Ammonia-lyase and O-methyl transferase activities related to lignification in wheat leaves infected with botrytis

The deposition of lignin around wounds in wheat leaves infected with the non-pathogenic fungus Botrytis cinerea, was preceded by increases in ammonia-lyase and O-methyl transferase activities. The increases were localised in the lignifying tissues. Phenylalanine ammonia-lyase and tyrosine ammonia-lyase increased concurrently and were inseparable by gel filtration or DEAE cellulose chromatography, the two activities probably being the function of a single protein. Infection-specific isoenzymes for either of the ammonia-lyase activities were absent. Increases in caffeic acid O-methyl transferase and 5-hydroxyferulic acid O-methyl transferase activities closely followed those of the ammonia- lyases. It is unlikely that the increased proportion of syringyl groups found in infection-induced lignin is controlled by O-methyl transferase activity. A modified method for the estimation of O-methyl transferase activity in crude wheat extracts is described.     

棉铃虫持续取食对棉花三种防御酶活性的作用

昆虫取食作为一种关键的生物胁迫因子对棉花防御机制产生了重要影响。植物对昆虫取食产生的防御响应,在昆虫与植物的生态关系中具有重要作用。为了明确棉铃虫Helicoverpa armigera取食与棉花防御性之间的动态互作关系,本文研究了棉铃虫持续取食下及停止取食后,棉花中3种防御相关酶活性变化的时间效应。在明确了棉花受损程度与棉铃虫取食时间关系的基础上,分别考察了棉铃虫持续取食2、6、12、18和24h,对棉花中苯丙氨酸解氨酶(PAL)、脂氧合酶(LOX)和多酚氧化酶(PPO)活性的影响。针对棉铃虫持续取食棉叶12h后停止取食,研究了去除虫害胁迫后0、6、12、24和36h,棉花体内PAL、LOX、PPO活性的变化。结果表明:在棉铃虫持续取食棉叶24h内,棉花中3种防御酶的活性响应有所不同,其中,棉铃虫持续取食2和6h对棉花体内PAL活性没有产生显著影响,而持续取食12h显著诱导了PAL活性,持续取食24和36h,均极显著诱导了PAL活性;棉铃虫持续取食2、6、12、和18h均显著诱导了棉花体内LOX活性,持续取食24h极显著诱导了LOX活性;棉铃虫持续取食6h极显著诱导了棉花体内PPO活性,持续取食24h显著诱导了PPO活性。棉铃虫取食12h后停止取食,在去除虫害除胁迫后0、6、12、24和36h,棉花体内PAL活性均显著升高;而LOX活性则呈现出先升高后恢复正常的现象;PPO活性开始无变化,但在胁迫去除后12和24h显著增高,到36h恢复正常。可见,棉花体内PAL、LOX和PPO活性对棉铃虫取食产生的防御响应,与其受虫害持续取食胁迫时间的增长呈正相关,随着取食时间和受危害的程度加大而升高。并且,在虫害胁迫去除后的一定时间内,棉花体内PAL、LOX和PPO活性依然会保持较高的活性状态,而同等程度机械损伤后的棉叶内PAL、LOX、PPO活性均没有发生显著性变化。说明棉花对于棉铃虫取食胁迫的防御与棉花生理生化性质的改变有关,且具有持续性。     

Changes in defence-related enzymes in rice responding to challenges by Rhizoctonia solani

Sheath blight disease caused by Rhizoctonia solani Kuhn is becoming a major constraint to rice production, especially in the intensified cultivation system. To know the in rice, it is important to get the knowledge of the activity of defence-related enzymes due to the fungal infection. The pathogen induced superoxide dismutase (SOD) and chitinase activities in rice plants, while suppressing peroxidase (POD) and phenylalanine ammonia-lyase (PAL) activities at 36 and 24 h after inoculation, respectively. Induction of two POD isozymes, POD-3 and -4, up to 48 h after inoculation and disappearance of the said isomers at 72 h onwards in rice–Rhizoctonia interaction implicated the role of these isomers in susceptible host–pathogen interaction. Apart from POD and SOD, the activities of other stress-related enzymes, viz. PAL, polyphenol oxidase (PPO) and β-1,3-glucanase were also studied. From this study, it was found that these defence-related enzymes are most significantly related to host–pathogenic interaction.     

