Cloning and Characterization of a Novel Vacuolar Na(+)/H(+) Antiporter Gene (Dgnhx1) from Chrysanthemum

Plant vacuolar Na(+)/H(+) antiporter genes play significant roles in salt tolerance. However, the roles of the chrysanthemum vacuolar Na(+)/H(+) antiporter genes in salt stress response remain obscure. In this study, we isolated and characterized a novel vacuolar Na(+)/H(+) antiporter gene DgNHX1 from chrysanthemum. The DgNHX1 sequence contained 1920 bp with a complete open reading frame of 1533 bp encoding a putative protein of 510 amino acids with a predicted protein molecular weight of 56.3 kDa. DgNHX1 was predicted containing nine transmembrane domains. Its expression in the chrysanthemum was up-regulated by salt stress, but not by abscisic acid (ABA). To assess roles of DgNHX1 in plant salt stress responses, we performed gain-of-function experiment. The DgNHX1-overexpression tobacco plants showed significant salt tolerance than the wild type (WT). The transgenic lines exhibited more accumulation of Na(+) and K(+) under salt stress. These findings suggest that DgNHX1 plays a positive regulatory role in salt stress response.