Comparison among the isozyme profiles associated with ethrel treatments of leaves, and with senescence and plum pox virus infection in Chenopodium foetidum

Changes in the isozyme profiles of peroxidases (POX, EC 1.11.1.7), glutamate oxaloacetate transaminase (GOT, EC 2.6.1.1) and esterases (EST, EC 3.1.1.1) have been studies in leaves of Chenopodium foetidum S. treated with ethrel. Different systems for administration of the ethrel led to different responses. In intact plants, treatment of the complete surface of leaves or local administration by pricking the leaves induced senescence and wilting as well as quick changes, characteristic of ageing, in the isozyme patterns of the treated leaves. Isolated leaves treated with ethrel in vitro also showed a senescence response, but this was followed by a necrosis that displayed an isozyme pattern highly similar to that of necrotic lesions induced by plum pox virus (PPV) infection. An accelerated senescence process seems to be involved in the induction of changes in the isozyme patterns of expression during the hypersensitive response of Chenopodium foetidum to PPV infection, and ethylene could participate in this process. However, other factors may also be required for necrotization.     

Alterations in peroxidase activity and peroxidase isozymes in virus-infected plants

Peroxidase activity and isozyme patterns were investigated in two leguminous species infected with viruses which produced either local necrotic or systemic chlorotic symptoms. Highest peroxidase activity was recorded when the hosts reacted to infection with necrotic local lesions. No new virus-specific isozymes were found as a result of infection, but some isozymes, apparently associated with senescence, appeared earlier in extracts from leaves showing necrosis than in extracts from healthy leaves, or from infected leaves showing only very mild chlorosis. Increase in peroxidase activity was accompanied by alteration in isozyme pattern.     

Peroxidase isozyme analysis of factors involved in development of symptoms in Nicotiana clevelandii infected by plum pox virus

Isozyme profiles of peroxidases (POX, EC 1.11.1.7) have been determined in leaves at different developmental stages as well as in other tissues of Nicotiana clevelandii . Modifications of the POX profiles associated with infection by plum pox virus and their relationship to senescence and wounding have also been determined. Systemically infected leaves displaying symptoms of infection showed a pattern highly similar to that of old leaves. Extensive alterations in the POX profile were observed in the inoculated leaves, and both ageing and wounding seemed to contribute to these transformations. The isozyme profile of POX after ethrel treatments suggested that ethylene could be involved in the senescence reaction produced by the virus infection.     

十种淫羊藿属植物的谷草转氨酶同工酶研究

用聚丙烯酰胺凝胶电泳技术对淫羊藿属植物10个种(含7个大花种和3个小花种)32个幼叶样品的谷草转氨酶同工酶进行了研究.结果发现,谷草转氨酶同工酶酶带共15条.不同物种的酶带数为2～15条,不同植株的谱带数为2～10条.种间存在明显差异,可以作为物种鉴定的辅助依据.     

Peroxidase Activity and Isoperoxidase Pattern in Tobacco Leaves Infected with Tobacco Necrosis Virus and Other Viruses Inducing Necrotic and Non-Necrotic Alterations

The level of peroxidase activity was greatly enhanced in tobacco leaves infected by tobacco necrosis virus (TNV) and other viruses which induce necrotic symptoms (TMV, ToMV and PVY^N). The intensity was related to the age of the leaves infected: absent or neglible in mature leaves and very pronounced in young growing infected leaves. On the contrary, changes in peroxidase activity were negligible when the infection was provoked by viruses which do not produce necrotic reactions (TMV and PVY^O). Analysis of the peroxidase isoenzymes, pattern in tobacco leaves infected by TNV and other necrosis-inducing viruses revealed in all cases, a slight increase in anionic (pl 3.5–3.7) and a considerable increase in moderately anionic isoenzymes particularly the pl 4.6 isoenzyme which in TNV and PVY^N-infected leaves reached levels up to 21 and 72 times the healthy control values. A considerable increase in the cationic (pl9.3–8.8) isoenzymes and the appearance of one moderately cationic isoenzyme (pl 8.2) was also detected. In leaf extracts from-virus-infected tobacco leaves with nonnecrotic response, no, or negligible alterations on the isoenzyme pattern were detected. However, infection by a fungal parasite (Erisyphe cichoracearum), which established a fully compatible, non-necrotic, interaction with tobacco leaves, like the necrosis-inducing viruses, changed the isoperoxidase pattern. The data suggest the necrotic alterations and associated changes in the peroxidase activity and isoperoxidase pattern in virus-infected leaves are not clearly related.     

