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1.
Scytosiphon lomentaria (Lingb.) Link. (Phaeophyceae) is one of the two dominant seaweeds in a coastal area of northern Chile affected by copper mine wastes, where the concentration of copper in water and algal tissues remains higher than in nonimpacted sites. Copper‐loaded plants develop oxidative stress, as demonstrated by the increased levels of reactive oxygen species and lipoperoxides. This stress was associated with 1) an enhanced activity of the antioxidant enzymes catalase, glutathione peroxidase, ascorbate peroxidase, monodehydroascorbate reductase, and dehydroascorbate reductase and 2) an inhibition of the glutathione reductase activity. Furthermore, stressed plants showed a decrease in glutathione and phenolic compounds levels and an increase in total ascorbate. Reciprocal transplants revealed that plants rapidly adjusted their antioxidant system in response to the conditions of the receiving site. In individuals transplanted from the copper‐enriched environment to the control site, normal levels of lipoperoxides and antioxidant compounds were restored in 48 h and antioxidant enzymes recovered their basal activities in 96 h. Individuals transplanted from the control site to the copper‐enriched area adjusted their antioxidant compounds and antioxidant enzymes within 48 h and 96 h, respectively, and reached the functional status of the local plants. We conclude that S. lomentaria inhabiting the copper‐enriched area buffered oxidative stress by a simultaneous involvement of antioxidant enzymes and water‐soluble antioxidant compounds. These antioxidant responses were rapid and reversible, suggesting that copper resistance in S. lomentaria is a constitutive trait and that copper enrichment of the area did not result in a locally adapted copper‐tolerant ecotype. 相似文献
2.
Shunhua Ding Qingtao Lu Yan Zhang Zhipan Yang Xiaogang Wen Lixin Zhang Congming Lu 《Plant molecular biology》2009,69(5):577-592
To investigate the possible mechanisms of glutathione reductase (GR) in protecting against oxidative stress, we obtained transgenic
tobacco (Nicotiana tabacum) plants with 30–70% decreased GR activity by using a gene encoding tobacco chloroplastic GR for the RNAi construct. We investigated
the responses of wild type and transgenic plants to oxidative stress induced by application of methyl viologen in vivo. Analyses
of CO2 assimilation, maximal efficiency of photosystem II photochemistry, leaf bleaching, and oxidative damage to lipids demonstrated
that transgenic plants exhibited enhanced sensitivity to oxidative stress. Under oxidative stress, there was a greater decrease
in reduced to oxidized glutathione ratio but a greater increase in reduced glutathione in transgenic plants than in wild type
plants. In addition, transgenic plants showed a greater decrease in reduced ascorbate and reduced to oxidized ascorbate ratio
than wild type plants. However, there were neither differences in the levels of NADP and NADPH and in the total foliar activities
of monodehydroascorbate reductase and dehydroascorbate reductase between wild type and transgenic plant. MV treatment induced
an increase in the activities of GR, ascorbate peroxidase, superoxide dismutase, and catalase. Furthermore, accumulation of
H2O2 in chloroplasts was observed in transgenic plants but not in wild type plants. Our results suggest that capacity for regeneration
of glutathione by GR plays an important role in protecting against oxidative stress by maintaining ascorbate pool and ascorbate
redox state. 相似文献
3.
Oxidative stress responses were tested in the unicellular cyanobacterium Synechococcus PCC 7942 (R2). Cells were exposed to hydrogen peroxide, cumene hydroperoxide and high light intensities. Activities of ascorbate peroxidase and catalase were correlated with the extent and time-course of oxidative stresses. Ascorbate peroxidase was found to be the major enzyme involved in the removal of hydrogen peroxide under the tested oxidative stresses. Catalase activity was inhibited in cells treated with high H2O2 concentrations, and was not induced under photo-oxidative stress. Regeneration of ascorbate in peroxide-treated cells was found to involve mainly monodehydroascorbate reductase and to a lesser extent dehydroascorbate reductase. The induction of the antioxidative enzymes was dependent on light and was inhibited by chloramphenicol. Peroxide treatment was found to induce the synthesis of eight proteins, four of which were also induced by heat shock.Abbreviations ASC
ascorbate
- DHA
dehydroascorbate
- MDA
monodehydroascorbate
- GSH
reduced glutathione
- GSSG
oxidized glutathione
- ASC Per
ascorbate peroxidase
- DHA red.
