Cloning and characterization of the Salicorniabrachiata Na+/H+ antiporter gene SbNHX1 and its expression by abiotic stress

Salinity causes multifarious adverse effects to plants. Plants response to salt stress involves numerous processes that function in coordination to alleviate both cellular hyperosmolarity and ion disequilibrium. A Na+/H+ antiporter NHX1 gene has been isolated from a halophytic plant Salicornia brachiata in this study. Predicted amino acid sequence similarity, protein topology and the presence of functional domains conserved in SbNHX1 classify it as a plant vacuolar NHX gene. The SbNHX1 cDNA has an open reading frame of 1,683 bp, encoding a polypeptide of 560 amino acid residues with an estimated molecular mass 62.44 kDa. The SbNHX1 shows high amino acid similarity with other halophytic NHX gene and belongs to Class-I type NHXs. TMpred suggests that SbNHX1 contains 11 strong transmembrane (TM). Real time PCR analysis revealed that SbNHX1 transcript expresses maximum at 0.5 M. Transcript increases gradually by increasing the treatment duration at 0.5 M NaCl, however, maximum expression was observed at 48 h. The overexpression of SbNHX1 gene in tobacco plant showed NaCl tolerance. This study shows that SbNHX1 is a potential gene for salt tolerance, and can be used in future for developing salt tolerant crops.