Correlation between Chlorophyll and Chlorogenic Acid Content in Tobacco Leaves

Developmental stages of tobacco (Nicotiana tabacum L. cv. Burley 21) flower and capsule were correlated with tissue contents of polyphenols and activities of phenylalanine ammonialyase, polyphenoloxidase, and peroxidase. Chlorogenic acid, scopolin, and scopoletin were present in most tissues, whereas rutin and two dihydroxyphenolic glycosides concentrated primarily in the corolla and placenta, respectively. Ovules contained only chlorogenic acid. As development progressed, polyphenols accounted for nearly 15% of the dry weight in the green capsule of field-grown plants. Fertilization triggered a rapid increase of chlorogenic acid in the ovary. When l-phenylalanine-U-¹⁴C was fed to the detached green capsules and capsule parts, an incorporation of radioactivity into chlorogenic acid and dihydroxyphenolic glycosides occurred which suggested in situ synthesis of these compounds. This was subtantiated by a positive correlation between phenylalanine ammonia-lyase activity and polyphenol accumulation. High polyphenoloxidase activity was associated mainly with the ovary, whereas peroxidase activity was maximal during senescence of all tissues. Polyacrylamide gel slab electrophoresis revealed five cathodic bands and one diffuse zone with poly-phenoloxidase activity in flower extracts. Two anodic poly-phenoloxidase isozymes appeared only in the fertilized ovary. Among 17 peroxidase isozymes, six cathodic forms were present throughout floral development, and the anodic ones increased in number and activity at the later stages of capsule growth.     

Changes in Amount of Polyphenols and Activity of Related Enzymes during Growth of Tobacco Flower and Capsule

Developmental stages of tobacco (Nicotiana tabacum L. cv. Burley 21) flower and capsule were correlated with tissue contents of polyphenols and activities of phenylalanine ammonialyase, polyphenoloxidase, and peroxidase. Chlorogenic acid, scopolin, and scopoletin were present in most tissues, whereas rutin and two dihydroxyphenolic glycosides concentrated primarily in the corolla and placenta, respectively. Ovules contained only chlorogenic acid. As development progressed, polyphenols accounted for nearly 15% of the dry weight in the green capsule of field-grown plants. Fertilization triggered a rapid increase of chlorogenic acid in the ovary. When l-phenylalanine-U-(14)C was fed to the detached green capsules and capsule parts, an incorporation of radioactivity into chlorogenic acid and dihydroxyphenolic glycosides occurred which suggested in situ synthesis of these compounds. This was subtantiated by a positive correlation between phenylalanine ammonia-lyase activity and polyphenol accumulation. High polyphenoloxidase activity was associated mainly with the ovary, whereas peroxidase activity was maximal during senescence of all tissues. Polyacrylamide gel slab electrophoresis revealed five cathodic bands and one diffuse zone with poly-phenoloxidase activity in flower extracts. Two anodic poly-phenoloxidase isozymes appeared only in the fertilized ovary. Among 17 peroxidase isozymes, six cathodic forms were present throughout floral development, and the anodic ones increased in number and activity at the later stages of capsule growth.     

The isozymic similarity of indoleacetic Acid oxidase to peroxidase in birch and horseradish

The relationship of indoleacetic acid oxidase activity to peroxidase activity is complicated by numerous multiple forms of this enzyme system. It is not known if all isozymes of this complex system contain both types of activity. Isozyme analysis of commercial horseradish peroxidase and leaf extracts of yellow birch (Betula alleghaniensis) by isoelectric focusing in polyacrylamide gels was used to examine this problem. Horseradish and birch exhibited 20 and 13 peroxidase isozymes, respectively, by staining with benzidine or scopoletin. Guaiacol was less sensitive. Indoleacetic acid oxidase staining (dimethylaminocinnamaldehyde) generally showed fewer bands, and left doubt as to the residence of both types of activity on all isozymes. Elution of the isozymes from the gels and wet assays verified that all peroxidase isozymes contained indoleacetic acid oxidase activity as well. Estimation of oxidase to peroxidase ratios for the major bands indicated small differences in this parameter. A unique isozyme for one or the other type of activity was not found.     

