Showing papers on "Phytoalexin published in 1985"
TL;DR: It is suggested that a novel O2− generating NADPH oxidase system in the membrane of potato tissues may be activated following an incompatible cell reaction, which results in hypersensitive cell death and phytoalexin production.
Abstract: A membrane-rich fraction from wounded potato tubers showed increasing activity of NADPH-dependent cytochrome c, but not of acetylated cytochrome c reducing activity, during ageing after slicing (wound-induced activity, WIA). In the fraction from aged tissues inoculated with an incompatible, but not a compatible, race of Phyiophthora infestans, as increase in native and acetylated cytochrome c reducing activities was closely associated with the occurrence of hypersensitive cell death and phytoalexin production (infection-induced activity, IIA). Treatment of aged tissues with hyphal wall components (HWC), a hypersensitivity-eliciting factor of the fungus, also activated both native and acetylated cytochrome c reducing activities similarly to infection. IIA and WIA were inhibited by NADP+, but only the former was appreciably inhibited by superoxide dismutase (SOD).
Water-soluble glucans (WSG), a hypersensitivity-inhibiting factor from compatible, but not incompatible, races of P. infestans, significantly inhibited the IIA but not the WIA in vitro.
These results suggest that a novel O2− generating NADPH oxidase system in the membrane of potato tissues may be activated following an incompatible cell reaction, which results in hypersensitive cell death and phytoalexin production. The lack of IIA activation in the compatible interaction may result from an inhibition of the reaction system by the water-soluble glucans from the fungus, thus resulting in the establishment of a compatible interaction.
219 citations
TL;DR: The hypothesis that the accumulation of glyceollin I is an important early response of soybean roots to infection by P. megasperma is supported, but may not be solely responsible for inhibition of fungal growth in the resistant response.
Abstract: A radioimmunoassay specific for glyceollin I was used to quantitate this phytoalexin in roots of soybean (Glycine max [L.] Merr. cv Harosoy 63) after infection with zoospores of either race 1 (incompatible) or race 3 (compatible) of Phytophthora megasperma Drechs. f. sp. glycinea Kuan and Erwin. The sensitivity of the radioimmunoassay and an inmmunofluorescent stain for hyphae permitted quantitation of phytoalexin and localization of the fungus in alternate serial cryotome sections from the same root. The incompatible interaction was characterized by extensive fungal colonization of the root cortex which was limited to the immediate vicinity of the inoculation site. Glyceollin I was first detected in extracts of whole roots 2 hours after infection, and phytoalexin content rose rapidly thereafter. Significant concentrations of glyceollin I were present at the infection site in cross-sections (42 micrometers thick) of such roots by 5 hours, and exceeded 0.6 micromoles per milliliter (EC90in vitro for glyceollin I) by 8 hours after infection. Longitudinal sectioning (14 micrometers thick) showed that glyceollin I accumulated particularly in the epidermal cell layers, but also was present in the root cortex at inhibitory concentrations. No hyphae were observed in advance of detectable levels of the phytoalexin and, in most roots, glyceollin I concentrations dropped sharply at the leading edge of the infection. In contrast, the compatible interaction was characterized by extensive unchecked fungal colonization of the root stele, with lesser growth in the rest of the root. Only small amounts of glyceollin I were detected in whole root extracts during the first 14 hours after infection. Measurable amounts of glyceollin I were detected only in occasional cross-sections of such roots 11 and 14 hours after infection. The phytoalexin was present at inhibitory concentrations in the epidermal cell layers, but the inhibitory zone did not extend appreciably into the cortex. Altogether, these data support the hypothesis that the accumulation of glyceollin I is an important early response of soybean roots to infection by P. megasperma, but may not be solely responsible for inhibition of fungal growth in the resistant response.
157 citations
TL;DR: Increased 5-hydroxy-substituted isoflavonoid biosynthesis, wall-bound phenolic synthesis and synthesis of arabinosylated hydroxyproline-rich protein are all early events which are closely linked to the initial interaction between plant cell and fungal elicitor.
