Unraveling uranium induced oxidative stress related responses in Arabidopsis thaliana seedlings. Part I: responses in the roots

• Published in: Journal of environmental radioactivity Vol. 102; no. 6; pp. 630 - 637
• Main Authors: Vanhoudt, Nathalie, Vandenhove, Hildegarde, Horemans, Nele, Remans, Tony, Opdenakker, Kelly, Smeets, Karen, Bello, Daniel Martinez, Wannijn, Jean, Van Hees, May, Vangronsveld, Jaco, Cuypers, Ann
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.06.2011; Elsevier
• Subjects: Animal, plant and microbial ecology; Antioxidants - metabolism; Antioxidative defense system; Applied ecology; Arabidopsis - drug effects; Arabidopsis - growth & development; Arabidopsis - metabolism; Arabidopsis Proteins - metabolism; Arabidopsis thaliana; Ascorbic Acid - metabolism; Biological and medical sciences; Ecotoxicology, biological effects of pollution; Effects of pollution and side effects of pesticides on plants and fungi; Environmental impact; Fundamental and applied biological sciences. Psychology; Gene Expression; Glutathione - metabolism; Hydrogen Peroxide - metabolism; Oxidation-Reduction; Oxidative Stress; Oxidoreductases - metabolism; Plant Roots - drug effects; Plant Roots - growth & development; Plant Roots - metabolism; Radiation Dosage; Reactive Oxygen Species - metabolism; Seedlings - drug effects; Seedlings - growth & development; Seedlings - metabolism; Uranium - toxicity; Oxidative stress; GSSG; DTT; Antioxidative defense system; Uranium toxicity; PX; APX; SOD; GR; Gene expression; AsA; GPX; RBOH; Arabidopsis thaliana; LOX; CSD; FSD; CAT; ROS; SPX; DHA; GSH; MSD; Root; Toxicity; Plant juvenile growth stage; Radioisotope; Uranium; Cruciferae; Dicotyledones; Angiospermae; Spermatophyta; Experimental plant
• ISSN: 0265-931X; 1879-1700
• DOI: 10.1016/j.jenvrad.2011.03.015

When aiming to evaluate the environmental impact of uranium contamination, it is important to unravel the mechanisms by which plants respond to uranium stress. As oxidative stress seems an important modulator under other heavy metal stress, this study aimed to investigate oxidative stress related responses in Arabidopsis thaliana exposed to uranium concentrations ranging from 0.1 to 100 μM for 1, 3 and 7 days. Besides analyzing relevant reactive oxygen species-producing and -scavenging enzymes at protein and transcriptional level, the importance of the ascorbate–glutathione cycle under uranium stress was investigated. These results are reported separately for roots and leaves in two papers: Part I dealing with responses in the roots and Part II unraveling responses in the leaves and presenting general conclusions. Results of Part I indicate that oxidative stress related responses in the roots were only triggered following exposure to the highest uranium concentration of 100 μM. A fast oxidative burst was suggested based on the observed enhancement of lipoxygenase (LOX1) and respiratory burst oxydase homolog (RBOHD) transcript levels already after 1 day. The first line of defense was attributed to superoxide dismutase (SOD), also triggered from the first day. The enhanced SOD-capacity observed at protein level corresponded with an enhanced expression of iron SOD (FSD1) located in the plastids. For the detoxification of H2O2, an early increase in catalase (CAT1) transcript levels was observed while peroxidase capacities were enhanced at the later stage of 3 days. Although the ascorbate peroxidase capacity and gene expression (APX1) increased, the ascorbate/dehydroascorbate redox balance was completely disrupted and shifted toward the oxidized form. This disrupted balance could not be inverted by the glutathione part of the cycle although the glutathione redox balance could be maintained. ► Unravel response mechanisms to uranium stress in Arabidopsis thaliana roots. ► Oxidative stress related responses only present at 100 μM uranium. ► SOD constitutes first line of defense against O2−. ► H2O2 is postulated as signaling molecule. ► Controlling H2O2 levels by APX seems to be important. ► Regeneration of oxidized ascorbate by glutathione is hampered.