1,721,106 research outputs found
Evidence for a role of nitric oxide in iron homeostasis in plants
No full textNitric oxide (NO), once regarded as a poisonous air pollutant, is now understood as a regulatory molecule essential for several biological functions in plants. In this review, we summarize NO generation in different plant organs and cellular compartments, and also discuss the role of NO in iron (Fe) homeostasis, particularly in Fe-deficient plants. Fe is one of the most limiting essential nutrient elements for plants. Plants often exhibit Fe deficiency symptoms despite sufficient tissue Fe concentrations. NO appears to not only up-regulate Fe uptake mechanisms but also makes Fe more bioavailable for metabolic functions. NO forms complexes with Fe, which can then be delivered into target cells/tissues. NO generated in plants can alleviate oxidative stress by regulating antioxidant defense processes, probably by improving functional Fe status and by inducing post-translational modifications in the enzymes/proteins involved in antioxidant defense responses. It is hypothesized that NO acts in cooperation with transcription factors such as bHLHs, FIT, and IRO to regulate the expression of enzymes and proteins essential for Fe homeostasis. However, further investigations are needed to disentangle the interaction of NO with intracellular target molecules that leads to enhanced internal Fe availability in plants.RKT is grateful to Department of Science and Technology-Science and Engineering Research Board (DST-SERB) New Delhi, for a Teachers Associateship for Research Excellence (TAR/2019/000064).Tewari, RK (corresponding author), Univ Lucknow, Dept Bot, Lucknow 226007, Uttar Pradesh, India.
[email protected]
Flowering under enhanced ionising radiation conditions and its regulation through epigenetic mechanisms
No full textAs sessile organisms, plants have to deal with unfavourable conditions by acclimating or adapting in order to survive. Regulation of flower induction is one such mechanism to ensure reproduction and species survival. Flowering is a tightly regulated process under the control of a network of genes, which can be affected by environmental cues and stress. The effects of ionising radiation (IR) on flowering, however, have been poorly studied. Understanding the effects of ionising radiation on flowering, including the timing, gene pathways, and epigenetics involved, is crucial in the continuing effort of environmental radiation protection. The review shows that plants alter their flowering pattern in response to IR, with various flowering related genes (eg. FLOWERING LOCUS C (FLC), FLOWERING LOCUS T (FT), CONSTANS (CO), GIGANTEA (GI), APETALA1 (AP1), LEAFY (LFY)) and epigenetic processes (DNA methylation, and miRNA expression eg. miRNA169, miR156, miR172) being affected. Thereby, showing a hypothetical IR-induced flowering mechanism. Further research on the interaction between IR and flowering in plants is, however, needed to elucidate the mechanisms behind the stress-induced flowering response.The authors would like to thank SCK CEN and the University of Hasselt for the financing of the project as well as PL’s PhD
Calcium affects uranium responses in Arabidopsis thaliana: From distribution to toxicity
No full textUranium, a heavy metal and primordial radionuclide, is present in surface waters and soils both naturally and due to industrial activities. Uranium is known to be toxic to plants and its uptake and toxicity can be influenced by multiple factors such as pH and the presence of different ions. However, the precise role of the different ions in uranium uptake is not yet known. Here we investigated whether calcium influences uranium uptake and toxicity in the terrestrial plant Arabidopsis thaliana. To this end, A. thaliana plants were exposed to different calcium and uranium concentrations and furthermore, calcium channels were blocked using the calcium channel blocker lanthanum chloride (LaCl3). Fresh weight, relative growth rate, concentration of nutrients and uranium and gene expression of oxidative stress-related genes and calcium transporters were determined in roots and shoots. Calcium affected plant growth and oxidative stress in both control (no uranium) and uranium-exposed plants. In shoots, this was influenced by the total calcium concentration, but not by the different tested uranium concentrations. Uranium in turn did influence calcium uptake and distribution. Uranium-exposed plants grown in a medium with a higher calcium concentration showed an increase in gene expression of NADPH oxidases RBOHC and RBOHE and calcium transporter CAX7 after uranium exposure. In roots, these calcium-dependent responses in gene expression were not observed. This indicates that calcium indeed affects uranium toxicity, but only in shoots. In addition, a clear influence of uranium and LaCl3 (separately and combined) on the expression of calcium transporters was observed.PhD fellowship for A. M. was financially supported by the Belgian Nuclear Research Centre (SCK CEN). We would also like to thank our colleagues at BIS for the technical help in the setup and execution of the experiment
Interception of radionuclides by planophile crops: A simple semi-empirical modelling approach in case of nuclear accident fallout
