A Dehydration-Responsive Element Binding (DREB) Transcription Factor from the Succulent Halophyte Salicornia brachiata Enhances Abiotic Stress Tolerance in Transgenic Tobacco

Dehydration-responsive element binding (DREB) transcription factor (TF) plays a key role for abiotic stress tolerance in plants. Earlier, we have published the isolation and characterisation of an A-2-type SbDREB2A TF from an extreme halophyte Salicornia brachiata. The SbDREB2A protein lacks potential proline (P), glutamic acid (E), serine (S) and threonine (T) (PEST) sequence which is known to act as signal peptide for protein degradation. In this study, SbDREB2A TF was over-expressed in tobacco plants without any modification in polypeptide sequence. Transgenic plants showed better seed germination and growth characteristics in both hyperionic and hyperosmotic stresses. Transgenic plants exhibited higher water content, membrane stability and less electrolyte leakage in stress conditions. The transgenic plants accumulated less Na+ and higher K+ than wildtype (WT) plants. The transgenic plants revealed higher chlorophyll content, water use efficiency (WUE) and net photosynthesis rate. Transgenics exhibited higher level of proline and low amount of MDA and H2O2 under stress conditions. The real-time PCR of transgenics showed higher expression of downstream heat shock genes (Hsp18, Hsp26 and Hsp70), TFs (AP2 domain containing TF, HSF2 and ZFP), signalling components (PLC3 and Ca2+/calmodulin) and dehydrins (ERD10B, ERD10D and LEA5) under different abiotic stress treatments.