Crosstalk between MAPKs and GSH under stress: A critical review

Plants are frequently exposed to a plethora of unfavourable climatic catastrophes, be it abiotic or biotic stresses, viz., salinity, water (drought or water logging), extreme temperature, heavy metal, nutrient deficiency, ozone, pathogen attack, etc., which badly affect the yield and productivity of crops. Plants, as part of their defence machinery, employ different tolerance mechanisms to survive under adverse conditions. In addition to other stress responses, the mitogen-activated protein kinase (MAPK) signalling cascade and accumulation of glutathione (GSH) are two important aspects of plant defence response. Induction of the MAPK cascade is one of the earliest responses when a plant is under any environmental stress, and there is documentary evidence of this signalling pathway, in turn, regulating various phytohormone-signalling networks and other defence-related pathways during stress. Similarly, GSH being a low molecular weight metabolite also has a key role in environmental stress tolerance. It is known to be involved in multi-step interactions with various phytohormones, many signalling molecules, and redox molecules such as reactive oxygen species (ROS). This review provides an outline on GSH-MAPK crosstalk to better understand its role in the context of defence signalling in plants.