dehydroascorbate reductase
- MDA red.
monodehydroascorbate reductase
- GSSG red.
glutathione reductase
- HSP
heat shock proteins
- PSP
peroxide shock proteins
- Cm
chloramphenicol 相似文献
4.
Effects of exogenous hydrogen sulfide on the ascorbate and glutathione metabolism in wheat seedlings leaves under water stress 总被引:1,自引:0,他引:1
Chang-juan Shan Sheng-li Zhang Dong-fang Li Yuan-zeng Zhao Xue-liang Tian Xin-liang Zhao Ying-xia Wu Xiu-ying Wei Run-qiang Liu 《Acta Physiologiae Plantarum》2011,33(6):2533-2540
This study investigated the effects of exogenous hydrogen sulfide on the ascorbate and glutathione metabolism in wheat seedlings
leaves under water stress. The results showed that pretreatment with sodium hydrosulfide (NaHS), hydrogen sulfide donor, increased
the activities of ascorbate peroxidase, glutathione reductase, dehydroascorbate reductase and gamma-glutamylcysteine synthetase,
and the contents of reduced ascorbic acid, reduced glutathione, total ascorbate and total glutathione under water stress,
compared to control and water stress without NaHS. Meanwhile, pretreatment with NaHS decreased the malondialdehyde content
and electrolyte leakage induced by water stress in plants, compared to control and water stress without NaHS. Our results
suggested that exogenous hydrogen sulfide alleviated oxidative damage by regulating the ascorbate and glutathione metabolism
in wheat seedlings under water stress. 相似文献
5.
Copper‐imposed oxidative stress and antioxidative defence responses were investigated in the primary leaves of Phaseolus vulgaris L. plants grown on hydroponics containing 50 μM CuSO4. Copper mainly accumulates in roots; therefore, an increase of the copper content in the leaves was only observed 48 h after the start of the copper supply. Nevertheless, an increase of the thiobarbituric acid reactive metabolites (TBArm) content, an indication of stress, occurred immediately following copper application. Because the ascorbate‐glutathione pathway is considered as a major antioxidative defence mechanism, the evolution of the enzymes and the related metabolites involved in this pathway were studied in the primary leaves as a function of plant copper assimilation. The capacities of monodehydroascorbate reductase (EC 1.6.5.4), dehydroascorbate reductase (EC 1.8.5.1), and glutathione reductase (EC 1.6.4.2) were increased before elevated amounts of copper could be detected in the leaves. The early enhancement of glutathione reductase was only temporary. After copper accumulation in the leaves, a second increase of the glutathione reductase capacity and also an increase of the ascorbate peroxidase capacity (EC 1.11.1.11) were observed. These changes in enzymatic capacity modified the level of the metabolites involved. Increase of the ascorbate pool and maintenance in its reduced form was observed immediately after the start of the treatment. In the beginning of the experiment, the glutathione disulphide/reduced glutathione ratio was higher in the treated plants as compared to the controls. However, towards the end of the experiment, the total glutathione pool, as well as the reduced glutathione content, increased, resulting in a lower ratio value for the treated plants. In conlusion, copper‐imposed oxidative stress, as well as the antioxidative defence response in the leaves, appears to be biphasic. An indirect preventive effect on the antioxidative defence system was observed during the first phase before the leaf copper content increased. A root‐to‐shoot signalling system appears to be involved. Direct oxidation by copper of reduced cell metabolites occurred during the second phase when the leaf copper content was enhanced. 相似文献
6.
