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 upregulated 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.