Effects of uranium and phosphate concentrations on oxidative stress related responses induced in Arabidopsis thaliana.
The production of reactive oxygen species (ROS) and the induction of the antioxidative defense mechanism are very important in heavy metal toxicity. In this study, biological effects induced after uranium contamination were investigated for Arabidopsis thaliana. Three-week-old seedlings were exposed for 4days to 100microM U in an adjusted Hoagland solution. Uranium exposure caused a decreased growth of leaves (38%) and roots (70%) and a modified nutrient profile was observed. Investigation of lipid peroxidation products indicated a significant increase of membrane damage. Important ROS-producing and -scavenging enzymes were studied at transcriptional and protein level to investigate the importance of the ROS-signature in uranium toxicity. Elevated gene expression was observed for NADPH-oxidase, a ROS-producing enzyme. Changes in gene expression for different ROS-scavenging enzymes as Cu/ZnSOD, FeSOD and APX were also observed. Analysis of enzyme capacities showed little effects after uranium contamination. Higher ascorbate levels in uranium exposed leaves suggested an increase of antioxidative defense via the ascorbate-glutathione pathway after uranium exposure. Theoretical calculations indicated rapid formation of uranium-phosphate precipitates if normal phosphate concentrations are used. Precipitation tests recommend the use of 25microM P in combination with 100microM U to inhibit uranium precipitation. Because this combination was used for uranium toxicity investigation, the influence of this low phosphate concentration on plant growth and oxidative stress had to be evaluated. Minor differences between low phosphate (25microM P) and high phosphate (100microM P) treatments were observed justifying the use of the low phosphate concentration in combination with uranium.
Vanhoudt
Nathalie
N
Belgian Nuclear Research Centre (SCK*CEN), Biosphere Impact Studies, Boeretang 200, 2400 Mol, Belgium. nvanhoud@sckcen.be
Vandenhove
Hildegarde
H
Smeets
Karen
K
Remans
Tony
T
Van Hees
May
M
Wannijn
Jean
J
Vangronsveld
Jaco
J
Cuypers
Ann
A
D000975:Antioxidants / Q000502:physiology*; D017360:Arabidopsis / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D015870:Gene Expression; D015227:Lipid Peroxidation; D018384:Oxidative Stress / Q000187:drug effects* / Q000502:physiology; D010710:Phosphates / Q000633:toxicity*; D018515:Plant Leaves / Q000187:drug effects / Q000254:growth & development; D018517:Plant Roots / Q000187:drug effects / Q000254:growth & development; D017382:Reactive Oxygen Species / Q000378:metabolism; D036226:Seedlings / Q000187:drug effects / Q000254:growth & development; D014501:Uranium / Q000633:toxicity*
D000975:Antioxidants; D010710:Phosphates; D017382:Reactive Oxygen Species; D014501:Uranium