通过盆栽实验, 对干旱胁迫下黄土高原地区冰草(Agropyron cristatum)叶片的抗坏血酸和谷胱甘肽合成及循环代谢相关酶及物质含量进行了研究。结果表明: 冰草可以通过增强叶片的抗坏血酸和谷胱甘肽合成及循环代谢酶: 抗坏血酸过氧化物酶、谷胱甘肽还原酶、脱氢抗坏血酸还原酶、单脱氢抗坏血酸还原酶、L-半乳糖酸-1, 4-内酯脱氢酶和γ-谷氨酰半胱氨酸合成酶活性, 维持植物体内抗坏血酸和谷胱甘肽水平及氧化还原状态, 从而抵御干旱造成的氧化胁迫。但叶片抗坏血酸和谷胱甘肽合成及循环代谢对不同水平干旱胁迫的响应, 随胁迫时间的延长而不同。在胁迫24天以前, 严重干旱下叶片的抗坏血酸和谷胱甘肽合成及循环代谢增强较显著; 在胁迫24天后, 由于该胁迫下植物所遭受的氧化胁迫较为严重, 叶片中上述6种酶的活性均呈降低趋势。而在中度干旱下叶片抗坏血酸和谷胱甘肽合成及循环代谢相关的6种酶在整个胁迫过程中均保持较高的活性。这说明, 冰草能够长时间有效地抵御中度干旱所造成的氧化胁迫, 但只能在一定时间范围内有效地抵御严重干旱所造成的氧化胁迫, 胁迫时间延长则会降低其抵御严重干旱的能力。 相似文献
7.
This study investigated the regulation of ascorbate and glutathione metabolism by nitric oxide in Agropyron cristatum leaves under water stress. The activities of ascorbate peroxidase (APX), glutathione reductase (GR), monodehydroascorbate
reductase (MDHAR), dehydroascorbate reductase (DHAR), L-galactono-1,4-lactone dehydrogenase (GalLDH) and γ-glutamylcysteine
synthetase (γ-ECS), and the contents of NO, reduced ascorbic acid (AsA), reduced glutathione (GSH), total ascorbate and total
glutathione increased under water stress. These increases were suppressed by pretreatments with NO synthesis inhibitors N
G-nitro-L-arginine methyl ester (L-NAME) and 4-carboxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO). However,
application of L-NAME and cPTIO to plants sufficiently supplied with water did not affect the activities of above mentioned
enzymes and the contents of NO and above mentioned antioxidants. Pretreatments with L-NAME and cPTIO increased the malondialdehyde
(MDA) content and electrolyte leakage of plants under water stress. Our results suggested that water stress-induced NO is
a signal that leads to the upregulation of ascorbate and glutathione metabolism and has important role for acquisition of
water stress tolerance. 相似文献
8.
Protoplasts isolated from Nicotiana tabacum (L.) leaves were cultured for 6 days in liquid medium and some features of their antioxidant capacity were investigated.
Ascorbate exported into the culture medium was oxidized non-enzymically, whereas important modifications of the enzymic scavenging
activity were detected inside protoplasts. A new pool of isoenzymes, most of them with cytoplasmic characteristics, ensures
the increased ascorbate peroxidase activity. The specific activity of other enzymes involved in the ascorbate/glutathione
cycle, such as dehydroascorbate reductase and glutathione reductase, and of glutathione peroxidase were modified, resulting
in cultured protoplasts with quantitative differences in antioxidant capacity compared to leaves. The hypothesis presented
here suggests that the new scavenging system is related to differences in the compartment-specific accumulation of active
oxygen species following protoplast isolation.
Received: 8 December 1997 / Revision received: 27 March 1998 / Accepted: 10 April 1998 相似文献
9.
