NADPH oxidase-dependent hydrogen peroxide production, induced by salinity stress, may be involved in the regulation of total calcium in roots of wheat

Hydrogen peroxide (H(2)O(2)) is often generated by cells and tissues under environmental stress. In this work, we provide evidence that plasma membrane (PM) NADPH oxidase-dependent H(2)O(2) production might act as an intermediate step in the NaCl-induced elevation of calcium (Ca) in roots of wheat. Remarkable increases in the content of total Ca were observed not only in roots exposed to NaCl but also in roots of seedlings exposed to exogenous H(2)O(2). In roots, H(2)O(2) production increased upon exposure to salt stress. PM vesicles were isolated from roots, and NADPH oxidase activity was determined by measuring superoxide anion (O(2)(-)) production. NADPH oxidase-dependent O(2)(-) production was 11.6nmolmg(-1)proteinmin(-1) in control vesicles, but 19.6nmol after NaCl treatment (24h), indicating that salt stress resulted in the activation of the PM NADPH oxidase. Furthermore, the NaCl-induced increase in total Ca was partially abolished by the addition of 150U/mL catalase (CAT), a H(2)O(2) scavenger, and also by 10microM diphenylane iodonium (DPI), a NADPH oxidase inhibitor. This data suggest that NADPH oxidase-dependent H(2)O(2) production might be involved in the modulation of the Ca content in wheat roots. In conclusion, our results show that salinity stress increases the total Ca content of wheat roots, which is partly due to PM NADPH oxidase-dependent H(2)O(2) generation.     

Iron and reactive oxygen responses in Pinus sylvestris root cortical cells infected with different species of Heterobasidion annosum sensu lato

Defence mechanisms in trees are not well understood. We assessed whether distribution of iron ions and their co-localisation with reactive oxygen species in Pinus sylvestris root cells reflect differential preferences of the pathogens Heterobasidion annosum sensu stricto, H. parviporum and H. abietinum to the host. Strains of H. annosum s.s. characterised by a greater preference for P. sylvestris induced accumulation of superoxide (O(2) (-)) in host cells 6?h after inoculation, whereas two peaks in accumulation of O(2) (-) (after 4 and 48?h) were observed after infection with strains of the pathogens H. parviporum and H. abietinum, which have a lower preference for P. sylvestris. Moreover, strains of H. annosum s.s. caused increased production of hydrogen peroxide (H(2)O(2)) in P. sylvestris cells, in contrast with strains of the other two species (H. parviporum and H. abietinum). Following inoculation with H. annosum s.s. strains, H(2)O(2) was correlated negatively with O(2) (-) and correlated positively with ferrous iron (Fe(2+)). Co-localisation of Fe(3+) with H(2)O(2) may suggest that they are involved in inducing hypersensitive responses and eventually cell death in roots inoculated with H. annosum s.s. strains, in contrast with H. parviporum, in which other mechanisms operate when the host is parasitised.     

Drought acclimation reduces O2*- accumulation and lipid peroxidation in wheat seedlings

Abiotic stresses cause ROS accumulation, which is detrimental to plant growth. It is well known that acclimation of plants under mild or sub-lethal stress condition leads to development of resistance in plants to severe or lethal stress condition. The generation of ROS and subsequent oxidative damage during drought stress is well documented in the crop plants. However, the effect of drought acclimation treatment on ROS accumulation and lipid peroxidation has not been examined so far. In this study, the effect of water stress acclimation treatment on superoxide radical (O(2)(-z.rad;)) accumulation and membrane lipid peroxidation was studied in leaves and roots of wheat (Triticum aestivum) cv. C306. EPR quantification of superoxide radicals revealed that drought acclimation treatment led to 2-fold increase in superoxide radical accumulation in leaf and roots with no apparent membrane damage. However under subsequent severe water stress condition, the leaf and roots of non-acclimated plants accumulated significantly higher amount of superoxide radicals and showed higher membrane damage than that of acclimated plants. Thus, acclimation-induced restriction of superoxide radical accumulation is one of the cellular processes that confers enhanced water stress tolerance to the acclimated wheat seedlings.     

