Assessment of the oxidative stress intensity and the integrity of cell membranes under the manganese nanoparticles toxicity in wheat seedlings.

A response to manganese nanoparticles was studied in seedlings of two wheat cultivars and a model system of plant cell membranes. Nanoparticles at concentrations of 125 and 250 mg/ml were applied foliar. The application of NPs enhanced the content of Mn in plant cells, indicating its penetration through the leaf surface. The stressful effect in the plant cells was estimated based on changes in the activity of antioxidant enzymes, content of chlorophylls and starch. MnNPs evoked no significant changes in the leaf morphology, however, an increase in enzyme activity, starch accumulation, and a decrease in chlorophyll synthesis indicated the stress occurrence. Moreover, a rise in the electrokinetic potential of the chloroplast membrane surface and the reconstruction of their hydrophobic parts toward an increase in fatty acid saturation was found.

Manganese protects wheat from the mycotoxin zearalenone and its derivatives.

Searching for factors that reduce zearalenone (ZEN) toxicity is an important challenge in wheat production, considering that this crop is a basic dietary ingredient. ZEN, absorbed by cells, is metabolized into α-zearalenol and α-zearalanol, and this study focused on the function of manganese ions as potential protectants against the mycotoxins. Stress effects were invoked by an application of 30 µM ZEN and its derivatives. Manganese ions were applied at 100 µM, not stress-inducing concentration. Importance of the biomembrane structures in the absorption of the mycotoxins was demonstrated in in vitro wheat calli and on model membranes. ZEN showed the greatest and α-zearalanol the smallest stressogenic effect manifested as a decrease in the calli growth. This was confirmed by variable increase in antioxidant enzyme activity. Mn ions added to the toxin mixture diminished stressogenic properties of the toxins. Variable decrease in total lipid content and the percentage of phospholipid fraction detected in calli cells exposed to ZEN and its metabolites indicated significance of the membrane structure. An analysis of physicochemical parameters of model membranes build from phosphatidylcholine, a basic lipid in native membranes, and its mixture with the tested toxins made by Langmuir technique and verified by Brewster angle microscopy, confirmed variable contribution of ZEN and its derivatives to the modification of membrane properties. The order of toxicity was as follows: ZEN ≥ α-zearalenol > α-zearalanol. Manganese ions present in the hydrophilic phase interacted with polar lipid groups and reduced the extent of membrane modification caused by the mycotoxins.

Translocation of elements and sugars in wheat genotypes at vegetative and generative stages under continuous selenium exposure.

BACKGROUND: Biofortification with selenium (Se) elevates its concentration in feed and fodder plants and helps to prevent health problems in animals and humans. The aim of this study was to describe Se-induced modifications in the accumulation of elements important for the proper functioning of wheat, one of the most popular cereals. The presence of Se correlated with carbohydrate synthesis and electron paramagnetic resonance (EPR). This explained the mechanisms of Se's antioxidant activity. RESULTS: Selenium accumulation in vegetative and generative leaves, and in the grains of three wheat genotypes (cv. Parabola, cv. Raweta and cv. Manu), differing in their stress tolerance and grown hydroponically in the presence of 10 or 20 µM Na2 SeO4, , was proportional to its content in the medium. Stronger Se accumulation was typical of a stress-sensitive genotype. Selenium generally promoted the uptake of macronutrients and micronutrients but their distribution depended on tissue and genotype. Changes in the Se-induced EPR signals of paramagnetic metals and organic radicals corresponded with stress tolerance of the tested genotypes. CONCLUSIONS: Se application increased the accumulation of nutrients and carbohydrates that are vital for proper plant growth and development. Accelerated uptake of molybdenum (Mo), an element improving dietary properties of grains, may be an additional advantage of Se fertilization. The mechanisms of Se-induced changes in removing Mn and iron (Fe) ions from macromolecules may be one of the factors that differentiate plant tolerance to oxidative stress. © 2019 Society of Chemical Industry.

The role of chloroplasts in the oxidative stress that is induced by zearalenone in wheat plants - The functions of 24-epibrassinolide and selenium in the protective mechanisms.

