title: Unraveling uranium induced oxidative stress related responses in Arabidopsis thaliana seedlings. Part I: responses in the roots.
abstract: 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 H(2)O(2), 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.
authors.affiliation: Belgian Nuclear Research Center (SCK•CEN), Biosphere Impact Studies, Boeretang 200, 2400 Mol, Belgium. nvanhoud@sckcen.be
authors.forename: Nathalie
authors.initials: N
authors.lastname: Vanhoudt
authors.forename: Hildegarde
authors.initials: H
authors.lastname: Vandenhove
authors.forename: Nele
authors.initials: N
authors.lastname: Horemans
authors.forename: Tony
authors.initials: T
authors.lastname: Remans
authors.forename: Kelly
authors.initials: K
authors.lastname: Opdenakker
authors.forename: Karen
authors.initials: K
authors.lastname: Smeets
authors.forename: Daniel Martinez
authors.initials: DM
authors.lastname: Bello
authors.forename: Jean
authors.initials: J
authors.lastname: Wannijn
authors.forename: May
authors.initials: M
authors.lastname: Van Hees
authors.forename: Jaco
authors.initials: J
authors.lastname: Vangronsveld
authors.forename: Ann
authors.initials: A
authors.lastname: Cuypers
mesh_terms: D000975:Antioxidants / Q000378:metabolism*; D017360:Arabidopsis / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D001205:Ascorbic Acid / Q000378:metabolism; D015870:Gene Expression; D005978:Glutathione / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D010088:Oxidoreductases / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D011829:Radiation Dosage; D017382:Reactive Oxygen Species / Q000378:metabolism; D036226:Seedlings / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D014501:Uranium / Q000633:toxicity*
chemical_list: D000975:Antioxidants; D029681:Arabidopsis Proteins; D017382:Reactive Oxygen Species; D014501:Uranium; D006861:Hydrogen Peroxide; D010088:Oxidoreductases; D005978:Glutathione; D001205:Ascorbic Acid