Azoxystrobin induces lignification-related enzymes and phenolics in rice (Oryza sativa L.) against blast pathogen (Pyricularia grisea)

Abstract

This study was conducted to analyse the induction of lignification-related enzymes and phenolic content in rice to blast disease caused by Pyricularia grisea using azoxystrobin. The severity of rice blast was reduced (70% over control) through treatment by azoxystrobin. This reduction in disease severity was mainly associated with induction of host defense mechanisms by azoxystrobin. Increased production of secondary metabolite – phenolic and lignification – related enzymes, namely, peroxidase (POD), polyphenol oxidase (PPO) and phenylalanine ammonia-lyase (PAL) were observed in rice plants treated with azoxystrobin.     

南美斑潜蝇为害对黄瓜体内4种防御酶活性的影响

植物对昆虫取食产生的防御反应,在昆虫与植物相互作用关系中起着重要的作用。为明确南美斑潜蝇Liriomyza huidobrensis(Blanchard)取食与植物防御之间的作用关系,本文分别测定了南美斑潜蝇幼虫持续为害1、3、5、7及9d后黄瓜叶片中苯丙氨酸解氨酶(PAL)、多酚氧化酶(PPO)、过氧化物酶(POD)及超氧化物歧化酶(SOD)活性的变化。结果表明：在南美斑潜蝇幼虫持续取食下,PAL、PPO、POD和SOD等4种酶活性显著上升;PAL、PPO和POD等3种酶活性随受害程度的加重而上升幅度加大,即重度受害>轻度受害>系统对照>健康对照,而SOD活性变化没有规律。在系统对照黄瓜叶片中,PAL、PPO、POD和SOD等4种酶活性最大值分别在第5、1、5和5d;在轻度受害黄瓜叶片中,PAL、PPO、POD和SOD等4种酶活性最大值分别在第5、9、5和9d;在重度受害黄瓜叶片中,PAL、PPO、POD和SOD等4种酶活性最大值分别在第7、7、5和5d。黄瓜叶片受害后,POD和PPO活性上升幅度较大,PAL和SOD活性上升幅度较小,说明POD和PPO对取食胁迫响应比PAL和SOD更灵敏。     

Expression of phenolics and defence-related enzymes in relation to red root rot disease of tea plants

Red root rot caused by Poria hypolateritia is a dreadful disease in tea plant due to sudden death of bushes. In response to fungal pathogen, variation in the defence-related enzymes was investigated. The infected tea root was undertaken to study about various defence-related and pathogen-related enzymes. The infected root, as a prime response to disease attack, was subjected to the analysis of phenolics, phenylalanine ammonia lyase, tyrosine ammonia lyase, peroxidase, polyphenol oxidase, catalase, chitinase, β-1,3-glucanase and protease were assayed. The results on assay of defence-related enzymes revealed that the activity was significantly higher in infected roots when compared with healthy roots. Phenolics were accumulated more in infected roots. The sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) analysis further confirmed the presence of induced pathogenesis-related proteins in the infected root tissues. The activity of all enzymes was increased up to threefold amount when compared with normal ones. The accumulation of defence enzymes in plants revealed the virulence of root pathogen in stimulating induced systemic resistance of tea plants and phytopathogenicity causing pathogenesis. This study exemplify to recognise underlying processes in causing infection and to identify the existence of host–pathogen relationship.     