Organelle-specific Isozymes of Aspartate-alpha-Ketoglutarate Transaminase in Spinach Leaves

Four distinct isozymes of aspartate-α-ketoglutarate transaminase in a spinach (Spinacia oleracea L.) leaf extract were separated by starch gel electrophoresis. Of the total aspartate-α-ketoglutarate transaminase activity, approximately 45% was represented by the chloroplast isozyme, 26% by the cytosol isozyme, 19% by the mitochondrial isozyme, and 3 to 10% by the peroxisomal isozyme. The aspartate-α-ketoglutarate transamination activity in the four subcellular compartments behaved similarly. It was freely reversible and α-ketoglutarate was preferred to pyruvate or glyoxylate as the amino group acceptor. With glutamate as the amino group donor, oxaloacetate was superior to pyruvate or glyoxylate as the acceptor in chloroplasts, mitochondria, and cytosol, while pyruvate or glyoxylate was preferred to oxaloacetate as the acceptor in peroxisomes.     

Changes in phenol and peroxidase in the leaves ofJava citronella infected withCurvularia andropogonis

The contet of phenols, o—dihydroxyphenols and peroxidase activity in healthy andCurvularia andropogonis (Zimm.) Boedijn infected leaves ofJava citronella were determined. As a result of infection, the content of phenols and peroxidase increased two- and four-fold, respectively in necrotic lesions compared to healthy leaves. In surrounding tissue of lesions, their increase was one-and half fold only. The peroxidase activity decreased with the maturity of the necrotic lesions. Necrotic lesions produced in response to infection appear to be the consequence of higher accumulation of phenols and their oxidation by peroxidase.     

Enzymes of nitrogen mobilization in detached leaves of Lolium temulentum during senescence

During the senescence of Lolium temulentum leaf sections in the dark, asparagine and glutamine accumulated as the level of soluble protein declined. During the first 3–4 days after detachment, when the rate of protein loss was maximal, a four-fold increase in acid protease activity (EC 3.4.4.?) occurred. Subsequently this activity was replaced by proteases with a higher pH optimum. There was also a pronounced and continued activation of glutamate dehydrogenase (EC 1.4.1.2) during senescence. Glutamate pyruvate transaminase (EC 2.6.1.2), benzoylarginine-p-nitroanilide hydrolase (EC 3.4.?.?) and leucyl-p-nitroanilide hydrolase (EC 3.4.1.1) declined from high initial activities after 3–4 days. Glutamate oxaloacetate transaminase (GOT, EC 2.6.1.1) was fairly stable although a marked increase occurred in the activity of one of two major GOT isoenzymes over the first two days. Glutamine synthetase (EC 6.3.1.2) was highly active in non-senescent leaves but fell sharply during the first three days of senescence. Little asparagine synthetase (EC 6.3.1.1) was detected. The role of these enzymes in the nitrogen metabolism of senescent detached leaves is discussed.     

