Effects of pH on uranium uptake and oxidative stress responses induced in Arabidopsis thaliana

• Published in: Environmental toxicology and chemistry Vol. 32; no. 9; pp. 2125 - 2133
• Main Authors: Saenen, Eline, Horemans, Nele, Vanhoudt, Nathalie, Vandenhove, Hildegarde, Biermans, Geert, Van Hees, May, Wannijn, Jean, Vangronsveld, Jaco, Cuypers, Ann
• Format: Journal Article
• Language: English
• Published: Pensacola, FL Blackwell Publishing Ltd 01.09.2013; SETAC
• Subjects: Animal, plant and microbial ecology; Antioxidants - metabolism; Applied ecology; Arabidopsis - drug effects; Arabidopsis - metabolism; Arabidopsis thaliana; Biological and medical sciences; Chelation; Chemical speciation; Ecotoxicology, biological effects of pollution; Effects of pollution and side effects of pesticides on plants and fungi; Flowers & plants; Fundamental and applied biological sciences. Psychology; Glutathione - metabolism; Hydrogen-Ion Concentration; Oxidative stress; Oxidative Stress - drug effects; Plant Leaves - drug effects; Plant Leaves - metabolism; Plant Roots - drug effects; Plant Roots - metabolism; Risk assessment; Seedlings; Seedlings - drug effects; Seedlings - metabolism; Speciation; Superoxide Dismutase - metabolism; Toxicity; Translocation; Uranium; Uranium - metabolism; Uranium - pharmacology; Oxidative stress; Enzyme; Toxicity; Glutathione-disulfide reductase; Environmental factor; Superoxide dismutase; Radioisotope; Antioxidant; Arabidopsis thaliana; Absorption; Phytotoxicity; Uranium; Peroxidases; Enzymatic activity; Catalase; Cruciferae; Dicotyledones; Angiospermae; pH; Defense mechanism; Spermatophyta; Peroxidase; Oxidoreductases
• ISSN: 0730-7268; 1552-8618
• DOI: 10.1002/etc.2290

Uranium (U) causes oxidative stress in Arabidopsis thaliana plants grown at pH 5.5. However, U speciation and its toxicity strongly depend on environmental parameters, for example pH. It is unknown how different U species determine U uptake and translocation within plants and how they might affect the oxidative defense mechanisms of these plants. The present study analyzed U uptake and oxidative stress‐related responses in A. thaliana (Columbia ecotype) under contrasted U chemical speciation conditions. The 18‐d‐old seedlings were exposed for 3 d to 25 µM U in a nutrient solution of which the pH was adjusted to 4.5, 5.5, 6.5, or 7.5. Results indicate that there is a different rate of U uptake and translocation at the different pHs, with high uptake and low translocation at low pH and lower uptake but higher translocation at high pH. After U exposure, an increased glutathione reductase activity and total glutathione concentration were observed in U‐exposed roots, pointing toward an important role for glutathione in the root defense system against U either by chelation or by antioxidative defense mechanisms. In leaves, antioxidative defense mechanisms were activated on U exposure, indicated by increased superoxide dismutase and catalase activity. As it seems that U toxicity is influenced by pH, it is important to consider site‐specific characteristics when making U risk assessments. Environ Toxicol Chem 2013;32:2125–2133. © 2013 SETAC