Differential effects of ethylene on pith peroxidase of intact tobacco plants and excised tissue

Ethylene increases the pith peroxidase activity of intact tobacco plants (Nicotiana tabacum) but not of excised pith, either at atmospheric or reduced pressures. In the intact plant, the increased activity involves augmentation of the two constitutive anodic isoperoxidases. In the excised pith, ethylene strongly represses one injury-induced isoperoxidase, while not markedly affecting other isozymes known to be repressed by auxin. Thus, the previously described auxin-induced repression of peroxidase is not due mainly to auxin-induced ethylene formation.     

Extracellular Enzyme Activities during Lignocellulose Degradation by Streptomyces spp.: A Comparative Study of Wild-Type and Genetically Manipulated Strains

The wild-type ligninolytic actinomycete Streptomyces viridosporus T7A and two genetically manipulated strains with enhanced abilities to produce a water-soluble lignin degradation intermediate, an acid-precipitable polymeric lignin (APPL), were grown on lignocellulose in solid-state fermentation cultures. Culture filtrates were periodically collected, analyzed for APPL, and assayed for extracellular lignocellulose-catabolizing enzyme activities. Isoenzymes were analyzed by polyacrylamide gel electrophoresis and activity staining on the gels. Two APPL-overproducing strains, UV irradiation mutant T7A-81 and protoplast fusion recombinant SR-10, had higher and longer persisting peroxidase, esterase, and endoglucanase activities than did the wild-type strain T7A. Results implicated one or more of these enzymes in lignin solubilization. Only mutant T7A-81 had higher xylanase activity than the wild type. The peroxidase was induced by both lignocellulose and APPL. This extracellular enzyme has some similarities to previously described ligninases in fungi. This is the first report of such an enzyme in Streptomyces spp. Four peroxidase isozymes were present, and all catalyzed the oxidation of 3,4-dihydroxyphenylalanine, while one also catalyzed hydrogen peroxide-dependent oxidation of homoprotocatechuic acid and caffeic acid. Three constitutive esterase isozymes were produced which differed in substrate specificity toward α-naphthyl acetate and α-naphthyl butyrate. Three endoglucanase bands, which also exhibited a low level of xylanase activity, were identified on polyacrylamide gels as was one xylanase-specific band. There were no major differences in the isoenzymes produced by the different strains. The probable role of each enzyme in lignocellulose degradation is discussed.     

Structural physiological, and biochemical gradients in tobacco pith tissue

Explants of tobacco pith taken at various distances from the apex of a mature stem show a sharp gradient in growth potential in vitro; growth is highest in the extreme apical and basal explants, and is minimal in explants removed ca. 75 cm from the apex. Calluses produced by the vigorously growing basal explants are harder and more compact than those produced from more apical explants. The gradient in growth potential is directly correlated with gradients in RNA, protein of cell sap and soluble N per unit fresh weight, but is inversely correlated with peroxidase activity. Cell size increases from apex to base of plants.

The peroxidase activity of pith explants is electrophoretically resolvable into 2 isoperoxidases, moving anodically at pH 9.0. During in vitro culture, this activity rises, due to the formation of several new isozymes moving toward the cathode. The appearance of these isozymes occurs most rapidly in apical and extreme basal explants.

     

Tissue specificity of tobacco peroxidase isozymes and their induction by wounding and tobacco mosaic virus infection

Peroxidases (EC 1.11.1.7) have been implicated in the responses of plants to physical stress and to pathogens, as well as in a variety of cellular processes including cell wall biosynthesis. Tissue samples from leaf, root, pith, and callus of Nicotiana tabacum were assayed for specific peroxidase isozymes by analytical isoelectric focusing. Each tissue type was found to exhibit a unique isozyme fingerprint. Root tissue expressed all of the detectable peroxidase isozymes in the tobacco plant, whereas each of the other tissues examined expressed a different subset of these isozymes. In an effort to determine which peroxidase isozymes from Nicotiana tabacum are involved in cell wall biosynthesis or other normal cellular functions and which respond to stress, plants were subjected to either wounding or infection with tobacco mosaic virus. Wounding the plant triggered the expression of several cationic isozymes in the leaf and both cationic and anionic isozymes in pith tissue. Maximum enzyme activity was detected at 72 hours after wounding, and cycloheximide treatment prevented this induction. Infection of tobacco with tobacco mosaic virus induced two moderately anionic isozymes in the leaves in which virus was applied and also systemically induced in leaves which were not inoculated with virus.     

