Antiporter gene from Hordum brevisubulatum (Trin.) Link and its overexpression in transgenic tobaccos

A vacuolar-Na+/H+ antiporter cDNA gene was successfully isolated from Hordeum brevisubulatum (Trin.) Link using the rapid amplification of cDNA ends (RACE) method. The gene was named HbNHX1 and was found to consist of 1 916 bp encoding a predicted polypeptide of 540 amino acids with a conserved amiloride-binding domain. Phylogenctic tree analysis of the Na+/H+ antiporters showed that the HbNHX1 gene shares 55.3%-74.8% similarity with the vacuolar-type Na+/H+ antiporters. Transgenic tobaccos that contain the HbNHX1 gene, integrated by forward insertion into the tobacco genome, were obtained via Agrobacterium tumerfaciens and characterized for the determination of the concentration of Na+ and K+ ions, as well as proline, in the presence of 300 mmol/L NaCl. The T-1 transgenic plants showed more tolerance to salt and drought than did wild-type plants. Our data suggest that overexpression of the HbNHX1 gene could improve the tolerance of transgenic tobaccos to salt and drought through the function of the vacuolar Na+/H+ antiporter.