![]() ![]() ![]() H 2O 2 is the most stable ROS transported actively across membranes by aquaporins ( Miller et al., 2010 Mittler, 2017 Smirnoff and Arnaud, 2019).ĭepending on the generated ROS concentration, severity of stress, antioxidant capacity, and cellular energetic status, different cellular and physiological outcomes may be obtained. However, they differ in their stability, reactivity, and ability to be transported across membranes. They quickly interconvert, thus providing a high level of functional variability. −), hydrogen peroxide (H 2O 2), and hydroxyl radical (OH.Only four ROS, namely singlet oxygen ( 1O 2), superoxide (O 2 Apoplastic peroxidases also possess ROS generating capacity ( Bindschedler et al., 2006). Apoplastic ROS are produced by plasma membrane-localized NADPH oxidase, oxalate oxidase ( Voothuluru and Sharp, 2013), or by the degradation of spermidine by polyamine oxidase ( Geilfus et al., 2015). Plant ROS are generated mainly by electron transport chains in chloroplasts ( Pospíšil, 2016 Foyer, 2018) and mitochondria ( Gleason et al., 2011) as well as during photorespiration in peroxisomes ( del Río et al., 2006 del Río and López-Huertas, 2016). ROS are produced from atmospheric oxygen by its partial monovalent reduction, which occurs in the presence of electron donors. Reactive oxygen species (ROS), as unavoidable byproducts of metabolism, have important signaling roles in living organisms under optimal and adverse environmental conditions ( Apel and Hirt, 2004 Baxter et al., 2014 Waszczak et al., 2018). This review aimed to summarize the current knowledge on signaling processes regulating the enzymatic antioxidant capacity of plants. Fast ROS production requires the immediate mobilization of the antioxidant defense system, which may occur via retrograde signaling, redox-based modifications, and the phosphorylation of ROS detoxifying enzymes. The transcriptional activation of antioxidant enzymes accompanies the long-term exposure of plants to unfavorable environmental conditions. Therefore, the deregulation of the antioxidant machinery may lead to the overaccumulation of ROS in plants, with negative consequences both in terms of plant development and resistance to environmental challenges. Enzymatic antioxidant defense occurs as a series of redox reactions for ROS elimination. Antioxidant enzymes represent a major ROS-scavenging force and are crucial for stress tolerance in plants. The ROS content is controlled on the side of their production but also by scavenging machinery. They are produced as byproducts of aerobic metabolism and are affected by adverse environmental conditions. Reactive oxygen species (ROS) are signaling molecules essential for plant responses to abiotic and biotic stimuli as well as for multiple developmental processes. Department of Cell Biology, Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science, Palacký University, Olomouc, Czechia.Petr Dvořák, Yuliya Krasylenko, Adam Zeiner, Jozef Šamaj and Tomáš Takáč * ![]()
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