4-Hydroxycinnamic Acid Hydroxylase and Polyphenolase Activities in Sorghum vulgare

Green shoots and first internodes of Sorghum vulgare var. Wheatland milo contain three phenoloxidase activities separable by means of Sephadex G-100 gel filtration. Two of these are found only in green leaves. I, eluted at the void volume and presumably a high molecular weight form, has both monophenol and diphenol oxidase functions; II, an intermediate molecular weight form displays only a diphenol function; III, a low molecular form found only in first internodes, catalyzes the hydroxylation of 4-hydroxycinnamic acid to caffeic acid and may have a weak diphenol activity. The hydroxylase activities of peaks I and III were completely inhibited by boiling or by 1 millimolar diethyldithiocarbamate and were partially inhibited by 1 millimolar KCN. The time courses of the two monophenol activities differ in that the activity of internode tissue was linear for at least 3 hours while that of the leaf began to decrease after 15 minutes. Both O₂ and a suitable electron donor were obligatory. At pH 6, ascorbic acid and 2-amino-4-hydroxy-6, 7-dimethylpteridine were the best electron donors, while NADPH was less effective. The diphenol oxidase functions of forms I and II in leaf preparations were not identical. The activity of I was less stable than that of II. While both were more active with chlorogenic acid, the ratio of activity with chlorogenic acid to that with 3,4-dihydroxyphenylalanine was less than 50 for I and greater than 50 for II.     

Peroxidase Activity in Relation to Suberization and Respiration in White Spruce (Picea glauca [Moench] Voss) Seedling Roots

Peroxidase (EC 1.11.1.7) activity is associated with suberization during endodermal development and metacutization in roots of white spruce (Picea glauca [Moench] Voss) seedlings. Histochemical analysis indicates a relationship between suberization and peroxidase activity, but peroxidase is ubiquitous. Increased peroxidase activity results from the induction of four anodic peroxidase isozymes in addition to quantitative increases in two anodic peroxidase isozymes. Four of these polymerized eugenol. Cold temperatures induce formation of two anodic isozymes and result in suberization. The increased peroxidase activity associated with suberization is correlated to residual respiration. In an attempt to elucidate this relationship, the effect of respiratory inhibitors on respiration and peroxidase activity are compared.     

Catalase, Peroxidase, and Polyphenoloxidase Activities during Rice Leaf Senescence

The activities of catalase, peroxidase, and polyphenoloxidase were studied in attached and detached rice (Oryza sativa L. cv. Ratna) leaves. Catalase activity decreased while peroxidase and polyphenoloxidase activities increased during senescence of both attached and detached rice leaves. Kinetic (5 mum) and benzimidazole (1 mm), which are known to delay the senescence of detached rice leaves, retarded the decrease of catalase activity during detached leaf senescence. On the other hand, these chemicals accelerated the increase of peroxidase and polyphenoloxidase activities over the water control. Total phenolics accumulated in detached and darkened rice leaves, but in attached leaf senescence in light no accumulation of phenolics was observed.     

The Role of Peroxidase and Polyphenol Oxidase Isozymes in Wheat Resistance to Alternaria triticina

Polyphenol oxidase activity was higher in resistant wheat cultivar ACC-8226 than in susceptible cultivar MP-845 in control sets and after inoculation of Alternaria triticina. However, similar polyphenol oxidase isozyme pattern was found in control and inoculated sets of both the cultivars, but the band intensity was higher after inoculation. Three and four peroxidase isozymes were found in ACC-8226 and MP-845, respectively. An extra peroxidase isozyme band was observed in both the cultivars after inoculation. The results suggest an active role of peroxidase and polyphenol oxidase in defence mechanism of wheat plants.     

Modification of Tobacco Leaf Glycolate Oxidase Activity by Chlorogenic Acid and Other Polyphenols

Glycolate oxidase extracted from tobacco leaves (Nicotiana tabacum L. cv. NC-95) and assayed by the 2,6-dichlorophe-nolindophenol reduction method was stimulated by chlorogenic acid and other o-diphenols but not by p-diphenols such as hydroquinone. Chlorogenic acid also protected the enzyme against certain enzyme antagonists. A novel assay utilizing horseradish peroxidase with the chromogen o-dianisidine was developed for detecting glycolate oxidase in conjunction with disc electrophoresis. Dissociation of glycolate oxidase into an active monomer during ammonium sulfate fractiona-tion was confirmed electrophoretically. After electrophoresis, flavin mononucleotide was required for monomer activity whereas chlorogenic acid was inhibitory to enzyme band development.     

