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Effects of salt stress on H + ‐ ATPase and H + ‐PPase activities of tonoplast‐enriched vesicles isolated from sunflower roots
Author(s) -
Ballesteros Emilia,
Donaire Juan Pedro,
Belver Andres
Publication year - 1996
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1034/j.1399-3054.1996.970208.x
Subject(s) - vacuole , electrochemical gradient , atpase , biochemistry , vesicle , sunflower , membrane , chemistry , helianthus annuus , antiporter , proton transport , cytosol , enzyme , sucrose , nigericin , biophysics , biology , cytoplasm , agronomy
The control of ion concentration in the cytosol and the accumulation of ions in vacuoles are thought to be key factors in salt tolerance. These processes depend on the establishment in vacuolar membranes of an electrochemical H + gradient generated by two distinct H + ‐translocating enzymes: a H + ‐PPase and a H + ‐ATPase. H + ‐lrans locating activities were characterized in tonoplast‐enriched membrane fractions isolated by sucrose gradient centrifugation from sunflower ( Helianthus annuus L.) roots exposed for 3 days to different NaCl regimes. The 15/32% sucrose interface was enriched in membrane vesicles possessing a vacuolar‐type H + ‐ATPase and a H + ‐PPase, as indicated by inhibitor sensitivity, pH optimum, substrate specificity, ion effects kinetic data and immunolabelling with specific antibodies. Mild and severe stress did not alter the pH profile, ion dependence, apparent K m nor the amount of antigenic protein of either enzyme. Saline treatments slightly increased K + ‐stimulaied PPase activity with no change in ATPase activity, while both PP i ‐dependent and NO 3 ‐sensitive ATP‐dependent H + transport activities were strongly stimulated. These results are discussed in terms of an adaptative mechanism of the moderately tolerant sunflower plants to salt stress.