Metabolic engineering of SK2-type of dehydrin1 (DHN1) gene isolated from Sorghum bicolor enhances tolerance to water-deficit and NaCl stresses in transgenic tobacco

摘要

A stress-inducible dehydrin (DHN1) gene was isolated from S. bicolor and its role in water-deficit and NaCl stresses was studied in transgenic tobacco. The cDNA sequence of SbDHN1 gene was 638bp in length and the ORF encoded a predicted polypeptide of 153 amino acid residues. Multiple alignment of amino acid sequence of SbDHN1 with DHN from other plant species revealed the presence of two K-segments and an S-segment, revealing it to be an SK2 type of dehydrin. Induction of SbDHN1 under water-deficit, salinity, high and low temperature stresses indicated its role in various abiotic stresses. Assays carried out using transformed E.coli cells expressing SbDHN1 showed enhanced tolerance to multiple abiotic stresses. Transgenic tobacco plants expressing SbDHN1 gene were generated. GUS histochemical assay and PCR analysis indicated the transgenic nature of the putative T0 transgenics. Molecular characterization of the T1 and T2 transgenics using PCR, RT-PCR and Southern analysis confirmed the stable integration, expression and carrying forward of the transgene. When subjected to water-deficit (-1.0 MPa) and salt (300 mM NaCl) stresses, the transgenics exhibited higher germination rate as well as shoot and root lengths. Also the leaf discs of the transgenics retained more leaf water content (10.12%) and chlorophyll content (22.5%) in comparison to their untransformed controls. Water-deficit stress tolerance of the T2 transgenics was revealed by maintenance of higher relative water content, membrane stability and superoxide dismutase activity. Thus, these results indicate the role of SbDHN1 gene in imparting tolerance to water-deficit and NaCl stresses.