Role of Catalase in Inducing Chilling Tolerance in Pre-Emergent Maize Seedlings

The mechanisms of chilling acclimation and the role of antioxidant enzymes, catalase in particular, in inducing chilling tolerance in pre-emergent maize (Zea mays L.) seedlings have been investigated. Seedlings were acclimated to chilling stress in two different ways. Three-day-old seedlings did not survive 7 d of 4[deg]C stress unless acclimated by exposure to either 14[deg]C for 1 d or 4[deg]C for 1 d followed by recovery at 27[deg]C for 1 d. Although no changes in superoxide dismutase and ascorbate peroxidase activities were observed, both kinds of acclimated seedlings had higher catalase (CAT), glutathione reductase, and guaiacol peroxidase activities compared with nonacclimated seedlings during low-temperature stress and recovery conditions. To study the role of CAT in chilling tolerance, aminotriazole (AT) was used as a tool to artificially inhibit CAT activity and to initiate oxidative stress in the seedlings. Treatment of acclimating seedlings with 3 mM AT for 18 h abolished the acclimation phenomenon. AT treatment was found to be specific to CAT inhibition, because the total activities or isozyme profiles of the other investigated antioxidant enzymes were not altered in AT-treated seedlings. Protein carbonyl content, an indication of oxidative damage, was increased 2-fold in nonacclimated and AT-treated acclimated seedlings. These results collectively indicate that acclimation to prolonged chilling stress can be achieved by briefly pre-exposing the seedlings to 4[deg]C chilling stress and that acclimation-induced (oxidative stress-induced) CAT seems to play a major role, probably along with other antioxidant enzymes, in inducing chilling tolerance in pre-emergent maize seedlings.     

钙对玉米幼苗谷胱甘肽还原酶活性的影响

CaCl2浸种或酶提取液中加入CaCl2均可显著提高两品种玉米幼苗中谷胱甘肽还原酶（GR）活性,且不同钙盐对GR的激活效应基本相同。Ca^2 专一螯合剂EGTA浸种或加入到酶提取液中则可显著抑制GR活性,表明GR活性至少部分受Ca^2 调控。     

Acclimation,Hydrogen Peroxide,and Abscisic Acid Protect Mitochondria against Irreversible Chilling Injury in Maize Seedlings

Our previous results indicated that 3-d-old dark-grown chilling-sensitive maize (Zea mays L.) seedlings did not survive 7 d of 4[deg]C chilling stress, but 69% of them survived similar stress when the seedlings were either preexposed to 14[deg]C for 3 d or pretreated with 0.1 mM H2O2 for 4 h at 27[deg]C (T.K. Prasad, M.D. Anderson, B.A. Martin, C.R. Stewart [1994] Plant Cell 6: 65-74) or 1 mM abscisic acid (ABA) for 24 h at 27[deg]C (M.D. Anderson, T.K. Prasad, B.A. Martin, C.R. Stewart [1994] Plant Physiol 105: 331-339). We discovered that chilling imposed oxidative stress on the seedlings. Since H2O2 accumulated during the periods of both acclimation and nonacclimation, we concluded that H2O2 had dual effects at low temperature: (a) During acclimation, its early transient accumulation signals the induction of antioxidant enzymes such as catalase 3 and peroxidase to scavenge H2O2; and (b) at 4[deg]C in nonacclimated seedlings, it accumulates to damaging levels in the tissues because of low levels of these and perhaps other antioxidant enzymes. Three-day-old seedlings pretreated with H2O2 (a mild oxidative stress) or ABA showed induced chilling tolerance. In the present study, we investigated whether mitochondria are a target for chilling-induced oxidative stress and, if so, what differences do acclimation, H2O2, or ABA make to protect mitochondria from irreversible chilling injury. The results indicated that chilling, in general, impairs respiratory activity, the cytochrome pathway of electron transport, and ATPase activity regardless of the treatment. In pretreated seedlings, the activities of catalase 3 and peroxidase in the mitochondria increased severalfold compared with control and nonacclimated seedlings. The increases in these antioxidant enzymes imply that mitochondria are under oxidative stress and such increases could initiate a protective mechanism in the mitochondria. Mitochondrial respiration is partially cyanide resistant during chilling stress and also after the 1st d of recovery. Upon further recovery over 3 d, in contrast to nonacclimated seedlings, the mitochondria of acclimation-, H2O2-, and ABA-treated seedlings showed the following recovery features. (a) The mitochondrial respiration changed from a cyanide-resistant to a cyanide-sensitive cytochrome pathway, (b) cytochrome oxidase activity recovered to control levels, (c) the ability of mitochondria to generate ATP was regained, and (d) the antioxidant enzyme activities remained at or above control levels. Based on these results, we conclude that chilling impairs mitochondrial function and that chilling-induced oxidative stress seems to be a factor, at least in part, for causing possible irreversible damage to the mitochondrial membrance components. Acclimation, H2O2, and ABA provide a protective mechanism by inducing antioxidant enzymes to protect mitochondria from irreversible oxidative damage that is absent in nonacclimated seedlings. Therefore, we conclude that the ability of the seedlings to recover from chilling injury is, at least in part, due to the ability of the mitochondria to resume normal function.     