Origin of cadmium-induced reactive oxygen species production: mitochondrial electron transfer versus plasma membrane NADPH oxidase

* Cadmium (Cd(2+)) is an environmental pollutant that causes increased reactive oxygen species (ROS) production. To determine the site of ROS production, the effect of Cd(2+) on ROS production was studied in isolated soybean (Glycine max) plasma membranes, potato (Solanum tuberosum) tuber mitochondria and roots of intact seedlings of soybean or cucumber (Cucumis sativus). * The effects of Cd(2+) on the kinetics of superoxide (O2*-), hydrogen peroxide (H(2)O(2)) and hydroxyl radical ((*OH) generation were followed using absorption, fluorescence and spin-trapping electron paramagnetic resonance spectroscopy. * In isolated plasma membranes, Cd(2+) inhibited O2*- production. This inhibition was reversed by calcium (Ca(2+)) and magnesium (Mg(2+)). In isolated mitochondria, Cd(2+) increased and H(2)O(2) production. In intact roots, Cd(2+) stimulated H(2)O(2) production whereas it inhibited O2*- and (*)OH production in a Ca(2+)-reversible manner. * Cd(2+) can be used to distinguish between ROS originating from mitochondria and from the plasma membrane. This is achieved by measuring different ROS individually. The immediate (相似文献   

Antioxidant activity of isocoumarins isolated from Paepalanthus bromelioides on mitochondria

The isocoumarins (1-50 microM) paepalantine (9,10-dihydroxy-5,7-dimethoxy-1H-naptho(2,3c)pyran-1-one), 8,8'-paepalantine dimer, and vioxanthin isolated from Paepalanthus bromelioides, were assessed for antioxidant activity using isolated rat liver mitochondria and non-mitochondrial systems, and compared with the flavonoid quercetin. The paepalantine and paepalantine dimers, but not vioxanthin, were effective at scavenging both 1,1-diphenyl-2-picrylhydrazyl (DPPH(*)) and superoxide (O(2)(-)) radicals in non-mitochondrial systems, and protected mitochondria from tert-butylhydroperoxide-induced H(2)O(2) accumulation and Fe(2+)-citrate-mediated mitochondrial membrane lipid peroxidation, with almost the same potency as quercetin. These results point towards paepalantine, followed by paepalantine dimer, as being a powerful agent affording protection, apparently via O(2)(-) scavenging, from oxidative stress conditions imposed on mitochondria, the main intracellular source and target of those reactive oxygen species. This strong antioxidant action of paepalantine was reproduced in HepG2 cells exposed to oxidative stress condition induced by H(2)O(2).     

Role of Antioxidant Systems in Wheat Genotypes Tolerance to Water Stress

The role of plant antioxidant systems in stress tolerance was studied in leaves of three contrasting wheat genotypes. Drought imposed at two different stages after anthesis resulted in an increase in H2O2 accumulation and lipid peroxidation and decrease in ascorbic acid content. Antioxidant enzymes like superoxide dismutase, ascorbate peroxidase and catalase significantly increased under water stress. Drought tolerant genotype C 306 which had highest ascorbate peroxidase and catalase activity and ascorbic acid content also showed lowest H2O2 accumulation and lipid peroxidation (malondialdehyde content) under water stress in comparison to susceptible genotype HD 2329 which showed lowest antioxidant enzyme activity and ascorbic acid content and highest H2O2 content and lipid peroxidation. HD 2285 which is tolerant to high temperature during grain filling period showed intermediate behaviour. Superoxide dismutase activity, however, did not show significant differences among the genotypes under irrigated as well as water stress condition. It seems that H2O2 scavenging systems as represented by ascorbate peroxidase and catalase are more important in imparting tolerance against drought induced oxidative stress than superoxide dismutase alone. This revised version was published online in July 2006 with corrections to the Cover Date.     

