Sulfate is both a substrate and an activator of the voltage-dependent anion channel of Arabidopsis hypocotyl cells.
On the basis of the anion content of in vitro-cultured Arabidopsis plantlets, we explored the selectivity of the voltage-dependent anion channel of the plasma membrane of hypocotyl cells. In the whole-cell configuration, substitution of cytosolic Cl(-) by different anions led to the following sequence of relative permeabilities: NO(3)(-) (2.6) >/= SO(4)(2-) (2.0) > Cl(-) (1.0) > HCO(3)(-) (0.8) >> malate(2-) (0.03). Large whole-cell currents were measured for NO(3)(-) and SO(4)(2-), about five to six times higher than the equivalent Cl(-) currents. Since SO(4)(2-) is usually considered to be a weakly permeant or non-permeant ion, the components of the large whole-cell current were explored in more detail. Aside from its permeation through the channel with a unitary conductance, about two-thirds that of Cl(-), SO(4)(2-) had a regulatory effect on channel activity by preventing the run-down of the anion current both in the whole-cell and the outside-out configuration, increasing markedly the whole-cell current. The fact that the voltage-dependent plasma membrane anion channel of hypocotyl cells can mediate large NO(3)(-) and SO(4)(2-) currents and is regulated by nucleotides favors the idea that this anion channel can contribute to the cellular homeostasis of important metabolized anions.
Frachisse
J M
JM
Institut des Sciences Végétales, Centre National de la Recherche Scientifique, Unité Propre de Recherche 40, Avenue de la Terrasse, 91198 Gif sur Yvette cedex, France. frachisse@isv.cnrs-gif.fr
Thomine
S
S
Colcombet
J
J
Guern
J
J
Barbier-Brygoo
H
H
D000838:Anions / Q000378:metabolism; D017360:Arabidopsis / Q000166:cytology* / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002463:Cell Membrane Permeability; D004553:Electric Conductivity; D018546:Hypocotyl / Q000166:cytology / Q000378:metabolism*; D015640:Ion Channel Gating; D007473:Ion Channels / Q000378:metabolism*; D009566:Nitrates / Q000378:metabolism; D009711:Nucleotides / Q000378:metabolism; D018408:Patch-Clamp Techniques; D013431:Sulfates / Q000378:metabolism*; D013997:Time Factors
D000838:Anions; D007473:Ion Channels; D009566:Nitrates; D009711:Nucleotides; D013431:Sulfates; D002118:Calcium