Enhanced lipoxygenase activity is involved in the stress response but not in the harmful lipid peroxidation and cell death of short-term cadmium-treated barley root tip

Root growth inhibition and radial root swelling were the characteristic symptoms of barley root tips after the short-term exposure of roots to 15 and 30 μM Cd. Higher Cd concentrations caused extensive cell death and root growth arrest. Enhanced lipid peroxidation was observed as early as 1 h after the short-term treatment in a Cd concentration-dependent manner. In contrast to lipid peroxidation, the induction of lipoxygenase activity was detected only 3 h after the exposure of roots to 15 or 30 μM Cd. In addition, it was not observed in 60 μM Cd-treated root tips. The highest lipoxygenase activity was detected 6 h after 15 μM Cd treatment in the meristematic and elongation zone of root tip and was probably associated with the radial expansion of cells. Our results indicate that the upregulation of lipoxygenase is an important component of stress response in barley roots to toxic Cd. It is probably involved in the morphological stress response of root tips or/and in the alleviation of Cd-induced toxic alterations in plant cell membranes, but it is not responsible for the Cd-induced harmful lipid peroxidation and cell death.     

Role of oxidative stress on growth responses of spring barley exposed to different environmental stressors

Aims Oxidative stress is one of the most important mechanisms in a plant's reaction to the effects of different stressors; however, its role in plants' resistance is still poorly understood. The objective of this study is to evaluate an influence of oxidative stress induced by stress factors of different origin—ozone, ultraviolet (UV)-B radiation, drought, cadmium (Cd) and copper (Cu), to growth of spring barley and to check the hypothesis, that intensification of oxidative stress is the main factor of growth depression induced by strong treatments of different stressors; meanwhile, mitigation of oxidative stress determines eustress-induced growth stimulation.Methods A pot experiment was carried out in phytotron chambers with a controlled environment. Spring barley (Hordeum vulgare L.) plants were exposed to different doses of investigated environmental stress factors (O 3, UV-B radiation, drought, Cd and Cu), and their effects on shoots growth, accumulation of superoxide (O 2 .?), intensification of lipid peroxidation and antioxidative protection (superoxide dismutase, glutathione reductase and catalase activities and concentration of carotenoids) were measured. Analysis of variance (ANOVA) with classical eta-squared (η 2) values was used to evaluate and to compare the contribution of non-specific oxidative stress and stressor-specific mechanisms on plants growth.Important findings Low doses of most stressors stimulated antioxidative protection and growth of barley shoots, reduced the concentration of O 2 .? and/or intensity of lipid peroxidation. Whereas an impairment of growth and intensification of oxidative stress as well as a reduction in concentration of carotenoids and further increase in activity of antioxidative enzymes were noticed when the intensity of the stressors was increased. In the cases of ozone and UV-B stress, the effects of oxidative stress on plant growth was mitigated by strong antioxidative protection—highly increased catalase (CAT) and superoxide dismutase (SOD) activities, respectively. In the cases of drought and Cu, relatively strong oxidative stress was the major cause of plant growth depression. Additionally, mitigation of oxidative stress due to increased SOD activity was likely to be one of the main causes of growth stimulation induced by low doses of UV-B, Cd and Cu stress. Possible reasons for O 3 -induced growth stimulation were increased CAT activity and concentration of carotenoids. Generalizing the effects of different stressors, the contribution of non-specific oxidative stress on plant growth was stronger compared with stressor-specific action mechanisms: oxidative stress determined 42% of the changes in plants' dry biomass, whereas the contribution of stressor-specific mechanisms accounted for 35% of variability in barley growth.     

Alterations of the gene expression, lipid peroxidation, proline and thiol content along the barley root exposed to cadmium

Barley seedlings grown on filter paper moistened with 1mM Cd showed 50% root growth inhibition within 24h of exposure. The amount of cadmium after 24h Cd treatment was highest in the first 2mm-long apical root segment, while it was slightly higher in the fourth segment, 6-8mm behind the root tip, after 48h. In recovery experiments, when Cd-treated plants were transferred onto filter paper moistened with distilled water, a large amount of Cd was localised in the apoplast and considerable cell death was detected even though root growth was renewed. This indicates that cell death is likely an active physiological process that contributes to the removal of Cd from the root during root growth recovery. Elevated lipid peroxidation and thiol contents were detected in all individual segments of Cd-treated barley root. On the other hand, proline accumulation was disturbed during Cd stress, showing a significant decrease in all of the studied segments except the first. Cd-induced alteration in the expression of genes involved in metal signalling and detoxification and in drought and oxidative stress responses indicates that Cd-induced water and oxidative stress is responsible for the root growth inhibition, probably through an accelerated differentiation of root tissues.     

