Effect of K+ nutrition on growth and activity of leaf tonoplast V-H+-ATPase and V-H+-PPase of Suaeda salsa under NaCl stress

Suaeda salsa L. seedlings grown in Hoagland nutrient solution were treated with different concentrations of NaCl combined with two levels of K+ (12 mumol/L and 6 mmol/L) to study the K+ nutrition effect on plant growth and leaf tonoplast V-H+-ATPase and V-H+-PPase activity. Increase of K+ supply in the culture solution markedly increased the fresh weight, dry weight and K+ content of S. salsa plants. Western blot analysis showed that the leaf V-H+-ATPase of S. salsa was at least composed of A, B, C, D, E and c subunits, and their expression decreased with the increase of NaCl concentration under K+ starvation ( 12 mumol/L K+), but increased under normal K+ application (6 mmol/L K+). Leaf V-H+-PPase molecular weight was about 72.6 kD and its expression increased as NaCl concentration increased under both high or low levels of K+ concentration in nutrient solution. There was a positive correlation between of V-H+-ATPase or V-H+-PPase activity and the amounts of their expression. Results in this study suggest that K+ nutrition plays an important role in the salt tolerance of S. salsa, and K+ is involved in the regulation of V-H+-ATPase or V-H+-PPase activity under salt stress.