The effect of magnesium (Mg2+)‐deficiency on the antioxidant responses of Capsicum annuum was investigated over a 60‐day period under controlled conditions. This Mg2+‐deficiency aimed to mimic the physiological conditions that plants may experience in the field. At each harvest time, five different leaf‐levels (L2 to L6) were distinguished. L2 and L6 correspond to the second and sixth youngest leaves, respectively. The following parameters were determined: Mg2+, chlorophyll and protein contents, total and redox pools of ascorbate and glutathione, and the activities of superoxide dismutase, ascorbate peroxidase, dehydroascorbate reductase, and glutathione reductase. Under Mg2+‐deficiency, leaf Mg2+ contents decreased over time in all leaf‐levels except in the second youngest leaves (L2), where they remained constant at about 0.25% (dry weight basis). Mg2+‐deficiency led to an increase in the antioxidant enzyme activities concomitant with an increase in the ascorbate and glutathione pools, whereas total chlorophyll and soluble protein contents decreased. The L2 leaves showed an increase in glutathione reductase activity and in the ascorbate redox state whereas no difference was observed for the other parameters. Superoxide dismutase activities increased in L5 leaves from day 15 and, afterwards, in L3 to L5 leaves, irrespective of Mg2+ content. At day 30, glutathione reductase activities increased in L2 to L4 leaves and dehydroascorbate reductase activities in L4 leaves. At day 45, we observed an increase in the ascorbate peroxidase activities in L3 to L5 leaves. At the same time, ascorbate and glutathione pools increased in intermediate leaves, whereas chlorophyll content decreased in L3 and L4 leaves, and protein content decreased in L4 leaves. Results suggest that pepper leaves enhance their defence capacities against oxidative stress by increasing ascorbate more than glutathione synthesis. However, cells showed higher regeneration rates for the glutathione redox state than for the ascorbate redox state. 相似文献
10.
Antioxidant defences of the apoplast 总被引:1,自引:0,他引:1
Summary The apoplast of barley and oat leaves contained superoxide dismutase (SOD), catalase, ascorbate peroxidase, dehydroascorbate reductase, monodehydroascorbate reductase, and glutathione reductase activities. The activities of these enzymes in the apoplastic extracts were greatly modified 24 h after inoculation with the biotrophic fungal pathogenBlumeria graminis. The quantum efficiency of photosystem II, which is related to photosynthetic electron transport flux, was comparable in inoculated and healthy leaves during this period. Apoplastic soluble acid invertase activity was also modified in inoculated leaves. Inoculation-dependent increases in apoplastic SOD activity were observed in all lines. Major bands of SOD activity, observed in apoplastic protein extracts by activity staining of gels following isoelectric focusing, were similar to those observed in whole leaves but two additional minor bands were found in the apoplastic fraction. The apoplastic extracts contained substantial amounts of dehydroascorbate (DHA) but little or no glutathione (GSH). Biotic stress decreased apoplastic ascorbate and DHA but increased apoplastic GSH in resistant lines. The antioxidant cycle enzymes may function to remove apoplastic H2O2 with ascorbate and GSH derived from the cytoplasm. DHA and oxidized glutathione may be reduced in the apoplast or returned to the cytosol for rereduction.Abbreviations AA
reduced ascorbate
- APX
ascorbate peroxidase
- DHA
dehydroascorbate (oxidised ascorbate)
- DHAR
dehydroascorbate reductase
- G6PDH
glucose-6-phosphate dehydrogenase
- GSH
reduced glutathione
- GSSG
glutathione disulphide
- GR
glutathione reductase
- MDHA
monodehydroascorbate
- MDHAR
monodehydroascorbate reductase
- SOD
superoxide dismutase 相似文献
11.
