Considering recent ROS-induced genome-wide expression analyses, the possible functions and mechanisms for ROS sensing and signaling in plants are compared with those in animals and yeast. ROS are generated by multiple cellular organelles, including mitochondria, peroxisomes, and endoplasmic reticulum 1 3. New insights into the complexity and roles that ROS play in plants have come from genetic analyses of ROS detoxifying and signaling mutants. Reactive oxygen species (ROS) are generally small, short-lived, and highly reactive molecules that are formed by incomplete one-electron reduction of oxygen. This review describes the mechanisms of ROS generation and removal in plants during development and under biotic and abiotic stress conditions. This ROS production contributes to mitochondrial damage in a range of pathologies and is also important in redox signalling from the organelle to the rest of the cell 3, 9. Whereas plants are surfeited with mechanisms to combat increased ROS levels during abiotic stress conditions, in other circumstances plants appear to purposefully generate ROS as signaling molecules to control various processes including pathogen defense, programmed cell death, and stomatal behavior. Mitochondria are an important source of ROS (reactive oxygen species) within most mammalian cells 1 8. 1 2 3 Generation of mitochondrial ROS mainly takes place at the electron transport chain located on the inner mitochondrial membrane during the process of oxidative phosphorylation. Oxidative stress refers to the imbalance due to excess ROS or oxidants over the capability of the cell to mount an effective antioxidant response. Among the more susceptible targets are polyunsaturated. The initial reaction generates a second radical, which in turn can react with a second macromolecule to continue the chain reaction. Depending on the nature of the ROS species, some are highly toxic and rapidly detoxified by various cellular enzymatic and nonenzymatic mechanisms. Mitochondrial ROS ( mtROS or mROS) are reactive oxygen species (ROS) that are produced by mitochondria. Reactive oxygen species (ROS) are generated during mitochondrial oxidative metabolism as well as in cellular response to xenobiotics, cytokines, and bacterial invasion. Reactive oxygen species, in particular the hydroxyl radical, can react with all biological macromolecules (lipids, proteins, nucleic acids and carbohydrates). ![]() Cellular ROS are generated endogenously during mitochondrial oxidative metabolism as well as in. 1 Disturbances in the normal redox state of cells can cause toxic effects through the production of peroxides and free radicals. Reactive oxygen species (ROS), such as superoxide anion (O 2- ), hydrogen peroxide (H 2 O 2 ), and hydroxyl radical (HO), consist of radical and non-radical oxygen species formed by the partial reduction of oxygen. Several reactive oxygen species (ROS) are continuously produced in plants as byproducts of aerobic metabolism. Oxidative stress reflects an imbalance between the systemic manifestation of reactive oxygen species and a biological systems ability to readily detoxify the reactive intermediates or to repair the resulting damage.
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