Effects of Cold Acclimation and Salicylic Acid on Changes in ACC and MACC Contents in Maize during Chilling

The effect of 0.5 mM salicylic acid (SA) pretreatment and of growing at hardening temperatures on chilling-induced changes in 1-aminocyclopropane-1-carboxylic acid (ACC) and malonyl 1-aminocyclopropane-1-carboxylic acid (MACC) was investigated in young maize (Zea mays L.) plants grown in hydroponic solution at 22/20 °C. Chilling at 5 °C caused an increase in ACC content;however, this increase was less pronounced in plants cold acclimated at 13/11 °C 4 d before the chilling treatment, and in those which were pretreated with SA for 1 d before the cold stress. Changes in MACC at low temperature showed no correlation with chilling tolerance in maize.     

谷胱甘肽还原酶和超氧化物歧化酶在玉米幼苗热激诱导的交叉适应中的作用

玉米幼苗经过热激处理后,在随后的高温、低温、干旱和盐胁迫环境中,其存活率明显高于未热激的幼苗,表明热激能提高植物的抗热性、抗冷性、抗旱性和抗盐性,证实了玉米幼苗交叉适应现象的存在;热激还可提高谷胱甘肽还原酶(GR)和超氧化物歧化酶(SOD)的活性,且在上述4种胁迫过程中GR、SOD活性水平与玉米幼苗的存活率呈正相关,表明GR和SOD参与玉米幼苗交叉适应的形成.     

Induction of Nitrate Reductase and Peroxidase Activity in the Seedlings of Normal and High Lysine Maize

Steady state levels of in vivo nitrate reductase activity in the endosperm, scutella, roots and shoots of maize seedlings were higher in normal maize than those in high lysine maize. Activity of peroxidase in the roots, however, was higher in the high lysine cultivar. The nitrate reductase activity increased with the supply of nitrate in all parts of the seedlings of both cultivars, although the rates of increment in the endosperm were lower than those in scutella, roots and shoots. In relation to substrate concentration, a saturation was achieved at 5 to 10 mM of nitrate except in the endosperm, where activity increased slowly up to 100 mM at least. Final levels of enzyme activity were significantly higher in the scutella of normal than in that of high lysine seedlings. In vitro enzyme activity in the roots also increased with the supply of nitrate in both cultivars, reaching maximum at 5 to 10 mM nitrate.     

Differential Expression of Glutathione Reductase and Cytosolic Glutathione Peroxidase,GPX1, in Developing Rat Lungs and Kidneys

A mutant rat GPX1 (a cytosolic predominant form), in which the selenocysteine residue in the catalytic center was replaced by cysteine, was prepared and an antibody against the mutant enzyme was raised. The resultant antibody specifically reacted with rat GPX1 and was, together with the Glutathione reductase (GR) antibody, used in a Western blot analysis and immunohistochemistry experiments. To elucidate the physiological coupling of these enzymes under oxidative stress which accompanies the birth, developmental changes of the protein levels and enzymatic activities of GR and GPX1 were examined for lungs and kidneys from prenatal fetus to adult rats. The expression of GR was already evident at the prenatal stage and remained high in lungs at all stages. However, GR activity in kidneys gradually increased after birth reaching maximal levels at adulthood. An immunohistochemical study showed that GR was strongly bound to the bronchial epithelia in lungs and the epithelial cells of renal tubes. GPX1 was expressed in the renal tube epithelial cells and its level gradually increased after birth in a manner similar to that of GR. The expression of GPX1 in the lungs was, on the other hand, variable and occurred in some alveolar cells and bronchial epithelia only at restricted periods. It preferentially localized in nuclei at a late stage of development. Thus, the expression of the two functionally coupled enzymes via GSH did not appear to coordinate with development, tissue localization or under oxidative stress. Since many gene products show GSH-dependent preoxidase activity, other peroxidase(s) may be induced to compensate for the low GPX1 levels at stages with high GR expression.     