Urzica EI Adler LN Page MD Linster CL Arbing MA Casero D Pellegrini M Merchant SS Clarke SG 《The Journal of biological chemistry》2012,287(17):14234-14245
The L-galactose (Smirnoff-Wheeler) pathway represents the major route to L-ascorbic acid (vitamin C) biosynthesis in higher plants. Arabidopsis thaliana VTC2 and its paralogue VTC5 function as GDP-L-galactose phosphorylases converting GDP-L-galactose to L-galactose-1-P, thus catalyzing the first committed step in the biosynthesis of L-ascorbate. Here we report that the L-galactose pathway of ascorbate biosynthesis described in higher plants is conserved in green algae. The Chlamydomonas reinhardtii genome encodes all the enzymes required for vitamin C biosynthesis via the L-galactose pathway. We have characterized recombinant C. reinhardtii VTC2 as an active GDP-L-galactose phosphorylase. C. reinhardtii cells exposed to oxidative stress show increased VTC2 mRNA and L-ascorbate levels. Genes encoding enzymatic components of the ascorbate-glutathione system (e.g. ascorbate peroxidase, manganese superoxide dismutase, and dehydroascorbate reductase) are also up-regulated in response to increased oxidative stress. These results indicate that C. reinhardtii VTC2, like its plant homologs, is a highly regulated enzyme in ascorbate biosynthesis in green algae and that, together with the ascorbate recycling system, the L-galactose pathway represents the major route for providing protective levels of ascorbate in oxidatively stressed algal cells. 相似文献
12.
24-Epibrassinolide maintains elevated redox state of AsA and GSH in radish (Raphanus sativus L.) seedlings under zinc stress 总被引:1,自引:0,他引:1
Exogenous-applied 24-epibrassinolide (EBR) increased the seedling growth of radish (Raphanus sativus L.) in terms of seedling length, fresh weight and dry weight both in zinc (Zn2+)-stressed and unstressed conditions. Moreover, EBR lowered the Zn2+ uptake and bioaccumulation. Increased oxidation of ascorbate (AsA) and glutathione (GSH) pools to dehydroascorbate and glutathione disulfide respectively was observed in Zn2+-stressed seedlings, a clear indication of oxidative stress. However, exogenous application of EBR to stressed seedlings inhibited the oxidation of ascorbate and glutathione, maintaining redox molecules in reduced form. Under Zn2+ stress, enzymatic activities of ascorbate–glutathione cycle such as ascorbate peroxidase, monodehydroascorbate reductase increased but the dehydroascorbate reductase, glutathione reductase decreased. Zn2+ stress induced the gamma-glutamylcysteine synthetase, and glutathione-s-transferase activities in radish seedlings were further enhanced with EBR application. Zn2+ toxicity decreased the thiol content but, EBR supplementation resulted in restoration of thiol pool. The results of present study clearly demonstrated that external application of EBR modulates the AsA and GSH redox status to combat the oxidative stress of Zn2+ in seedlings via the AsA–GSH cycle and glutathione metabolism as an antioxidant defense system. 相似文献
13.
Zhang L Yang T Gao Y Liu Y Zhang T Xu S Zeng F An L 《Biological trace element research》2006,113(2):193-208
The physiological effects of lanthanum(III) ions on the ferritin-regulated antioxidant process were studied in wheat (Triticum aestivum L.) seedlings under polyethylene glycol (PEG) stress. Treatment with 0.1 mM La3+ resulted in increased levels of chlorophyll, carotenoid, proline, ascorbate, and reduced glutathione. The activities of superoxide dismutase, catalase, ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase, glutathione reductase, and peroxidase were also increased after La3+ treatment. Treatment with La3+ seems to enhance the capacity of the reactive oxygen species scavenging system, affect the Fe2+ and Fe3+ electron-transfer process in ferritin, and restrain the formation of hydroxyl radical (OH.), alleviating the oxidative damage induced by PEG stress. 相似文献
14.
Ex vitro transfer is often stressful for in vitro grown plantlets. Water stress and photoinhibition, often accompanying the acclimatization of in vitro grown plantlets to ex vitro conditions, are probably the main factors promoting production of reactive oxygen species (ROS) and in consequence oxidative
stress. The extent of the damaging effects of ROS depends on the effectiveness of the antioxidative systems which include
low molecular mass antioxidants (ascorbate, glutathione, tocopherols, carotenoids, phenols) and antioxidative enzymes (superoxide
dismutase, ascorbate peroxidase, catalase, glutathione reductase, monodehydroascorbate reductase, dehydroascorbate reductase).
