Coordinate role of ascorbate-glutathione in response to abiotic stresses

Abstract

Glutathione (GSH), the tripeptide (nonprotein) thiol (γ-glutamyl cysteinyl glycine) and ascorbic acid (AsA, vitamin C) are the most prominent and worth functional low molecular weight soluble antioxidants in plant cells. Environmental fluctuations can lead the plants/crops to abiotic stress conditions. Thus a prompt and effective response, involving many genes and biochemical-molecular mechanism to cope with these conditions is inevitable. In response to these stresses, the ratio of reduced glutathione (GSH) and oxidized form of glutathione (GSSG) tends to decrease due to the oxidation of GSH during the detoxification of reactive oxygen species and changes in its metabolism, which leads to the activation of various defence mechanisms through a redox signalling pathway, including several oxidants, antioxidants, and stress hormones. Glutathione along with AsA plays a pivotal role in protecting cell function. They detoxify H2O2 in the AsA-GSH cycle and are involved in cellular redox regulation and buffering. The ascorbate and glutathione (AsA/DHA and GSH/GSSG) redox pairs are often found to be coupled in plants favours net electron flow from reduced glutathione to dehydroascorbate (DHA). The antioxidation property of ascorbate and glutathione plays a key role in the redox signal transduction process. The plausible reasons could be: (a) signal transduction is influenced as ascorbate and glutathione regulate the cellular H2O2. (b) As these metabolites are responsible for regulating gene expression, so the compartment-specific variations in AsA/DHA and GSH/GSSG ratios may have substantial significance for redox signalling. The aim of present chapter is: firstly, to enlighten the pivotal role of AsA and GSH in plant metabolism and tolerance to abiotic stresses such as oxidative, drought, salinity, heat, and cold stress. Secondly, to emphasize the importance of identification and analysis of AsA-GSH genes responsible for multiple stress tolerance in plant species.