No full textShortly after an atmospheric release, the interception of radionuclides by crop canopies represents the main uptake pathway leading to food chain contamination. The food chain models currently used in European emergency decision support systems require a large number of input parameters, which inevitably leads to high model complexity. In this study, we have established a new relationship for wet deposited radionuclides to simplify the current modelling approaches. This relationship is based on the hypothesis that the stage of plant development is the key factor governing the interception of radionuclides by crops having horizontally oriented leaves (planophile crops). The interception fraction (f) and the leaf area index normalized (f(LAI)) and mass normalized (f(B)) interception fractions were assessed for spinach (Spinacia oleracea) and radish (Raphanus sativus) at different stages of plant development and for different contamination treatments and plant densities. A database of 191 f values for Cs-137 and Th-229 was built and complemented with existing literature covering various radionuclides and crops with similar canopy structure. The overall f increased with the plant growth, while the reverse was observed for f(B). The f(LAI) significantly decreased by doubling the contaminated rainfall deposited. Fitting a multiple linear regression to predict the f value as a function of the standing biomass (B), and the radionuclide form (anion and cation) led to a better estimation of the interception (R-2 = 81%) than the ECOSYS-87 model (R-2 = 35%). Hence, the simplified modelling approach here proposed seems to be a suitable risk assessment tool as fewer parameters will minimize the model complexity and facilitate the decision-making procedures in case of emergencies, when countermeasures need to be identified and implemented promptly. (C) 2020 Elsevier Ltd. All rights reserved.The authors wish to thank dr. Gerard Prohl (International € Atomic Energy Agency) for proof reading the article, dr. Ella Roelant (University of Antwerp) for providing statistical and modelling assistance, dr. Diederik Jacques (SCK CEN) for his contribution to modeling the speciation of radionuclides, the lab-technicians Axel Van Gompel and Robin Nauts (Biosphere Impact Study, SCK CEN) for helping during laboratory activities, and the ing. Leen Verheyen
(Low-level Radiactivity Measurements, SCK CEN), expert in gamma spectrometry. This work was funded by the Belgian Nuclear Research Centre (SCK CEN) as PhD grant for Antonella CristinaCristina, A (corresponding author), Belgian Nucl Res Ctr SCK CEN, Fdn Publ Util, Biosphere Impact Studies, B-2400 Mol, Belgium ; Univ Antwerp, Dept Biosci Engn, Groenenborgerlaan 171, B-2020 Antwerp, Belgium.
[email protected]
A dynamic dosimetry model for radioactive exposure scenarios in Arabidopsis thaliana
No full textTo obtain a better understanding on how non-human biota are affected by exposure to environmental radioactivity, it is essential to link observed effects to a correct estimate of absorbed ionising radiation dose. Current wildlife dose rate and risk assessment tools are not set up to assess changes in dose rate during organism development. This paper presents a dosimetry model for assessing dose rate and absorbed dose during seedling development of the model plant Arabidopsis thaliana. We included growth and radionuclide absorption dynamics into the dose calculations. This model was subsequently used to compare the dose and dose rate calculations for three radionuclides, 241Am (α-radiation), 90Sr (β-radiation) and 133Ba (γ-radiation), in a standard exposure scenario. We show that growth influences dose and dose rate and that this influence depends on the radionuclide and the organ involved. The use of dynamic dosimetry models greatly improves the dose calculations for effect studies.This research was funded by the Research Foundation Flanders (FWO) grant no. 1.1.763.10N in joint funding with SCK.CEN
Exposing mice to low Cd doses triggers a biphasic oxidative stress response in the kidney: a role for Prdx2 and Nox4?
No full textIn 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 response was observed after 23 weeks. Interestingly, the expression of renal NADPH oxidase 4 (Nox4) increased. Nox4 has not been studied yet in Cd nephrotoxicity. The antioxidants catalase, glutathione peroxidase 4 and heme oxygenase 1 also responded. In conclusion our study reveals a two-step oxidative stress response in the kidney. Clearly the kidney was in control of Cd-induced oxidative stress after exposure to low Cd concentrations
Study of biological effects and oxidative stress related responses in gamma irradiated Arabidopsis thaliana plants
No full textThis study aimed at investigating biological effects in Arabidopsis thaliana leaves and roots irradiated for 72 h with 3.5 Gy or 30 Gy of gamma radiation, and to unravel oxidative stress related responses to achieve a better understanding of the importance of the cellular redox balance as a modulator in gamma radiation stress. A. thaliana performs like a rather radioresistant plant species as no alterations on growth and only minor alterations in the nutrient profile were observed. Gamma irradiation did not seem to induce an NADPH mediated oxidative burst and lipid peroxidation appeared to be directly induced by ionizing radiation rather than mediated through LOX activity. As ionizing radiation can cause indirect damage via water radiolysis, H2O2 is hypothesized to be an important reactive oxygen species under radiation stress. Although most H2O2-scavenging enzymes remained unchanged, important alterations were observed for CAT1, CAT2 and CAT3 expression
Exposing mice to low Cd doses triggers a biphasic oxidative stress response in the kidney: a role for Prdx2 and Nox4?
No full textIn 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 response was observed after 23 weeks. Interestingly, the expression of renal NADPH oxidase 4 (Nox4) increased. Nox4 has not been studied yet in Cd nephrotoxicity. The antioxidants catalase, glutathione peroxidase 4 and heme oxygenase 1 also responded. In conclusion our study reveals a two-step oxidative stress response in the kidney. Clearly the kidney was in control of Cd-induced oxidative stress after exposure to low Cd concentrations
- …
