Contribution of glutathione in heavy metal stress tolerance in plants

Plants are exposed to myriad of abiotic stresses such as salt stress, heavy metal, ozone, UV-B radiation, low and high temperatures, drought, and many more which are posing threats to agricultural soil. Among these abiotic stresses, the heavy metal pollutants, added by anthropogenic activities, had enormous impact on different ecosystems including plants. The increment of toxic heavy metals in the atmosphere is a serious problem to living organisms. Heavy metal induces excess generation of reactive oxygen species (ROS) which in turn is responsible for oxidative stress and impairs processes at physiological, biochemical, and molecular level resulting in loss of crop productivity. Plants possess wellorganized antioxidant defense system to mitigate oxidative stress. The plant antioxidant system constitutes various antioxidant enzymes and metabolites. Reduced glutathione (GSH) is an important constituent of ascorbate (AsA)- GSH (AsA-GSH). Glutathione consists of Glu-Cys-Gly with GSH-related enzymes such as GSH reductase (GR), GSH peroxidase (GPX), and GSH sulfotransferases (GSTs), involved in controlling the ROS concentrations in cell by protecting plants against oxidative stress induced by heavy metals. This chapter highlights (a) responses of plants to heavy metals and its consequences on photosynthesis and growth, (b) heavy metal stress detoxification and antioxidants, and (c) importance of glutathione and its biosynthesis, transport, and signaling under optimal and metal stress condition.