Ethylene Production and Activation of Hydrolytic Enzymes during Acclimation of Maize Seedlings to Partial Flooding

The effects of partial flooding on the partial pressure of oxygen and carbon dioxide in water around the roots, ethylene production by intact maize (Zea mays L.) seedlings, the activities of hydrolytic enzymes (pectinase, xylanase, and cellulase) in adventitious roots, and the growth of adventitious and main roots were studied. Aggravated hypoxia resulted in the accelerated ethylene production and the activation of enzymes destroying cell walls in the adventitious roots; as a result, the latter changed their growth pattern. The conclusion is that the interrelated responses are adaptive ones, and the adventitious roots play a key role in plant adaptation.     

Changes in Sugar Content during Cold Acclimation and Deacclimation of Cabbage Seedlings

The relationship between freezing tolerance and sugar contentin cabbage seedlings was investigated. Seedlings exposed tonon-freezing low temperature (5 °C) acquired freezing tolerancedown to -6 °C. The degree of freezing tolerance increasedwith duration of exposure to low temperature (up to 10 d). Sucrose,glucose, fructose and myo -inositol were detected as solublesugars in cabbage leaves, and all soluble sugars, except formyo -inositol, and starch increased gradually during cold acclimationsuch that their levels were positively correlated with the degreeof freezing tolerance. The induced freezing tolerance was attributednot to ontogenetic changes but to cold acclimation. However,the induced freezing tolerance was lost after only 1 d of deacclimationat control temperatures, and this change was associated witha large reduction in sugar content. These results reveal that the sugar content of cabbage leavesis positively correlated with freezing tolerance. Brassica oleracea L.; cabbage; cold acclimation; deacclimation; freezing tolerance; sugars     

亚硒酸钠对小麦幼苗中谷胱甘肽过氧化物酶和谷胱甘肽转硫酶活性以及谷胱甘肽含量的影响

用1.0 mg·L-1的亚硒酸钠根施小麦幼苗,测定亚硒酸钠对谷胱甘肽过氧化物酶和谷胱甘肽转硫酶活性以及还原性谷胱甘肽含量的结果表明,外源亚硒酸钠对麦苗地上部的谷胱甘肽过氧化物酶和谷胱甘肽转硫酶活性均有诱导作用,使麦苗体内的谷胱甘肽含量水平增加.     

Superoxide Dismutase, Catalase, and Glutathione Peroxidase Activities in Copper/Zinc-Superoxide Dismutase Transgenic Mice

Copper/zinc-superoxide dismutase (CuZn-SOD) transgenic mice overexpress the gene for human CuZn-SOD. To assess the effects of the overexpression of CuZn-SOD on the brain scavenging systems, we have measured the activities of manganese-SOD (Mn-SOD), catalase, and glutathione peroxidase (GSH-Px) in various regions of the mouse brain. In nontransgenic mice, cytosolic CuZn-SOD activity was highest in the caudate-putamen complex; this was followed by the brainstem and the hippocampus. The lowest activity was observed in the cerebellum. In transgenic mice, there were significant increases of cytosolic CuZn-SOD activity in all of these regions, with ratios varying from a twofold increase in the brainstem to 3.42-fold in the cerebellum in comparison with nontransgenic mice. Particulate Mn-SOD was similarly distributed in all brain regions, and its levels also were significantly increased in superoxide dismutase (SOD)-transgenic mice. In the brains of nontransgenic mice, cytosolic catalase activity was similar in all brain regions except the cortex, which showed less than 50% of the activity observed in the other regions. In transgenic mice, cytosolic catalase activity was significantly increased, with the cortex showing the greatest changes (133%) in comparison with nontransgenic mice. The smallest increases were observed in the hippocampus (34%). In contrast to what was observed for SOD and catalase, there were no significant changes in cytosolic GSH-Px activity in any of the brain regions examined. The present results indicate that, in addition to displaying marked increases in the levels of brain CuZn-SOD activity, SOD-transgenic mice also exhibit increases in other enzymes that scavenge oxygen-based radicals.(ABSTRACT TRUNCATED AT 250 WORDS)     

氯化钙浸种对玉米幼苗抗逆性的影响及其与谷胱甘肽还原酶的关系

两个抗逆性不同的玉米品种经过CaCl2 浸种处理后 ,能显著提高其幼苗在低温、高温、干旱和盐胁迫下的存活率 ;相反 ,Ca2 螯合剂EGTA浸种处理会降低玉米幼苗在上述逆境胁迫下的存活率 ,表明外源Ca2 处理能增强玉米幼苗对低温、高温、干旱和盐胁迫的多重抗逆性。此外 ,Ca2 浸种处理能使玉米幼苗在多种逆境胁迫下保持相对较高的谷胱甘肽还原酶 (GR)活性 ,而EGTA处理正好相反 ,表明GR可能参与了Ca2 提高的玉米幼苗多重抗逆性的调控     