This review is focused on ROS production and development of antioxidative system during in vitro growth and their further changes during ex vitro transfer. 相似文献
15.
In order to elucidate the role of lanthanum (La) in response of Vigna radiata to a salt stress, we investigated the effects of La on the ascorbate and glutathione metabolism. The results show that in comparison with a control, the salt stress increased the activities of ascorbate peroxidase (APX), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), γ-glutamylcysteine synthetase (γ-ECS), and L-galactono-1,4-lactone dehydrogenase (GalLDH), and the content of ascorbic acid (AsA) and glutathione (GSH). It also increased the malondialdehyde content (MDA) and electrolyte leakage. The salt stress significantly decreased the ratios of AsA/dehydroascorbate (DHA) and GSH/glutathione disulphide (GSSG) compared with the control. The pretreatment with La not only significantly increased the activities of the above enzymes, the content of AsA, GSH, and the ratios of AsA/DHA and GSH/GSSG, but also significantly reduced the MDA content and electrolyte leakage compared with the salt stress alone. Our results suggest that La could up-regulate the ascorbate and glutathione metabolisms and could have an important role for acquisition of salt stress tolerance in Vigna radiata. 相似文献
16.
17.
Dunaliella species accumulate carotenoids and their role in protection against photooxidative stress has been investigated extensively. By contrast, the role of other antioxidants in this alga, has received less attention. Therefore, the components of the ascorbate–glutathione cycle, along with superoxide dismutase (E.C. 1.15.1.1) and peroxidase (E.C. 1.11.1.11) activity were compared in two strains of Dunaliella salina. Strain IR‐1 had two‐fold higher chlorophyll and β‐carotene concentration than Gh‐U. IR‐1 had around four‐fold higher superoxide dismutase, ascorbate peroxidase and pyrogallol peroxidase activities than Gh‐U on a protein basis. Ascorbate and glutathione concentrations and redox state did not differ between strains and there was little difference in the activity of ascorbate–glutathione cycle enzymes (monodehydroascorbate reductase [E.C. 1.6.5.4], dehydroascorbate reductase [E.C. 1.8.5.1] and glutathione reductase [E.C. 1.8.1.7]). The response of these antioxidants to high light and low temperature was assessed by transferring cells from normal growth conditions (28°C, photon flux density of 100 μmol m?2 s?1)to 28°C/1200 μmol m?2 s?1; 13°C/100 μmol m?2 s?1; 13°C/1200 μmol m?2 s?1 and 28°C/100 μmol m?2 s?1 for 24 h. Low temperature and combined high light‐low temperature decreased chlorophyll and β‐carotene in both strains indicating that these treatments cause photooxidative stress. High light, low temperature and combined high light‐low temperature treatments increased the total ascorbate pool by 10–50% and the total glutathione pool by 20–100% with no consistent effect on their redox state. Activities of ascorbate–glutathione cycle enzymes were not greatly affected but all the treatments increased superoxide dismutase activity. It is concluded that D. salina can partially adjust to photooxidative conditions by increasing superoxide dismutase activity, ascorbate and glutathione. 相似文献
18.
Dipierro N Mondelli D Paciolla C Brunetti G Dipierro S 《Journal of plant physiology》2005,162(5):529-536
The involvement of the ascorbate (AsA) system in the response of pumpkin (Cucurbita pepo L.) roots to aluminium stress was studied. The treatment of 5-day-old pumpkin seedlings with 50 microM aluminium sulphate resulted in approximately 60% inhibition of root growth within 48-60 h of treatment, while aluminium accumulated in the roots reaching a maximum within 48h. During the same period, the hydrogen peroxide content of the roots was strongly enhanced. The increased level of hydrogen peroxide was matched by both increased ascorbate peroxidase (APX) (EC 1.11.1.11) activity and ascorbate free radical reductase (AFRR) (EC 1.1.5.4) activity, while dehydroascorbate reductase (DHAR) (EC 1.8.5.1) and glutathione reductase (GR) (EC 1.6.4.2) did not change. The levels of AsA in the roots were also increased by the Al treatment. It was concluded that an oxidative burst is probably involved in the toxicity of Al in pumpkin roots and that plants react to the enhanced production of reactive oxygen species by expressing higher levels of scavenging systems such as the AsA-APX system. 相似文献
19.