This study focused on the idea that the toxic effect of zearalenone (ZEA) and the protective actions of the brassinosteroid - 24-epibrassinolide (EBR) as well as selenium are dependent on its accumulation in chloroplasts to a high degree. These organelles were isolated from the leaves of oxidative stress-sensitive and stress-tolerant wheat cultivars that had been grown from grains that had been incubated in a solution of ZEA (30 µM), Na2SeO4 (Se, 10 µM), EBR (0.1 µM) or in a mixture of ZEA with Se or EBR. Ultra-high performance liquid chromatography techniques indicated that ZEA was adsorbed in higher amounts in the chloroplasts in the sensitive rather than tolerant cultivar. Although the brassinosteroids and Se were also accumulated in the chloroplasts, higher levels were only found in the tolerant cultivar. The application of EBR increased the homocastasterone content, especially in the chloroplasts of the tolerant plant and after the addition of ZEA. The presence of both protectants caused a decrease in the ZEA content in studied organelles and resulted in diminishing of the oxidative stress (i.e. changes in the activity of the antioxidative enzymes). Moreover, a recovery of photosystem II and decrease in the negative impact of ZEN on Hsp90 transcript accumulation was observed in plants.

Foliar application of selenium for protection against the first stages of mycotoxin infection of crop plant leaves.

BACKGROUND: The aim of this study was to investigate whether the application of selenium (Se) ions directly to the leaf surface can protect plants against infection by the fungal toxin zearalenone (ZEA). The experiments were performed for the most common and agronomically important crops such as wheat, oat, and barley (both tolerant and sensitive varieties) because mycotoxin accumulation in plants is the cause of many diseases in animals and people. RESULTS: ZEA at a concentration of 10 µmol L-1 either alone or in combination with Se (5 µmol L-1 Na2 SeO4 ) was applied to the second leaf of seedlings. Visualization of leaf temperature profiles by infrared thermography demonstrated a decrease in temperature at the location of ZEA infection that was more noticeable in sensitive genotypes. The presence of Se significantly suppressed changes at the site of ZEA application in all tested plants, especially the tolerant genotypes. Microscopic observations confirmed that foliar administration of ZEA resulted in its penetration to deeper localized cells and that damage induced by ZEA (mainly to chloroplasts) decreased after Se application. Analyses of antioxidant enzymes demonstrated the involvement of Se in antioxidation mechanisms, in particular by activating SOD and CAT under ZEA-induced stress conditions. CONCLUSION: The foliar application of Se to seedling leaves may be a non-invasive method of protecting crops against the first steps of ZEA infection. © 2018 Society of Chemical Industry.

Regulation of the membrane structure by brassinosteroids and progesterone in winter wheat seedlings exposed to low temperature.

Steroids constitute one of the most important groups of compounds of regulatory properties both in the animal and plant kingdom. In plants, steroids such as brassinosteroids or progesterone, by binding to protein receptors in cell membranes, regulate growth and initiate processes leading to increased tolerance to stress conditions. Due to their structural similarities to sterols, these steroids may also directly interact with cellular membranes. Our aim was to determine the changes of the structural parameters of lipid membranes under the influence of hydrophobic steroid compounds, i.e., 24-epibrassinolide (EBR) and its precursor-24-epicastasterone (ECS) and progesterone (PRO). Lipids were isolated from wheat seedlings with different tolerances to frost, grown at low temperatures (5 °C) for 1.5 and 3 weeks (acclimation process). Control plants were cultured continuously at 20 °C. From galactolipids and phospholipids, the main polar lipid fractions, the monolayers were formed, using a technique of Langmuir trough. EBR and ECS were introduced into monolayers, together with lipids, whereas the PRO was dissolved in the aqueous sub-phase upon which the monolayers were spread. Measurements performed at 25 °C and 10 °C showed a significant action of the tested compounds on the physicochemical properties of the monolayers. EBR and PRO increased the area per lipid molecule in monolayers, resulting in formation of more flexible surface structures while the presence of the ECS induced the opposite effect. The influence of the polarity of lipids and steroids on the interactions in the monolayer was discussed. Lipids extracted from the membranes of wheat with the most tolerance to frost were characterized by the highest fatty acid unsaturation and steroids had a relatively weak effect on the parameters of the structure of their monolayers.