Abstract: Treatment of cell suspension cultures of bean (Phaseolus vulgaris c.v. Immuna) with an elicitor preparation heat-released from the cell walls of the phytopathogenic fungus Colletotrichum lindemuthianum resulted in rapid changes in the composition of the bean cell walls. These consisted of (a) increases in phenolic material bound to the cellulosic and hemicellulosic fractions of the wall, (b) loss of material (mainly glucose) from the hemicellulosic fraction and (c) an increase in wall-associated hydroxyproline. The increases in wall-bound phenolics were preceded by (a) rapid decreases in the intracellular levels of free hydroxycinnamic acids and (b) transient increases in the extractable activities of L-phenylalanine ammonia-lyase and cinnamic acid 4-hydroxylase. 4-Hydroxycinnamic acid 3-hydroxylase activity was present at a high level in control cultures and was not induced by elicitor. Changes in the levels of cytochrome P-450, as determined by dot blot assays utilising an anti-(P-450) monoclonal antibody, paralleled the changes in cinnamic acid 4-hydroxylase activity. The accumulation of cell wall hydroxyproline was associated with rapid transient increases in the extractable activities of proline 2-oxoglutarate dioxygenase and a protein arabinosyl transferase. An hydroxyproline-rich acceptor protein of Mr 42 500 was the major protein to incorporate [3H]arabinose following elicitation of the bean cells, and the kinetics of the extent of labelling of this protein paralleled the accumulation of hydroxyproline protein in the endomembrane system. The above metabolic changes associated with cell wall components followed rapid kinetics similar to those involved in the formation of the phytoalexin kievitone in the elicited cultures [Robbins, M. P. et al. (1985) Eur. J. Biochem. 148, 563-569]. It is therefore concluded that increased 5-hydroxy-substituted isoflavonoid biosynthesis, wall-bound phenolic synthesis and synthesis of arabinosylated hydroxyproline-rich protein are all early events which are closely linked to the initial interaction between plant cell and fungal elicitor.
122 citations
TL;DR: It is concluded that expression of the phy toalexin defense response in biologically stressed cells of P. vulgaris characteristically involves co‐ordinate induction of synthesis of phytoaleXin biosynthetic enzymes.
Abstract: Changes in the rates of synthesis of three enzymes of phenyl-propanoid biosynthesis in Phaseolus vulgaris L. (dwarf French bean) have been investigated by immunoprecipitation of [35S]methionine-labeled enzyme subunits with mono-specific antisera. Elicitor causes marked, rapid but transient co-ordinated increases in the rate of synthesis of phenyl-alanine ammonia-lyase, chalcone synthase and chalcone isomerase concomitant with the phase of rapid increase in enzyme activity at the onset of accumulation of phenyl-propanoid-derived phytoalexin antibiotics in suspension cultures of P. vulgaris. Co-ordinate induction of enzyme synthesis is also observed in hypocotyl tissue during race:cultivar-specific interactions with Colletotrichum lindemuthianum, causal agent of anthracnose. In an incompatible interaction (host resistant) there are early increases apparently localized to the initial site of infection prior to the onset of phytoalexin accumulation and expression of hypersensitive resistance. In contrast, in a compatible interaction (host susceptible) there is no induction of synthesis in the early stages of infection, but a delayed widespread response at the onset of lesion formation associated with attempted lesion limitation. It is concluded that expression of the phytoalexin defense response in biologically stressed cells of P. vulgaris characteristically involves co-ordinate induction of synthesis of phytoalexin biosynthetic enzymes.
114 citations
TL;DR: It is concluded that the major enzymic changes occurring in elicitor-treated bean cells are probably those directly associated with defence mechanisms such as the formation of isoflavonoid phytoalexins or accumulation of phenolic compounds and hydroxyproline-protein in the cell walls.
