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ABSTRACT
Research Interests: Plant Biology, Comparative Study, Antioxidants, Plant Physiology, Glutathione, and 14 moreIberian Peninsula, Endemic species, Cadmium, Soil sciences, Plant Physiology and Biochemistry, Ascorbic Acid, Acid Soil, Ericaceae, Physiological Stress Markers, Environment, Antioxidant Capacity, Soil Pollutants, Total Antioxidant Capacity, and Plant Leaves
In previous studies exposing animals to Cd caused oxidative stress and kidney damage. Mostly high doses were applied, often by injection. In the present study mice were exposed up to 23 weeks to low Cd concentrations (10 and 100 mg... more
In previous studies exposing animals to Cd caused oxidative stress and kidney damage. Mostly high doses were applied, often by injection. In the present study mice were exposed up to 23 weeks to low Cd concentrations (10 and 100 mg CdCl2/l) in the drinking water. Antioxidant gene expression levels as well as glutathione, ascorbate and lipid peroxidation levels were measured. Metallothionein 1 and 2 were upregulated from 1 week of exposure on. An early induction of the Prdx2 gene suggested that peroxiredoxin might be involved in the early response as well. After 8 weeks Cd reduced antioxidant expression of Bcl2, Prdx2 and Sod1 which might indicate a toxic effect. No significant effect was seen on lipid peroxidation however, and the overall redox status remained in balance throughout the whole experiment. Levels of reduced glutathione and ascorbate and of transcription of Sod2 remained stable. This suggested that the energy maintenance in mitochondria was under control. A second respo...
... 12(2009): 364-372. [3] Cuypers Ann, Karen Smeets, Jos Ruytinx, Kelly Opdenakker, Els Keunen, Tony Remans, Nele Horemans, Nathalie Vanhoudt, Suzy Van Sanden ... [5] Vandenhove H., Cuypers A., Van Hees M., Koppen G. and Wannijn J.,... more
... 12(2009): 364-372. [3] Cuypers Ann, Karen Smeets, Jos Ruytinx, Kelly Opdenakker, Els Keunen, Tony Remans, Nele Horemans, Nathalie Vanhoudt, Suzy Van Sanden ... [5] Vandenhove H., Cuypers A., Van Hees M., Koppen G. and Wannijn J., Plant Physiology and Biochemistry. ...
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ABSTRACT
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Oxidative stress has been shown to be of great importance in the toxicity of several metals (copper, zinc, ...). In this study, the relationship of cadmium phytotoxicity and antioxidative reactions in bean (Phaseolus vulgaris L.) plants... more
Oxidative stress has been shown to be of great importance in the toxicity of several metals (copper, zinc, ...). In this study, the relationship of cadmium phytotoxicity and antioxidative reactions in bean (Phaseolus vulgaris L.) plants was investigated. Eleven-day-old seedlings were exposed to an environmentally realistic concentration of cadmium (2 microM CdSO(4)). Several biochemical and physiological parameters were influenced even by these low concentrations. At the biochemical level, the antioxidative defence mechanism was significantly activated after 24 h of cadmium exposure. Some enzymes able of quenching reactive oxygen species (syringaldazine peroxidase, EC 1.11.1.7; guaiacol peroxidase, EC 1.11.1.7) as well as enzymes important in the reduction of NAD(P)(+) (isocitrate dehydrogenase, EC 1.1.1.42; malic enzyme, EC 1.1.1.40) were significantly elevated by cadmium exposure. Furthermore, the ascorbate-glutathione cycle appeared to be a very important mechanism against cadmium-induced oxidative stress. In leaves, significant increases of ascorbate peroxidase (EC 1.11.1.11) and glutathione reductase (EC 1.6.4.2) and significant changes in the ascorbate and glutathione pool were observed. Morphological and other biochemical parameters (lipid peroxidation) were significantly enhanced 48 h after the start of the cadmium exposure. At the end of the experiment (72 h after the start of the metal treatment), even visual effects, such as chlorosis, were observed. The present data indicate that cadmium, like other metals, induces cellular redox disequilibrium suggesting that an environmentally realistic concentration of cadmium can cause oxidative stress.