Electron Paramagnetic Resonance (EPR) Spectroscopy in Studies of the Protective Effects of 24-Epibrasinoide and Selenium against Zearalenone-Stimulation of the Oxidative Stress in Germinating Grains of Wheat.

These studies concentrate on the possibility of using selenium ions and/or 24-epibrassinolide at non-toxic levels as protectors of wheat plants against zearalenone, which is a common and widespread mycotoxin. Analysis using the UHPLC-MS technique allowed for identification of grains having the stress-tolerant and stress-sensitive wheat genotype. When germinating in the presence of 30 µM of zearalenone, this mycotoxin can accumulate in both grains and hypocotyls germinating from these grains. Selenium ions (10 µM) and 24-epibrassinolide (0.1 µM) introduced together with zearalenone decreased the uptake of zearalenone from about 295 to 200 ng/g and from about 350 to 300 ng/g in the grains of tolerant and sensitive genotypes, respectively. As a consequence, this also resulted in a reduction in the uptake of zearalenone from about 100 to 80 ng/g and from about 155 to 128 ng/g in the hypocotyls from the germinated grains of tolerant and sensitive wheat, respectively. In the mechanism of protection against the zearalenone-induced oxidative stress, the antioxidative enzymes-mainly superoxide dismutase (SOD) and catalase (CAT)-were engaged, especially in the sensitive genotype. Electron paramagnetic resonance (EPR) studies allowed for a description of the chemical character of the long-lived organic radicals formed in biomolecular structures which are able to stabilize electrons released from reactive oxygen species as well as the changes in the status of transition paramagnetic metal ions. The presence of zearalenone drastically decreased the amount of paramagnetic metal ions-mainly Mn(II) and Fe(III)-bonded in the organic matrix. This effect was particularly found in the sensitive genotype, in which these species were found at a smaller level. The protective effect of selenium ions and 24-epibrassinolide originated from their ability to inhibit the destruction of biomolecules by reactive oxygen species. An increased ability to defend biomolecules against zearalenone action was observed for 24-epibrassinolide.

Studies of Lipid Monolayers Prepared from Native and Model Plant Membranes in Their Interaction with Zearalenone and Its Mixture with Selenium Ions.

The impact of zearalenone and selenate ions on the monolayers of 1,2-dipalmitoyl-phosphatidylcholine (DPPC), 1,2-dipalmitoyl-3-trimethylammonium-propane (DPTAP), and the lipid mixtures (phospholipids and galactolipids) extracted from wheat plasmalemma has been studied using Langmuir trough technique and Brewster angle microscopy (BAM). The zearalenone is a mycotoxin that exerts toxic effects on the cells of plants and animals. Monolayers' properties were characterized by surface pressure (π)-molecular area (A) isotherms. It was found that zearalenone interacts with lipid monolayers causing their expansion. The selenate ions, added to the subphase together with zearalenone, reduce the effect of this mycotoxin on the surface properties of lipid films.

Protective effect of ascorbic acid after single and repetitive administration of cadmium in Swiss mice.

The aim of the study was to delineate the protective effect of ascorbic acid with plausible mechanism after single and repetitive cadmium administration to Swiss mice. The effects of single high dose administration of CdCl(2) (6 mg/kg) or ascorbic acid (AsA) (50 mg/kg) and chronic (three times) administration of Cd at low dose (2 mg/kg) or AsA at same dose (50 mg/kg) were compared in Swiss albino mice. Changes of lipid peroxidation [determined by the malonyldialdehyde (MDA) concentration] were taken as a measure of the oxidative stress intensity. Lipid fatty acid's unsaturation related to the permeability of cell membranes was also examined. Mobilization of the immune system was determined by analyzing changes in antioxidant concentrations of AsA and glutathione (GSH), and by measuring the activation of antioxidant enzymes SOD, GPx and CAT. In addition, the level of free polyamines and variation in their proportions were examined. In conclusion, exposure to higher levels of cadmium will have more deleterious effects on the body rather than chronic exposure at lower levels with this toxic metal, while this study clearly demonstrated the protective effects of AsA in a mouse model.