Phenylalanine Ammonia-Lyase from Tomato Cell Cultures Inoculated with Verticillium albo-atrum

Tomato (Lycopersicon esculentum Mill.) cell suspension cultures accumulated wall-bound phenolic materials in response to inoculation with Verticillium albo-atrum Reinke et Berth. in a fashion analogous to that observed in whole plants. Both monomeric and polymeric materials were recovered. Deposition of phenolics into the cell walls of inoculated tomato cell cultures was inhibited by the phenylalanine ammonia-lyase (PAL) inhibitor, 2-amino-2-indanephosphate. Tomato PAL activity was induced over 12-fold by fungal inoculation, with a concomitant increase in the corresponding mRNA. The enzyme was purified >3400-fold, to apparent homogeneity, by anion-exchange chromatography, chromatofocusing, and gel filtration. The holoenzyme had a molecular mass of 280 to 320 kilodaltons, comprising 74-kilodalton subunits, and displayed an isoelectric point of 5.6 to 5.7. Induced PAL displayed apparent Michaelis-Menten kinetics (K_m = 116 micromolar) and was not appreciably inhibited by its product cinnamic acid. Chromatographic analysis did not reveal multiple forms of the enzyme in either inoculated or uninoculated cultures.     

Biochemical Changes in Root Exudate and Xylem Sap of Tomato Plants Infected with Meloidogyne incognita

Under two monoxenic culture techniques of growing plants (filter paper and silica sand cultures), sugar in root exudate from Meloidogyne incognita-infected tomato increased 133 to 836% over controls. In contrast, amino acids were moderately reduced 52 to 56%. Chromatographic analysis showed that galled root exudate contained three sugars, twelve amino acids, and three organic acids, whereas healthy root exudate contained four sugars, fifteen amino acids, and four organic acids. Polysaccharide was responsible for the large increase of sugars in galled root exudates. The concn and the absolute amount of total sugars in the infected plant xylem sap were greater than in healthy plant xylem sap up to 6 wk after inoculation, whereas amino acids were moderately lower than in controls throughout the test period. Chromatographic analysis showed that xylem sap from both healthy and infected plants at 4 wk after inoculation contained four sugars and five organic acids. We identified 18 and 17 amino acids in the healthy and infected plant xylem sap, respectively. The concn of sugar increased as the nematode inoculum increased at 2, 4 and 6 wk after inoculation. The amino acids in all samples from the infected plant moderately decreased with an increase of nematode inoculum. We suggest that changes in total sugars and amino acids, of infected plant xylem sap and root exudate are a probable mechanism by which tomato plants are predisposed to Fusarium wilt.     

Growth Regulator Changes in Cotton Associated with Defoliation Caused by Verticillium albo-atrum

Cotton plants, variety Acala 4-42 family 77 (Gossypium hirsutum L.,), were stem puncture-inoculated with either a defoliating isolate (T9) or a nondefoliating isolate (SS4) of Verticillium albo-atrum (Reinke and Berth.). As symptoms developed, growth regulators were assayed in diseased plants to discern their importance in the disease syndrome.     

Verticillium albo－atrum激发子诱导的番茄组织培养细胞的反应性氧迸发

从对Ｖｅｒｔｉｃｉｌｌｉｕｍａｌｂｏ－ａｔｒｕｍ感抗性不同的两株近等位基因番茄获得细胞悬浮培养物Ｓ－ＧＣＲ２６和Ｒ－ＧＣＲ２１８。用．ａｌｂｏ－ａｔｒｕｍ激发子处理后,敏感性的Ｓ－ＧＣＲ２６未表现出明显的反应性氧改变。抗性的Ｒ－ＧＣＲ２１８则响应以反应性氧迸发。反应性氧迸发中的细胞,其反应性氧累积量与激发子浓度的关系呈近Ｓ形。悬浮介质、某些无机离子、培养物的生长状况和培养日龄等因素均影响细胞对激发子的反应性氧迸发响应。     

