The Role of H+/OH− Channels in the Salt Stress Response of Chara australis

The Role of H+/OH− Channels in the Salt Stress Response of Chara australis We investigate the electrophysiological salt stress response of the salt-sensitive charophyte Chara australis as a function of time in saline artificial pond water (saline APW) containing 50 mM NaCl and 0.1 mM CaCl2. The effects are due to an increase in Na+ concentration rather than an increase in Cl− concentration or medium osmolarity. A previous paper (Shepherd et al. Plant Cell Environ 31:1575–1591, 2008) described the rise in the background conductance and inhibition of proton pumping in saline APW in the first 60 min. Here we investigate the shift of membrane potential difference (PD) to levels above −100 mV and the change of shape of the current–voltage (I/V) profiles to upwardly concave. Arguing from thermodynamics, the I/V characteristics can be modeled by channels that conduct H+ or OH−. OH− was chosen, as H+ required an unrealistic increase in the number/permeability of the channels at higher pH levels. Prolonged exposure to saline APW stimulated opening of more OH− channels. Recovery was still possible even at a PD near −50 mV, with partial return of proton pumping and a decrease in OH− current following APW wash. Upon change of pH from 7 to 9, the response was consistent with previously observed I/V characteristics of OH− channels. For a pH change to 6, the response was transient before channel closure but could still be modeled. The consequences of opening of H+ or OH− channels while the cell is under salt stress are discussed. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Membrane Biology Springer Journals

The Role of H+/OH− Channels in the Salt Stress Response of Chara australis

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Publisher
Springer-Verlag
Copyright
Copyright © 2009 by Springer Science+Business Media, LLC
Subject
Life Sciences; Human Physiology ; Biochemistry, general
ISSN
0022-2631
eISSN
1432-1424
D.O.I.
10.1007/s00232-009-9182-4
Publisher site
See Article on Publisher Site

Abstract

We investigate the electrophysiological salt stress response of the salt-sensitive charophyte Chara australis as a function of time in saline artificial pond water (saline APW) containing 50 mM NaCl and 0.1 mM CaCl2. The effects are due to an increase in Na+ concentration rather than an increase in Cl− concentration or medium osmolarity. A previous paper (Shepherd et al. Plant Cell Environ 31:1575–1591, 2008) described the rise in the background conductance and inhibition of proton pumping in saline APW in the first 60 min. Here we investigate the shift of membrane potential difference (PD) to levels above −100 mV and the change of shape of the current–voltage (I/V) profiles to upwardly concave. Arguing from thermodynamics, the I/V characteristics can be modeled by channels that conduct H+ or OH−. OH− was chosen, as H+ required an unrealistic increase in the number/permeability of the channels at higher pH levels. Prolonged exposure to saline APW stimulated opening of more OH− channels. Recovery was still possible even at a PD near −50 mV, with partial return of proton pumping and a decrease in OH− current following APW wash. Upon change of pH from 7 to 9, the response was consistent with previously observed I/V characteristics of OH− channels. For a pH change to 6, the response was transient before channel closure but could still be modeled. The consequences of opening of H+ or OH− channels while the cell is under salt stress are discussed.

Journal

The Journal of Membrane BiologySpringer Journals

Published: Jul 17, 2009

References

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