Overexpression of the Na+/H+ antiporter gene from Suaeda salsa confers cold and salt tolerance to transgenic Arabidopsis thaliana

Na+/H+ exchanger catalyzes the countertransport of Na+ and H+ across membranes. By using reverse transcription PCR (RT-PCR) technique and Rapid Amplification of cDNA Ends (RACE), a Suaeda salsa cDNA clone was isolated and the sequence contains 2133 bp with an open reading frame of 1674 bp. The deduced amino acid sequence is similar to that of AtNHX1 and NHE isoforms in mammals, and shares high similarity with the sequences within predicted transmembrane segments and an amiloride-binding domain. In an attempt to improve salt tolerance of Arabidopsis plants, an expression vector containing SsNHX1 cDNA driven by a cauliflower mosaic virus 35S promoter was transferred into Arabidopsis plants. Transgenic plants could normally grow and complete life cycle under treatment with 200 mM NaCl but the wild-type Arabidopsis plant growth were severely retarded. Transgenic seedlings could resume and keep normal growth after treatment at -7 degrees C for 5 h but wt plants became hoariness and then all died.