Monophenolase activity of avocado polyphenol oxidase

Polyphenol oxidase of avocado mesocarp catalyses (a) the orthohydroxylation of monophenols like l-tyrosine, d-tyrosine, tyramine and p-cresol, and (b) the oxidation of the corresponding o-dihydroxyphenols to quinones. The rate of step b is much greater than that of step a. The hydroxylation of monophenols occurs after a lag period. DOPA or ascorbate effectively eliminate the lag but not dl-6-methyltetrahydropteridine or tetrahydrofolic acid. At 1.66 × 10^?4 M, α,α-dipyridyl has no effect, while diethyldithiocarbamate at this concentration inhibits the hydroxylation reaction by 90%. The tyrosinase activity of avocado polyphenol oxidase is inactivated in the course of the reaction; this inactivation occurs faster and is more pronounced in the presence of exogenously added DOPA. This inactivation is partially prevented by a large excess of ascorbate. The K_m values indicate that tyramine, dopamine, p-cresol and 4-methyl catechol are better substrates for avocado polyphenol oxidase than tyrosine or DOPA.     

Salt Stress Induced Changes in Growth and Enzyme Activities in Germinating Phaseolus Mungo Seeds

NaCl salt stress induced changes in growth and enzyme activities in blackgram (Phaseolus mungo L.) seeds during germination were studied. A decrease in germination percentage, root length, shoot length, and fresh mass was noticed with an increase in NaCl concentration. With the increase in NaCl concentration and duration of stress proline content increased and catalase (CAT), peroxidase (POX) and polyphenol oxidase (PPO) activities decreased.     

The dual role of oxygen in avocado fruit respiration: Kinetic analysis and computer modelling of diffusion-affected respiratory oxygen isotherms

Abstract. Oxygen plays a dual role in affecting the rate of respiration of avocado fruit ( Persea americana Mill, cv. Hass). The respiration rate v. oxygen concentration curve for steady state avocado fruit respiration is biphasic. The curve becomes monophasic, however, when measured under conditions of rapidly changing oxygen concentration in a closed circulating system. The results are interpreted as indicating that oxygen at relatively high concentrations modulates respiration independent of its interaction with the terminal oxidase—presumably cytochrome oxidase.
A computer model is presented which takes into account the effect of diffusion barriers on the kinetics of oxygen utilization as a function of concentration in avocado fruit. The model is used to make predictions concerning the apparent K _m of the terminal oxidase or oxidases in avocado fruit. It is concluded that the apparent K _m of the terminal oxidase of uninhibited avocado fruit is that of cytochrome oxidase, and that the alternative, cyanide-resistant oxidase of avocado fruit does not contribute appreciably to the uninhibited respiration of preclimacteric or climacteric avocado fruit.     

低温与GA_3诱导菠萝黑心病的生理机制

菠萝黑心病是PPO催化氧化酚类物质形成褐色产物所致。低温或GA_3处理提高了PPO活性及其底物——儿茶酚、绿原酸和咖啡酸的含量,也导致了PAL活性增加;低温还使乙烯释放率增大。这些变化均有利于黑心病的发生和发展。     

外源激素对四倍体刺槐硬枝扦插生根及其关联酶活性的影响

取四倍体刺槐3年生采穗圃中当年生枝条为插穗,研究了外源激素种类、浓度、处理时间对硬枝插穗生根的影响及生根过程中3种关联酶吲哚乙酸氧化酶(IAAO)、过氧化物酶(POD)和多酚氧化酶(PPO)活性变化规律,以揭示四倍体刺槐插穗生根难的机理.结果显示:(1)四倍体刺槐硬枝插穗生根过程可分愈伤组织诱导期(0～20d)、根源基诱导期(20～30 d)、不定根表达与伸长期(30～45 d)3个阶段.(2)未经外源激素处理的插穗不生根,而激素处理可显著提高插穗生根率,促进根系发育,且IBA处理效果优于GGR6;激素处理浓度与时间无显著互作效应,但插穗生根综合效果随着处理时间和浓度的增加而升高;插穗的平均生根量和生根率在1 000 mg?L-1IBA处理6 h时达到最高,分别为11.74和55.56%.(3)IAAO、PPO是影响四倍体刺槐生根的关键酶,POD影响较小;外源激素处理插穗内IAAO和PPO活性呈先升高后下降的趋势,且均在根源基诱导期达到峰值;对照插穗内IAAO活性峰值出现在愈伤组织诱导期,而其PPO活性一直降低;激素处理和对照插穗内POD活性随着处理时间持续升高.研究表明,外源IBA和GGR6处理均可明显改变与四倍体刺槐插穗生根密切关联的氧化酶IAAO和PPO活性,提高生根率,促进根系发育,且IBA处理效果优于GGR6.     

