Medicago-Catalase - Catalase Expression in Normal...

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Catalase Expression in Normal Metabolism and Under Stress in the Model Legume Medicago truncatula A.N. Polidoros 1 , P.V. Mylona 2 , K. Pasentsis 1 and A.S. Tsaftaris 1 ' 3 1 Institute of Agrobiotechnology, CERTH, Thermi, Greece; 2 Agricultural Research Center of Macedonia-Thrace, NAGREF, Thermi, Greece; 3 Department of Genetics and Plant Breeding, AUTh, Thessaloniki, Greece Summary Legume N 2 fixation is particularly sensitive to adverse environmental conditions linked to enhanced production of reactive oxygen species (ROS). Successful defense against oxidative stress is crucial for survival, and the protective mechanisms and their roles are under thorough investigation. In this study we examined the well characterized in other species antioxidant system of catalase in the model legume Medicago truncatula. We determined the isoenzymic profile of CAT in leaves, stems and roots and analyzed the enzyme responses to osmotic and oxidative stress. Our results demonstrated that at least two CAT isozymes are expressed in different tissues of M. truncatula, which respond differently to stress conditions. We also examined the expression profiles of catalase in leaves, stems, and roots after stress treatments. Catalase induction in leaves was higher than that in roots. In roots the highest induction was observed in NaCl stressed plants while in leaves the highest induction was observed in iron-treated plants. Introduction Aerobic organisms gain significant energetic advantage by using molecular oxygen as the terminal oxidant in respiration. However, they can be severely damaged by the partially reduced oxygen species superoxide radical (O 2 .- ), hydroxyl radical (*OH) and hydrogen peroxide (H 2 O 2 ), which are produced through normal or aberrant metabolic processes, and are commonly known reactive oxygen species (ROS). To minimize the adverse effects of ROS aerobic organisms evolved antioxidant defenses including catalases (CATs), ©2003 by MEDIMOND S.r.l. D719C0027 147
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148 XII th International Congress on "Genes, Gene Families and Isozymes" among others. Many plants subjected to a variety of environmental stresses respond by increasing the levels of mRNA and/or enzyme activity of anti- oxidant defense enzymes (Scandalios et al, 1997). Successful defense against oxidative stress is crucial for survival, and the protective mechanisms and their roles are under thorough investigation. In several recent studies, attempts were made to enhance protection with constitutive overexpression of defense enzymes in transgenic plants (Alien, 1995). Results of these studies confirm the important role of antioxidant defense enzymes in protection from oxidative stress of various types and origins, and point to the significance of transgenic plants as tools for plant improvement. Legume N
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Medicago-Catalase - Catalase Expression in Normal...

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