Overexpression of the DREB1A gene under stress-inducible promoter delays leaf senescence and improves drought tolerance in rice

Rice (Oryza sativa) is the major source of food as over half of the world's population relies on rice as their major source of nutrition. Drought stress is the main factor negatively affecting rice growth and productivity worldwide. As DREB transcriptional factors are important for plant growth and abiotic stress responses, they are promising molecular plant breeding candidates. Overexpression of DREB1A gene in plants improves drought tolerance but also causes various growth abnormalities such as retarded growth, delay in flowering and reduced seed setting. In the present work, DREB1A gene under the control of inducible Oshox24 promoter was expressed in rice to study plant growth and abiotic stress tolerance. The inheritance of DREB1A in individual transgenic rice plants was confirmed using PCR analysis. The overexpression of POshox24; DREB1A indicated its positive role in delaying hormone-induced leaf senescence and chlorophyll breakdown induced by Methyl-Jasmonates (MeJA) Abscisic Acid (ABA), and Ethylene (ETH). The upper four leaves of POshox24:DREB1A-OX#2 and POshox24:DREB1A-OX#5 exhibited higher chlorophyll contents compared to control plants. Under drought stress treatment POshox24:DREB1A-OX#2 and POshox24:DREB1A-OX#5 exhibited 67% (27/40) and 63% (25/40) survival rate compared to control plants 35% (13/40). Our results suggest that stress-inducible expression of DREB1A under Oshox24 promoter produces no pleiotropic effects on plant growth and development and confers drought stress tolerance.