A new Na+/H+ antiporter gene KvNHX1 isolated from the halophyte Kosteletzkya virginica improves salt tolerance in transgenic tobacco

Vacuolar Na+/H+ antiporters (NHXs) play an important role in plant salt tolerance and a large number of NHX genes have been identified in many plant species. In this study, we isolated and characterized a novel vacuolar-type KvNHX1 cDNA from the halophyte Kosteletzkya virginica. It is 2047 bp long, with an open reading frame of 1632 bp, encoding a protein of 543 amino acids with a theoretical molecular weight of 60.03 kDa. Bioinformatics and phylogenetic analysis showed that it was highly similar to the known vacuolar-type NHXs, especially with 92% identity with GhNHX1 of Gossypium hirsutum from the same Malvaceae family. Quantitative RT-PCR showed that the expression analysis of KvNHX1was significantly increased by NaCl, abscisic acid (ABA) and polyethylene glycol (PEG), but its expression levels and patterns differed under different abiotic stresses, implying that KvNHX1 might be involved in various abiotic stress responses. In addition, overexpression of KvNHX1 enhanced the salt tolerance in transgenic tobacco lines with better growth, more chlorophyll, higher antioxidant enzyme activities and osmoregulation capability by accumulating more proline, Na+ and K+ in the leaves than the wild type under salt stress. Our result suggested that KvNHX1 may have potential use for improving the salt tolerance of plants via genetic engineering