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1.
Heavy metal-contaminated sites are excellent areas to examine the antioxidative machinery responsible for physiological adaptations of many plant species.Superoxide dismutase (SOD), guaiacol peroxide (GPX), ascorbate peroxide (APX), catalase (CAT) activity and hydrogen peroxide (H 2O 2) content were analyzed in leaves and roots of Viola tricolor ( Viola) from contaminated soils (‘Bukowno’, ‘Saturn’, ‘Warpie’ heaps), and non-contaminated soil (‘Zakopane meadow’) to examine the level of oxidative stress and antioxidative response.In leaves, six isoforms of SOD were recognized. Roots possessed two additional bands, named manganese superoxide dismutase (MnSOD)-like form (MnSODI) and Cu/ZnSOD-like form (Cu/ZnSODIV). The H 2O 2 content in leaves ranged from 554 to 5 098 μmol H 2O 2/g f.w. and was negatively correlated with CAT activity. The non-contaminated population was characterized by the lowest CAT activity combined with the highest H 2O 2 concentration. Two isoforms of CAT, CAT-1 and CAT-2, were recognized in leaves of plants from non-contaminated and contaminated sites, respectively. In roots of individuals from two heaps (‘Warpie’ and ‘Saturn’), two distinct bands for each CAT isoform were observed. A slower migrating band may be an aggregate, exhibiting CAT and MnSODs activities. Both peroxidases (APX and GPX) presented the same pattern of activity, depending on the organ, indicating that in leaves and roots APX and GPX were regulated in parallel.Differences in enzyme activities and H 2O 2 content between plants from different contaminated sites were statistically significant, but were tightly maintained at a very similar level. Prolonged and permanent heavy metal stress evoked a very similar mode of antioxidative response in specimens of analyzed metalliferous populations not causing measurable oxidative stress. Thus, our results clearly indicate that V. tricolor is a taxon well adapted to heavy metal-contaminated soils, and that differences in enzyme activities and H 2O 2 content result from adjustment of plants to a variety of conditions. 相似文献
2.
Spraying mustard ( Sinapis alba L.) seedlings with salicylic acid (SA) solutions between 10 and 500 μm significantly improved their tolerance to a subsequent heat shock at 55°C for 1.5 h. The effects of SA were concentration dependent, with higher concentrations failing to induce thermotolerance. The time course of thermotolerance induced by 100 μm SA was similar to that obtained with seedlings acclimated at 45°C for 1 h. We examined the hypothesis that induced thermotolerance involved H 2O 2. Heat shock at 55°C caused a significant increase in endogenous H 2O 2 and reduced catalase activity. A peak in H 2O 2 content was observed within 5 min of either SA treatment or transfer to the 45°C acclimation temperature. Between 2 and 3 h after SA treatment or heat acclimation, both H 2O 2 and catalase activity significantly decreased below control levels. The lowered H 2O 2 content and catalase activity occurred in the period of maximum thermoprotection. It is suggested that thermoprotection obtained either by spraying SA or by heat acclimation may be achieved by a common signal transduction pathway involving an early increase in H 2O 2. 相似文献
3.
We investigated the adaptative response of S. cerevisiae in sod mutants ( sod1Δ, sod2Δ and sod1Δsod2Δ) after H 2O 2 treatment in the stationary phase. sod2Δ and sod1Δsod2Δ demonstrated the highest levels of GSH in the control, suggesting that pathways which include GSH protect these double mutants against oxidative stress. In addition, sod1Δ and sod1Δsod2Δ had higher iron levels than the wild-type, independently of H 2O 2 stress. Fe levels were increased in sod2Δ following H 2O 2 In addition, the sod2Δ mutant was more sensitive to H 2O 2 treatment than the wild-type. These results suggest that sod2Δ sensibility may be associated with •OH production by the Fenton reaction. This increased iron demand in the sod2Δ mutant may be a reflection of the cells’ efforts to reconstitute proteins that are inactivated in conditions of excess superoxide. MDA levels were assayed by HPLC in these mutants. The highest MDA levels could be observed after 10mM H 2O 2 treatment in the sod1Δsod2Δ double mutant. After treatment with a GSH inhibitor, the MDA level was still higher in the same strain. Thus, both direct and indirect GSH pathways are involved in the protection of lipid membranes and proteins in these mutants and may constitute an adaptative response to enhanced basal oxidative damage produced by superoxide. 相似文献
4.