2-Benzoxazolinone (BOA) induced oxidative stress, lipid peroxidation and changes in some antioxidant enzyme activities in mung bean (Phaseolus aureus)

2-Benzoxazolinone (BOA), a well-known allelochemical with strong phytotoxicity, is a potential herbicidal candidate. The aim of the present study was to determine whether phytotoxicity of BOA is due to induction of oxidative stress caused by generation of reactive oxygen species (ROS) and the changes in levels of antioxidant enzymes induced in response to BOA. Effect of BOA was studied on electrolyte leakage, lipid peroxidation (LP), hydrogen peroxide (H(2)O(2)) generation, proline (PRO) accumulation, and activities of antioxidant enzymes-superoxide dismutase (SOD, 1.15.1.1), ascorbate peroxidase (APX, 1.11.1.11), guaiacol peroxidase (GPX, 1.11.1.7), catalase (CAT, 1.11.1.6) and glutathione reductase (GR, 1.6.4.2) in Phaseolus aureus (mung bean). BOA significantly enhanced malondialdehyde (MDA) content, a product of LP, in both leaves and roots of mung bean. The amount of H(2)O(2), a product of oxidative stress, and endogenous PRO increased many-fold in response to BOA. Accumulation of PRO, MDA and H(2)O(2) indicates the cellular damage in the target tissue caused by ROS generated by BOA. In response to BOA, there was a significant increase in the activities of scavenging enzymes SOD, APX, GPX, CAT, and GR in root and leaf tissue of mung bean. At 5 mM BOA, GR activity in roots showed a nearly 22-fold increase over that in control. The present study concludes that BOA induces oxidative stress in mung bean through generation of ROS and upregulation of activities of various scavenging enzymes.     

Differential antioxidative responses to cadmium in roots and leaves of pea (Pisum sativum L. cv. Azad).

Pea (Pisum sativum L. cv. Azad) plants exposed to 4 and 40 microM of Cd for 7 d in hydroponic culture were analysed with reference to the distribution of metal, the accumulation of biomass and the metal's effects on antioxidants and antioxidative enzymes in roots and leaves. Cd-induced a decrease in plant biomass. The maximum accumulation of Cd occurred in roots followed by stems and leaves. An enhanced level of lipid peroxidation and an increased tissue concentration of hydrogen peroxide (H2O2) in both roots and leaves indicated that Cd caused oxidative stress in pea plants. Roots and leaves of pea plants responded differently to Cd with reference to the induction of enhanced activities of most of the enzymes monitored in the present study. These differential responses to Cd were further found to be associated with levels of Cd to which the plants were exposed. Cd-induced enhancement in superoxide dismutase (SOD) activity was more at 40 microM than at 4 microM in leaves. While catalase (CAT) prominently increased in leaves both at 4 and 40 microM Cd, ascorbate peroxidase (APX) showed maximum stimulation at 40 microM Cd in roots. Enhancement in glutathione reductase (GR) activity was also more at 40 microM than at 4 microM Cd in roots. While glutathione peroxidase (GPOX) activity decreased in roots and remained almost unmodified in leaves, glutathione S-transferase (GST) showed pronounced stimulation in both roots and leaves of pea plants exposed to 40 microM Cd. Increased activities of antioxidative enzymes in Cd-treated plants suggest that they have some additive function in the mechanism of metal tolerance in pea plants.     

Oxidative Stress Induced by Lead in Chloroplast of Spinach

Seedlings of spinach were grown in Hoagland's medium containing 0, 20, 40, 60, 80, 100 microM PbCl2, respectively, for 4 weeks. Chloroplasts were assayed for overproduction of reactive oxygen species (ROS) such as superoxide radicals (O2(*-)) and hydrogen peoxide (H2O2) and of lipid peroxide (malonyldialdehyde) and for activities of the antioxidant enzymes such as superoxide dismutase, catalase, ascorbate peroxidase, and guaiacol peroxidase and glutathione content, oxygen-evolving rate, and chlorophyll content. Increase in both ROS and lipid peroxide content and reduction in photosynthesis and activities of the antioxidant defense system indicated that spinach chloroplast underwent a stress condition due to an oxidative attack. Seedling growth cultivated in containing Pb2+ media was significantly inhibited. The results imply that spinach chloroplast was not able to tolerate the oxidative stress induced by Pb2+ due to having no effective antioxidant defense mechanism.     

