Molecular Cloning and Different Expression of a Vacuolar Na<sup>+</sup>/H<sup>+</sup> antiporter gene in Suaeda salsa Under Salt Stress

A Na+/H+ antiporter catalyzes the transport of Na+ and H+ across the tonoplast membrane. We isolated a vacuolar Na+/H+ antiporter cDNA (SsNHX1) clone from a euhalophyte, Suaeda salsa. The nuclear sequence contains 2262 bp with an open reading frame of 1665 bp. The deduced amino acid sequence is similar to that of AtNHX1 and OsNHX1 in rice, with the highest similarities within the predicted transmembrane segments and an amiloride-binding domain. Northern blot analysis shows that the expression of the S. salsa gene was increased by salt stress. The results suggest that the SsNHX1 product is likely a Na+/H+ antiporter and may play important roles in the salt tolerance of S. salsa.