Salinity, as a serious and prevalent abiotic stress, causes widespread crop losses by restricting plant growth and production throughout the world. In this study, the biochemical and molecular responses of the pistachio (Pistacia vera L.) plant were studied under NaCl and salicylic acid (SA) treatments using hydroponically grown salt tolerant (Ghazvini) and salt sensitive (Sarakhs) pistachio cultivars. NaCl treatment (250 mM) increased the production of hydrogen peroxide (H2O2) and malondialdehyde (MDA) and the activity of antioxidant enzymes in both cultivars. In the sensitive cultivar, the H2O2 content was higher than the tolerant cultivar, especially in the roots. SA application to both salt-stress-treated cultivars resulted in an increase in photosynthetic pigment contents and antioxidant enzyme activity and a decrease in the H2O2 and MDA contents. After NaCl treatment, the isochorismate synthase (ICS) gene was upregulated in Ghazvini which leads to an increase in the SA content of the salt tolerant pistachio cultivar. In contrast, the salt treatment downregulated the expression of the ICS gene in Sarakhs. The ICS gene expression was positively regulated by SA treatment under the salt stress condition. Our results suggest that Ghazvini has higher salinity tolerance than Sarakhs due to its higher antioxidant capacity, photosynthetic pigment content, and the cultivar-specific expression pattern of the ICS gene. In this study, the potential alleviative effects of SA on the adverse effect of salt stress in P. vera (Pistacia vera) were also identified and highlighted. 相似文献
5.
We evaluated the involvement of nitric oxide (NO) in salicylic acid (SA)-induced accumulation of ginsenoside in adventitious
roots of Panax ginseng and its mediation by reactive oxygen species (ROS). Related effects of SA on components of the antioxidant system were also
sought. Adventitious roots of P. ginseng were grown in suspension culture for 3 weeks in MS medium and treated over 5 days with SA (100 μM) alone, SA in combination
with the NO scavenger 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO), or PTIO alone. Nitric oxide, the superoxide
anion (O 2·−), H 2O 2, nitrite, nonprotein thiol, and ascorbate were monitored together with ginsenoside, NADPH oxidase activity, and several antioxidant
enzymes. Salicylic acid did not inhibit root growth but induced accumulation of ginsenoside, lipid peroxidation, and generation
of NO and O 2·−. It also enhanced activities of NADPH oxidase, superoxide dismutase, catalase, and peroxidase, including ascorbate peroxidase.
These effects were suppressed by PTIO. Salicylic acid also decreased glutathione reductase activity. Inclusion of PTIO with
SA decreased the activity of glutathione reductase further. Treatment with SA plus PTIO also decreased nonprotein thiol and
ascorbate contents but caused nitrite to overaccumulate. Salicylic acid applied to adventitious roots in culture induced accumulation
of ginsenoside in an NO-dependent manner that was mediated by the associated increases in O 2·−, which gave other antioxidant responses that were dependent on NO. 相似文献
6.
