Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:1.6.5.4 (SOR)
720 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Senescence is a developmentally regulated and highly ordered sequence of events. Senescence leads to abscission of plant organs and eventually leads to death of a plant or part of it. Present study revealed that Phalaenopsis flower undergo senescence due to over activation of O(2) (.-)generating xanthine oxidase (XO), which consequently increases the concentrations of O(2) (.-) leading to enhanced oxidative damage and disturbed cellular redox environment as indicated by increased lipid peroxidation and DHA/AsA + DHA ratio, respectively. While activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), and non-specific peroxidase (POD) were enhanced in sepals and petals of old flower, activities of catalase (CAT) and glutathione reductase (GR) were decreased. Exogenous application of nitric oxide (NO) retarded H(2)O(2)-induced senescence of Phalaenopsis flower by downregulating activity of XO and concentrations of O(2) (.-), H(2)O(2) and malondialdehyde (MDA, an index of lipid peroxidation). Exogenous application of NO also downregulated SOD activity and upregulated antioxidant enzymes involved in the detoxification of H(2)O(2) (CAT and APX), and in the regulation of redox couples viz, monodehydroascorbate reductase (MDHAR) and GR, together with the modulation in non-protein thiol status and DHA/AsA + DHA ratio.
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PMID:Nitric oxide retards xanthine oxidase-mediated superoxide anion generation in Phalaenopsis flower: an implication of NO in the senescence and oxidative stress regulation. 1898 52

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 CO(2) 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 H(2)O(2) 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.
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PMID:Enhanced sensitivity to oxidative stress in transgenic tobacco plants with decreased glutathione reductase activity leads to a decrease in ascorbate pool and ascorbate redox state. 1904 65

Changes in antioxidant metabolism because of the effect of salinity stress (0, 80, 160 or 240 mM NaCl) on protective enzyme activities under ambient (350 micromol mol(-1)) and elevated (700 micromol mol(-1)) CO(2) concentrations were investigated in two barley cultivars (Hordeum vulgare L., cvs Alpha and Iranis). Electrolyte leakage, peroxidation, antioxidant enzyme activities [superoxide dismutase (SOD), EC 1.15.1.1; ascorbate peroxidase (APX), EC 1.11.1.11; catalase (CAT), EC 1.11.1.6; dehydroascorbate reductase (DHAR), EC 1.8.5.1; monodehydroascorbate reductase (MDHAR), EC 1.6.5.4; glutathione reductase (GR), EC 1.6.4.2] and their isoenzymatic profiles were determined. Under salinity and ambient CO(2), upregulation of antioxidant enzymes such as SOD, APX, CAT, DHAR and GR occurred. However, this upregulation was not enough to counteract all ROS formation as both ion leakage and lipid peroxidation came into play. The higher constitutive SOD and CAT activities together with a higher contribution of Cu,Zn-SOD 1 detected in Iranis might possibly contribute and make this cultivar more salt-tolerant than Alpha. Elevated CO(2) alone had no effect on the constitutive levels of antioxidant enzymes in Iranis, whereas in Alpha it induced an increase in SOD, CAT and MDHAR together with a decrease of DHAR and GR. Under combined conditions of elevated CO(2) and salinity the oxidative damage recorded was lower, above all in Alpha, together with a lower upregulation of the antioxidant system. So it can be concluded that elevated CO(2) mitigates the oxidative stress caused by salinity, involving lower ROS generation and a better maintenance of redox homeostasis as a consequence of higher assimilation rates and lower photorespiration, being the response dependent on the cultivar analysed.
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PMID:The oxidative stress caused by salinity in two barley cultivars is mitigated by elevated CO2. 1912 Oct 97