Abstract: 1
Treatment of cell suspension cultures of bean (Phaseolus vulgaris cv Immuna) with an elicitor preparation heat-released from the cell walls of the phytopathogenic fungus Colletotrichum lindemuthianum resulted in rapid changes in the composition of the bean cell walls These consisted of (a) increases in phenolic material bound to the cellulosic and hemicellulosic fractions of the wall, (b) loss of material (mainly glucose) from the hemicellulosic fraction and (c) an increase in wall-associated hydroxyproline
2
The increases in wall-bound phenolics were preceded by (a) rapid decreases in the intracellular levels of free hydroxycinnamic acids and (b) transient increases in the extractable activities of l-phenylalanine ammonia-lyase and cinnamic acid 4-hydroxylase 4-Hydroxycinnamic acid 3-hydroxylase activity was present at a high level in control cultures and was not induced by elicitor Changes in the levels of cytochrome P-450, as determined by dot blot assays utilising an anti-(P-450) monoclonal antibody, paralleled the changes in cinnamic acid 4-hydroxylase activity
3
The accumulation of cell wall hydroxyproline was associated with rapid transient increases in the extractable activities of proline 2-oxoglutarate dioxygenase and a protein arabinosyl transferase An hydroxyproline-rich acceptor protein of Mr 42 500 was the major protein to incorporate [3H]arabinose following elicitation of the bean cells, and the kinetics of the extent of labelling of this protein paralleled the accumulation of hydroxyproline protein in the endomembrane system
4
The above metabolic changes associated with cell wall components followed rapid kinetics similar to those involved in the formation of the phytoalexin kievitone in the elicited cultures [Robbins, M P et al (1985) Eur J Biochem 148, 563–569] It is therefore concluded that increased 5-hydroxy-substituted isoflavonoid biosynthesis, wall-bound phenolic synthesis and synthesis of arabinosylated hydroxyproline-rich protein are all early events which are closely linked to the initial interaction between plant cell and fungal elicitor
82 citations
TL;DR: The basis of the structures of Oryzalexins A, B and C was laid by spectroscopic methods and their inhibitory activities against spore germination and germ tube growth of P. oryzae were assayed.
Abstract: Oryzalexins A, B and C were isolated as a group of novel phytoalexins from rice (Oryza saliva) blast leaves infected with Pyricularia oryzae. The basis of the structures of Oryzalexins A, B and C was laid by spectroscopic methods and their inhibitory activities against spore germination and germ tube growth of P. oryzae were assayed.
81 citations
TL;DR: The addition of autoclaved mycelia of Aspergillus niger and the known phytopathogenic fungus Phytophtora cinnamomi to cultured cells of Cinchona ledgeriana Moens caused a marked increase in the Anthraquinone content of the plant cells, leading to the conclusion that anthraquinones are phytoalexins.
Abstract: The addition of autoclaved mycelia of Aspergillus niger and the known phytopathogenic fungus Phytophtora cinnamomi to cultured cells of Cinchona ledgeriana Moens. caused a marked increase in the anthraquinone content of the plant cells. This finding in combination with the antimicrobial activity of the anthraquinones isolated from calli of Cinchona pubescens Vahl. led to the conclusion that anthraquinones are phytoalexins.
70 citations
TL;DR: The differential response to the fungal elicitor seemed to be highly specific as genetic differences between cultivars were not observed in tissue cultures treated with other biotic (Phytophthora infestans) and abiotic elicitors.
Abstract: With the aim of ascertaining the existance of a correlation between in vivo resistance to Fusarium oxysporum f sp dianthi and in vitro response to fungal elicitors and toxic substances, phenylalanine ammonialyase and phytoalexin accumulation, on one hand, and resistance to culture filtrate, on the other, were assayed in “in vitro” cultures of three susceptible and four resistant Dianthus caryophyllus cultivars Cultivars showing varying degrees of resistance in vivo either tolerated higher culture filtrate concentrations (‘Niki’) or showed high PAL activity and phytoalexin production when treated with Fusarium elicitor (‘Duca’), or responded positively to both treatments (‘Mei-Ling’, ‘Pulcino’) No such responses were shown in tissue cultures of susceptible cultivars The differential response to the fungal elicitor seemed to be highly specific as genetic differences between cultivars were not observed in tissue cultures treated with other biotic (Phytophthora infestans) and abiotic (HgCl2) elicitors
51 citations
TL;DR: Three stilbene phytoalexins, elicited by slicing and incubating imbibed peanut kernels under aerobic conditions, inhibited spore germination and hyphal extension of Aspergillus flavus with ED50 values in the range 4.9-12.8 micrograms ml-1.8 ml, and negatively correlated with dry kernel colonization by A. flavus when the incubation period was extended to 96 h.