The effects of methyl jasmonate (MJ) and salicylic acid (SA) on changes of the activities of major antioxidant enzymes, superoxide anion accumulation (O 2
−), ascorbate, total glutathione (TG), malondialdehyde (MDA) content and ginsenoside accumulation were investigated in ginseng roots ( Panax ginseng L.) in 4 l (working volume) air lift bioreactors. Single treatment of 200 μM MJ and SA to P. ginseng roots enhanced ginsenoside accumulation compared to the control and harvested 3, 5, 7 and 9 days after treatment. MJ and SA treatment induced an oxidative stress in P. ginseng roots, as shown by an increase in lipid peroxidation due to rise in O 2
− accumulation. Activity of superoxide dismutase (SOD) was inhibited in MJ-treated roots, while the activities of monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), SOD, guaiacol peroxidase (G-POD), glutathione peroxidase (GPx) and glutathione reductase (GR) were induced in SA-treated roots. A strong decrease in the activity of catalase (CAT) was obtained in both MJ- and SA-treated roots. Activities of ascorbate peroxidase (APX) and glutathione S transferase (GST) were higher in MJ than SA while the contents of reduced ascorbate (ASC), redox state (ASC/(ASC+DHA)) and TG were higher in SA- than MJ-treated roots while oxidized ascorbate (DHA) decreased in both cases. The result of these analyses suggests that roots are better protected against the O 2
− stress, thus mitigating MJ and SA stress. The information obtained in this work is useful for efficient large-scale production of ginsenoside by plant-root cultures. 相似文献
7.
The role of salicylic acid (SA) in alleviating cadmium (Cd) toxicity was investigated in a hydroponic cultivation system. Short-term exposure of bean ( Phaseolus vulgaris) plants to 20 μM Cd inhibited biomass production and intensively increased accumulation of Cd in both roots and leaves. At leaf level, Cd significantly decreased mineral ions, chlorophyll and carotenoids concentrations. Concomitantly, Cd enhanced electrolyte leakage, H 2O 2 content and lipid peroxidation as indicated by malondialdehyde (MDA) accumulation. SA pretreatment decreased the uptake and the transport of Cd, alleviated the Cd-induced inhibition of nutrient absorption and led to a significant increase of chlorophyll and carotenoid content. SA application alleviated the oxidative damages as evidenced by the lowered H 2O 2 and MDA content. SA particularly induced an increase in both CAT and APX activities accompanied by a significant reduction in SOD and POD activities. As important antioxidants, ascorbate and glutathione contents in bean leaves exposed to cadmium were significantly decreased by SA treatment. These results reveal the potentiating effect of salicylic acid in regulating cadmium induced oxidative stress in bean plants. 相似文献
8.
It has been reported that salicylic acid (SA) induces both immediate spike and long lasting phases of oxidative burst represented by the generation of reactive oxygen species (ROS) such as superoxide anion radical (O 2•−). In general, in the earlier phase of oxidative burst, apoplastic peroxidase are likely involved and in the late phase of the oxidative burst, NADPH oxidase is likely involved. Key signaling events connecting the 2 phases of oxidative burst are calcium channel activation and protein phosphorylation events. To date, the known earliest signaling event in response to exogenously added SA is the cell wall peroxidase-catalyzed generation of O 2•− in a hydrogen peroxide (H 2O 2)-dependent manner. However, this model is incomplete since the source of the initially required H 2O 2 could not be explained. Based on the recently proposed role for H 2O 2-independent mechanism for ROS production catalyzed by plant peroxidases (Kimura et al., 2014, Frontiers in Plant Science), we hereby propose a novel model for plant peroxidase-catalyzed oxidative burst fueled by SA. 相似文献
9.
In Arabidopsis thaliana, LESION SIMULATING DISEASE 1 (LSD1), ENHANCED DISEASE SUSCEPTIBILITY 1 (EDS1) and PHYTOALEXIN DEFICIENT 4 (PAD4) proteins are regulators of cell death (CD) in response to abiotic and biotic stresses. Hormones, such as salicylic acid (SA), and reactive oxygen species, such as hydrogen peroxide (H 2O 2), are key signaling molecules involved in plant CD. The proposed mathematical models presented in this study suggest that LSD1, EDS1 and PAD4 together with SA and H 2O 2 are involved in the control of plant water use efficiency (WUE), vegetative growth and generative development. The analysis of Arabidopsis wild‐type and single mutants lsd1, eds1, and pad4, as well as double mutants eds1/lsd1 and pad4/lsd1, demonstrated the strong conditional correlation between SA/H 2O 2 and WUE that is dependent on LSD1, EDS1 and PAD4 proteins. Moreover, we found a strong correlation between the SA/H 2O 2 homeostasis of 4‐week‐old Arabidopsis leaves and a total seed yield of 9‐week‐old plants. Altogether, our results prove that SA and H 2O 2 are conditionally regulated by LSD1/EDS/PAD4 to govern WUE, biomass accumulation and seed yield. Conditional correlation and the proposed models presented in this study can be used as the starting points in the creation of a plant breeding algorithm that would allow to estimate the seed yield at the initial stage of plant growth, based on WUE, SA and H 2O 2 content. 相似文献
10.