Xylem Sap from Actinidia chinensis: seasonal Changes in Composition

Seasonal variation was followed in the content of total a-aminoacids, arginine, calcium, total carbohydrate, ß-galactosidaseactivity, magnesium, nitrate, phosphatase activity, phosphateand sulphate in vacuum-extracted xylem sap from Actinidia chinensisvar. hispida, the Chinese gooseberry or kiwifruit. There wasa marked increase in the concentration of most sap componentsjust prior to leaf emergence followed by a rapid decrease afterthe leaves had expanded. Experiments with excised extensionshoots showed that much of this spring-time increase in concentrationsof sap components was due to mobilization of nutrients withinthe shoot itself. Sap from the trunk and the older brancheschanged less in composition than did sap from the younger partsof the plant. The amplitude and direction of trends in concentrationof sap from the different parts of the plant varied with nutrientand with time. Analysis of vacuum-extracted xylem sap collectedduring periods of rapid transpiration from early summer onwardsgives a reliable indication of the composition of the transpirationstream. Actinidia chinensis, Chinese gooseberry, kiwifruit, storage reserves, xylem sap, amino acids, arginine, calcium, carbohydrate, ßgalactosidase, magnesium, nitrate, phosphatase, phosphate, potassium, sulphate     

Occurrence of Falcarinol and Falcarindiol In Tomato Plants after Infection with Verticillium albo-atrum and Characterization of Four Phytoalexins by Capillary Gas Chromatography-Mass Spectrometry

Falcarinol and falcarindiol were isolated from tomato vascular tissue infected with Verticillium albo-atrum and identified. Separation and characterization of trimethylsilyl derivatives of four tomato phytoalexins could be obtained by capillary gas chromatographymass spectrometry. We are most grateful to Dr. P. J. G. M. de Wit , Agricultural University, Wageningen, to Dr. D. T. Coxon , Food Research Institute, Norwich and to Dr. M. S. Kemp , Long Ashton Research Station, Bristol for making their analytical data available for us. Also thanks are due to Miss J. I. Liem , Mr. G. Verweij and C. Loriaux for their assistance.     

Water deficit in potato plants infected with Verticillium albo-atrum

Potato plants infected with Verticillium albo-atrum , whether they showed disease symptoms or not, invariably had a lower leaf water content than healthy plants. This water content fell throughout the growing season as the disease progressed and showed greater diurnal fluctuations than in healthy plants. Wilting appeared in diseased plants when a water saturation deficit of c . 20% was attained, but in healthy plants occurred at marginally lower deficits. The acropetal development of wilting symptoms was reflected in the gradient of water deficits along the main axis of the plant.
Deficits of 10–28%, which commonly occurred in infected plants grown both in pots and in the field, would suggest that these plants are experiencing internal water stress throughout much of the season, and consequently may have reduced rates of photosynthesis.     

Changes in Phenolic Acid Content During Alternaria alternata Infection in Tomato Fruit

Phenolic acids are components of the plant defence system; however few studies had been done with fruits. The objective of this experiment was to elucidate the changes in phenolic acid content in tomato fruits in response to pathogenic attack. Tomato fruit ‘Pinto’ was inoculated with spores of Alternaria alternata and stored for 10 days at 25°C and 90–92% of relative humidity. Sampling of epicarp and mesocarp tissues of control and infected tomato fruits were done every 2 days. Phenolic acids were extracted from each tissue and identified by HPLC coupled to a mass spectrometer. Quantification was done based in standard curves. In vitro evaluation of the phenolic acid effect either one‐by‐one and in a mixture of phenolic acids (MPA) over A. alternata spore germination was done with 25, 50, 100, 200 and 500 mm . It was found caffeic, chlorogenic and vanillic acids in both epicarp and mesocarp tomato tissues before the beginning of the experiment. Infected tomato fruits showed significantly higher concentrations of vanillic acid in the epicarp, only. Chlorogenic acid and the MPA inhibit spore germination by 30%, whereas caffeic acid and vanillic acid inhibit 16% at 500 mm . It was concluded that chlorogenic, vanillic and caffeic acids are phytoanticipins in tomato fruit. The concentration of vanillic acid also increases in tomato fruit epicarp as part of the defence system during a pathogenic attack.     

几种生理因素对玉米木质部汁液中蛋白质含量的影响

受干旱胁迫的玉米叶和茎木质部汁液中蛋白质含量降低,根中蛋白质含量升高.偏酸性营养液中的玉米各营养器官木质部汁液中蛋白质含量降低,中性或碱性营养液中的则升高.以100mmol·L-1的ABA营养液处理后的玉米根、茎和叶片的木质部汁液中蛋白质含量都升高;而用2 mmol·L-1EGTA、80 mmol·L-1三氟啦嗪或100mmol·L-1异博定处理后的木质部汁液中蛋白质含量变化不明显.     