Abstract: SUMMARY: Three stilbene phytoalexins, elicited by slicing and incubating imbibed peanut kernels under aerobic conditions, inhibited spore germination and hyphal extension of Aspergillus flavus with ED50 values in the range 4·9-12·8 γ ml-1. Phytoalexin yield was dependent on cultivar, conditions and duration of incubation after slicing, and crop history. The yield of phytoalexin from ten cultivars studied, after slicing and incubating at 25°C for 24 h, ranged from 28 to 935 γg per g fresh weight and was negatively correlated with dry kernel colonization by A. flavus [r = -0·868 when plotted as In (phytoalexin concn) against In (percentage peanut colonization)]. When the incubation period was extended to 96 h there was no such correlation. Reduced phytoalexin yields were obtained when sliced kernels of one cultivar studied were incubated in water or at 37°C, and no phytoalexin was obtained when the slices were incubated under nitrogen gas or frozen before aerobic incubation. Drought stress during pod development in four cultivars studied reduced phytoalexin yields of sliced kernels incubated at 25°C for 24 h by 17-65% compared with non-stressed controls.
50 citations
48 citations
TL;DR: The results suggest that soybean cells respond to the glucan elicitor by major metabolic changes at the RNA level including the enhanced capacity for phytoalexin synthesis, as indicated by two-dimensional electrophoresis of the translation products.
TL;DR: Pretreatment of resistant calli with subherbicidal levels of the inhibitor glyphosate lowered the production of medicarpin, reduced the browning response of callus cells and enhanced colonization by the fungus.
Abstract: Callus cultures derived from seeds of lucerne (Medicago saliva L.) were challenged with a lucerne isolate of Verticillium albo-atrum using agar blocks or spore suspensions as inoculum. The rate of colonization of different callus lines by the fungus varied from complete overgrowth of tissues in susceptible lines, to a rapid browning reaction of host cells accompanied by a restriction of fungal growth in resistant lines. The phytoalexin medicarpin accumulated in both resistant and susceptible reaction types, but resistant callus lines accumulated higher levels of this compound upon challenge with spore suspensions of V. albo-atrum. Pretreatment of resistant calli with subherbicidal levels of the inhibitor glyphosate lowered the production of medicarpin, reduced the browning response of callus cells and enhanced colonization by the fungus. Possible links between these in vitro responses and those of intact lucerne plants to V. albo-atrum are discussed.
TL;DR: Oryzalexins A, B and C, isolated from rice leaves infected with P. oryzae as a group of novel phyto-alxins, were confirmed to be (+)-sandaracopimaradiene derivatives by chemical and spectroscopic studies.
Abstract: Oryzalexins A, B and C, isolated from rice leaves infected with P. oryzae as a group of novel phytoalexins, were confirmed to be (+)-sandaracopimaradiene derivatives by chemical and spectroscopic studies, i.e. A: 3-oxy-7-oxo- (I); B: 3-oxo-7-oxy- (II) and C: 3, 7-dioxo-(+)-sandaracopimaradiene (III).
TL;DR: It is suggested that both lipid and non-lipid materials in the mycelium of P. infestans are able to elicit the hypersensitive response in potato tuber tissue.
Abstract: The hypersensitive reaction of potato tuber tissue, measured by necrosis and phytoalexin accumulation, was elicited by lipids and lipid-containing and lipid-free fractions extracted from mycelium of Phytophthora infestans . The most active fraction extracted after homogenization in phosphate buffer was composed of carbohydrate, protein and lipid. A heat-released preparation containing very low levels of eicosapentaenoic, arachidonic and dihomo-γ-linolenic acids was more active than a lipid extract of the mycelium. The majority of the elicitor of the mycelium remained associated with the wall residue after extraction. No relation was found between the activity of the fractions and their content of specific fatty acid elicitors. The activity of most fractions could not be explained by synergism between the eliciting fatty acids and mycelial carbohydrate. Furthermore, the activity of the lipid fractions appeared to be attenuated by some fungal component. Many of the fractions were shown by analytical isoelectric focussing to contain carbohydrate and protein bands also present in an elicitor obtained from culture filtrates of P. infestans . It is suggested that both lipid and non-lipid materials in the mycelium of P. infestans are able to elicit the hypersensitive response in potato tuber tissue.