Control of Some Enzymes of Nitrogen Metabolism during Senescence of Detached Barley (Hordeum vulgare L.) Leaves

The effects of chloramphenicol, cycloheximide and kinetin onthe changes in activity of glutamate dehydrogenase (GDH), glutamatepyruvate transaminase (GPT), glutamate oxaloacetate transaminase(GOT) and nitrite reductase were studied during the senescenceof detached barley leaves in the light and dark. The four enzymesseemed to be synthesized at least during the first hours ofsenescence. The rate of synthesis of GDH was clearly higherthan that of its degradation, thus continuously increasing duringsenescence. Chloramphenicol and kinetin delayed the enzyme degradationprocesses of senescence in the dark. However, chloramphenicolaccelerated senescence in the light. Kinetin had no significanteffect on the enzyme activities in the light. Cycloheximidetreatments produced lower enzyme levels than their respectivecontrols in both the light and dark, but the enzyme levels werehigher in cycloheximide treated leaves in the light than inthe controls in water in the dark. The results are discussedwith reference to the requirement for protein synthesis in thedifferent processes of senescence. (Received August 17, 1981; Accepted February 22, 1982)     

Assignment to chromosome 16 of a gene necessary for the expression of human mitochondrial glutamate oxaloacetate transaminase (aspartate aminotransferase) (E.C. 2.6.1.1.)

A gene necessary for the expression of human mitochondrial glutamate oxaloacetate transaminase (GOT-2) has been assigned to chromosome 16 on the basis of an immunochemical analysis of human-mouse somatic cell hybrids. Mitochondrial GOT cosegregates with adenine phosphoribosyl transferase (E.C. 2.4.2.7.).     

Untangling metabolic and spatial interactions of stress tolerance in plants. 1. Patterns of carbon metabolism within leaves

The localization of the key photoreductive and oxidative processes and some stress-protective reactions within leaves of mesophytic C₃ plants were investigated. The role of light in determining the profile of Rubisco, glutamate oxaloacetate transaminase, catalase, fumarase, and cytochrome-c-oxidase across spinach leaves was examined by exposing leaves to illumination on either the adaxial or abaxial leaf surfaces. Oxygen evolution in fresh paradermal leaf sections and CO₂ gas exchange in whole leaves under adaxial or abaxial illumination was also examined. The results showed that the palisade mesophyll is responsible for the midday depression of photosynthesis in spinach leaves. The photosynthetic apparatus was more sensitive to the light environment than the respiratory apparatus. Additionally, examination of the paradermal leaf sections by optical microscopy allowed us to describe two new types of parenchyma in spinach—pirum mesophyll and pillow spongy mesophyll. A hypothesis that oxaloacetate may protect the upper leaf tissue from the destructive influence of active oxygen is presented. The application of mathematical modeling shows that the pattern of enzymatic distribution across leaves abides by the principle of maximal ecological utility. Light regulation of carbon metabolism across leaves is discussed.     

Stress Proteins and Isozymology of Acid Phosphatase, Esterase, and Peroxidase in Phaseolus vulgaris Following Peanut Mottle Virus Infection

The present work was undertaken to study soluble protein changes and enzyme alterations in "Topcrop" bean ( Phaseolus vulgaris L.) primary leaves following inoculation with peanut mottle virus (PMV) in an attempt to elucidate the biochemical basis of the hypersensitive reaction in this host virus combination. Using the discontinuous polyacrylamide gel electrophoresis (disc-PAGE) technique, at least four apparently "novel" protein bands at Rf values of 0.80, 0.77, 0.74 and 0.68 were observed in infected tissue. The band at Rf 0.76 seems to be injury related and is shown here to be an isozyme of acid phosphatase. It is believed that these proteins are neither the cause nor the product of necrosis and may thus play a role in the active defense mechanism of the plant. In this virus host combination it was found that heating soluble protein fractions at 55 °C for 10 min before electrophoresis dramatically reduced the background and improved resolution on gels. While the biological function(s) of these proteins needs further investigations it is almost certain that none of them is an isozyme of alkaline phosphatase, acid phosphatase, esterase, or peroxidase. Zymogram analysis has additionally revealed the absence of alkaline phosphatase activity in untreated, abraded and PMV-infected primary leaves and no qualitative or quantitative changes in esterase isozymes have been observed in primary leaf tissues following abrasion or PMV–infection. By contrast, qualitative alterations in acid phosphatase after PMV-infection and both qualitative and quantitative changes in peroxidase after mechanical abrasion and PMV-infection have also been demonstrated.     