Involvement of salicylic acid and nitric oxide in protective reactions of wheat under the influence of heavy metals

This article studies the effect of salicylic acid (SA) and nitric oxide (NO) on Triticum aestivum L. wheat plants exposed to the influence of high concentrations of copper and zinc compounds. It is shown that heavy metals (HMs) caused a decrease in the growth parameters in the overground and underground plant parts and contributed to a sharp deterioration in the energy balance and the situation regarding oxidative stress. SA and NO exerted a protective effect, which was expressed in the increased ability to accumulate shoot and root mass, stabilize the energy balance, and reduced lipid peroxidation. Resemblance of protective reactions of wheat plants affected by SA and NO appeared as the alteration of energy (Rtot/Pnet and alternative respiration) and antioxidant (MDA) balance of studied plants was identified. The resemblance possibly evidences of common signaling pathway for SA and NO caused by effect of toxic concentrations of heavy metals.     

Cadmium-induced changes in antioxidant enzymes from the marine alga Nannochloropsis oculata

Cadmium-induced oxidative stress symptoms such as lipid peroxidation and H₂O₂ production were examined in the marine alga Nannochloropsis oculata. Changes in antioxidant enzyme levels and isozyme patterns were also examined. Increasing concentrations of Cd produced growth inhibition. Among the responses to added Cd, the H₂O₂ content and malonyldialdehyde accumulation increased significantly, indicating a state of oxidative stress. In the case of ascorbate peroxidase activity the increase was about 2.5 times and a marked induction of the isozyme APX2 contributed to this increase. Guaiacol peroxidase activity increased about 4-fold, this being due mainly to the isozyme GPX3. Catalase activity increased slightly, whereas superoxide dismutase and glutathione reductase activity decreased markedly. Alterations of antioxidant enzyme levels and isozyme pattern changes in Cd-treated alga suggest that they might be involved in the heavy metal tolerance in this alga.     

Salt tolerance of barley induced by the root endophyte Piriformospora indica is associated with a strong increase in antioxidants

The root endophytic basidiomycete Piriformospora indica has been shown to increase resistance against biotic stress and tolerance to abiotic stress in many plants. Biochemical mechanisms underlying P. indica-mediated salt tolerance were studied in barley (Hordeum vulgare) with special focus on antioxidants. Physiological markers for salt stress, such as metabolic activity, fatty acid composition, lipid peroxidation, ascorbate concentration and activities of catalase, ascorbate peroxidase, dehydroascorbate reductase, monodehydroascorbate reductase and glutathione reductase enzymes were assessed. Root colonization by P. indica increased plant growth and attenuated the NaCl-induced lipid peroxidation, metabolic heat efflux and fatty acid desaturation in leaves of the salt-sensitive barley cultivar Ingrid. The endophyte significantly elevated the amount of ascorbic acid and increased the activities of antioxidant enzymes in barley roots under salt stress conditions. Likewise, a sustained up-regulation of the antioxidative system was demonstrated in NaCl-treated roots of the salt-tolerant barley cultivar California Mariout, irrespective of plant colonization by P. indica. These findings suggest that antioxidants might play a role in both inherited and endophyte-mediated plant tolerance to salinity.     

The role of ascorbic acid role in the differentiation of sclerotia in Sclerotinia minor

Sclerotinia minor in culture produces ascorbic acid in levels dependent on oxidative growth conditions and stage of development. During differentiation reduced/oxidized ascorbate ratio decreased by 12 and 6 fold at high and low oxidative stress, respectively. Exogenous ascorbate caused a concentration-dependent decrease of oxidative stress (lipid peroxidation), inhibition of sclerotial differentiation (up to 100%) and delay of differentiatlon (up to 10 days). Ascorbic acid may be produced to help the fungus reduce oxidative stress during growth. The data of this study support our theory proposing that oxidative stress is the inducing factor of sclerotial differentiation in fungi.This revised version was published online in October 2005 with corrections to the Cover Date.     

