Nickel-induced oxidative stress and the role of antioxidant defence in rice seedlings

Abstract

Seedlings of rice (Oryza sativa L.) cv. Pant-12 grown in sand cultures containing 200 and 400 lM NiSO 4 , showed a decrease in length and fresh weight of roots and shoots. Nickel was readily taken up by rice seedlings and the concentration was higher in roots than shoots. Nickeltreated seedlings showed increased rates of superoxide anion (O 2•2 ) production, elevated levels of H 2 O 2 and thiobarbituric acid reactive substances (TBARS) demonstrating enhanced lipid peroxidation, and a decline in protein thiol levels indicative of increased protein oxidation compared to controls. With progressively higher Ni concentrations, non-protein thiol and ascorbate (AsA) increased, whereas the level of low-molecular-weight thiols (such as glutathione and hydroxyl-methyl glutathione), the ratio of these thiols to their corresponding disulphides, and the ratio of AsA to dehydroascorbic acid declined in the seedlings. Among the antioxidant enzymes studied, the activities of all isoforms of superoxide dismutase (Cu-Zn SOD, Mn SOD and Fe SOD), guaiacol peroxidases (GPX) and ascorbate peroxidase (APX) increased in Ni-treated seedlings, while no clear alteration in catalase activity was evident. Activity of the ascorbate-glutathione cycle enzymes monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR) and glutathione reductase (GR)-significantly increased in Ni-treated seedlings. However such increase was apparently insufficient to maintain the intracellular redox balance. Results suggest that Ni induces oxidative stress in rice plants, resulting in enhanced lipid peroxidation and decline in protein thiol levels, and that (hydroxyl-methyl) glutathione and AsA in conjunction with Cu-Zn SOD, GPX and APX are involved in stress response.

Reactive Oxygen Species, Oxidative Damage, and Antioxidative Defense Mechanism in Plants under Stressful Conditions

“…Tissues injured by oxidative stress generally contain increased concentrations of carbonylated proteins which is widely used marker of protein oxidation [93]. Enhanced modification of proteins has been reported in plants under various stresses [8,11,12,94]. The amino acids in a peptide differ in their susceptibility to attack by ROS.…”

“…AsA level has been reported to alter in response to various stresses [8,11,13,14,125,126]. The level of AsA under environmental stresses depends on the balance between the rates and capacity of AsA biosynthesis and turnover related to antioxidant demand [127].…”

“…In plants, ROS are always formed by the inevitable leakage of electrons onto O 2 from the electron transport activities of chloroplasts, mitochondria, and plasma membranes or as a byproduct of various metabolic pathways localized in different cellular compartments [1][2][3][4][5]. Environmental stresses such as drought, salinity, chilling, metal toxicity, and UV-B radiation as well as pathogens attack lead to enhanced generation of ROS in plants due to disruption of cellular homeostasis [6][7][8][9][10][11][12][13][14][15]. All ROS are extremely harmful to organisms at high concentrations.…”

Key plant products and common mechanisms utilized by plants in water deficit stress responses

“…Activation of antioxidant systems against oxidative stress damage.-Various environmental stresses such as drought, salinity, metal toxicity, cold and heat stress interrupt the normal cell metabolism (Maheshwari & Dubey 2009) and this unfavourable condition leads to enhance production of Reactive Oxygen Species or ROS (Kele & Ünyayar 2004 OH, H 2 O 2 , 1 O 2 ) are produced in cellular compartments as a by-product of various biochemical reactions or in chloroplasts, mitochondria and plasma membranes by exposing to high energy electron leak from electron transport activities (Foyer et al 1994, Foyer 1997, Luis et al 2006, Blokhina & Fagerstedt 2010, Heyno et al 2011. These toxic molecules damage cells by oxidation of vital macromolecules such as proteins, membrane lipids, DNA, pigments and nucleic acids (Dat et al 2000, Maheshwari & Dubey 2009). Various studies have established the enhancement of ROS under osmotic stress conditions (Serrato et al 2004, Borsani et al 2005, Miao et al 2006, Abbasi et al 2007).…”

Changes in Antioxidant Enzyme Activities of European Mistletoe (Viscum album L. subsp. Album) Leaves as a Response to Environmental Stress Caused by Pollution of the Atmosphere by Nitrogen Dioxide

“…Biotic factors such as bacterial or fungal pathogens, abiotic pollutants of soil and atmosphere, changes of temperature or humidity as well as solar exposure can cause disorders of cell metabolism called oxidative stress [1][2][3][4][5][6][7]. These factors disturb respiration processes, which results in generation of excess amounts of reactive oxygen species (ROS) in the form of singlet oxygen ( 1 O 2 ) and hydroxyl radical (OH • ) but mainly of superoxide radical (O 2…”