The Effects of Mg Deficiency on Activities and Isoenzyme Patterns of Antioxidant Enzymes in Cotton Roots

Abstract

Magnesium (Mg) is an essential nutrient that takes vital roles in biochemical processes related to energy metabolism, regulation of enzyme activity, nucleic acid biosynthesis and carbohydrate metabolism. Mg deficiency in arable lands is an emerging problem. Loss of balance in different metabolic pathways due to Mg deficiency causes increased production of reactive oxygen species (ROS) such as O₂^.-, H₂O₂ and HO^. in the roots.  The aim of this work was to elucidate the antioxidant response of roots of cotton (Gossypium hirsutum) to Mg deficiency. For this aim, antioxidant enzyme activities were measured and changes in their isoenzymes were determined. In addition, NADPH oxidase (NOX) activity was investigated to determine the changes in ROS signaling. Moreover, H₂O₂ and lipid peroxidation levels were also measured as an indicator of oxidative damage. Findings of this work indicate that Mg deficiency does not cause oxidative load in roots of Gossypium hirsutum plants that overwhelms cellular antioxidant defence system, as evident by H₂O₂ and TBARS levels. However, to adjust to the new redox status, root cells drastically downregulate NOX dependent ROS production and induced total superoxide dismutase activity. These findings indicate that site of O₂^.- production is mitochondria in roots. Although, catalase and ascorbate peroxidase activities were decreased with Mg deficiency induced peroxidase activity seems to limit H₂O₂ accumulation. These adaptive responses and changes in antioxidant defence were sufficient to prevent excess ROS accumulation and occurrence of oxidative damage in roots of Gossypium hirsutum plants under Mg deficiency

Keywords

• antioxidant enzymes,cotton,Gossypium hirsutum,magnesium deficiency,reactive oxygen species,Antioxidant defense system,reactive oxygen species

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