应用同工酶进行宽皮柑桔分类及其进化研究

利用聚丙烯酰胺凝胶电泳法,分析了50个宽皮柑桔生物型及5个甜橙品种的过氧化物酶、谷氨酸草酰乙酸转氨酶、四唑氧化酶、6-磷酸葡萄糖异构酶、6-磷酸葡萄糖变位酶、超氧化物歧化酶、苹果酸酶以及酯酶等8种酶系统同工酶。运用数量分类学的原理及方法,对同工酶资料进行了聚类分析。结果表明,宽皮柑桔的起源是多元的,小果类桔属于宽皮柑桔的原始类型,在进化过程中起着较为重要的作用。中国原产宽皮柑桔的代表种以道县野桔、马鼻桔或狗屎柑为佳。柑的来源有两条途径,即桔橙杂种和桔的单元演化;蕉柑是栟柑与甜橙的杂种;温州蜜柑来源于黄岩本地广桔的实生变异。     

Hepatotoxicity and cholestasis in rats induced by the sesquiterpene, 9-oxo-10,11-dehydroageraphorone, isolated from Eupatorium adenophorum

Eupatorium adenophorum leaves cause hepatotoxicity and cholestasis in rats. The hepatotoxicant has been characterized as 9-oxo-10,11-dehydroageraphorone (ODA), a cadinene sesquiterpene. Oral administration of ODA, mixed in feed to rats, caused jaundice in 24 h. The liver of the intoxicated animals had focal areas of hepatocellular necrosis, proliferation, and dilation of bile ducts with degenerative changes in the lining epithelium. There was marked increase in the conjugated form of plasma bilirubin and in the activities of the enzymes glutamate oxaloacetate transaminase, glutamate pyruvate transaminase, alkaline phosphatase, lactate dehydrogenase, gamma-glutamyltranspeptidase, glutamate dehydrogenase, and 5'-nucleotidase. The histopathological lesions in liver and biochemical profile of marker enzymes show that ODA induced hepatotoxicity and cholestasis in rats. This is the first report on the toxicity of a cadinene sesquiterpene in rats.     

Isozyme modifications and plant regeneration through somatic embryogenesis in sweet potato (Ipomoea batatas (L.) Lam.)

Summary The potential of somatic embryogenesis was evaluated for 10 cultivars of sweet potato through extensive embryogenic response and isozyme analysis. Embryogenic callus was induced by incubating lateral buds on Murashige and Skoog medium containing 10 M 2,4-dichlorophenoxyacetic acid for 6–8 weeks. The frequency of embryogenic response was low, and varied with genotypes, ranging from 0 to 17%. Embryo to plantlet formation could be enhanced by the use of the combination of 2,4-dichlorophenoxyacetic acid with kinetin, both used at 0.01 M. Embryogenic callus with its potential of plantlet formation has constantly been maintained for over two years. However, after several subcultures, 0.5 to 12% of embryogenic callus reverted irreversibly into friable fast-growing non-embryogenic callus whose ability to regenerate shoots was then definitively lost. The isozymes of esterase, peroxidase, glutamate oxaloacetate transaminase and acid phosphatase investigated in this study were found appropriate to distinguish compact embryogenic from friable non-embryogenic callus in sweet potato. In fact, the callus reversion was associated with a loss of bands or a decline in isozyme activity. On the contrary, very small changes in isozyme activity or no specific changes at all were observed during the differentiation of embryogenic callus into globular embryos.Abbreviations Acp acid phosphatase - BAP 6-benzylaminopurine - cv cultivar - df degree of freedom - 2,4-D 2,4-dichlorophenoxyacetic acid - Est esterase - Got glutamate oxaloacetate transaminase - IAA indole-3-acetic acid - MS Murashige and Skoog (1962) medium - Prx peroxidase - Tris tris(hydroxymethyl)aminomethane     