Research Interests: Plant Biology, Oxidative Stress, Antioxidants, Peroxidase, Copper, and 15 moreReactive Oxygen Species, Glutathione, Zinc, Phaseolus, Cadmium, Soil sciences, Enzyme, Lipid peroxidation, Plant Physiology and Biochemistry, Phaseolus vulgaris, Peroxidases, Time Factors, Glutathione Reductase, Plant Leaves, and Ascorbate Peroxidase
This study aimed to investigate effects on growth and development and alterations in the nutrient profiles for Arabidopsis thaliana seedlings following uranium exposure. Seventeen-day-old Arabidopsis thaliana seedlings, grown in... more
This study aimed to investigate effects on growth and development and alterations in the nutrient profiles for Arabidopsis thaliana seedlings following uranium exposure. Seventeen-day-old Arabidopsis thaliana seedlings, grown in hydroponics, were exposed to 0, 0.1, 1, ...
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ABSTRACT The effects of cadmium (0.05–50 ppm in soils) on the antioxidant mechanisms of Erica andevalensis have been investigated under laboratory-controlled conditions. E. andevalensis, an endemic metal-tolerant species from SW Iberian... more
ABSTRACT The effects of cadmium (0.05–50 ppm in soils) on the antioxidant mechanisms of Erica andevalensis have been investigated under laboratory-controlled conditions. E. andevalensis, an endemic metal-tolerant species from SW Iberian Peninsula, is able to colonize extreme mine environments and to survive in very acid and metal enriched soils. Cadmium was taken up and accumulated in the leaves up to 0.5 ppm in plants watered with the highest concentration of this metal. The plants exposed to cadmium showed an increase in the levels of ascorbic acid and a decrease in the glutathione content. The activities of the antioxidative enzymes superoxide dismutase (SOD) and ascorbate peroxidase (APX) were enhanced whereas those of dehydroascorbate reductase (DHAR) and glutathione reductase (GR) were depleted in cadmium treated plants. Despite the fact that cadmium reached the leaves of the plant, and microscopy analysis revealed that mainly accumulated in the photosynthetic tissue, no significant changes were observed in the chlorophyll contents. Moreover, no damages were observed, neither visually, nor reflected in the lipid peroxidation, suggesting the great effectiveness of the mechanisms of this species to cope against metals.
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Research Interests: Aquatic Toxicology, Oxidative Stress, Biological Sciences, Environmental Sciences, Copper, and 22 moreAnimals, Fishes, Glutathione, Catalase, Metallothionein, Freshwater Fish, Superoxide Dismutase, Enzyme, CHEMICAL SCIENCES, Goldfish, Ascorbic Acid, Rainbow trout, Gills, Biological markers, Enzyme activity, Carps, Species Specificity, Oncorhynchus Mykiss, Cyprinus Carpio, Glutathione Reductase, Carassius Auratus, and Common Carp
Anthropogenic activities have led to a widespread uranium (U) contamination in many countries. The toxic effects of U at the cellular level have mainly been investigated at a pH around 5.5, the optimal pH for hydroponically grown plants.... more
Anthropogenic activities have led to a widespread uranium (U) contamination in many countries. The toxic effects of U at the cellular level have mainly been investigated at a pH around 5.5, the optimal pH for hydroponically grown plants. However, since the speciation of U, and hence its toxicity, is strongly dependent on environmental factors such as the pH, it is important to investigate the effects of U at different environmentally relevant pH levels. Although U is poorly translocated from the roots to the shoots, resulting in a low U concentration in the leaves, it has been demonstrated that toxic effects in the leaves were already visible after 1 day exposure at pH 5.5, although only when exposed to relatively high U concentrations (100 μM). Therefore, the present study aimed to analyse the effects of different U concentrations (ranging from 0 to 100 μM) at pH 4.5 in leaves of Arabidopsis thaliana plants. Results indicate that U induces early senescence in A. thaliana leaves as was suggested by a decreased expression of CAT2 accompanied by an induction of CAT3 expression, a decreased CAT capacity and an increased lipid peroxidation. In addition, miRNA398b/c is involved in the regulation of the SOD response in the leaves. As such, an increased MIR398b/c expression was observed leading to a decreased transcript level of CSD1/2. Finally, the biosynthesis of ascorbate was induced after U exposure. This can point towards an important role for this metabolite in the scavenging of reactive oxygen species under U stress.