Hymenolepis diminuta: Activity of anti-oxidant enzymes in different parts of rat gastrointestinal tract

The aim of this study was to assess the intensity of oxidative stress by measuring levels of lipid peroxidation products in the duodenum, jejunum and colon of rats infected with Hymenolepis diminuta and evaluate the effectiveness of protection against oxidative stress by measuring the glutathione levels and activity of anti-oxidant enzymes: superoxide dismutase, catalase, glutathione reductase and glutathione peroxidase.In exposed rats we observed a significant increase of lipid peroxidation products in the duodenum and jejunum. A significant decrease in superoxide dismutase activity in all the examined parts of the digestive tract was observed. Additionally, rats from 16 to 40 days post H. diminuta infection (dpi) had a decreased catalase activity in the colon, while at 60 dpi it increased. The glutathione peroxidase activity increased significantly in the colon at 60 dpi. The increase in glutathione reductase activity was observed in the colon in rats 60 dpi. There was a lack of changes in the levels of glutathione in the duodenum and a significant increase in its concentration in the jejunum and colon from 40 to 60 dpi and from 16 to 40 dpi, respectively. In this study we observed altered activity of anti-oxidant enzymes and glutathione level in experimental hymenolepidosis, as a consequence of oxidative stress. It may indicate a decrease in the efficiency of intestinal protection against oxidative stress induced by the presence of the parasite. The imbalance between oxidant and anti-oxidant processes may play a major role in pathology associated with hymenolepidosis.     

Plant growth regulators improve growth,photosynthesis, mineral nutrient and antioxidant system under cadmium stress in menthol mint ( Mentha arvensis L.)

Menthol mint (Mentha arvensis L.) cultivation is significantly affected by the heavy metals like cadmium (Cd) which also imposes severe health hazards. Two menthol mint cultivars namely Kosi and Kushal were evaluated under Cd stress conditions. Impact of plant growth regulators (PGRs) like salicylic acid (SA), gibberellic acid (GA3) and triacontanol (Tria) on Cd stress tolerance was assessed. Reduced growth, photosynthetic parameters, mineral nutrient concentration, and increased oxidative stress biomarkers like electrolyte leakage, malondialdehyde, and hydrogen peroxide contents were observed under Cd stress. Differential upregulation of proline content and antioxidant activities under Cd stress was observed in both the cultivars. Interestingly, low electrolyte leakage, lipid peroxidation, hydrogen peroxide and Cd concentration in leaves were observed in Kushal compared to Kosi. Among all the PGRs tested, SA proved to be the best in improving Cd-stress tolerance in both the cultivars but Kushal responded better than Kosi.     

Lifelong caloric restriction prevents age-induced oxidative stress in the sympathoadrenal system of Fischer 344 x Brown Norway rats

Aging is associated with oxidative damage and an imbalance in redox signaling in a variety of tissues, yet little is known about the extent of age-induced oxidative stress in the sympathoadrenal system. Lifelong caloric restriction has been shown to lower levels of oxidative stress and slow the aging process. Therefore, the aims of this study were twofold: (1) to investigate the effect of aging on oxidative stress in the adrenal medulla and hypothalamus and (2) determine if lifelong 40% caloric restriction (CR) reverses the adverse effects of age-induced oxidative stress in the sympathetic adrenomedullary system. Adult (18 months) and very old (38 months) male Fischer 344 x Brown Norway rats were divided into ad libitum or 40% CR groups and parameters of oxidative stress were analyzed in the adrenal medulla and the hypothalamus. A significant age-dependent increase in lipid peroxidation (+20%, P < 0.05) and tyrosine nitration (+111%, P < 0.001) were observed in the adrenal medulla while age resulted in a reduction in the protein expression of key antioxidant enzymes, CuZnSOD (−27%, P < 0.01) and catalase (−27%, P < 0.05) in the hypothalamus. Lifelong CR completely prevented the age-induced increase in lipid peroxidation in the adrenal medulla and restored the age-related decline in antioxidant enzymes in the hypothalamus. These data indicate that aging results in a significant increase in oxidative stress in the sympathoadrenal system. Importantly, lifelong CR restored the age-related changes in oxidative stress in the adrenal medulla and hypothalamus. Caloric restriction could be a potential non-pharmacological intervention to prevent increased oxidative stress in the sympathetic adrenomedullary system with age.     

Lead and cadmium-induced oxidative stress impacting mycelial growth of <Emphasis Type="Italic">Oudemansiella radicata</Emphasis> in liquid medium alleviated by microbial siderophores

In this study, the effects of siderophores produced by six bacteria on mycelium growth, Cd and Pb accumulation, lipid peroxidation, protein content and antioxidant enzyme in Oudemansiella radicata were investigated in Cd and Pb-containing liquid medium. The results showed that inoculation with siderophore-containing filtrates (SCF) partly enhanced the growth of O. radicata after 15 days, with 0.8–32.4% biomass increase for Cd and 0.7–20.8% for Pb compared to control(s), which lacked siderophore. The maximum enhancement for accumulation were found to be confined to Bacillus sp. FFQ2(s) (26.5%) for Cd and Pseudomonas sp. CY63(s) (158.9%) for Pb. A significant decrease in MDA content indicated that lipid peroxidation in O. radicata was alleviated by siderophores. Besides, antioxidant enzyme SOD and POD activities also displayed obviously decrease in SCF-treated mycelium compared to control(s) treatment, while CAT activity did not present significant change. Protein level in O. radicata treated by SCF increased from 0.3 to 138.0% for Cd and from 10.9 to 107.1% for Pb compared to control(s). Therefore, the present work suggests that microbial siderophores can reduce the toxicity of metals to mycelium and then alleviate heavy metals-inducing oxidative stress in O. radicata.     

