Identification and characterization of differentially expressed genes in the halophyte Halostachys caspica under salt stress

To understand the molecular and cellular mechanisms underlying salinity stress tolerance in the halophyte Halostachys caspica, a suppression subtractive hybridization forward library was constructed using plants treated with 600 mM NaCl for 0, 6, 12, 24, 36, and 48 h. A total of 86 unique ESTs were identified as positive clones by reverse Northern dot-blotting and submitted to the Genbank database. Of these ESTs, 53 have sequence similarity with known proteins, 31 have sequence similarity with unidentified sequences, and 2, which could not be annotated, may represent novel genes. The annotated sequences were classified into nine different categories according to their putative functions, and many were found to be homologous to genes involved in the response to abiotic stress. Six ESTs were randomly selected to assess their transcript levels under salt stress; although they exhibited different expression patterns at different time points, all six tended to be induced by salt treatment. The ESTs identified in the present study as genes induced by salt stress may help elucidate the factors in H. caspica that underlie the extreme salt tolerance of this species.