Coordinate up-regulation of V-H+-ATPase and vacuolar Na+/H+ antiporter as a response to NaCl treatment in a C3 halophyte Suaeda salsa

The strategy of Suaeda salsa adaptation to high salinity was shown in this study. Our results firstly demonstrated that Na+ was a beneficial element rather than toxic ion for S. salsa plants. The biomass of S. salsa seedlings increased significantly after salt-treatment (100–400 mmol/L NaCl). Secondly, S. salsa had strong ability to accumulate Na+ under saline condition. Ninety-four percent of Na+ absorbed by salt-treated S. salsa plant accumulated in the shoot, especially in the leaves, and 98% of Na+ in the leaves accumulated in leaf symplast. Thirdly, measurement on isolated tonoplast-enriched membrane vesicles derived from the leaves of S. salsa showed that increased V-H+-ATPase hydrolytic activity, V-H+-ATPase proton pump activity and the tonoplast Na+/H+ antiport activity were found in salt-treated leaves compared with the control leaves. Up-regulation of the tonoplast Na+/H+ antiport activity was due to increase of both transcription and translation. These results suggested that coordinate up-regulation of V-H+-ATPase activity and Na+/H+ antiporter activity play a pivotal role in Na+ sequestering into vacuoles of S. salsa.