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Convergence of Pathways Towards Ascorbate–Glutathione for Stress Mitigation
Asthir Bavita 한국식물학회 2020 Journal of Plant Biology Vol.63 No.4
In plants, exposure to temperature extremes, heavy metal-contaminated soils, drought, air pollutants, and pathogens results in the generation of reactive oxygen species (ROS) that alter the intracellular redox environment, which in turn influences signaling pathways and cell fate. As part of their response to these stresses, plants produce ascorbate and glutathione. Since ascorbate is an essential metabolite implicated in vital cell functions, it is surprising that the pathway of ascorbate synthesis in plants remains to be fully established which involve various intermediates, namely GDP-mannose, GDP-L-galactose, L-galactose, and L-galactono-1,4-lactone. On the other hand, glutathione acts as an antioxidant by quenching ROS and is involved in the ascorbate–glutathione cycle that eliminates damaging peroxides. Two enzymes catalyze glutathione synthesis: glutamate-cysteine ligase and glutathione synthetase. Here, we explore the biosynthesis/functions of ascorbate and glutathione not only in relation to stress conditions, but also in the wider contexts of plant development and environmental responses.
Gurpreet Kaur Goraya,Bavita Asthir 한국식물학회 2016 Journal of Plant Biology Vol.59 No.3
Environmental stresses are often associated with production of certain deleterious chemical entities called reactive oxygen species (ROS), which include hydrogen peroxide (H2O2), superoxide radical (O 2 − ), hydroxyl radical (OH−). In plants, ROS are formed by the inevitable leakage of electrons onto O2 from the electron transport activities of chloroplasts, mitochondria, peroxisomes, vacuole and plasma membranes or as a byproduct of various metabolic pathways. Plants have their own antioxidant defense mechanisms to encounter ROS that is of enzymic and non-enzymic nature. Coordinated activities of these antioxidants regulate ROS detoxification and reduces oxidative load in plants. Though ROS are always regarded to impart negative impact on plants, some reports consider them to be important in regulating key cellular functions; however, such reports in plant are limited. On the other hand, specific ROS function as signaling molecules and activate signal transduction processes in response to various stresses is a matter of investigation.
Rapid injuries of high temperature in plants
Gurpreet Kaur Goraya,Balraj Kaur,Bavita Asthir,Shashi Bala,Gurpreet Kaur Goraya,Muhammad Farooq 한국식물학회 2017 Journal of Plant Biology Vol.60 No.4
Global climate changes particularly high temperature is predicted to have a general negative effect on plant growth and development, that might lead to catastrophic loss of crop productivity. High temperature has a wide range of effect on plant in terms of plant physiological, biochemical processes such as photosynthesis, respiration water relations, and gene regulatory pathways. The injury inflicted on plant tissues under such extremes weakens the cell membrane, which leads to the production of reactive oxygen species that attacks major sites i.e photosynthetic apparatus, the photosystems, mainly photosystem II (PSII) and the respiratory pathways. To cope with rising temperature conditions, plants possess a number of adaptive, avoidance, or acclimation mechanisms. In addition to major tolerance mechanisms, plants also employ ion transporters, proteins, osmoprotectants, antioxidants and many other factors involved in signaling cascades and transcriptional control that are activated to offset stress-induced biochemical and physiological alterations. This article reviews the recent findings on high temperature induced injuries and responses at the cellular, organellar and whole plant levels.