Distribution of superoxide and hydrogen peroxide in Arabidopsis root and their influence on root development: possible interaction with peroxidases

The respective distribution of superoxide (O(2) (.-)) and hydrogen peroxide (H(2)O(2)), two reactive oxygen species (ROS) involved in root growth and differentiation, was determined within the Arabidopsis root tip. We investigated the effect of changing the levels of these ROS on root development and the possible interactions with peroxidases. H(2)O(2) was detected by confocal laser-scanning microscopy using hydroxyphenyl fluorescein (HPF). Both O(2) (.-) accumulation and peroxidase distribution were assessed by light microscopy, using nitroblue tetrazolium (NBT) and o-dianisidine, respectively. Root length and root hair length and density were also quantified following ROS scavenging. O(2) (.-) was predominantly located in the apoplast of cell elongation zone, whereas H(2)O(2) accumulated in the differentiation zone and the cell wall of root hairs in formation. Treatments that decrease O(2) (.-) concentration reduced root elongation and root hair formation, while scavenging H(2)O(2) promoted root elongation and suppressed root hair formation. The results allow to precise the respective role of O(2) (.-) and H(2)O(2) in root growth and development. The consequences of their distinct accumulation sites within the root tip are discussed, especially in relation to peroxidases.     

Lead induced changes in the growth and antioxidant metabolism of the lead accumulating and non-accumulating ecotypes of Sedum alfredii

The phytotoxicity and antioxidative adaptations of lead （Pb） accumulating ecotype （AE） and non-accumulating ecotype （NAE） of Sedum alfredii Hance were investigated under different Pb treatments involving 0, 0.02 mmol/L Pb, 0.1 mmol/L Pb and 0.1 mmol/L Pb/0.1 mmol/L ethylenediaminetetraacetic acid （EDTA） for 6days. With the increasing Pb level, the Pb concentration in the shoots of AE plants enhanced accordingly, and EDTA supply helped 51% of Pb translocation to shoots of AE compared with those treated with 0.1 mmol/L Pb alone. Moreover, the presence of EDTA alleviated Pb phytotoxicity through changes in plant biomass, root morphology and chlorophyll contents. Lead toxicity induced hydrogen peroxide （H2O2） accumulation and lipid peroxidation in both ecotypes of S. alfredii. The activities of superoxide dismutase （SOD）, guaiacol peroxidase （G-POD）, ascorbate peroxidase, and dehydroascorbate reductase elevated in both leaves and roots of AE as well as in leaves of NAE with the increasing Pb levels, but SOD and G-POD declined in roots of NAE. Enhancement in glutathione reductase activity was only detected in roots of NAE while a depression in catalase activity was recorded in the leaves of NAE. A significant enhancement in glutathione and ascorbic acid （AsA） levels occurred in both ecotypes exposed to Pb and Pb/EDTA treatment compared with the control, however, the differences between these two treatments were insignificant. The dehydroascorbate （DHA） contents in roots of both ecotypes were 1.41 to 11.22-fold higher than those in leaves, whereas the ratios of AsA to DHA （1.38 to 6.84） in leaves altering more to the reduced AsA form were much higher than those in roots. These results suggested that antioxidative enzymes and antioxidants play an important role in counteracting Pb stress in S. alfredii.     

Reactive oxygen metabolism in mycorrhizal and non-mycorrhizal citrus (Poncirus trifoliata) seedlings subjected to water stress

The effect of the arbuscular mycorrhizal (AM) fungus, Glomus versiforme, on growth and reactive oxygen metabolism of trifoliate orange (Poncirus trifoliata) seedlings was studied in potted plants under well-watered (WW) and water stressed (WS) conditions. Water stress significantly decreased root colonization. Shoot dry weight, plant height and stem diameter were higher in AM than in non-AM seedlings regardless of the water status. Inoculation with G. versiforme increased root dry weight and leaf number per plant of WW seedlings. There was less malondialdehyde (MDA) concentration in leaves and roots of AM seedlings, as well as lower hydrogen peroxide (H(2)O(2)) and superoxide anion radical (O(2)(-)) concentrations in AM roots under WW and WS conditions. AM inoculation did not affect the H(2)O(2) and O(2)(-) concentrations of WW leaves. Whether WS or not, AM symbiosis notably increased the guaiacol peroxidase (G-POD) activity of leaves, glutathione reductase (GR) activity of leaves and ascorbate peroxidase (APX) activity of roots. AM infection also markedly increased the APX activity of WS leaves. Soluble proteins and glutathione (GSH) in leaves and roots and ascorbate (ASC) in leaves were higher in WW AM than in WW non-AM seedlings. AM infection also enhanced the ASC and GSH contents of leaves and roots in WS seedlings. Cross-tolerance might occur in AM plants and be enhanced by AM symbiosis. Our results suggest that the increased concentrations of antioxidant enzymes and non-enzymatic antioxidants found in AM plants may serve to protect the organism against oxidative damage, enhancing drought tolerance.     

