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Induction of Oxidative Stress and Antioxidative Mechanisms in Arabidopsis thaliana after Uranium Exposure at pH 7.5.

Saenen E, Horemans N, Vanhoudt N, Vandenhove H, Biermans G, Van Hees M, Wannijn J, Vangronsveld J, Cuypers A - Int J Mol Sci (2015)

Bottom Line: In the roots, the increased capacities of ascorbate peroxidase and glutathione reductase indicate an important role for the ascorbate-glutathione cycle during U-induced stress.However, a significant decrease in the ascorbate redox state was observed after exposure to 75 and 100 µM U, indicating that those roots are severely stressed.However, at higher U concentrations it seems that the antioxidative defence system of the leaves collapses as reductions in enzyme activities and gene expression levels were observed.

View Article: PubMed Central - PubMed

Affiliation: Belgian Nuclear Research Centre (SCK•CEN), Biosphere Impact Studies, Boeretang 200, 2400 Mol, Belgium. eline.saenen@sckcen.be.

ABSTRACT
To evaluate the environmental impact of uranium (U) contamination, it is important to investigate the effects of U at ecologically relevant conditions. Since U speciation, and hence its toxicity, strongly depends on environmental pH, the present study aimed to investigate dose-dependent effects of U at pH 7.5. Arabidopsis thaliana plants (Mouse-ear Cress) were exposed for three days to different U concentrations at pH 7.5. In the roots, the increased capacities of ascorbate peroxidase and glutathione reductase indicate an important role for the ascorbate-glutathione cycle during U-induced stress. However, a significant decrease in the ascorbate redox state was observed after exposure to 75 and 100 µM U, indicating that those roots are severely stressed. In accordance with the roots, the ascorbate-glutathione cycle plays an important role in the antioxidative defence systems in A. thaliana leaves exposed to U at pH 7.5 as the ascorbate and glutathione biosynthesis were upregulated. In addition, small inductions of enzymes of the antioxidative defence system were observed at lower U concentrations to counteract the U-induced stress. However, at higher U concentrations it seems that the antioxidative defence system of the leaves collapses as reductions in enzyme activities and gene expression levels were observed.

No MeSH data available.


Related in: MedlinePlus

Fresh weight (mg per plant) of roots (grey bars) and leaves (white bars) of Arabidopsis thaliana plants exposed to different U concentrations for three days at pH 7.5. Statistical analyses were done separately for leaves and roots. Values represent the mean ± S.E. of at least 100 biological replicates. Data points with different letters are significantly different (p < 0.05).
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ijms-16-12405-f002: Fresh weight (mg per plant) of roots (grey bars) and leaves (white bars) of Arabidopsis thaliana plants exposed to different U concentrations for three days at pH 7.5. Statistical analyses were done separately for leaves and roots. Values represent the mean ± S.E. of at least 100 biological replicates. Data points with different letters are significantly different (p < 0.05).

Mentions: After U exposure, a significant decrease in root and leaf fresh weight was observed (Figure 2). This decrease was already significant after exposure to the lowest U concentration applied (6.25 µM). For the growth reduction in roots and leaves (growth of controls = 100%), a dose response curve was modelled using the four-parameter Weibull function [29,30] in the statistical software package R (version 2.15.0) (R Foundation for Statistical Computing, Vienna, Austria) since this model is the best-fit model for our data. The curve fitting enabled to calculate effect concentrations (ECs) together with a corresponding standard error. The ECx is the concentration that causes × per cent effect compared to a control. For roots exposed for 3 days to U, the EC10, EC30 and EC50 values for root growth reduction were 2.84 ± 1.80, 22.67 ± 6.43 and 70.24 ± 10.48 µM U, respectively. For leaf growth reduction 1.08 ± 0.30, 13.55 ± 1.43 and 53.74 ± 3.51 µM U were calculated to be the EC10, EC30 and EC50, respectively.