Summary A mutant strain of Anabaena variabilis, strain SA-1 that supported growth of wheat plants in a hydroponic co-culture in nitrogen (N) free medium also produced enough oxygen (O 2) to support root respiration. The steady-state concentration of net O 2 in the co-culture was dependent on incident light intensity. At an incident photosynthetic photoflux (PPF) of 1000 mol photons·m –2·s –1, net O 2 evolution by the co-culture in the root zone reached a maximum value of about 220 mol O 2 evolved·h –1·mg chlorophyll (Chl) –1. The O 2 concentration in the rhizosphere of the co-culture stayed above the ambient air level. O 2 uptake in the dark by strain SA-1-supplemented wheat roots washed free of cyanobacterium was higher than the root respiration of nitrate-grown plants. Nitrate-grown plants required aeration for maximum growth while the wheat-cyanobacterial co-culture can be cultured without aeration. These results show that O 2 produced by strain SA-1 can be used to supply the O 2 needs for root respiration of wheat. Respiration reduced net O 2 evolution by the mutant SA-1, decreasing the partial pressure of O 2 at the sites of cyanobacterial attachment to the roots. This led to an increase in the specific activity of nitrogenase of the co-culture at the high light intensities used to support wheat growth. This activity of about 30 mol ethylene produced·mg Chl –1·h –1 was three-fold higher than the activities obtained with the free-living strain SA-1 assayed at the same light intensity. In the co-culture, ammonia produced by the mutant strain SA-1 was not detectable. The NH
inf4
sup+
produced by strain SA-1 was used by the wheat plants and, under these conditions, the total N content of the plants reached as high as 85% of the total N content of nitrate-grown plants. In the co-culture system the metabolism of wheat and the cyanobacterium complemented each other, leading to higher plant growth in N-free medium.
Offprint requests to: M. Gunasekaran 相似文献
12.
The metabolism of salicylic acid (SA) in tobacco ( Nicotiana tabacum L. cv. KY 14) cell suspension cultures was examined by adding [7– 14C]SA to the cell cultures for 24 h and identifying the metabolites through high performance liquid chromatography analysis. The three major metabolites of SA were SA 2- O-- D-glucose (SAG), methylsalicylate 2- O-- D-glucose (MeSAG) and methylsalicylate. Studies on the intracellular localization of the metabolites revealed that all of the SAG associated with tobacco protoplasts was localized in the vacuole. However, the majority of the MeSAG was located outside the vacuole. The tobacco cells contained an SA inducible SA glucosyltransferase (SAGT) enzyme that formed SAG. The SAGT enzyme was not associated with the vacuole and appeared to be a cytoplasmic enzyme. The vacuolar transport of SAG was characterized by measuring the uptake of [ 14C]SAG into tonoplast vesicles isolated from tobacco cell cultures. SAG uptake was stimulated eightfold by the addition of MgATP. The ATP-dependent uptake of SAG was inhibited by bafilomycin A 1 (a specific inhibitor of the vacuolar H +-ATPase) and dissipation of the transtonoplast H +-electrochemical gradient. Vanadate was not an inhibitor of SAG uptake. Several -glucose conjugates were strong inhibitors of SAG uptake, whereas glutathione and glucuronide conjugates were only marginally inhibitory. The SAG uptake exhibited Michaelis–Menten type saturation kinetics with a Km and Vmax value of 11 M and 205 pmol min –1 mg –1, respectively, for SAG. Based on the transport characteristics it appears as if the vacuolar uptake of SAG in tobacco cells occurs through an H +-antiport-type mechanism. 相似文献
13.