外源一氧化氮对渗透胁迫下小麦幼苗叶片膜脂过氧化的缓解作用

采用15%的聚乙二醇-6000(PEG-6000)对扬麦158三叶一心期的幼苗根部进行轻度渗透胁迫处理,并通过添加不同浓度的一氧化氮(nitric oxide,NO)供体硝普钠(sodium nitropussidi,SNP)和相应的对照(BO-3/NO-2),研究外源NO处理对渗透胁迫下小麦幼苗叶片膜脂过氧化作用的影响.结果发现,0.1 nnol/L的SNP能降低渗透胁迫造成的小麦幼苗叶片脂氧合酶(lipoxygenase,LOX)活性的提高,降低超氧阴离子(O-2)的产生速率和质膜相对透性的增加以及丙二醛(MDA)和H2O2的累积;0.1 mmol/L的SNP还能够诱导超氧化物歧化酶(superoxide dismutase,SOD)活性,加速脯氨酸(Pro)的累积,而0.5mmo1/L的SNP和0.1mmo1/L的NO3/NO2(对照)处理的效果则不明显.上述结果表明低浓度NO对渗透胁迫造成的膜脂过氧化有明显的缓解效应.     

Role of EDTA in alleviating lead toxicity in accumulator species of Sedum alfredii H

The effects of Pb chelater (EDTA-Pb) and ionic Pb (Pb(NO(3))(2)) on root cell death, Pb accumulation, changes of ROS, activities of antioxidant enzymes and uptake of mineral elements in response to Pb toxicity in Sedum alfredii H. were compared. Loss of plasma membrane integrity became serious by increasing Pb concentration in the medium, 200 microM Pb + 200 microM EDTA has alleviated the root cell death. The biomass was significantly affected by high concentration of Pb, and root growth was also affected by EDTA-Pb compared with ionic Pb. Lead accumulation was higher in the samples treated with ionic lead than that of the control. The concentration of reactive oxygen species (ROS) was determined by fluorescence microscopy, which indicates that the Pb stress increased the content of ROS significantly, whereas the EDTA-Pb decreased the burst of H(2)O(2). High Pb concentrations increase the activity of SOD and LOX. The Cu concentration in root increased significantly under Pb and EDTA-Pb treatment, and 200 microM Pb markedly increased the Fe content in roots. Under ionic Pb condition, the contents of Mg, Ca and K in shoots decreased, whereas they were significantly increased in case of EDTA-Pb. These results suggested that accumulating ecotype of S. alfredii roots were inefficient in uptake of higher concentration of EDTA-chelated Pb for long treatment duration, and that lead toxicity could be alleviated by EDTA.     

Calcium-calmodulin is required for abscisic acid-induced antioxidant defense and functions both upstream and downstream of H2O2 production in leaves of maize (Zea mays) plants

* Using pharmacological and biochemical approaches, the role of calmodulin (CaM) and the relationship between CaM and hydrogen peroxide (H(2)O(2)) in abscisic acid (ABA)-induced antioxidant defense in leaves of maize (Zea mays) plants were investigated. * Treatment with ABA or H(2)O(2) led to significant increases in the concentration of cytosolic Ca(2+) in the protoplasts of mesophyll cells and in the expression of the calmodulin 1 (CaM1) gene and the content of CaM in leaves of maize plants, and enhanced the expression of the antioxidant genes superoxide dismutase 4 (SOD4), cytosolic ascorbate peroxidase (cAPX), and glutathione reductase 1 (GR1) and the activities of the chloroplastic and cytosolic antioxidant enzymes. The up-regulation of the antioxidant enzymes was almost completely blocked by pretreatments with two CaM antagonists. * Pretreatments with CaM antagonists almost completely inhibited ABA-induced H(2)O(2) production throughout ABA treatment, but pretreatment with an inhibitor or scavenger of reactive oxygen species (ROS) did not affect the initial increase in the contents of CaM induced by ABA. * Our results suggest that Ca(2+)-CaM is involved in ABA-induced antioxidant defense, and that cross-talk between Ca(2+)-CaM and H(2)O(2) plays a pivotal role in ABA signaling.     

