes and yeast. Hyperpolarizing as well as depolarizing membrane voltages elicited instantaneous K+ currents, which were blocked by extracellular calcium and cytoplasmic protons. Functional complementation assays using a K+ transport-deficient yeast confirmed the biophysical and pharmacological properties of the AtTPK4 channel. The features of AtTPK4 point toward a role in potassium homeostasis and membrane voltage control of the growing pollen tube. Thus, AtTPK4 represents a member of plant tandem-pore-K+ channels, resembling the characteristics of its animal counterparts as well as plant-specific features with respect to modulation of channel activity by acidosis and calcium.