Elucidation of the Mechanisms Underlying Hypo-osmotically Induced Turgor Pressure Regulation in the Marine Alga Valonia utricularis

Elucidation of the Mechanisms Underlying Hypo-osmotically Induced Turgor Pressure Regulation in... Exposure of the giant marine alga Valonia utricularis to acute hypo-osmotic shocks induces a transient increase in turgor pressure and subsequent back-regulation. Separate recording of the electrical properties of tonoplast and plasmalemma together with turgor pressure was performed by using a vacuolar perfusion assembly. Hypo-osmotic turgor pressure regulation was inhibited by external addition of 300 μM of the membrane-permeable ion channel blocker 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB). In the presence of 100 μM NPPB, regulation could only be inhibited by simultaneous external addition of 200 μM 4,4′-diisothiocyanatostilbene-2,2′-disulfonic acid (DIDS), a membrane-impermeable inhibitor of Cl− transport. At concentrations of about 100 μM, NPPB seems to selectively inhibit Cl− transporters in the tonoplast and K+ transporters in the plasmalemma, whereas 300 μM NPPB inhibits K+ and Cl− transporters in both membranes. Evidence was achieved by measuring the tonoplast and plasmalemma conductances (G t and G p) in low-Cl− and K+-free artificial seawater. Inhibition of turgor pressure regulation by 300 μM NPPB was accompanied by about 85% reduction of G t and G p. Vacuolar addition of sulfate, an inhibitor of tonoplast Cl− transporters, together with external addition of DIDS and Ba2+ (an inhibitor of K+ transporters) also strongly reduced G p and G t but did not affect hypo-osmotic turgor pressure regulation. These and many other findings suggest that KCl efflux partly occurs via electrically silent transport systems. Candidates are vacuolar entities that are disconnected from the huge and many-folded central vacuole or that become disconnected upon disproportionate swelling of originally interconnected vacuolar entities upon acute hypo-osmotic challenge. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Membrane Biology Springer Journals

Elucidation of the Mechanisms Underlying Hypo-osmotically Induced Turgor Pressure Regulation in the Marine Alga Valonia utricularis

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Publisher
Springer-Verlag
Copyright
Copyright © 2007 by Springer Science+Business Media, Inc.
Subject
Life Sciences; Biochemistry, general; Human Physiology
ISSN
0022-2631
eISSN
1432-1424
D.O.I.
10.1007/s00232-006-0047-9
Publisher site
See Article on Publisher Site

Abstract

Exposure of the giant marine alga Valonia utricularis to acute hypo-osmotic shocks induces a transient increase in turgor pressure and subsequent back-regulation. Separate recording of the electrical properties of tonoplast and plasmalemma together with turgor pressure was performed by using a vacuolar perfusion assembly. Hypo-osmotic turgor pressure regulation was inhibited by external addition of 300 μM of the membrane-permeable ion channel blocker 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB). In the presence of 100 μM NPPB, regulation could only be inhibited by simultaneous external addition of 200 μM 4,4′-diisothiocyanatostilbene-2,2′-disulfonic acid (DIDS), a membrane-impermeable inhibitor of Cl− transport. At concentrations of about 100 μM, NPPB seems to selectively inhibit Cl− transporters in the tonoplast and K+ transporters in the plasmalemma, whereas 300 μM NPPB inhibits K+ and Cl− transporters in both membranes. Evidence was achieved by measuring the tonoplast and plasmalemma conductances (G t and G p) in low-Cl− and K+-free artificial seawater. Inhibition of turgor pressure regulation by 300 μM NPPB was accompanied by about 85% reduction of G t and G p. Vacuolar addition of sulfate, an inhibitor of tonoplast Cl− transporters, together with external addition of DIDS and Ba2+ (an inhibitor of K+ transporters) also strongly reduced G p and G t but did not affect hypo-osmotic turgor pressure regulation. These and many other findings suggest that KCl efflux partly occurs via electrically silent transport systems. Candidates are vacuolar entities that are disconnected from the huge and many-folded central vacuole or that become disconnected upon disproportionate swelling of originally interconnected vacuolar entities upon acute hypo-osmotic challenge.

Journal

The Journal of Membrane BiologySpringer Journals

Published: Mar 13, 2007

References

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