Filis Morina Ljubinko Jovanovic Milos Mojovic Marija Vidovic Dejana Pankovic Sonja Veljovic Jovanovic 《Physiologia plantarum》2010,140(3):209-224
Oxidative stress is one aspect of metal toxicity. Zinc, although unable to perform univalent oxido‐reduction reactions, can induce the oxidative damage of cellular components and alter antioxidative systems. Verbascum thapsus L. plants that were grown hydroponically were exposed to 1 and 5 mM Zn2+. Reactive oxygen species (ROS) accumulation was demonstrated by the fluorescent probe H2DCFDA and EPR measurements. The extent of zinc‐induced oxidative damage was assessed by measuring the level of protein carbonylation. Activities and isoform profiles of some antioxidant enzymes and the changes in ascorbate and total phenolic contents of leaves and roots were determined. Stunted growth because of zinc accumulation, preferentially in the roots, was accompanied by H2O2 production in the leaf and root apoplasts. Increased EPR signals of the endogenous oxidant quinhydrone, ?CH3 and ?OH, were found in the cell walls of zinc‐treated plants. The activities of the antioxidative enzymes ascorbate peroxidase (APX) (EC 1.11.1.11), soluble superoxide dismutase (SOD) (EC 1.15.1.1), peroxidase (POD), (EC 1.11.1.7) and monodehydroascorbate reductase (EC 1.6.5.4) were increased; those of glutathione reductase (EC 1.6.4.2), dehydroascorbate reductase (EC 1.8.5.1) and ascorbate oxidase (AAO) (EC 1.10.3.3) were decreased with zinc treatment. Zinc induced a cell‐wall‐bound SOD isoform in both organs. Leaves accumulated more ascorbate and phenolics in comparison to roots. We propose a mechanism for zinc‐promoted oxidative stress in V. thapsus L. through the generation of charge transfer complexes and quinhydrone because of phenoxyl radical stabilisation by Zn2+ in the cell wall. Our results suggest that the SOD and APX responses are mediated by ROS accumulation in the apoplast. The importance of the POD/Phe/AA (ascorbic acid) scavenging system in the apoplast is also discussed. 相似文献
20.
Changes in ascorbate, glutathione, and related enzyme activities during thidiazuron-induced bud break of apple 总被引:13,自引:0,他引:13
The changes of ascorbic acid, dehydroascorbic acid, and glutathione content and related enzyme activities were studied in apple buds during dormancy and thidiazuron-induced bud break. An increase in ascorbic acid, reduced form of glutathione (GSH), total glutathione, total non-protein thiol (NPSH) and non-glutathione thiol (RSH) occurred as a result of induction by thidiazuron during bud break, whereas dehydroascorbic acid and oxidized glutathione (GSSG) decreased during the same period. Thidiazuron also enhanced the ratio of GSH/GSSG, and activities of ascorbate free radical reductase (AFR; EC 1.6.5.4), ascorbate peroxidase (EC 1.11.1.11). dehydroascorbate reductase (DHAR; EC 1.8.5.1) and glutathione reductase (GR; EC 1.6.4.2). The ascorbic acid content and the activities of AFR, ascorbate peroxidase, and DHAR peaked when buds were in the side green or green tip stage just prior to the start of rapid expansion, and declined thereafter. The GSH, NPSH, RSH, ratio of GSH/GSSG, and activities of GR increased steadily during bud development. 相似文献