The reactive oxygen species (ROS) acts as a signaling molecu...

created [InstanceEdit:9607101] Naithani, Sushma, 2018-04-30
dbId 9607089
displayName The reactive oxygen species (ROS) acts as a signaling molecu...
literatureReference
modified [InstanceEdit:9916142] Naithani, Sushma, 2024-07-23
schemaClass Summation
text The reactive oxygen species (ROS) acts as a signaling molecule and plays an important role in various plant developmental processes, including cell elongation, tissue/organ differentiation, and programmed cell death (Mittler et al., 2011). During normal metabolic activity and in response to abiotic stress conditions, most living cells produce ROS, including the singlet oxygen (1O2), superoxide radical (O2??), hydrogen peroxide (H2O2), and hydroxyl radical (OH?), which are unstable and extremely reactive and cause damage to various cellular components (DNA/proteins) and subcellular structure (membranes). Therefore, cells have evolved various strategies to neutralize these chemicals into less toxic or neutral derivatives. Under normal circumstances, the cells are capable of handling the ROS; however, under stress conditions, the levels of ROS surpass a cell's capacity for detoxification and lead to programmed cell death. The removal of ROS involves two reactions: In the first step, superoxide dismutase catalyzes the reduction of superoxide radicals into H2O2 and water. SODs are differentiated with regard to their metal cofactor. There are manganese-dependent and copper/zinc-dependent SODs, which differ not only in their metal cofactor but also in their subcellular location. In the second step, Hydrogen peroxide can be converted to water and molecular oxygen by the glutathione peroxidases or catalase. Hydrogen peroxide can also spontaneously form hydroxyl radicals. Due to its extremely short lifetime, the hydroxyl radical cannot be eliminated by an enzymatic reaction and reacts with many types of biomolecules. However, the hydroxyl radical can be neutralized by interaction with antioxidants such as L-ascorbate. Higher plants also contain plant-specific peroxidases (class III peroxidase; Prxs; EC 1.11.17). Prxs function as catalytic enzymes that oxidize phenolic compounds while consuming hydrogen peroxide and/or as generators of reactive oxygen species. Prxs are involved in lignification, cell elongation, stress defense, and seed germination (Shigeto J. and Tsutsumi Y, 2015).