Regulation of Reactive Oxygen Species and Antioxidant Defense in Plants under Salinity

Abstract

The generation of oxygen radicals and their derivatives, known as reactive oxygen species, (ROS) is a part of the signaling process in higher plants at lower concentrations, but at higher concentrations, those ROS cause oxidative stress. Salinity-induced osmotic stress and ionic stress trigger the overproduction of ROS and, ultimately, result in oxidative damage to cell organelles and membrane components, and at severe levels, they cause cell and plant death. The antioxidant defense system protects the plant from salt-induced oxidative damage by detoxifying the ROS and also by maintaining the balance of ROS generation under salt stress. Different plant hormones and genes are also associated with the signaling and antioxidant defense system to protect plants when they are exposed to salt stress. Salt-induced ROS overgeneration is one of the major reasons for hampering the morpho-physiological and biochemical activities of plants which can be largely restored through enhancing the antioxidant defense system that detoxifies ROS. In this review, we discuss the salt-induced generation of ROS, oxidative stress and antioxidant defense of plants under salinity.

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“…Salinity hampers many different physiological and biochemical processes in plants by ion toxicity and osmotic stress. This then accelerates the generation of reactive oxygen species (ROS) due to imbalances created in redox homeostasis, and ROS cause oxidative damage to plant tissues [ 3 , 4 ].…”

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“…Oxidative stress has a major detrimental effect on plants due to salinity-induced excessive ROS generation. Plants with high resistance to abiotic or biotic stress generally have a high antioxidative ability and rapid responses to oxidative stress [ 3 , 5 , 6 ]. A high antioxidative ability confers plants stable adaptation to adverse environments and improves their tolerance to stress [ 4 ].…”

“…Plants use specialized strategies to cope with salt stress. For example, plants alleviate hyperosmotic stress damage by accumulating osmoprotectants, such as proline, polyamines, glycine-betaine, and sugars, that are synthesized by certain metabolic pathways [ 5 , 6 ]. For toxic ion stress, primarily Na + and Cl − , plants minimize their harmful effects by activating certain ion transporters that squeeze Na + out of cells and/or compartmentalize Na + into vacuoles, such as salt overly sensitive 1 (SOS1), which is a Na + /H + antiporter expressed in root epidermal cells that extrudes Na + into the soil [ 7 ].…”

“…Salt stress-induced osmotic stress and ionic stress trigger the excessive accumulation of reactive oxygen species (ROS), which results in oxidative damage to plant cells. The antioxidant system protects plants from oxidative stress damage by detoxifying ROS and maintaining the balance of ROS generation under salt stress [ 6 ]. The antioxidant defense system includes enzymatic and non-enzymatic components in plants.…”

“…The antioxidant defense system includes enzymatic and non-enzymatic components in plants. The major antioxidant enzymes include superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR), and non-enzymatic components, such as glutathione (GSH), ascorbic acid, flavonoids, and carotenoids [ 5 , 6 , 10 ]. Previous studies reported that many phytohormones, such as abscisic acid (ABA), ethylene, jasmonates (JA), and salicylic acid (SA), are also associated with signaling and antioxidant defense systems to protect plants exposed to salt stress [ 7 , 11 , 12 ].…”