Stomatal Closure in Flooded Tomato Plants Involves Abscisic Acid and a Chemically Unidentified Anti-Transpirant in Xylem Sap

We address the question of how soil flooding closes stomata of tomato (Lycopersicon esculentum Mill. cv Ailsa Craig) plants within a few hours in the absence of leaf water deficits. Three hypotheses to explain this were tested, namely that (a) flooding increases abscisic acid (ABA) export in xylem sap from roots, (b) flooding increases ABA synthesis and export from older to younger leaves, and (c) flooding promotes accumulation of ABA within foliage because of reduced export. Hypothesis a was rejected because delivery of ABA from flooded roots in xylem sap decreased. Hypothesis b was rejected because older leaves neither supplied younger leaves with ABA nor influenced their stomata. Limited support was obtained for hypothesis c. Heat girdling of petioles inhibited phloem export and mimicked flooding by decreasing export of [14C]sucrose, increasing bulk ABA, and closing stomata without leaf water deficits. However, in flooded plants bulk leaf ABA did not increase until after stomata began to close. Later, ABA declined, even though stomata remained closed. Commelina communis L. epidermal strip bioassays showed that xylem sap from roots of flooded tomato plants contained an unknown factor that promoted stomatal closure, but it was not ABA. This may be a root-sourced positive message that closes stomata in flooded tomato plants.     

Elicitation of Ethylene by Verticillium albo-atrum Phytotoxins in Potato

Petioles from a susceptible cultivar (Désirèe) of Solanum tuberosum treated with a low‐molecular mass toxin, separated from culture fluid of Verticillium albo‐atrum, produced greater quantities of ethylene than did petioles of a tolerant cultivar (Home Guard). Pretreatment of leaflets from cv. Désirèe with silver thiosulphite, which inhibits perception of ethylene, prevented the chlorosis and necrosis normally associated with exposure to the toxin. Similarly, application of aminoethoxyvinylglycine (AVG) an inhibitor of aminocyclopropane‐1‐carboxylic acid (ACC) synthase, to petioles of cv. Désirèe reduced toxin‐induced ethylene synthesis and symptom development. The data indicate that, in part, Verticillium‐toxin acts through induction of ethylene biosynthesis in the host tissues, and different responses of susceptible and tolerant potato cultivars to V. albo‐atrum are the result of differential production of ethylene.     

Antitranspirant Activity in Xylem Sap of Maize Plants

Xylem sap from unwatered maize plants was collected and testedfor antitranspirant activity. Two assays were used. These werea transpiration assay with detached wheat leaves and a stomatalbio-assay involving the direct microscopic observation of epidermisof Commelina communis. The reduction in transpiration of detached wheat leaves promotedby xylem sap could be duplicated almost exactly by the applicationof solutions of ABA of equivalent concentration to that foundin the xylem sap. Removal of virtually all the ABA from thexylem sap, using an immunoaffinity column, removed virtuallyall the antitranspirant activity in both assays. These results are discussed in the context of other resultswhich suggest the presence of as-yet unidentified inhibitorsin the xylem sap of unwatered plants. We suggest that with maize plants at least, stomatal responsesto soil drying can be entirely explained by enhanced concentrationof ABA in the xylem stream. Key words: Antitranspirant activity, ABA, ABA bio-assay, xylem sap     

Protein Changes in the Vascular Wilt Disease of Lucerne caused by Verticillium albo-atrum R. et B

Field trials confirmed that, whereas the Du Puits variety oflucerne was highly susceptible to Verticillium albo-atrum, ‘Gaetula’hybrids showed slight resistance and certain ‘Swedish’material was moderately resistant. Symptom-free ‘Gaetula’and Swedish plants were used to produce uninfected clonal materialby root propagation. Comparisons of the proteins of such plants with seed-grown DuPuits produced no evidence of a correlation between proteinpattern before inoculation and differences in susceptibilityand resistance. Disc electrophoretic comparisons of infected host material showedthat the pathogen gradually induced a change in the shoot proteinsof Du Puits whereas in the resistant host, after an initialmarked change, there was a development towards normality. Bythe terminal stages of wilting there was a noticeable fall inthe numbers of proteins in both roots and shoots of Du Puits,a finding confirmed both by double diffusion and immunoelectrophoresis.At the same time there was good evidence for a slight increasein protein bands in the resistant material after inoculation. After feeding tritium-labelled leucine to infected Du Puitsplants, a small protein component of fungal origin was detectedin the host. Labelled components from both healthy and infectedDu Puits plants were separated on Sephadex G.25 and compared.