1,2,4-三氯苯胁迫对萌发大豆种子中活性氧的影响

以盆栽法研究了不同浓度 1,2 ,4 三氯苯 (TCB)胁迫对萌发大豆种子中活性氧代谢的影响 .结果表明 ,10 0～ 30 0 μg·g-1TCB胁迫初期 (1～ 3天 )促使萌发大豆种子呼吸强度升高及其峰值提前出现 ,超氧阴离子自由基 (O2 - )及过氧化氢 (H2 O2 )的积累显著增加 ,同时伴随丙二醛 (MDA)含量升高 ,显示发生膜脂质过氧化作用 .TCB胁迫 1～ 6天使活性氧清除酶功能紊乱 ,其中过氧化物酶 (POD)活性升高 ,超氧化物岐化酶 (SOD)活性开始上升后转为下降 .在萌发大豆种子受TCB胁迫伤害过程中 ,活性氧代谢失衡造成的膜脂质过氧化将起着重要作用 .     

The role of nitric oxide synthase-derived reactive oxygen species in the altered relaxation of pulmonary arteries from lambs with increased pulmonary blood flow

Congenital cardiac defects associated with increased pulmonary blood flow (Q(p)) produce pulmonary hypertension. We have previously reported attenuated endothelium-dependent relaxations in pulmonary arteries (PA) isolated from lambs with increased Q(p) and pulmonary hypertension. To better characterize the vascular alterations in the nitric oxide-superoxide system, 12 fetal lambs underwent in utero placement of an aortopulmonary vascular graft (shunt). Twin lambs served as controls. PA were isolated from these lambs at 4-6 wk of age. Electron paramagnetic resonance spectroscopy on fourth-generation PA showed significantly increased superoxide anion generation in shunt PA that were decreased to control levels following inhibition of nitric oxide synthase (NOS) with 2-ethyl-2-thiopseudourea. Preconstricted fifth-generation PA rings were relaxed with a NOS agonist (A-23187), a nitric oxide donor [S-nitrosyl amino penicillamine (SNAP)], polyethylene glycol-conjugated superoxide dismutase (PEG-SOD), or H(2)O(2). A-23187-, PEG-SOD-, and H(2)O(2)-mediated relaxations were impaired in shunt PA compared with controls. Pretreatment with PEG-SOD significantly enhanced the relaxation response to A-23187 and SNAP in shunt but not control PA. Inhibition of NOS with nitro-L-arginine or scavenging superoxide anions with tiron enhanced relaxation to SNAP and inhibited relaxation to PEG-SOD in shunt PA. Pretreatment with catalase inhibited relaxation of shunt PA to A-23187, SOD, and H(2)O(2). We conclude that NOS catalyzes the production of superoxide anions in shunt PA. PEG-SOD relaxes shunt PA by converting these anions to H(2)O(2), a pulmonary vasodilator. The redox environment, influenced by the balance between production and scavenging of ROS, may have important consequences on pulmonary vascular reactivity in the setting of increased Q(p).     

二氧化硫对小麦的氧化胁迫及其某些信号分子的调节

通过在密闭的培养箱中一次性通入不同体积浓度的SO₂气体,研究了小麦幼苗超氧自由基O2-含量和3种抗氧化酶活性的变化,探讨了信号分子水杨酸、乙烯和过氧化氢对SO₂氧化胁迫的调节作用.结果表明,当通入10和40 μl·L^-1 SO₂时,小麦叶片中O2-含量递增,过氧化物酶(POD)和过氧化氢酶(CAT)活性增强,但超氧化物歧化酶(SOD)活性降低.当SO₂浓度达到50 μl·L^-1时,POD和CAT活性也开始降低,此时叶片尖端出现坏死,叶片绿色部位滋生大量真菌.用1 mmol·L^-1水杨酸(SA)(pH6.5)浸泡小麦干种子6 h,或用10 mmol·L^-1 H₂O₂浸泡幼苗,O2-含量低于对照植株,而3种酶的活性高于对照植株,均可有效地减轻SO₂的氧化胁迫.在SO₂熏蒸下,乙烯显著抑制3种酶的活力,提高O2-的形成速率.SA与乙烯同时使用时,SA几乎完全消除了乙烯的负面作用.