Carotenoids in pulp,peel and leaves of Persea americana

A complex pattern of chloroplast pigments was found to be common to pulp, peel and leaves of avocado. This is explained by the presence of chlorophyll in the ripe fruit and its peel. Two chromoplast-specific pigments were found in ripe pulp and are tentatively identified as α-citraurin and mimulaxanthin. The identity of the latter and of neochrome, was established inter alia by the MS. The xanthophylls occur esterified to a major extent in pulp but entirely free in peel. The coexistence of chloroplast and chromoplast pigments in avocado fruit make this a suitable object for the ultrastructural studies of the origin of the chromoplasts.     

Phenolic oxidase activities in glandular trichomes of Solanum berthaultii

Polyphenol oxidase and peroxidase activities were detected in foliar glandular trichomes of the wild, insect-resistant potato species, Solanum berthaultii. These enzyme activities may provide the basis for conversion of clear, viscous trichome exudate into a hard, brown substance which is formed rapidly after insect attack.     

Control of root-knot nematode (Meloidogyne javanica) with combination of Arthrobotrys oligospora and salicylic acid and study of some plant defense responses

Root-knot nematodes (RKN) (Meloidogyne spp.) are economically the most important pathogens of agricultural products. The aim of the present study was to control Meloidogyne javanica by using Arthrobotrys oligospora and salicylic acid (SA) and to analyse the kinetics of enzymes, phenylalanine ammonia lyase (PAL), peroxidase (POX), polyphenol oxidase (PPO) and phenolic compounds accumulation in the root system of tomato after inoculation with M. javanica, A. oligospora and SA. The ability of A. oligospora to produce extracellular proteases was also examined. In greenhouse studies, we used soil drenching of A. oligospora (10⁶ spores/ml) and soil drenching or leaf spraying of SA (5 mM) in six-leaf stage, separately and in combination. Experiments were performed in a completely randomised design. The efficiencies of treatments were appraised by using diameter of galls, number of galls per plant, number of egg masses per plant, number of eggs per egg mass, root and foliage fresh weight. The results showed that the combined application of A. oligospora and SA provided the best nematode control. The activity of the enzymes and phenolic compounds increased in comparison with the control. The nematophagous fungus A. oligospora produced extracellular proteases in the broth culture. Using A. oligospora and SA could be effective in control of M. javanica in tomato.     

β-oxidation enzymes and the carnitine-dependent oxidation of palmitate and palmitoyl CoA in mitochondria from avocado

Two sites for the β-oxidation of fatty acids in avocado (Persea americana L.) mesocarp exist. One site is the microbody, the other the mitochondrion. It is apparent that the mitochondrial membrane barrier, which remains intact after sucrose density gradient centrifugation, prevents rapid access of acyl CoA substrates to matrix β-oxidation sites. Thus, intact mitochondria showed little β-oxidation enzyme activity. Rupturing of the mitochondrial membrane allowed rapid access of the acyl CoA substrates to matrix sites. Consequently, in ruptured mitochondria, high O₂-oxidation enzyme activities were measured. O₂ uptake studies further distinguished the two organellar sites of β-oxidation. During palmitoyl CoA oxidation, O₂ uptake was reduced by catalase and increased by KCN in the microbodies, whilst mitochondrial O₂ uptake was unaffected by catalase and reduced by KCN. This reflected the differing fates of FADH₂, produced during the first β-oxidation step, in the two organelles. In addition, only the mitochondrial β-oxidation of fatty acids was carnitine-dependent.     