While polyamines (PAs) have been suggested to protect cells against Reactive Oxygen Species (ROS), their catabolism is known to generate ROS. We compared the activities of several enzymes and cellular metabolites involved in the ROS scavenging pathways in two isogenic cell lines of poplar (Populus nigraxmaximowiczii) differing in their PA contents. Whereas the control cell line was transformed with beta-glucuronidase (GUS), the other, called HP (High Putrescine), was transformed with a mouse ornithine decarboxylase (mODC) gene. The expression of mODC resulted in several-fold increased production of putrescine as well its enhanced catabolism. The two cell lines followed a similar trend of growth over the seven-day culture cycle, but the HP cells had elevated levels of soluble proteins. Accumulation of H(2)O(2) was higher in the HP cells than the control cells, and so were the activities of glutathione reductase and monodehydroascorbate reductase; the activity of ascorbate peroxidase was lower in the former. The contents of reduced glutathione and glutamate were significantly lower in the HP cells but proline was higher on some days of analysis. There was a small difference in mitochondrial activity between the two cell lines, and the HP cells showed increased membrane damage. In the HP cells, increased accumulation of Ca was concomitant with lower accumulation of K. We conclude that, while increased putrescine accumulation may have a protective role against ROS in plants, enhanced turnover of putrescine actually can make them vulnerable to increased oxidative damage.
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PMID:Putrescine overproduction negatively impacts the oxidative state of poplar cells in culture. 1913 66

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 beta-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 degrees C, photon flux density of 100 micromol m(-2) s(-1))to 28 degrees C/1200 micromol m(-2) s(-1); 13 degrees C/100 micromol m(-2) s(-1); 13 degrees C/1200 micromol m(-2) s(-1) and 28 degrees C/100 micromol m(-2) s(-1) for 24 h. Low temperature and combined high light-low temperature decreased chlorophyll and beta-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.
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PMID:The effect of acute high light and low temperature stresses on the ascorbate-glutathione cycle and superoxide dismutase activity in two Dunaliella salina strains. 1923 61

Apple replant is a widespread agricultural problem documented in all of the major fruit-growing regions of the world. In order to better understand the phytotoxic mechanisms induced by allelochemicals involved with this problem, Malus prunifolia plants were grown hydroponically to the six-leaf-stage in the presence of phthalic acid (0 or 1 mM) for 5, 10, or 15 days. Apple plants were evaluated for: shoot and root length, fresh and dry weight, malondialdehyde (MDA) content, hydrogen peroxide (H(2)O(2)) content, superoxide radical (O(2) (*-)) generation rate, and antioxidant enzyme activities. Shoot and root lengths and fresh and dry weights of M. prunifolia decreased in plants exposed to phthalic acid. MDA and H(2)O(2) content increased in phthalic acid-treated plants as did the generation rate of O(2) (*-) in M. prunifolia roots. The activities of superoxide dismutase (EC 1.15.1.1), peroxidase (EC 1.11.1.7), catalase (EC 1.11.1.6), ascorbate peroxidase (EC 1.11.1.11), glutathione reductase (EC 1.6.4.2), dehydroascorbate reductase (EC 1.8.5.1), and monodehydroascorbate reductase (EC 1.6.5.4) increased in phthalic acid-stressed roots compared with control roots. These results suggest that activation of the antioxidant system by phthalic acid led to the formation of reactive oxygen species that resulted in cellular damage and the decrease of M. prunifolia growth.
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PMID:Phthalic acid induces oxidative stress and alters the activity of some antioxidant enzymes in roots of Malus prunifolia. 1935 74

A pot experiment was carried out to investigate the effect of exogenous salicylic acid (SA) on the growth, photosynthesis, oxidative stress and responses of chloroplastic antioxidant defense system of maize (Zea mays L.) plants grown in a nickel (Ni)-contaminated soil. The results indicate that exogenous SA significantly decreased the reduction in dry weight, chlorophyll and beta-carotene contents, and net photosynthetic rate of the Ni-stressed maize, demonstrating an alleviating effect of SA on Ni toxicity of plants. Superoxide anion generation rate, H(2)O(2) and malondialdehyde (MDA) contents, and lipoxygenase (LOX, EC 1.13.11.12) activity significantly increased in the chloroplasts of maize exposed to Ni stress, revealing an oxidative damage occurred in maize chloroplasts, whereas, the values of these parameters were markedly lowered in the SA-treated plants under Ni stress. Application of SA significantly enhanced the activities of superoxide dismutase (SOD, EC 1.15.1.1), ascorbate peroxidase (APX, EC 1.11.1.11), monodehydroascorbate reductase (MDHAR, EC 1.6.5.4), dehydroascorbate reductase (DHAR, EC 1.8.5.1) and glutathione reductase (GR, EC 1.6.4.2), and the poll of reduced ascorbate and glutathione in chloroplasts of the Ni-stressed maize. Accordingly, the fact that SA up-regulates the capacity of antioxidant defense system in chloroplasts, thus reducing the oxidative damage, is involved in the SA-induced alleviation of Ni toxicity in maize.
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PMID:Up-regulation of chloroplastic antioxidant capacity is involved in alleviation of nickel toxicity of Zea mays L. by exogenous salicylic acid. 1937 98