Effects of Nerve Growth Factor on Glutathione Peroxidase and Catalase in PC 12 Cells

Abstract: Nerve growth factor (NGF) is a member of the neuro- trophin family and is required for the survival and maintenance of peripheral sympathetic and sensory ganglia. In the CNS, NGF regulates cholinergic expression by basal forebrain cholinergic neurons. NGF also stimulates cellular resistance to oxidative stress in the PC12 cell line and protects PC12 cells from the toxic effects of reactive oxygen species. The hypothesis that NGF protection involves changes in antioxidant enzyme expression was tested by measuring its effects on catalase and glutathione per- oxidase (GSH Px) mRNA expression in PC12 cells. NGF increased catalase and GSH Px mRNA levels in PC 12 cells in a time- and dose-dependent manner. There was also a corresponding increase in the enzyme activities of catalase and GSH Px. Thus, NGF can provide cytoprotection to PC12 cells by inducing the free radical scavenging enzymes catalase and GSH Px.     

Drought-Stress-Induced Changes in Activities of Superoxide Dismutase, Catalase, and Peroxidase in Wheat Species

Activities of superoxide dismutase (SOD), catalase (CAT), andperoxidase (POD), as well as malondialdehyde (MDA) contentsand solute potentials, were studied in seedlings of seven wheat(Triticum) species (nine genotypes representing three ploidylevels: hexaploid, tetraploid, diploid) subjected to water stressfor 4, 8, and 12 days by withholding water. Solute potentialsof all genotypes were lowered by water stress. In most species,SOD and CAT activities showed an increase or maintenance inthe early phase of drought and then a decrease with furtherincrease in magnitude of water stress. On the contrary, PODactivities and MDA contents greatly increased in response towater stress. Enzymatic activities partly recovered and MDAcontents decreased with rewatering. Under drought, hexaploidwheats had higher POD activities and MDA contents than tetraploidand diploid wheats; solute potentials and activities of SODand CAT, however, were similar among the three groups. Theseresults suggest that water stress alters the equilibrium betweenfree radical production and enzymatic defense reactions in wheatspecies and that hexaploid wheats have less efficient antioxidantsystems (e.g., the ascorbate-glutathione cycle and the nonenzymaticsystem) than tetraploid and diploid wheats. (Received February 9, 1994; Accepted April 22, 1994)     

Polymorphism of the Catalase and Glutathione Peroxidase Genes and Macrovascular Complications in Non-Insulin-Dependent Diabetic Hypertensives

Allelic and genotypic distributions of the polymorphic markers C1167T and Pro197Leu of the genes of catalase (CAT) and glutathione peroxidase (GPX1), respectively, were studied in patients with non-insulin-dependent diabetes mellitus (NIDDM) and hypertension without complications (the control group, n= 52) and with complications: myocardial infarction (MI, n= 53) or stroke (n= 50). No significant differences were found between complicated and uncomplicated patients with respect to the allelic or phenotypic distribution. Thus, there were no association between these polymorphic regions and either MI or stroke in hypertensive NIDDM patients.     

Thermal Kinetics of Glutathione Reductase and their Relation to Thermotolerance in Diverse Cultivars of Maize

The characteristics of glutathione reductase from a number ofmaize cultivars with contrasting thermotolerance have been investigated.The apparent K_m (Michaelis constant) for oxidised glutathione(GSSG) was measured between 10 and 45°C at constant pH.The enzyme from highland cultivars adapted to cool environmentshad a slightly lower apparent K_m for GSSG than that from lowlandtropical cultivars at low assay temperatures. Similarly theenzyme from lowland tropical cultivars had a lower apparentK_m for GSSG at high assay temperatures. However these effectswere small and regression lines plotted through the data werenot significantly different in slope or intercept. There wasa strong correlation (r = 0·939) between apparent K_mand V_max (maximum initial velocity) as assay temperature wasvaried. The interpretation of apparent K_m/temperature relationshipsis discussed with hypothetical examples of the effects of temperatureon enzyme activity/substrate concentration plots. It is demonstratedthat an increase in apparent K_m at higher assay temperaturesneed not necessarily reflect any temperature-dependent impairmentof enzyme function. The apparent K_m for GSSG of glutathionereductase from maize increased over four-fold when the temperaturewas raised from 10 to 45°C, but it is concluded that invivo rates of reaction are likely to be increased rather thandecreased by this same change in temperature. Glutathione reductasewould thus appear to be equally well adapted to function atall these temperatures. This suggests that the potential ofenzyme thermal kinetics to predict thermotolerance may be limited.Copyright1994, 1999 Academic Press Zea mays L., maize, glutathione reductase, thermal kinetics, thermotolerance     

