Reactive Oxygen Species and Antioxidant Defense in Plants under Abiotic Stress: Revisiting the Crucial Role of a Universal Defense Regulator

Abstract

Global climate change and associated adverse abiotic stress conditions, such as drought, salinity, heavy metals, waterlogging, extreme temperatures, oxygen deprivation, etc., greatly influence plant growth and development, ultimately affecting crop yield and quality, as well as agricultural sustainability in general. Plant cells produce oxygen radicals and their derivatives, so-called reactive oxygen species (ROS), during various processes associated with abiotic stress. Moreover, the generation of ROS is a fundamental process in higher plants and employs to transmit cellular signaling information in response to the changing environmental conditions. One of the most crucial consequences of abiotic stress is the disturbance of the equilibrium between the generation of ROS and antioxidant defense systems triggering the excessive accumulation of ROS and inducing oxidative stress in plants. Notably, the equilibrium between the detoxification and generation of ROS is maintained by both enzymatic and nonenzymatic antioxidant defense systems under harsh environmental stresses. Although this field of research has attracted massive interest, it largely remains unexplored, and our understanding of ROS signaling remains poorly understood. In this review, we have documented the recent advancement illustrating the harmful effects of ROS, antioxidant defense system involved in ROS detoxification under different abiotic stresses, and molecular cross-talk with other important signal molecules such as reactive nitrogen, sulfur, and carbonyl species. In addition, state-of-the-art molecular approaches of ROS-mediated improvement in plant antioxidant defense during the acclimation process against abiotic stresses have also been discussed.

Putrescine-functionalized carbon quantum dot nanoparticles (Put-CQD) effectively prime grape (Vitis vinifera cv. Sultana) against salt stress

“…It is likely that stabilizing membrane integrity by Put and CQDs and their conjugated form (Put-CQD NPs) could (at least in part) justify the decrease in MDA content under salinity condition. H 2 O 2 , a key regulator for multiple processes linked with growth, development and stress protection [46], has binary effects depending on its concentration. At low concentration, it acts as a signaling molecule needed for initiation of resistance mechanisms to biotic and abiotic stresses, while it results in oxidative stress [47] and programmed cell death when at high concentrations.…”

“…SOD enzymatic activity eliminates superoxide radicals by dissimulating to H 2 O 2, which is then detoxi ed by several antioxidant enzymes (e.g. CAT, POD, APX, GP) [46]. CAT, as the main enzyme for H 2 O 2 quenching, removeσ superoxide radicals as the rst step of defense against ROS to reduce oxidative stress damage.…”

“…APX removes H 2 O 2, similar to CAT, through the glutathioneascorbate cycle [54]. GP enzyme utilizes glutathione to detoxify H 2 O 2, reducing lipids and organic hydroperoxides [46]. As salinity causes oxidative stress via ROS generation and accumulation in plant cells, antioxidant enzymes (such as CAT, SOD, GP and APX) could act as a defense mechanism for ROS detoxi cation.…”

Superoxide Dismutase (SOD): From Genomics and Expression Profiling to Heritability and Phenotypic Variability in Triticale Under Drought Stress

“…SOD is one of the active antioxidant enzymes in dismutation pathways of oxygen free radicals. This enzyme orchestrates the breakdowns of the superoxide radicals (O2 -) into hydrogen peroxide (H2O2) in the different organelles (Hasanuzzaman et al, 2020;Saed-Moucheshi et al, 2014a). Since superoxide radial is the most abundant radicals in some organelles, such as chlorophyll cells (Dvořák et al), it might be said that SOD is the first defense level against occurring oxidative stress in plants (Saed-Moucheshi et al, 2014b) which is concordance with the results of the current study regarding high number of stress regulatory elements making SOD to quickly respond to the changing environment.…”

“…magnesium-SOD (Mn-SOD), copper/zinc-SOD (Cu/Zn-SOD), and iron-SOD (Fe-SOD). Many studies have substantiated altered expression rate for each of the SOD isozymes under varies situation and stresses in different plants species (Alscher et al, 2002;Hasanuzzaman et al, 2020;Saed-Moucheshi et al, 2014b) and even different genotypes within a species (Elshafei, 2020;Tabarzad et al, 2017;Zahedi et al, 2016). Therefore, delving over the SOD expressional mechanisms that are active in its responsive pathways along with identifying related regulatory elements may provide new insights toward understanding and recognizing the resistance mechanisms in plants.…”