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Human activity has led to an increasing amount of radionuclides in the environment and subsequently to an increased risk of exposure of the biosphere to ionising radiation. Due to their high linear energy transfer, α-emitters form a... more
Human activity has led to an increasing amount of radionuclides in the environment and subsequently to an increased risk of exposure of the biosphere to ionising radiation. Due to their high linear energy transfer, α-emitters form a threat to biota when absorbed or integrated in living tissue. Among these, (241)Am is of major concern due to high affinity for organic matter and high specific activity. This study examines the dose-dependent biological effects of α-radiation delivered by (241)Am at the morphological, physiological and molecular level in 14-day old seedlings of Arabidopsis thaliana after hydroponic exposure for 4 or 7 days. Our results show that (241)Am has high transfer to the roots but low translocation to the shoots. In the roots, we observed a transcriptional response of reactive oxygen species scavenging and DNA repair pathways. At the physiological and morphological level this resulted in a response which evolved from redox balance control and stable biomass at low dose rates to growth reduction, reduced transfer and redox balance decline at higher dose rates. This situation was also reflected in the shoots where, despite the absence of a transcriptional response, the control of photosynthesis performance and redox balance declined with increasing dose rate. The data further suggest that the effects in both organs were initiated in the roots, where the highest dose rates occurred, ultimately affecting photosynthesis performance and carbon assimilation. Though further detailed study of nutrient balance and (241)Am localisation is necessary, it is clear that radionuclide uptake and distribution is a major parameter in the global exposure effects on plant performance and health.
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Studies undertaken in the last decade by European and international organizations, have shown that regarding the nuclear sciences (including radioecology) there is a decreased student interest, decreased course numbers and ageing faculty... more
Studies undertaken in the last decade by European and international organizations, have shown that regarding the nuclear sciences (including radioecology) there is a decreased student interest, decreased course numbers and ageing faculty members and facilities. Taking this situation into account, the Mobility, Training and Education Work Package (WP6) of the STAR Network of Excellence (NoE) had three main objectives: 1) to strength and secure a sustainable integrated European education and training platform in radioecology that will attract top-level graduates; 2) to maintain a relevant workforce that is in a position to meet future economic and societal needs within the nuclear sciences, and 3) to enhance the mobility of teachers and STAR scientists as a means to secure a goal of competence building. Within the STAR NoE, a Radioecology Education and Training Platform (E&T platform) has been developed to be a website focal point for students and professionals interested in radioecol...
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Different redox-active compounds, such as ascorbate, glutathione, NAD(P)H and proteins from the thioredoxin superfamily, contribute to the general redox homeostasis in the plant cell. The myriad of interactions between redox-active... more
Different redox-active compounds, such as ascorbate, glutathione, NAD(P)H and proteins from the thioredoxin superfamily, contribute to the general redox homeostasis in the plant cell. The myriad of interactions between redox-active compounds, and the effect of environmental parameters on them, has been encapsulated in the concept of a cellular redox state. This concept has facilitated progress in understanding stress signalling and defence in plants. However, despite the proven usefulness of the concept of a redox state, there is no single, operational definition that allows for quantitative analysis and hypothesis testing.
Research Interests: Plant Biology, Oxidative Stress, Quantitative analysis, Signal Transduction, Antioxidants, and 13 moreGlutathione, Plants, Green Fluorescent Protein, Soil sciences, Plant Physiology and Biochemistry, Thioredoxin, Homeostasis, Quantitative Analysis, Plant Stem Cells, Environment, Oxidation-Reduction, Environmental Parameter, and Thioredoxin reductase
A Nicotiana tabacum L. SR-1 leaf protoplast system was used to study the effects of dehydroascorbate and glutathione on cellular development. We found that dehydroascorbate is readily taken up by protoplasts and internally reduced to... more
A Nicotiana tabacum L. SR-1 leaf protoplast system was used to study the effects of dehydroascorbate and glutathione on cellular development. We found that dehydroascorbate is readily taken up by protoplasts and internally reduced to ascorbate. Concomitantly, cell division was inhibited and cell expansion stimulated. In this respect, dehydroascorbate counteracted auxin-mediated leaf protoplast development. In contrast to the effects of dehydroascorbate, glutathione-induced cell dedifferentiation, and this effect is similar to that mediated by high auxin concentrations. We conclude that dehydroascorbate and glutathione affect the auxin-mediated regulation of cellular development. Therefore, the biological role of these compounds extends beyond stress tolerance and defense.