Copper and Resveratrol Attenuates Serum Catalase, Glutathione Peroxidase, and Element Values in Rats with DMBA-Induced Mammary Carcinogenesis

In this paper, a hypothesis was assessed whether or not the intoxication with copper and supplementation with copper plus resveratrol would result in changes in the activities of catalase and glutathione peroxidase and moreover if the characteristic changes would appear in concentrations of copper, iron, calcium, magnesium, and zinc in the serum of rats with chemically induced carcinogenesis. Female Sprague-Dawley rats were divided into study groups which, apart from the standard diet, were treated with copper (42.6 mg Cu/kg food as CuSO₄·5H₂O) or copper plus resveratrol (0.2 mg/kg body) via gavage for a period from 40 days until 20 weeks of age. In cancer groups, the rats were treated with a dose of 80 mg/body weight of 7,12-dimethyl-1,2-benz[a]anthracene (DMBA) given in rapeseed oil at 50 and 80 days of age to induce mammary carcinogenesis. The control groups included the rats kept in the same conditions and fed with the same diet as the animals from the study groups, but not DMBA-treated. The activity of catalase significantly decreased in groups of rats with mammary carcinogenesis that were supplemented with copper (p?<?0.05) or copper plus resveratrol (p?<?0.001) in comparison with the control groups that received the same diets. In cancer groups of nonsupplemented rats, the increase of glutathione peroxidase activity was observed. The process of carcinogenesis and the applied supplementation significantly altered the concentrations of trace elements in serum, in particular as concerns iron and copper. The mean serum iron levels in rats with breast cancer were significantly lower than those in the control groups (p?<?0.001). The mean serum copper levels significantly decreased in the groups of rats with mammary carcinogenesis that were supplemented with copper or copper plus resveratrol in comparison with the control groups that received the same diets (p?<?0.001). The characteristic changes in iron content and the zinc/copper and zinc/iron ratios in blood may be used as one of the prognostic factors in breast cancer research.     

A Simultaneous Visualization of the Antioxidant Enzymes Glutathione Peroxidase and Catalase on Polyacrylamide Gels

A simple and sensitive method for the simultaneous visualization of glutathione peroxidase and catalase on polyacrylamide gels is described. The procedure included: (I) running samples on a 7. 5% polyacryla-mide gel, (2) soaking the gel in a certain concentration of reduced glutathione (0.25–2.0 mM). (3) soaking the gel in GSH plus H_zO_z or cumene hydroperoxide, (4) finally staining with a 1% ferric chloride I% potassium ferricyanide solution. The best concentration of glutathione for simultaneous visualization of glutathione peroxidase and catalase was 0.25rnM; I.5mM glutathione was the best concentration for visualization of glutathione peroxidase alone. The method is sensitive enough to detect catalase and glutathione peroxidase in mouse liver homogenates and also it is specific for glutathione peroxidase since other peroxidases such as lactoperoxidase, horseradish peroxidase and glutathione S-transferase cannot be visualized. Using this method, it was found that unlike catalase. glutathione peroxidase is heat resistant (68°C. 1min), but sensitive to 10mM sodium iodoacetate.     

A Simultaneous Visualization of the Antioxidant Enzymes Glutathione Peroxidase and Catalase on Polyacrylamide Gels

A simple and sensitive method for the simultaneous visualization of glutathione peroxidase and catalase on polyacrylamide gels is described. The procedure included: (I) running samples on a 7. 5% polyacryla-mide gel, (2) soaking the gel in a certain concentration of reduced glutathione (0.25-2.0 mM). (3) soaking the gel in GSH plus H_zO_z or cumene hydroperoxide, (4) finally staining with a 1% ferric chloride I% potassium ferricyanide solution. The best concentration of glutathione for simultaneous visualization of glutathione peroxidase and catalase was 0.25rnM; I.5mM glutathione was the best concentration for visualization of glutathione peroxidase alone. The method is sensitive enough to detect catalase and glutathione peroxidase in mouse liver homogenates and also it is specific for glutathione peroxidase since other peroxidases such as lactoperoxidase, horseradish peroxidase and glutathione S-transferase cannot be visualized. Using this method, it was found that unlike catalase. glutathione peroxidase is heat resistant (68°C. 1min), but sensitive to 10mM sodium iodoacetate.