Biogenesis of rosmarinic acid in Mentha

The biogenesis of rosmarinic acid (alpha-O-caffeoyl-3,4-dihydroxyphenyl-lactic acid), the second most common ester of caffeic acid in the plant kingdom, was studied in Mentha arvense and Mentha piperita. Administration of (14)C-labelled compounds showed that, whereas the caffeoyl moiety was formed from phenylalanine via cinnamic acid and p-coumaric acid, the 3,4-dihydroxyphenyl-lactic acid moiety was formed from tyrosine and 3,4-dihydroxyphenylalanine. Time-course studies and the use of labelled rosmarinic acid showed that endogenous rosmarinic acid had a low turnover rate. The caffeoyl moiety did not appear to contribute to the formation of insoluble polymers, as has been suggested for chlorogenic acid in other plants.     

Peroxidatic oxidation of tyrosine to melanin in supernatant of crude mouse melanoma homogenates (Short Communication)

Peroxide-dependent enzymic oxidation of tyrosine to dopachrome and melanin was demonstrated in cell-free melanoma homogenates. Histochemical methods for distinguishing peroxidase activity from aerobic dopa (3,4-dihydroxyphenylalanine) oxidase activity are not reliable with cell-free preparations. Therefore the presence of peroxidase activity in such preparations precludes assay of cresolase activity of mammalian ;tyrosinase'.     

Repression of isoperoxidase formation in excised tobacco pith by exogenous, auxin-controlled RNA

Previous work has shown that tobacco pith tissue contains two constitutive isoperoxidases migrating toward the anode at pH 9·0. Within 24 hr of aseptic culture on basal medium, such tissue develops five new isoperoxidases, three cathodic and two anodic. The appearance of the new isoperoxidases involves de novo protein formation; it is inhibited by anaerobic conditions, by such inhibitors as Actinomycin D, and by the plant hormone indole-3-acetic acid (IAA). We now find that phenol RNA extracted from parent pith and injected or vacuum infiltrated into cultured pith explants prevents the appearance of the new isozymes; RNA from cultured pith has no such effect. Hydrolysis with 0·3 N KOH, ribonuclease or proteolytic enzymes partially destroys this activity, while treatment with both ribonuclease and proteolytic enzymes completely destroys it. Fractionation of the RNA indicates that part of the repressor activity is associated with an mRNA-like fraction.     

Indoleacetic Acid Oxidase: A Dual Catalytic Enzyme?

The isolation of a unique enzyme capable of oxidizing indoleacetic acid, but devoid of peroxidase activity, has been reported for preparations from tobacco roots and commercial horseradish peroxidase. Experiments were made to verify these results using enzyme obtained from Betula leaves and commercial horseradish peroxidase. Both indoleacetic acid oxidase and guaiacol peroxidase activity appeared at 2.5 elution volumes from sulfoethyl-Sephadex. These results were obtained with both sources of enzyme. In no case was a separate peak of indoleacetic acid oxidase activity obtained at 5.4 elution volumes as reported for the tobacco enzyme using the same chromatographic system. Both types of activity, from both sources of enzyme, also eluted together during gel filtration. Successful column chromatography of Betula enzyme was dependent upon previous purification by membrane ultrafiltration. These results indicate indoleacetic acid oxidase activity and guaiacol peroxidase activity are dual catalytic functions of a single enzyme.     

EFFECTS OF X IRRADIATION AND INDOLEACETIC ACID ON SPECIFIC PEROXIDASE ISOZYMES IN PITH TISSUE OF A NICOTIANA AMPHIPLOID

Two electrophoretically anodal peroxidase bands, designated A3 and A4, which normally develop in zymograms of incubated pith tissue of a Nicotiana amphiploid, were inhibited by the inclusion of 0.10 mg indoleacetic acid (IAA) in a liter of culture medium. The visibility of the bands was not inhibited, however, if the pith was irradiated or if unirradiated pith blocks were incubated in either irradiated IAA-containing media or in media supplemented with irradiated IAA. Irradiation inactivates IAA in media, and according to this isozyme test, damages the capability in irradiated tissue of using exogenously supplied IAA. Radiationinduced damage to IAA metabolism caused radiation-induced peroxidase stimulation, shown in the more rapid appearance of isozyme bands A3 and A4.     