In the present investigation, we studied the possible potentiating effect of salicylic acid (SA) under Cd toxicity in Oryza sativa L. leaves. Cd treatments for 24 h reduced the shoot length, dry biomass and total chlorophyll content followed by high Cd
accumulation in shoots. About 16 h presoaking with SA resulted in partial protection against Cd, as observed by minor changes
in length, biomass and total chlorophyll. SA priming resulted in low Cd accumulation. Enhanced thiobarbituric acid reactive
substances (TBARS), hydrogen peroxide (H 2O 2) and superoxide anion (O 2
−) content were seen when Cd was applied alone, while under SA priming the extent of TBARS, H 2O 2 and O 2
− were significantly low, suggesting SA-regulated protection against oxidative stress. The antioxidant enzymes like Catalase
(CAT), guaiacol peroxidase (GPx), glutathione reductase (GR) and superoxide dismutase (SOD) showed varied activities under
Cd alone. CAT activity increased after Cd treatment, followed by a decline in GPX and GR activity. SOD also declined at the
highest concentrations with an initial increase. Under SA-priming conditions, the efficiency of the antioxidant enzymes was
significantly elevated. GPx and SOD activity showed significant increase in activity. The ascorbate activity increased after
Cd treatment, followed by a decline in glutathione under SA-free condition. SA priming showed gradual increase in these non-enzymic
antioxidants. Our results indicate that Cd-induced oxidative stress can be regulated by SA. 相似文献
14.
Acclimation to excess light is required for optimizing plant performance under natural environment. The present work showed that the treatment of Arabidopsis leaves with exogenous H 2O 2 can increase the acclimation of PSII to excess light. Treatments with H 2O 2 also enhanced the capacity of the mitochondrial alternative respiratory pathway and salicylic acid (SA) content. Our work also showed that the lack in alternative oxidase (AOX1a) in AtAOX1a antisense line and the SA deficiency in NahG (salicylate hydroxylase gene) transgenic mutant attenuated the H 2O 2-induced acclimation of PSII to excess light. It indicates that the H 2O 2-induced acclimation of PSII to excess light could be mediated by the alternative respiratory pathway and SA. 相似文献
15.
The response of Arabidopsis thaliana plants to elevated sulfur dioxide could be related to their endogenous salicylic acid (SA) content and signaling. The wild
type (WT, ecotype Columbia) and its mutant snc1 with high SA content, npr1-1 with a blockage in SA signaling, transgenic line nahG with low SA content and double mutant snc1nahG plants were exposed to 0.5 mm 3 dm −3 SO 2 for 3 h d −1 for 14 d in a growth chamber. Under unstressed conditions, total SA contents in snc1 and npr1-1 were 7- and 2-fold higher than those in WT, respectively, but in nahG SA content was only 28 % of that in WT. The expression of nahG in snc1 plants decreased SA content to the WT level. Increased SA contents were observed in snc1, npr1-1 and WT after 12-h SO 2 exposure, whereas no major changes were detected in nahG and snc1nahG plants. The snc1 plants exhibited higher tolerance to SO 2 exposure than snc1nahG plants and especially nahG and npr1-1 plants according to plant biomass, total chlorophyll content and photosynthetic rate. The SO 2 exposure decreased net photosynthetic rate, maximum photochemical efficiency (F v/F m) and actual quantum efficiency of photosystem 2 (Φ PS2). SO 2-induced oxidative damage in the tested plants was confirmed by increased malondialdehyde (MDA) content and electrolyte leakage.
Increases in superoxide dismutase (SOD) and peroxidase (POD) activity, reduced glutathione (GSH) content and a ratio of reduced/oxidized
glutathione (GSSG) might be responsible for the decreased contents of H 2O 2 and alleviation of oxidative injury in snc1 plants compared with other lines exposed to SO 2. These observations implied that endogenous SA content and signaling may play an essential role in plant responses to SO 2 stress. 相似文献
16.