TL;DR: It is suggested that pectinolytic enzymes release elicitor-active cell wall fragments from carrot cells and that a certain degree of esterification of the galacturonosyl moiety in these pectic polysaccharides is required for elicitor activity.
TL;DR: The extent of induction of some metabolic activities in cultured parsley cells by an elicitor preparation from Phytophthora megasperma f.
Abstract: The extent of induction of some metabolic activities in cultured parsley cells (Petroselinum crispum) by an elicitor preparation from Phytophthora megasperma f. sp. glycinea varied with the growth stage of the cell culture. On the basis of cell fresh weight, the induction of phytoalexin accumulation was high until cell mass reached a maximum, and then declined to a low level which was indistinguishable from a level caused by an endogenous mechanism operating at this late growth stage. The induction of phenylalanine ammonia-lyase and 4-coumarate:CoA ligase activities by the elicitor showed a high degree of coordination and a sharp maximum preceding the stage of maximal cell mass. 1,3-β-Glucanase activity was induced to about the same level throughout all growth stages, with a large contribution by an endogenous mechanism at late stages.
TL;DR: In vitro tolerance to toxic filtrate does not seem in this case a good indicator of in vivo resistance to the pathogen and in vitro hypersensitive response and phytoalexin induction.
Abstract: The behaviour of Tomato cultures from known resistant and susceptible cultivars and lines was examined for callus growth on culture media containing increasing concentrations of Fusarium oxysporum f. sp. lycopersici race 1 culture filtrate and phytoalexin synthesis elicited by Fusarium cell wall components. A strict correlation was found between in vivo resistance to the fungus and in vitro hypersensitive response and phytoalexin induction. On the other hand in vitro tolerance to toxic filtrate does not seem in this case a good indicator of in vivo resistance to the pathogen.
TL;DR: The cotton-Verticillium system is another case of secondary metabolite elicitation in plant tissue culture and might be used for basic studies of hostpathogen interaction as well as for a selection tool to obtain resistance to an important disease.
Abstract: Elicitation of sesquiterpenoid aldehyde phytoalexins inGossypium arboreum cell suspension cultures was confirmed by thin layer chromatography, high performance reverse phase liquid chromatography, and an aniline-reaction assay after inoculation with heat-treated conidia ofVerticillium dahliae A 2.3X mean increase in total terpenoids was observed. Component phytoalexins varied, with either hemigossypol and gossypol being detected or the O-methylated terpenoids hemigossypol-6-methyl ether and related compounds. Long-termGossypium suspension cultures were mixoploid with an increase in chromosome number and mean DNA content. Addition ofV. dahliae elicitor(s) to the medium for embryo-proliferating callus ofG. hirsutum inhibited growth and embryo production with a linear correlation (r=−0.87;P<0.01) between the elicitor concentration and the number of embryos. Addition of14C-labeled NaOAc to suspension cells gave 30% incorporation, and from13C-NaOAc addition, labeled sesquiterpenoid aldehydes were recovered. The cotton-Verticillium system is another case of secondary metabolite elicitation in plant tissue culture and might be used for basic studies of hostpathogen interaction as well as for a selection tool to obtain resistance to an important disease.
TL;DR: Lower layers of tissue from discs treated with sodium arachidonate contained the highest levels of phytoalexins and yielded cell-free enzyme preparations with the greatest lubimin biosynthetic activity.
01 Jan 1985
TL;DR: Considerable evidence supports the view that the phytoalexin response is one mechanism by which plants resist diseases.
Abstract: Higher plants have aquired effective defence mechanisms during evolution, which secure their survival in the presence of a large variety of infective microorganisms. Resistance mechanisms of plants are expressed at different levels in host-parasite interactions including preformed physical and chemical defence barriers as well as defences triggered by the invader [16]. One type of active response of plants to attempted infection is the production of low molecular weight antimicrobial compounds called phytoalexins. Considerable evidence supports the view that the phytoalexin response is one mechanism by which plants resist diseases [6, 12, 14, 21].
