Melatonin in Plant Tolerance to Drought Stress: Physiological and Molecular Interventions

Plants are subjected to various abiotic stresses; one such abiotic stress of great concern is drought stress. Drought stress affects plant metabolism and functioning of plants decreasing overall plant productivity. Plants have innate ability to tolerate harsh environmental conditions. Various signaling molecules are produced in plants in response to any abiotic stress. One such signaling molecule is melatonin. Melatonin is known to have a protective role in plants, it functions as an antioxidant that eliminates or reduces the levels of reactive oxygen species (ROS) produced under drought stress thus restoring the damage caused by drought stress in plants. Melatonin also increases the level of antioxidant enzymes in plants which further provide tolerance to plants against water-deficit conditions. Endogenous and exogenous melatonin can activate various stress-responsive genes, cascade of signaling pathways which further upregulate defense-related pathways and downregulate the pathways that are activated by drought stress.