Salt stress tolerance of transgenic rice (Oryza sativa L.) expressing AtDREB1A gene under inducible or constitutive promoters

Salt stress is the important abiotic stresses depressing gainful crop production. This study assessed rice morphologically with DREB1A gene under inducible and constitutive promoters against salinity. Non transgenic and transgenic rice plants with two transgenic events (35S-DREB1A and LIP-9 DREB1A) were assessed under salt stress and controlled conditions. The germinated healthy and uniform seedlings of rice plants with two events were transplanted in pots (25 x 35 cm) filled with soil and irrigated with tap water. Nitrogen and Phosphorus fertilizers were applied at the ratio of 100 kg/ha and 50 kg/ha respectively in the form of DAP and murate of potash. Sodium chloride (NaCl) in different increments was added in medium till stress level of 12 +/- 2 dS m(-1)NaCl was obtained and maintained till maturity. The control medium without added salts, with an ECw of 0.50-0.90 dSm(-1) was also maintained. After maturity, harvesting was done and yield components data were recorded. Results showed significant decrease in all morphological parameters of transgenic rice. Among the tested rice plants, lowest reduction in whole plant weight was observed in Lip-9 DREB1A while the most sensitive were 35S-DREB1A and wild type. Plants with Lip9-DREB1A and 35S-DREB1A gene exhibited increased fertility than in wild type but eventually Lip9-DREB1A plants with Lip-9 promoter produced higher yield than 35S-DREB1A plants under salt stress. It indicated that Lip9 promoter helped in steady increase in transcription under salinity giving capability to produce more seeds that increases final yield. Conventional PCR system confirmed the presence of transgene (DREB1A) in all transgenic rice plants that give tolerance against salt stress. STIs values showed salt tolerance among rice plants which nominates Lip9-DREB1A to be the more salt tolerant transgenic rice line than wild type and 35S-DREB1A. Exploitation of inducible promoter (Lip9) in plants for abiotic stress tolerance may be more helpful than constitutive promoters (35S).