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Research Interests: Plant Biology and Ecology
ABSTRACT The chemical speciation of uranium (U), and hence its toxicity, is strongly dependent on pH. However, oxidative stress responses after U exposure have mainly been investigated in Arabidopsis thaliana plants at pH 5.5, the ideal... more
ABSTRACT The chemical speciation of uranium (U), and hence its toxicity, is strongly dependent on pH. However, oxidative stress responses after U exposure have mainly been investigated in Arabidopsis thaliana plants at pH 5.5, the ideal pH for growing plants in a hydroponic setup. As the pH of pore water can vary strongly, the aim of this study is to investigate oxidative stress responses induced in roots of Arabidopsis thaliana plants exposed to different U concentrations at pH 4.5 and hence at a high free uraynl (UO22+) concentration. In addition to analysing growth reduction, effects were analysed at enzyme, metabolite and genetic level. Results indicate that U is highly toxic at low pH resulting in a significant decrease in fresh weight (EC50 value for root growth reduction: 28.14 ± 1.59 μM U). In addition, no intact RNA could be extracted from the roots exposed to 75 and 100 μM U and the ascorbate concentrations could not be determined in roots exposed to 50, 75 or 100 μM U indicating that the roots are seriously damaged. Concerning the antioxidative defence system, the involvement of miRNA398b/c in the regulation of the superoxide dismutase (SOD) response was observed after U exposure. As such, a significant increase in MIR398b/c expression was observed, accompanied by a decreased copper/zinc SOD (CSD1/2) expression. The latter was compensated by an increased expression of iron SOD (FSD1) to maintain the SOD capacity in the plastids. While the involvement of miRNA398b/c was already reported before under copper or cadmium stress, this is the first time that it is reported for U.
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The action of ascorbate free radical as an electron acceptor to cytochrome b-mediated trans-plasma membrane electron transport is demonstrated. Addition of ascorbate free radical to ascorbate-loaded plasma membrane vesicles caused a rapid... more
The action of ascorbate free radical as an electron acceptor to cytochrome b-mediated trans-plasma membrane electron transport is demonstrated. Addition of ascorbate free radical to ascorbate-loaded plasma membrane vesicles caused a rapid oxidation of the cytochrome, followed by a slower re-reduction. The fully reduced dehydroascorbate was ineffective.
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Recently, the uptake of 14C-labeled ascorbate (ASC) into highly purified bean (Phaseolus vulgaris L.) plasma membrane vesicles was demonstrated in our laboratory. However, the question of the redox status of the transported molecule (ASC... more
Recently, the uptake of 14C-labeled ascorbate (ASC) into highly purified bean (Phaseolus vulgaris L.) plasma membrane vesicles was demonstrated in our laboratory. However, the question of the redox status of the transported molecule (ASC or dehydroascorbate [DHA]) remained unanswered. In this paper we present evidence that DHA is transported through the plasma membrane. High-performance liquid chromatography analysis of the redox status of ASC demonstrated that freshly purified plasma membranes exhibit a high ASC oxidation activity. Although it is not yet clear whether this activity is enzymatic, it complicates the interpretation of ASC-transport experiments in vitro and in vivo. In an attempt to correlate the ASC redox status to transport of the molecule, the ability of different compounds to reduce DHA was analyzed and their effect on ASC-transport activity tested. Administering of various reductants resulted in different levels of inhibition of ASC uptake (dithiothreitol > dit...
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ABSTRACT We exposed Arabidopsis thaliana seedlings of different ages to chronic γ-radiation.•Growth response differs between ages upon exposure.•Patterns of DNA repair and cell cycle transcription upon exposure are age-dependent.
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To study the impact of environmental uranium (U) contamination, effects should be analysed at different environmentally relevant pH levels as the speciation of U, and hence its toxicity, is strongly dependent on the pH. As photosynthesis... more
To study the impact of environmental uranium (U) contamination, effects should be analysed at different environmentally relevant pH levels as the speciation of U, and hence its toxicity, is strongly dependent on the pH. As photosynthesis is a major energy producing process in plants intimately connected to plant growth and known to be susceptible to metal stress, the effects of different U concentrations on photosynthesis in 18-day-old Arabidopsis thaliana (Columbia ecotype) are investigated at two contrasting pH levels, pH 4.5 and pH 7.5. At pH 4.5, U is highly taken up by the roots but is poorly translocated to the shoots, while at pH 7.5, less U is taken up but the translocation is higher. The lower U concentrations in the shoots at pH 4.5 are accompanied by a more reduced leaf growth as compared to pH 7.5. In addition, U does not influence the photosynthetic machinery at pH 7.5, while an optimization of the photosynthesis takes place after U exposure at pH 4.5. As such, more of the absorbed quanta are effectively used for photosynthesis accompanied by a decreased non-photochemical quenching and an increased electron transport rate. Since the enhanced photosynthesis at pH 4.5 is accompanied by a decreased growth, we suggest that the energy produced during photosynthesis is used for defence reactions against U-induced oxidative stress rather than for growth. As such, a high discrepancy was observed between the two pH levels, with an optimized photosynthetic apparatus at pH 4.5 and almost no effects at pH 7.5.