The effects of salicylic acid (SA) on growth parameters and enzyme activities were investigated in salt-stressed safflower ( Carthamus tinctorius L.). Twenty-five days after sowing, seedlings were treated with NaCl (0, 100, and 200?mM) and SA (1?mM), and were harvested at 21 days after treatments. Results showed that some growth parameters decreased under salinity, while malondialdehyde (MDA) and hydrogen peroxide (H 2O 2) content, phenolic compounds, and some enzyme activities increased. SA application increased some growth parameters, MDA and H 2O 2 content, and enzyme activities except catalase (CAT), which was different from the other enzymes and SA significantly reduced CAT activity in plants. These results suggest that SA-induced tolerance to salinity may be related to regulation of antioxidative responses and H 2O 2 level. Our study suggested that the resistant safflower can direct reactive oxygen species from a threat to an opportunity by using SA. Therefore, exogenous application of SA played this role through regulation of the antioxidant system. 相似文献
17.
Malformation of mango ( Mangifera indica L.) induced by Fusarium moniliforme var. subglutinans is a plant disease of international importance. The paper reports the downstream defence responses at the initial stage in a susceptible host (cultivar Amrapali) after treatment with biotic (isolated from the pathogen cell wall) (BEL) and abiotic (salicylic acid, SA) elicitors, and inoculation of vegetative buds with the pathogen (IVB). The SA was further tested to induce resistance in field trials. The inoculation and application of elicitors increased β-1, 3 glucanase that causes lysis of fungal hyphae by many folds. Hydrogen peroxide (H 2O 2) (active oxygen species) that induces hypersensitive cell death was reduced to the minimum level after treatment with BEL. The reduction of H 2O 2 in the inoculated vegetative buds was also substantial; however, comparatively less with SA treatment. Consequently, there was no hypersensitive cell death in the malformed mango. Salicylic acid that enhances H 2O 2 content by suppressing H 2O 2-degradation by catalase, increased marginally with the SA treatment and in the IVB, but reduced with the BEL. The reduction of SA in BEL-treated buds concomitantly reduced its H 2O 2 content. The activity of catalase, suppressor of resistance mechanism, was reduced in all the treatments, but the reduction was not enough to arrest H 2O 2-degradation. Magiferin (1, 3, 6, 7-tetrahdroxyxanthone C 2-β-D glucoside), a defence metabolite of mango, increased substantially in all the treatments; maximum with the BEL. A pathogenesis-related (PR) protein of 20 KDa that resists symptom development appeared in all the treatments except the control. But light colour of the spots for the PR-protein indicated low protein accumulation. The maximum accumulation was with the IVB followed by SA and BEL treatments. The amount of total protein reduced considerably in all the treatments. The SA treatment on healthy plants failed to induce defence against malformation. Contrarily, the treatment on malformed seedlings restored normal growth within two months. Hence, SA acted better over the infected plants in presence of the pathogen. Thus, a signal transduction system involving SA and H 2O 2 remained nonfunctional and enough defence chemicals could not be synthesised. Defence genes that produce phenolic and β-1, 3 glucanase, however, became activated and saved the plants from death although could not prevent symptom manifestations. 相似文献
18.