PCBs对红树林沉积物中微生物及酶活性的影响

研究了多氯联苯（PCBs）对沉积物及红树植物秋茄根区沉积物微生物及酶活性的影响。结果表明,种植秋茄可提高沉积物中细菌和放线菌的数量,但不能提高真菌的数量。PCBs处理可显著提高沉积物中细菌和放线菌的数量。土壤呼吸与微生物量具有相似的变化趋势。由于细菌在沉积物微生物中占有绝对的优势,因此细菌的数量是微生物多样性指数的决定性因素。与未种植红树植物的相比,种植沉积物微生物多样性指数相对较低,PCBs处理与对照相比,微生物多样性指数差异不显著。在试验过程中,未种植的PCBs处理组多酚氧化酶和过氧化物酶活性均高于对照组,表明这两种酶是沉积物PCBs污染的敏感指标,而这两种酶被报道在植物修复中与PCBs的降解有关。     

Wound-induced ethylene production, phenolic metabolism and susceptibility to russet spotting in iceberg lettuce

Mechanical wounding by cuts or punctures caused a brief increase in ethylene production by iceberg lettuce ( Lactuca sativa L.) leaf tissue. Wounding increased phenylalanine ammonia-lyase (PAL, EC 4.3.1.5) activity, which was a function of the degree of injury. Wound-induced PAL activity appeared after 4 h and reached maximum activity in about 24 h before slowly declining to normal levels in about a week. A signal for PAL induction was transmitted at about 0.5 cm h⁻¹ from the site of injury to cells up to 2.5 cm away. Treatment with 100 μ2-aminoethoxyvinylglycine prevented wound-induced ethylene production but did not affect induced PAL activity. Injury increased the concentration of several soluble phenolic compounds that were easily oxidized to brown substances by polyphenol oxidase (EC 1.10.3.2) isolated from lettuce tissue. Wounding also increased peroxidase (EC 1.11.1.7) activity and lignin content, with cell wall lignification localized in wounded and adjacent cells. Although wounding alone did not induce russet spotting, it did greatly increase susceptibility to ethylene-induced russet spot development. In the presence of 3 μ1⁻¹ ethylene, the russet spot score increased as the degree of injury increased.     

Plant hormone homeostasis and the control of avocado fruit size

Control of plant hormone homeostasis is crucial for normal organdevelopment in plants. To elucidate the contribution of plant hormonehomeostasis to fruit growth, tissue distribution and activity of xanthinedehydrogenase (XDH), abscisic aldehyde (AB-ald)- and indole acetaldehyde(IA-ald) oxidase, and cytokinin oxidase (CKOX) were determined in seed, seedcoat and mesocarp of normal 'Hass avocado and its small-fruitphenotype during the linear phase of growth. Activity of these enzymes wasrelated to the tissue content of indole-3-acetic acid (IAA) and abscisic acid(ABA). IA-ald oxidase was present only in seed tissue whereas AB-ald oxidase andXDH activity was found in seed and mesocarp tissue. Seed of the small'Hass fruit had increased XDH and AB-ald oxidase activity and highendogenous ABA, but reduced IA-ald oxidase activity and adenine. There was nodifference in seed, seed coat and mesocarp CKOX activity between normal andsmall fruit. Inhibition of XDH activity in whole fruit by treatment withallopurinol decreased IAA and increased ABA of seed tissue. In mesocarp ofripening fruit allopurinol increased ABA and IAA but had no effect on levels ofiP. Results indicate that activity of IA-ald and AB-ald oxidases in avocadofruit contribute to maintenance of the IAA/ABA ratio in seed and mesocarp tissueand that increased AB-ald oxidase, or reduced IA-ald oxidase, may be part of thesyndrome associated with the appearance of a small-fruit phenotype.     

不同番木瓜品种植株感染环斑花叶病毒后PAL、PPO、POD活性的变化

对不同品种番木瓜接种环斑花叶病毒后,测定植株苯丙氨酸解氨酶(PAL)、多酚氧化酶(PPO)、过氧化物酶(POD)的活性变化,比较各品种的抗病性。结果表明,未接种的5个品种间PAL、PPO、POD活性差异较小,其酶活性水平次序为马来10号> 蜜红3号> 马来6号> 马来2号> 台农2号。接种后,5个品种的PAL、PPO、POD活性明显高于各对照水平,其中马来10号变化最突出,台农2号变化最缓慢。