The relationship of the peroxidative indoleacetic Acid oxidase system to in vivo ethylene synthesis in cotton

Since peroxidase and manganese have been implicated in both auxin destruction and ethylene production, the effect of auxins and high tissue levels of manganese on the peroxidative indoleacetic acid oxidase system and the internal level of ethylene was determined in cotton (Gossypium hirsutum L. cv. Watson GL-7). The highest level of manganese tested produced manganese toxicity symptoms, including necrotic lesions, accompanied by an increase in internal ethylene levels at about 15 days after treatment initiation. Statistically significant increases in indoleacetic acid oxidase and peroxidase activity were first observed 2 days later and were paralleled by tissue manganese levels above 7.4 milligrams per gram dry weight and internal ethylene levels of 0.77 microliters per liter air. Eight hours after application of 2,4-dichlorophenoxyacetic acid or indoleacetic acid, the internal levels of ethylene were increased to above 6.6 microliters per liter air in cotton plants, and levels of this magnitude were maintained for a 72-hour period of observation. Modification of peroxidase and indoleacetic acid oxidase activity in auxintreated plants definitely occurred well after the elevation of internal ethylene levels. While ethylene levels and indoleacetic acid oxidase activity were increased by both experimental approaches, the earlier appearance of increased ethylene indicates that the peroxidative indoleacetic acid oxidase system in cotton is not involved in ethylene synthesis or that this enzyme is not the rate-limiting factor when ethylene synthesis is increased. Ethylene, as well as auxin destruction, may be involved in some of the long term plant responses to toxic levels of manganese. The findings also suggest that auxin-induced ethylene may play a role in the elevation of peroxidase and indoleacetic acid oxidase activity eventually seen in extracts of plants treated with auxins. The data support the assumption that the enzymatic portion of the indoleacetic acid oxidase system in cotton is a peroxidase.     

Solanum berthaultii trichomes contain unique polyphenoloxidases and a peroxidase

Glandular trichomes of Solanum berthaultii leaves contain two unique forms of polyphenoloxidase (α- and β-PPO) and a separate peroxidase. The β-PPO appeared to be a polymer of α-PPO and exhibited a similar K_m but an apparently higher specific activity with chlorogenic acid and caffeic acid. These data are directly related to studies on the insect defensive properties of the trichomes.     

Importance of Time after Excision and of pH on the Kinetics of Response of Wheat Coleoptile Segments to Added Indoleacetic Acid

Segments of coleoptiles of 3-day-old wheat (Triticum x Aestivum L. cv. Kharkov M.C. 22) grown at 24 C were strung on a glass rod and the kinetics of their elongation in 0.01 m K-phosphate buffer was examined photometrically. Measured rates of elongation in response to treatments were corrected by subtraction of endogenous rates. The customary practice of testing the effects of growth regulators added between the two endogenous surges of growth, that is, up to 3 hours after segments were excised from coleoptiles, gave erroneous kinetic data. Rates of response were then limited by the passive penetration of added auxin and the second endogenous surge interfered with late responses. It was necessary to wait for a phase of more rapid but more steady elongation after the second endogenous surge was over, about 4 hours for wheat at 25 C, to attain the active uptake required for nearly synchronous response through the segment. The more active uptake in this steady phase was confirmed with beta-[2-(14)C]indoleacetic acid and it was greater at pH 5 than at pH 7. The degree of dissociation of indoleacetic acid added at pH 7 was an impediment to penetration that could be compensated for by removal of intercellular air. The pH did not influence the endogenous rate of elongation. The dependence of the rate of elongation on the concentration of indoleacetic acid added at pH 5 was bell-shaped with maximum rate at 10 mum indoleacetic acid, in confirmation of previous measurements made over long intervals of time. The relation between the response and suboptimal concentrations was not sigmoid but was indicative of greater binding affinity than previously reported.