Effect of cadmium and temperature on the lipoxygenase activity in barley root tip

An analysis of different cell fractions isolated from barley roots revealed that lipoxygenase (LOX) activity occurred both extra- and intracellulary. Cadmium (Cd)-induced LOX activity was observed in the fraction containing cell walls, plasma membrane and the cytoplasm. High temperature-induced root growth inhibition and elevated LOX activity did not induce lipid peroxidation. In contrast, Cd inhibited root growth and caused both enhanced lipid peroxidation and elevated LOX activity at each of the temperatures analyzed. Spatial distribution studies revealed that the patterns of apoplastic LOX activity were different from those of cytoplasmic activity. Cd-induced intracellular LOX activity increased equally along the barley root tip, while Cd-induced apoplastic LOX activity was associated mainly with the differentiation zone of the barley root tip. Our results suggest the involvement of Cd-induced LOX activity in the premature differentiation of the barley root tip during Cd stress. We hypothesize that the role of LOX in plant metabolic processes in the root may depend on the level of reactive oxygen species in the roots: at physiological concentrations of ROS, LOX may be involved in the processes of root growth, while at the elevated harmful concentrations of ROS induced by different stress conditions, it may be involved in root growth inhibition through ectopic differentiation.     

Influence of Arsenate on Lipid Peroxidation Levels and Antioxidant Enzyme Activities in Bacillus cereus Strain XZM002 Isolated from High Arsenic Aquifer Sediments

Bacillus cereus strain XZM002 isolated from high arsenic aquifer sediments of Datong Basin was applied to examine the effects of arsenate stress on antioxidant enzyme activities, lipid peroxidation levels and cell growth inhibition rate. After 2 d exposure, the cell growth inhibition rate enhanced with an increase of As(V) concentrations (0, 800, 1600 μg/l). Reactive oxygen species and glutathione contents, lipid peroxidation levels, and antioxidant enzymes (glutathione peroxidase, and other three) activities of the treated cells were significantly higher than those of the controls during 3 d exposure (p < 0.05). Besides, the levels of nine parameters reached maximum after 2 d exposure and increased significantly with increasing arsenate stress (p < 0.05). However, they returned to levels similar to those of the control on the fourth day of exposure. The results suggested that the antioxidant defense system in B. cereus strain XZM002 could protect the cells from oxidative damage induced by arsenate.     

Role of peroxisome proliferator-activated receptor-α in fasting-mediated oxidative stress

The peroxisome proliferator-activated receptor-α (PPARα) regulates lipid homeostasis, particularly in the liver. This study was aimed at elucidating the relationship between hepatosteatosis and oxidative stress during fasting. Fasted Ppara-null mice exhibited marked hepatosteatosis, which was associated with elevated levels of lipid peroxidation, nitric oxide synthase activity, and hydrogen peroxide accumulation. Total glutathione (GSH), mitochondrial GSH, and the activities of major antioxidant enzymes were also lower in the fasted Ppara-null mice. Consequently, the number and extent of nitrated proteins were markedly increased in the fasted Ppara-null mice, although high levels of protein nitration were still detected in the fed Ppara-null mice while many oxidatively modified proteins were only found in the fasted Ppara-null mice. However, the role of inflammation in increased oxidative stress in the fasted Ppara-null mice was minimal based on the similar levels of tumor necrosis factor-α change in all groups. These results with increased oxidative stress observed in the fasted Ppara-null mice compared with other groups demonstrate a role for PPARα in fasting-mediated oxidative stress and that inhibition of PPARα functions may increase the susceptibility to oxidative damage in the presence of another toxic agent.     