Accelerated leaf senescence takes part in enhanced resistance in cucumber mosaic virus inoculated pepper leaves

Altered photosynthetic reactions in cucumber mosaic virus (CMV) inoculated leaves of virus resistant lines L113 and L57 and susceptible pepper (Capsicum annuum L.) plants cv. Albena grown in controlled environment and in the field were investigated. The CMV inoculated leaves of virus resistant lines developed different symptoms—necrotic local lesions on L113 and chlorotic spots on L57 while the same leaves of susceptible cv. Albena were symptomless. The changes in Photosystem II (PSII) and PSI electron transport were evaluated by chlorophyll fluorescence, and far-red (FR) light induced leaf absorbance A _810–860. CMV infection caused a decrease in maximal PSII quantum yield, F _v/F _m, in susceptible leaves. Increased non-photochemical fluorescence quenching in CMV-inoculated leaves of both resistant lines were observed. In CMV-inoculated leaves of all tested plants FR light induced P700 oxidation was decreased. In the present study, the viral-infected pepper plants grown in controlled environment to avoid the effects of abiotic factors were used as model system that allow us to investigate the differences in leaf senescence in CMV-inoculated leaves of susceptible and resistant pepper lines expressing different symptoms. Earlier leaf falls of inoculated leaves as a result of accelerated leaf senescence is important for building successful secondary virus resistance strategy following fast responses such as hypersensitive reaction.     

Reactions and resistance ofChenopodium species to tobacco mosaic virus

Chenopodium species react on infection with tobacco mosaic virus by the formation of chlorotic or necrotic lesions and later by the abscission of infected leaves. A transition of local infection into the stem has been observed exceptionally inChenopodium quinoa, C. hybridum, andC. rubrum, but no systemic infection of the leaves followed. Systemic infection was demonstrated only inC. polyspermum andC. murale. The recovery of new sprouts was demonstrated in C.murale in the late chronic phase of infection.     

The Relationship Between Peroxidase Activity and Resistance to Sphaerotheca fuliginea in Melons

The levels of peroxidase activity in leaves of non-infected melon plants resistant to Sphaerotheca fuliginea (Schl. ex. Fr.) Poll. were considerably higher than those in the leaves of susceptible plants. After infection the ratio of peroxidase activity to that in non-infected plants reached a value of up to 47.5 in susceptible plants whereas in resistant plants it remained between 1 and 2. Changes in isozyme pattern were investigated by polyacrylamide gel electrophoresis. In non-infected resistant leaves slowly migrating isozymes were found. Their intensities increased with time following infection. These isozymes were absent in the susceptible leaves but appeared after the leaves had been infected with S. fuliginea. The role of these isozymes in the resistance mechanism is discussed.     

THE EFFECT OF TEMPERATURE ON INFECTION WITH STRAINS OF CUCUMBER MOSAIC VIRUS

Cucumber mosaic virus strains differed in their ability to multiply in plants at 37° C. Some strains multiplied in inoculated leaves and produced systemic symptoms in plants at this temperature; plants systemically infected with one such strain remained infected after prolonged treatment at 37° C. Other strains did not appear to multiply in inoculated leaves at 37° C. and heat treatment was successful in freeing plants from infection with these. Tests with one strain of each type showed both to be rapidly inactivated in expressed sap at 37° C.
Strains of cucumber mosaic virus forming small necrotic local lesions in leaves of french bean var. Canadian Wonder, produced many fewer lesions in plants kept after inoculation at 25° C. for 24 hr. and then at 15° C. than in plants kept continuously at the lower temperature.