Towards dual-stress-tolerant rice crop: unraveling the physiological and molecular basis of salinity and drought tolerance

Abstract

Drought and salinity are two major abiotic stresses that reduce rice productivity. Rice plants respond mechanistically to drought stress by making osmotic adjustments, such as the accumulation of proline and sugars, and by closing their stomata to reduce transpiration. Deep penetration is avoided through root architecture adaptation, while antioxidant systems produced by both stresses reduce oxidative stress caused by reactive oxygen species (ROS). Salinity tolerance is achieved through ion homeostasis, which excludes or compartmentalises toxic sodium (Na⁺) and chloride (Cl⁻) ions within the plant. It is also achieved through osmotic adaptation to the extracellular water deficit. Genetic pathways induced by both stresses overlap and include dehydration-responsive element-binding proteins and abscisic acid, which regulate stress responses. These common mechanisms of osmotic stress induction leading to ROS production highlight the interconnected nature of plant responses to these stresses and allow for the development of dual-tolerant crops. However, the physiological and molecular basis of the overlap between drought and salt tolerance in rice remains unclear. This review focuses on how rice plants respond to these stresses, with a particular emphasis on oxidative stress management, ion homeostasis, and osmotic adjustment. The study provides knowledge to inform the development of salt- and drought-tolerant rice varieties.