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Summary Incubation of bean hook plasma membrane vesicles in the presence of L-[14C]ascorbate (ASC) resulted in a specific recovery of significant levels of the ligand with the vesicles. The strong decrease in radioactive ASC detected... more
Summary Incubation of bean hook plasma membrane vesicles in the presence of L-[14C]ascorbate (ASC) resulted in a specific recovery of significant levels of the ligand with the vesicles. The strong decrease in radioactive ASC detected after hypotonic disruption of the vesicles or after an assay at 4 °C indicated that ASC was probably transported from the medium into the lumen
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Summary. In cell suspension cultures of Nicotiana tabacum L. cv. Bright Yellow 2 (BY-2) a rapid and concentration-dependent accumulation of H2O2 is induced by excess concentrations of copper (up to 100 μM). This specific and early... more
Summary. In cell suspension cultures of Nicotiana tabacum L. cv. Bright Yellow 2 (BY-2) a rapid and concentration-dependent accumulation of H2O2 is induced by excess concentrations of copper (up to 100 μM). This specific and early response towards copper stress was shown to be extracellular. Addition of 300 U of catalase per ml decreased the level of H2O2. Superoxide dismutase (5 U/ml) induced an
Research Interests: Plant Biology, Tobacco, Cell Culture, Peroxidase, Copper, and 12 moreReactive Oxygen Species, Catalase, Superoxide Dismutase, Hydrogen Peroxide, Nicotiana Tabacum, Buffers, Cell Wall, Hydrogen-Ion Concentration, Copper sulfate, Respiratory Burst, Biochemistry and cell biology, and Cell Suspension Culture
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Summary Higher plant plasma membranes contain ab-type cytochrome that is rapidly reduced by ascorbic acid. The affinity towards ascorbate is 0.37 mM and is very similar to that of the chromaffin granule cytochromeb561. High levels of... more
Summary Higher plant plasma membranes contain ab-type cytochrome that is rapidly reduced by ascorbic acid. The affinity towards ascorbate is 0.37 mM and is very similar to that of the chromaffin granule cytochromeb561. High levels of cytochromeb reduction are reached when ascorbic acid is added either on the cytoplasmic or cell wall side of purified plasma membrane vesicles. This result points to a transmembrane organisation of the heme protein or alternatively indicates the presence of an effective ascorbate transport system. Plasma membrane vesicles loaded by ascorbic acid are capable of reducing extravesicular ferricyanide. Addition of ascorbate oxidase or washing of the vesicles does not eliminate this reaction, indicating the involvement of the intravesicular electron donor. Absorbance changes of the cytochromeb a-band suggest the electron transfer is mediated by this redox component. Electron transport to ferricyanide also results in the generation of a membrane potential gradient as was demonstrated by using the charge-sensitive optical probe oxonol VI. Addition of ascorbate oxidase and ascorbate to the vesicles loaded with ascorbate results in the oxidation and subsequent re-reduction of the cytochromeb. It is therefore suggested that ascorbate free radical (AFR) could potentially act as an electron acceptor to the cytochrome-mediated electron transport reaction. A working model on the action of the cytochrome as an electron carrier between cytoplasmic and apoplastic ascorbate is discussed.
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Genetic evidences indicate that alkaline/neutral invertases are present in plant cell organelles, and they might have a novel physiological function in mitochondria. The present study demonstrates an invertase activity in the... more
Genetic evidences indicate that alkaline/neutral invertases are present in plant cell organelles, and they might have a novel physiological function in mitochondria. The present study demonstrates an invertase activity in the mitochondrial matrix of Helianthus tuberosus tubers. The pH optimum, the kinetic parameters and the inhibitor profile of the invertase activity indicated that it belongs to the neutral invertases. In accordance with this topology, transport activities responsible for the mediation of influx/efflux of substrate/products were studied in the inner mitochondrial membrane. The transport of sucrose, glucose and fructose was shown to be bidirectional, saturable and independent of the mitochondrial respiration and membrane potential. Sucrose transport was insensitive to the inhibitors of the proton-sucrose symporters. The different kinetic parameters and inhibitors as well as the absence of cross-inhibition suggest that sucrose, glucose and fructose transport are mediated by separate transporters in the inner mitochondrial membrane. The mitochondrial invertase system composed by an enzyme activity in the matrix and the corresponding sugar transporters might have a role in both osmoregulation and intermediary metabolism.