Decrease of pH gradients in tonoplast vesicles by NO/sub 3//sup -/ and Cl/sup -/: evidence for H/sup +/-coupled anion transport
Chloride or nitrate decreased a pH gradient (measured as (/sup 14/C)methylamine accumulation) in tonoplast-enriched vesicles. The ..delta..pH decrease was dependent on the anion concentration. These effects are independent of the anion-sensitive H/sup +/-ATPase of the tonoplast, since the pH gradient (acid inside) was imposed artificially using a pH jump or a K/sup +/ gradient and nigericin. 4,4'-Diisothiocyano-2,2'-stilbene disulfonic acid partially prevented the decrease in pH gradient induced by Cl/sup -/. Two possible models to account for this anion-dependent decrease of ..delta..pH are: (a) H/sup +/ loss is accompanied by Cl/sup -/ or NO/sub 3//sup -/ efflux from the vesicles via H/sup +//anion symport systems on the tonoplast and (b) H/sup +/ loss is accompanied by Cl/sup -/ or NO/sub 3//sup -/ uptake into the vesicles via H/sup +//anion antiport systems. Depending on the requirements and conditions of the cell, these two systems would serve to either mobilize Cl/sup -/ and NO/sub 3//sup -/ stored in the vacuole for use in the cytoplasm or to drive anions into the vacuole. Chloride or nitrate also decreased a pH gradient in fractions containing plasma membrane and Golgi, implying that these membranes may have similar H/sup +/-coupled anion transport systems.
- Research Organization:
- Univ. of Maryland, College Park
- DOE Contract Number:
- AS05-82ER13015
- OSTI ID:
- 6401450
- Journal Information:
- Plant Physiol.; (United States), Vol. 83:3
- Country of Publication:
- United States
- Language:
- English
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59 BASIC BIOLOGICAL SCIENCES
CHLORIDES
MEMBRANE TRANSPORT
NITRATES
ANIONS
CARBON 14 COMPOUNDS
CATIONS
CELL MEMBRANES
HYDROGEN COMPOUNDS
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TRACER TECHNIQUES
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CHLORINE COMPOUNDS
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LABELLED COMPOUNDS
MEMBRANES
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OXYGEN COMPOUNDS
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