Changes in H + -ATPase activity of plasma membrane- enriched vesicles isolated from physic nut roots and leaves of energy and medicinal plant, Jatropha curcas L., as an adaptation mechanism to salinity

The plasma membrane H+-ATPase (PM H+-ATPase) plays a key role in the activation of ion and nutrient transport, and is proposed to be involved in salt tolerance. This study investigates the acclimation of PM H+-ATPase in physic nut (Jatropha curcas L.) roots and leaves treated with 0, 50 and 200 mM NaCl for 5 days. Upon comparison with control roots, the H+-ATPase hydrolytic activity, Vmax, Km, H+-pumping activity and pH gradient potential across the plasma membrane were significantly higher in roots treated with NaCl, especially under mild salt stress. The translational activation of PM H+-ATPase of physic nut roots helped to maintain K+ and Ca2+ uptake as well as nitrogen and phosphorus uptake in roots. Compared with the control leaves, the maintenance of H+ transport under 50 mM NaCl was attributed to a modification of the lipid membrane, and the increase in H+transport under 200 mM NaCl could be because of an acid-mediated activation. Differential expression of the H+-ATPase isoforms could also occur in leaves under salt stress. Thus, the stable pH gradient created by the H+-ATPase in leaves treated with 50 mM NaCl assisted normal leaf growth. These modulations of PM H+-ATPase in the roots and leaves of physic nuts could represent a set of adaptive mechanisms to salinity.   Key words: Immunoprecipitation, Jatropha curcas L., plasma membrane H+-ATPase, salt stress.