Isolation of Arachis hypogaea Na+/H+ antiporter and its expression analysis under salt stress

The plant Na + /H + antiporter gene plays a major role in salt tolerance. One Na + /H + antiporter (AhNHX1) gene was isolated from peanut (Arachis hypogaea ) in the present work. The full-length cDNA of AhNHX1 was 2,331 bp, which contains a complete ORF of 1,620 bp. The deduced protein sequence contains 546 amino acids with a molecular mass of 58.8 KDa and a pI of 7.23. The amino acid sequence of the AhNHX1 shares high similarity (shows more than 81.89% identity) with those of the previously isolated NHX1 from other plants. Meanwhile, the AhNHX1 protein has twelve putative transmembrane domains, and the conserved amiloride-binding sites ( 84 LFFIYLLPPI 93 ) were found in its N-terminal. Also, the expression of AhNHX1 was tissue-specific under different level NaCl treatments. Under 50 and 100 mM NaCl treatments, its expression showed higher in roots and lower in stems and leaves relative to control plants, respectively. In addition, its expression was time-specific, such that under 150 mM NaCl treatment, its expression usually increased and reached to a stable level in roots and leaves after 24 h but in stems after 48 h, respectively. These results implied that the AhNHX1 plays an important role under salt stress in peanut. Key words: Arachis hypogaea, AhNHX1, salt tolerance, gene expression patterns.