TL;DR: Bioassays of radial mycelial growth or of dry matter accumulation involving F. solani f.
Abstract: Phascollinisoflavan, an isoflavonoid phytoalexin produced by Phaseolus vulgaris , was metabolized by Fusarium solani f. sp. phaseoli . A major product of this reaction, designated metabolite-1 (M-1), was isolated from fungal cultures; whereas phaseollinisoflavan could not be recovered from the fungal culture medium 21 h after its addition, the level of M-1 rose steadily between nine and 24 h. Bioassays of radial mycelial growth or of dry matter accumulation involving F. solani f. sp. phaseoli, Pythium myrioylum, Phytophthora cryptogea and/or Rhizoctonia solani indicated that M-1 was less fungitoxic than phaseollinisoflavan. In addition to its production in liquid cultures treated with phaseollinisolflavan, M-1 was also isolated from Fusarium-infected bean tissues; trace amounts of M-1 were detected two days after inoculation and levels rose to at least I mg g −1 dry weight 8 days later. Purification of M-1 involved solvent partitioning, TLC, gel filtration and gas chromatography. Partial characterization indicated that the molecular weight of this metabolite was 342, 18 mass units greater than that of phaseollinisoflavan, suggesting the addition of the elements of water to the phytoalexin.
TL;DR: Using this technique, it was demonstrated that phytoalexin accumulation occurred earlier in the incompatible interaction between Verticillium albo-atrum and lucerne roots than in the compatible interaction.
Abstract: A method for growing axenic lucerne plants suitable for phytoalexin accumulation studies is described. Using this technique, it was demonstrated that phytoalexin accumulation occurred earlier in the incompatible interaction betweenVerticillium albo-atrum and lucerne roots than in the compatible interaction.
TL;DR: Media from germinating spores of Phytophthora infestans contain substances that elicit accumulation of the phytoalexin rishitin in potato tuber slices, and gel permeation chromatography of media extracts indicates the presence of several substance.
TL;DR: Survey of historical ground of isolation, structure, biosynthesis, biological activity, and role in plant-disease resistance of representative compounds identified as or called “phytoalexins” indicates that one of the most important studies to be done on phytoalxins is isolation and characterization of key enzymes leading to initial formation of ‘phytoalesins’.
Abstract: The term phytoalexin proposed by Muller and Borger in 1940 was recently revised as follows ; “phytoalexins are low molecular weight, antimicrobial compounds that are both synthesized by and accumulated in plants after exposure to microorganisms”. This definition has often been used as synonym of “stress compounds”. The present review describes survey of historical ground of isolation, structure, biosynthesis, biological activity, and role in plant-disease resistance of representative compounds identified as or called “phytoalexins”. Structural characteristics of “phytoalexins” and varieties of stresses causing formation of “phytoalexins” indicate that one of the most important studies to be done on phytoalexins is isolation and characterization of key enzymes leading to initial formation of “phytoalexins” and, if possible, endogeneous elicitors rather than exogeneous ones.
TL;DR: In this paper, the phytoalexin accumulation elicited by Phytophthora megasperma was studied in irradiated (0.1, 0.75, 1.5 kGy), heat treated (50 °C, 5 min) and combined (heat and irradiation) treated potato tubers (cultivar Bintje).
Abstract: Phytoalexin accumulation elicited byPhytophthora megasperma was studied in irradiated (0.1, 0.75, 1.5 kGy), heat treated (50 °C, 5 min) and combined (heat and irradiation) treated potato tubers (cultivar Bintje). Rishitin, lubimin and small amounts of phytuberol were found. The phytoalexin concentration was higher in the irradiated tubers than in the unirradiated ones. The heat treatment did not have an unambiguous effect on the phytoalexin production. On the samples containing highest phytoalexin level intensive growth ofP. megasperma could be observed; in the bioassay an increased amount of phytoalexins showed a stronger fungistatic effect onCladosporium cucumerinum. These results indicate that the phytoalexin accumulation is not clearly related to the mechanism of resistance against fungi.