The contamination of soils with dry olive-mill residue can represent a serious problem as being an environmental stressor in plants. It has been demonstrated that inoculation of aqueous extract of olive oil-mill residue (ADOR) with saprobe fungi removes some phenolic compounds. In this paper we studied the effect of ADOR uninoculated or inoculated with saprobe fungi in sunflower seedling roots. The germination and root growth, O 2· - generation, superoxide dismutase (SOD) and extracellular peroxidases (EC-POXs) activities, and the content of some metabolites involved in the tolerance of stress were tested. The roots germinated in ADOR uninoculated show a decrease in meristem size, resulting in a reduction of the root length and fresh weight, and in the number of layers forming the cortex, but did not alter the dry weight, protein and soluble amino acid content. ADOR caused the decreases in O 2· - generation and EC-POX′s activities and protein oxidation, but enhanced SOD activity, lipid peroxidation and proline content. Fluorescence imaging showed that ADOR induced O 2· - and H 2O 2 accumulation in the roots. The increase in SOD and the decrease in EC-POX′s activities might be involved in the enhancement of H 2O 2 content and lipid peroxidation. Control roots treated with ADOR for 10 min show an oxidative burst. Roots germinated in ADOR inoculated with saprobe fungi partially recovered normal levels of ROS, morphological characteristics and antioxidant activities. These results suggested that treatment with ADOR caused a phytotoxic effect during germination inducing an oxidative stress. The inoculation of ADOR with saprobe fungi limited the stress. 相似文献
19.
The effects of salicylic acid (SA) and hydrogen peroxide (H 2O 2) on freezing tolerance were studied in two potato ( Solanum tuberosum) cultivars (Alpha and Atlantic) that differ in cold sensitivity, Alpha being more tolerant to freezing than Atlantic. Lowest freezing survival rates were observed in 4-week-old plants. Freezing treatments consisting of exposure to 6° C for 4 h in the dark were applied 24 h after plants had been transferred from in vitro culture to soil. Catalase activity and H 2O 2 were estimated at the following harvest points: stage (a) 4-week-old in vitro plants treated with either 0.1 m M SA or 5 m M H 2O 2; stage (b) as in (a) but 24 h following transfer to soil prior to freezing treatment; stage (c) as in (b) but measured 15 days after a 4-h freezing treatment. The results show that (1) SA induced freezing tolerance in both cultivars; (2) SA inhibited ascorbate peroxidase activities in both cultivars at all harvest points but inhibited catalase activities in only at stage (a); (3) SA induced H 2O 2 accumulation only in Atlantic at stage (a); (4) H 2O 2 enhanced shoot catalase activities in Atlantic at stages (a) and (b) whereas this treatment had no effect on shoot catalase activities in Alpha; (5) H 2O 2 treatment induced freezing tolerance in Atlantic, even though shoot catalase activities were lower than those of the controls following exposure to freezing temperatures. We conclude that SA does not always lead to H 2O 2 accumulation even though catalase and ascorbate peroxidase activities are decreased as a result of the treatment. Moreover, H 2O 2 accumulation is not always associated with the induction of freezing tolerance, for example at stage (a) where SA-induced tolerance in Alpha was not accompanied by H 2O 2 accumulation. H 2O 2 was able to induce freezing tolerance only in Atlantic, even though H 2O 2 accumulated in both cultivars following this treatment. 相似文献
20.
β-Amyloid peptide (Aβ) 1–42, involved in the pathogenesis of Alzheimer’s disease, binds copper ions to form Aβ · Cu n complexes that are able to generate H 2O 2 in the presence of a reductant and O 2. The production of H 2O 2 can be stopped with chelators. More reactive than H 2O 2 itself, hydroxyl radicals HO (generated when a reduced redox active metal complex interacts with H 2O 2) are also probably involved in the oxidative stress that creates brain damage during the disease. We report in the present work a method to monitor the effect of chelating agents on the production of hydrogen peroxide by metallo-amyloid peptides. The addition of H 2O 2 associated to a pre-incubation step between ascorbate and Aβ · Cu n allows to study the formation of H 2O 2 but also, at the same time, its transformation by the copper complexes. Aβ · Cu n peptides produce but do not efficiently degrade H 2O 2. The reported analytic method, associated to precipitation experiments of copper-containing amyloid peptides, allows to study the inhibition of H 2O 2 production by chelators. The action of a ligand such as EDTA is probably due to the removal of the copper ions from Aβ · Cu n, whereas bidentate ligands such as 8-hydroxyquinolines probably act via the formation of ternary complexes with Aβ · Cu n. The redox activity of these bidentate ligands can be modulated by the incorporation or the modification of substituents on the quinoline heterocycle. 相似文献
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