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      Plant responses to stresses: Role of ascorbate peroxidase in the antioxidant protection


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          When plants are exposed to stressful environmental conditions, the production of Reactive Oxygen Species (ROS) increases and can cause significant damage to the cells. Antioxidant defenses, which can detoxify ROS, are present in plants. A major hydrogen peroxide detoxifying system in plant cells is the ascorbate-glutathione cycle, in which, ascorbate peroxidase (APX) enzymes play a key role catalyzing the conversion of H 2O 2 into H 2O, using ascorbate as a specific electron donor. Different APX isoforms are present in distinct subcellular compartments, such as chloroplasts, mitochondria, peroxisome, and cytosol. The expression of APX genes is regulated in response to biotic and abiotic stresses as well as during plant development. The APX responses are directly involved in the protection of plant cells against adverse environmental conditions. Furthermore, mutant plants APX genes showed alterations in growth, physiology and antioxidant metabolism revealing those enzymes involvement in the normal plant development.

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          Most cited references 77

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          Photoprotection and Other Responses of Plants to High Light Stress

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            Regulation and function of ascorbate peroxidase isoenzymes.

            Even under optimal conditions, many metabolic processes, including the chloroplastic, mitochondrial, and plasma membrane-linked electron transport systems of higher plants, produce active oxygen species (AOS). Furthermore, the imposition of biotic and abiotic stress conditions can give rise to excess concentrations of AOS, resulting in oxidative damage at the cellular level. Therefore, antioxidants and antioxidant enzymes function to interrupt the cascades of uncontrolled oxidation in each organelle. Ascorbate peroxidase (APX) exists as isoenzymes and plays an important role in the metabolism of H(2)O(2) in higher plants. APX is also found in eukaryotic algae. The characterization of APX isoenzymes and the sequence analysis of their clones have led to a number of investigations that have yielded interesting and novel information on these enzymes. Interestingly, APX isoenzymes of chloroplasts in higher plants are encoded by only one gene, and their mRNAs are generated by alternative splicing of the gene's two 3'-terminal exons. Manipulation of the expression of the enzymes involved in the AOS-scavenging systems by gene-transfer technology has provided a powerful tool for increasing the present understanding of the potential of the defence network against oxidative damage caused by environmental stresses. Transgenic plants expressing E. coli catalase to chloroplasts with increased tolerance to oxidative stress indicate that AOS-scavenging enzymes, especially chloroplastic APX isoenzymes are sensitive under oxidative stress conditions. It is clear that a high level of endogenous ascorbate is essential effectively to maintain the antioxidant system that protects plants from oxidative damage due to biotic and abiotic stresses.
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              Ascorbate peroxidase - a hydrogen peroxide-scavenging enzyme in plants

               Kozi Asada (1992)

                Author and article information

                Genet Mol Biol
                Genet. Mol. Biol
                Genetics and Molecular Biology
                Sociedade Brasileira de Genética (Ribeirão Preto, SP, Brazil )
                18 December 2012
                December 2012
                : 35
                : 4 (suppl)
                : 1011-1019
                [1 ]Programa de Pós-Graduação em Genética e Biologia Molecular, Departamento de Genética, Universidade Federal Rio Grande do Sul, Porto Alegre, RS, Brazil.
                [2 ]Programa de Pós-Graduação em Biologia Celular e Molecular, Centro de Biotecnologia, Universidade Federal Rio Grande do Sul, Porto Alegre, RS, Brazil.
                Author notes
                Send corresponce to Marcia Margis-Pinheiro. Departamento de Genética, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves 9500, 91501-970 Porto Alegre, RS, Brazil. E-mail: marcia.margis@ 123456ufrgs.br .
                Copyright © 2012, Sociedade Brasileira de Genética.

                License information: This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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