Induction of Oxidative Stress and Antioxidative Mechanisms in Arabidopsis thaliana after Uranium Exposure at pH 7.5.

Saenen E, Horemans N, Vanhoudt N, Vandenhove H, Biermans G, Van Hees M, Wannijn J, Vangronsveld J, Cuypers A - Int J Mol Sci (2015)

Fresh weight (mg per plant) of roots (grey bars) and leaves (white bars) of Arabidopsis thaliana plants exposed to different U concentrations for three days at pH 7.5. Statistical analyses were done separately for leaves and roots. Values represent the mean ± S.E. of at least 100 biological replicates. Data points with different letters are significantly different (p < 0.05).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4490451&req=5

ijms-16-12405-f002: Fresh weight (mg per plant) of roots (grey bars) and leaves (white bars) of Arabidopsis thaliana plants exposed to different U concentrations for three days at pH 7.5. Statistical analyses were done separately for leaves and roots. Values represent the mean ± S.E. of at least 100 biological replicates. Data points with different letters are significantly different (p < 0.05).
Mentions: After U exposure, a significant decrease in root and leaf fresh weight was observed (Figure 2). This decrease was already significant after exposure to the lowest U concentration applied (6.25 µM). For the growth reduction in roots and leaves (growth of controls = 100%), a dose response curve was modelled using the four-parameter Weibull function [29,30] in the statistical software package R (version 2.15.0) (R Foundation for Statistical Computing, Vienna, Austria) since this model is the best-fit model for our data. The curve fitting enabled to calculate effect concentrations (ECs) together with a corresponding standard error. The ECx is the concentration that causes × per cent effect compared to a control. For roots exposed for 3 days to U, the EC10, EC30 and EC50 values for root growth reduction were 2.84 ± 1.80, 22.67 ± 6.43 and 70.24 ± 10.48 µM U, respectively. For leaf growth reduction 1.08 ± 0.30, 13.55 ± 1.43 and 53.74 ± 3.51 µM U were calculated to be the EC10, EC30 and EC50, respectively.

Bottom Line: In the roots, the increased capacities of ascorbate peroxidase and glutathione reductase indicate an important role for the ascorbate-glutathione cycle during U-induced stress.However, a significant decrease in the ascorbate redox state was observed after exposure to 75 and 100 µM U, indicating that those roots are severely stressed.However, at higher U concentrations it seems that the antioxidative defence system of the leaves collapses as reductions in enzyme activities and gene expression levels were observed.

View Article: PubMed Central - PubMed

Affiliation: Belgian Nuclear Research Centre (SCK•CEN), Biosphere Impact Studies, Boeretang 200, 2400 Mol, Belgium. eline.saenen@sckcen.be.

ABSTRACT
To evaluate the environmental impact of uranium (U) contamination, it is important to investigate the effects of U at ecologically relevant conditions. Since U speciation, and hence its toxicity, strongly depends on environmental pH, the present study aimed to investigate dose-dependent effects of U at pH 7.5. Arabidopsis thaliana plants (Mouse-ear Cress) were exposed for three days to different U concentrations at pH 7.5. In the roots, the increased capacities of ascorbate peroxidase and glutathione reductase indicate an important role for the ascorbate-glutathione cycle during U-induced stress. However, a significant decrease in the ascorbate redox state was observed after exposure to 75 and 100 µM U, indicating that those roots are severely stressed. In accordance with the roots, the ascorbate-glutathione cycle plays an important role in the antioxidative defence systems in A. thaliana leaves exposed to U at pH 7.5 as the ascorbate and glutathione biosynthesis were upregulated. In addition, small inductions of enzymes of the antioxidative defence system were observed at lower U concentrations to counteract the U-induced stress. However, at higher U concentrations it seems that the antioxidative defence system of the leaves collapses as reductions in enzyme activities and gene expression levels were observed.

No MeSH data available.


Related in: MedlinePlus