Cloning and characterization of the Salicornia brachiata Na + /H + antiporter gene SbNHX1 and its expression by abiotic stress Anupama Jha • Mukul Joshi • Narendra Singh Yadav • Pradeep K. Agarwal • Bhavanath Jha Received: 22 January 2010 / Accepted: 3 September 2010 / Published online: 19 September 2010 Ó Springer Science+Business Media B.V. 2010 Abstract 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 halo- phytic 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 gradu- ally 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. Keywords Antiporter Á Halophyte Á Ion homeostasis Á Salicornia brachiata Á Vacuolar NHX Introduction The productivity of plants is greatly affected by various environmental stresses. Soil salinity affects plant growth and development by way of osmotic stress and injurious effects of higher concentration of Na ? and Cl - ions. Salinity stress response is multigenic. During salinity stress a number of tolerance mechanism are affected, such as various compatible solutes/osmolytes, polyamines, reactive oxygen species, antioxidant defense mechanism, and ion transport and compartmentalization. Mechanisms of con- ferring salt tolerance vary with the plant species; however the basic strategy works toward the maintenance of Na ? homeostasis in the cytosol [1]. Na ? homeostasis is main- tained either by active exclusion through plasma membrane Na ? /H ? antiporter AtSOS1 [2], or by sequestration of excess sodium into the vacuoles via vacuolar Na ? /H ? an- tiporters. When grown in saline environment all plants accumulate Na ? ions to some extent, except for some halophytic species that are able to effectively maintain very low Na ? influx [3, 4]. The strategy of accumulation of Na ? inside vacuoles is used by many plants to survive under salt stress, an active vacuolar antiporter utilizes the proton motive force generated by vacuolar ATPases and pyro- phosphatases to sequester excess Na ? into the vacuole, thereby reduce the toxic effects of Na ? inside the cytosol [4–6]. In this way, the translocation and storage of Na ? inside vacuoles in the shoot are suggested to be key factors for sustained growth during salt stress in some plant spe- cies. Other plant species tend to limit Na ? accumulation in shoots by reducing transport from root to shoot, Electronic supplementary material The online version of this article (doi:10.1007/s11033-010-0318-5) contains supplementary material, which is available to authorized users. A. Jha Á M. Joshi Á N. S. Yadav Á P. K. Agarwal (&) Á B. Jha (&) Discipline of Marine Biotechnology and Ecology, Central Salt and Marine Chemicals Research Institute (Council of Scientific and Industrial Research), Bhavnagar 364 002, Gujarat, India e-mail: pagarwal@csmcri.org B. Jha e-mail: bjha@csmcri.org 123 Mol Biol Rep (2011) 38:1965–1973 DOI 10.1007/s11033-010-0318-5