Oxidative stress induced by cadmium in <Emphasis Type="Italic">Nicotiana tabacum</Emphasis> L.: effects on growth parameters,oxidative damage and antioxidant responses in different plant parts

Tobacco (Nicotiana tabacum L.) is a tolerant species that accumulates cadmium. We studied the effect of Cd (0, 10, 25, 50, 100 μM) on growth parameters, chlorophyll and proline contents, enzymatic antioxidative response and lipid peroxidation of tobacco plants grown in hydroponic culture for 11 days to clarify the strategy of plant response against oxidative stress caused by this heavy metal. Cadmium accumulated more in roots than in shoots. Plant growth was not significantly affected by the cadmium concentrations used. Young leaves were more affected, showing visible chlorosis and a significant decrease in chlorophyll content at high Cd concentrations. Dry weight of both leaves and roots increased indicating a lower capacity for roots to absorb water. An increase in malondialdehyde levels was observed, indicating that lipid peroxidation occurred as a result of ROS formation. The activity of guaiacol peroxidase in leaves increased, indicating that it was very important in the scavenging of H₂O₂, while superoxide dismutase activity only increased in old leaves. Ascorbate peroxidase showed constant activity levels in tobacco leaves, suggesting that the ascorbate–glutathione pathway was less important as a defense mechanism.     

The inhibitory effects of UV-B radiation (280–315 nm) on Gunnera magellanica growth correlate with increased DNA damage but not with oxidative damage to lipids

Damage to DNA and disruption of membrane integrity by lipid peroxidation processes are two of the proposed causes of UV‐B‐induced growth inhibition in plants. However, the relative significance of these different types of molecular damage has not been established in experiments carried out under realistic physiological conditions. Plants of Gunnera magellanica (a native herb from southern Patagonia) were exposed to a gradient of biologically effective UV‐B doses (from 0 to 6.5 kJ m^?2 d^?1 of UV‐B_be) in a greenhouse study. Leaf expansion was measured and sensitive techniques were used to detect damage to DNA (in the form of cyclobutane pyrimidine dimers; CPDs) and lipid peroxidation (via electronic‐paramagnetic resonance; EPR). Leaf expansion decreased and the CPD density increased with increasing UV‐B doses, but the degree of lipid peroxidation remained unaffected. The highest UV‐B dose induced a transient oxidative stress situation (as evaluated using the ratio of ascorbyl radical to ascorbate, A^·/AH^–), which was rapidly controlled by an increase in the ascorbate pool. The present results suggest that under a range of UV‐B_be doses that overlaps the range of doses that G. magellanica plants experience in their natural environment, growth inhibition is better explained by DNA damage than by increased lipid peroxidation.     

Endophytic bacteria (Sphingomonas sp. LK11) and gibberellin can improve Solanum lycopersicum growth and oxidative stress under salinity

This study aims to understand the effects of salinity on the growth and oxidative stress enzymes of endophytic bacteria (Sphingomonas sp. LK11) and tomato plants. In response to salinity and gibberellic acid (GA₄), catalase (CAT), superoxide dismutase, and reduced glutathione were significantly regulated in LK11 as compared to peroxidase (POD) and polyphenol oxidase (PPO). Salinity stress to tomato plants caused significant cessation in growth and biomass, which was accompanied by threefold increase in lipid peroxidation and decrease in glutathione, CAT, POD, and PPO activities. In contrast, sole and combined treatment of LK11 and GA₄ rescued plant growth and biomass production whilst exhibited lower lipid peroxidation and higher glutathione content under salinity stress. The activities of CAT, POD, and PPO were either lower or nonsignificant as compared to control. In conclusion, inoculation of bacterial endophytes offers a relative stress counteracting potentials as evidenced by the known plant growth regulators.     

Involvement of salicylic acid and nitric oxide in protective reactions of wheat under the influence of heavy metals

This article studies the effect of salicylic acid (SA) and nitric oxide (NO) on Triticum aestivum L. wheat plants exposed to the influence of high concentrations of copper and zinc compounds. It is shown that heavy metals (HMs) caused a decrease in the growth parameters in the overground and underground plant parts and contributed to a sharp deterioration in the energy balance and the situation regarding oxidative stress. SA and NO exerted a protective effect, which was expressed in the increased ability to accumulate shoot and root mass, stabilize the energy balance, and reduced lipid peroxidation.     

Effect of the synthetic growth regulator Cytodef and heavy metals on oxidative status in cucumber plants

We studied the influence of a synthetic cytokinin-like growth regulator (Cytodef) and heavy metal ions—Pb²⁺, Sr²⁺, Zn²⁺, and Ni²⁺—on generation of superoxide anion (O₂^⊙−), lipid peroxidation, and carotenoids content in leaves of 7-day-old cucumber plants (Cucumis sativus L., cv. Izyashchnyi). In some instances Cytodef reduced the toxicity of heavy metals: it mitigated the negative effect of metals on oxidative processes and elevated the concentration of antioxidants (carotenoids).