Isolation and Characterization of a Putative Vacuolar Na+/H+ Antiporter Gene from Zoysia japonica L.

A Na⁺/H⁺ antiporter gene from Zoysia japonica (ZjNHX1) which is a member of plant NHX-genes family was cloned by reverse-transcription-polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE) technology. The isolated cDNA is 2,421 bp in length and contains one open-reading frame (ORF) which comprises 540 amino acid residues and shows higher homology with other plant Na⁺/H⁺ antiporters. ZjNHX1 could partially complement the salt-sensitive phenotypes of ∆nhx1 and ∆ena1-4∆nhx1 yeast mutants in the presence of NaCl, KCl, and LiCl. The expression of ZjNHX1 in Z. japonica increased after NaCl treatment and this result accords with that of Na⁺ contents determination under the same treatment. These results implied that ZjNHX1 functions as a vacuolar Na⁺/H⁺ antiporter and plays an important role in salt tolerance and ion homeostasis in Z. japonica.