Removal of reproductive 'sink' i.e. spikelets from wheat at anthesis delays the rate of flag leaf senescence. In this work, the antioxidant defense was studied in the flag leaf of Triticum aestivum cv. Kalyansona plants showing normal (S + plants) and delayed senescence via removal of spikelets (S- plants). This was done by measurement of metabolites and activities of enzymes such as superoxide dismutase, catalase, guaiacol peroxidase, ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase and glutathione reductase. S- plants had higher reduced glutathione/oxidized glutathione (GSH/GSSG) ratio and antioxidant enzyme activities than the control plants and the differences were apparent from 21 days after anthesis (DAA). The removal of the reproductive sink led to an increased antioxidant defense which may be contributing towards the delayed flag leaf senescence in wheat. Chloroplasts and mitochondria, important sources of ROS, were isolated at two stages representing early (7 DAA) and late (21 DAA) senescence. Oxidative damage to proteins was studied in these organelles in relation to SOD and APX. Mitochondria had higher levels of damaged proteins than chloroplasts at 7 DAA in both S+ and S- plants. Higher damage was related to the lower antioxidant enzyme levels of SOD and APX in mitochondria as compared to chloroplasts.
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PMID:Delayed wheat flag leaf senescence due to removal of spikelets is associated with increased activities of leaf antioxidant enzymes, reduced glutathione/oxidized glutathione ratio and oxidative damage to mitochondrial proteins. 1939 42

Lettuce plants were grown at low (LL), middle (ML), and high light (HL) conditions to examine the relationship between photoacclimatory plasticity, light energy utilization, and antioxidant capacity. With the increase in light intensity from LL to ML, the energy flux via DeltapH- and xanthophylls-regulated thermal dissipation, fluorescence and constitutive thermal dissipation, and electron transport for photorespiratory carbon oxidation all increased significantly. However, plants at HL exhibited reduced electron transport for photosynthetic carbon reduction and decreased maximal photochemical efficiency of photosytem II (PSII) as compared to that at ML. Increasing light level significantly increased the alternative electron transport, O(2)(*-) production rate, and H(2)O(2) and malondialdehyde (MDA) contents followed by increased ferric reducing antioxidant power (FRAP) and activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), and glutathione reductase (GR). Moreover, plants exposed to HL showed higher nutritional value as indicated by the high contents of ascorbate, glutathione, carotenoids, and alpha-tocopherol. It was concluded that absorption of excess photon energy at high light was associated with increased antioxidant capacity and that produce quality could be improved by short-term exposure to suboptimum irradiance.
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PMID:Impact of light variation on development of photoprotection, antioxidants, and nutritional value in Lactuca sativa L. 1943 54

Three-year-old 'Zaozhong No. 6' loquat (Eriobotrya japonica Lindl.) seedlings were foliar-sprayed with 0.2, 0.5, 1.0 and 1.5 mmol x L(-1) of sodium nitroprusside (SNP), subjected to low temperature (-3 degrees) stress for 6 hours, and then cultured at 25 degrees C for four days. The antioxidant metabolites and enzymes in the seedling leaves were determined 0, 1, and 4 days after recovery. Comparing with the control (water spraying), all SNP treatments had a decreased H2O2 content but an increased content of glutathione (GSH) and ascorbic acid (AsA) and increased activity of ascorbate peroxidase (APX), glutathione reductase (GR), dehydroascorbate reductase (DHAR) and monodehydroascorbate reductase (MDAR) in the seedling leaves. Four days after recovery, the H2O2 content in the seedling leaves treated with 0.5 mmol x L(-1) of SNP decreased by 75.53%, while the GSH and AsA contents and the APX, GR, DHAR and MDAR activities were increased by 29.12%, 23.40%, 50.0%, 44.4%, 49.53%, and 62.68%, respectively. All of these suggested that appropriate dosage of exogenous NO could enhance the activity of antioxidant system in loquat leaves and alleviated the cell injury of loquat leaves under low temperature stress. In this study, the appropriate dosage of NO was 0.5 mmol x L(-1) of SNP.
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PMID:[Effects of exogenous NO on ascorbate-glutathione cycle in loquat leaves under low temperature stress]. 1979 50


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