Showing papers on "Phytoalexin published in 1988"
TL;DR: The rapid inhibition of squalene synthetase in elicited cultures may operate to channel FPP away from sterol biosynthesis and towards the FPP-carbocyclase involved in the biosynthesis of the two sesquiterpenoid phytoalexins or may be part of a more general response of plant cells to treatment with elicitors.
147 citations
TL;DR: Phytoalexin synthesis can be favorably studied in experimental systems mimicking as closely as possible the natural infection process, as well as in systems of reduced complexity utilizing plant cell cultures and inducers of microbial origin (elicitors).
134 citations
TL;DR: Elicitor-active preparations from the fungal pathogen of bean Colletotrichum lindemuthianum stimulated the accumulation of products characteristic of lipid peroxidation in treated bean tissues, suggesting that generation of active oxygen species may be involved in lipidperoxidation triggered by elicitors.
Abstract: Elicitor-active preparations from the fungal pathogen of bean Colletotrichum lindemuthianum stimulated the accumulation of products characteristic of lipid peroxidation in treated bean tissues. Bean suspension cells treated with crude and purified elicitors accumulated `lipofuscin-like pigment9 (LEP) and malondialdehyde. The accumulation of LFP after about 6 h of treatment coincided with the onset of visible browning and production of the bean phytoalexins kievitone, phaseollin, and phaseollinisoflavan. The induction of phytoalexins and accumulation of LFP were also triggered by treatments with generators of activated oxygen species, xanthine:xanthine oxidase and Fe:ethylenediaminedi- o -hydroxyphenylacetic acid. These data suggest that generation of active oxygen species may be involved in lipid peroxidation triggered by elicitors.
102 citations
TL;DR: The response of parsley seedlings inoculated with zoospores of the soybean-pathogenic fungus, Phytophthora megasperma f.
Abstract: The response of parsley seedlings (Petroselinum crispum) inoculated with zoospores of the soybean-pathogenic fungus, Phytophthora megasperma f. sp. glycinea, ranged from “immunity” to “physiological susceptibility” depending on the post-inoculation environmental conditions. Typical nonhost resistance reactions, hypersensitive cell death and the formation of small local lesions, occurred under high relative humidity and 16 h illumination per day. Localized biochemical reactions were monitored using fluorescence microscopy combined with histochemical and immunohistochemical methods. The rapid accumulation of furanocoumarin phytoalexins, wall-bound phenolics and callose was detected around infection sites. Indirect antibody staining of frozen tissue sections demonstrated the local accumulation of phenylalanine ammonia-lyase, a key enzyme of general phenylpropanoid metabolism, and S-adenosyl-L-methionine: bergaptol O-methyltransferase, a specific enzyme of the furanocoumarin pathway. The results indicate that phenylpropanoid derivatives are synthesized de novo at infection sites.
100 citations
TL;DR: This appears to be the first report of elicitation of phytoalexins in crucifers upon being challenged by a fungal pathogen.
99 citations
TL;DR: In this article, a gas chromatography-mass spectrometry-selected ion monitoring (GC-MS-SIM) was used to detect phyto-alexins in rice leaves after pretreating with a BOND ELUT C18 cartridge.
Abstract: Accumulated phytoalexins in ultraviloet-irradiated detached rice leaves were detected by gas chromatography-mass spectrometry-selected ion monitoring (GC-MS-SIM) after pretreating with a BOND ELUT C18 cartridge. An accumulation of oryzalexins A, B, C and D, momilactones A and B, and an unknown antifungal substance accompanied by the appearance of brown spots on the leaf surface was observed. Momilactone A was detected in abundance, and among the oryzalexins, oryzalexin D was a major substance. The maximum accumulation of these phytoalexins, except for oryzalxins C and D, was found 3 days after irradiation. However, the maximum accumulation of oryzalexin D was observed 2 days after irradiation and that of oryzalexin C was observed 4 days after it. The content of these diterpenoid phytoalexins in rice leaves was dependent on leaf aging, an accumulation of these phytoalexins in the uppermost leaves being much lower than that in the aged leaves (lower leaves), and brown spots scarcely ever appeared on the sur...
97 citations
TL;DR: The analysis of the cis-acting sequences involved in the regulation of chalcone synthase has been facilitated by the use of electroporated protoplasts as a transient assay system and theUse of DNA footprinting and gel-retardation assays will help identify the corresponding trans-acting factors involved inThe regulation of these genes.
Abstract: . Plants respond actively to infection and other environmental stresses by synthesizing phytoalexins and defence-related proteins. This response can be induced in plant cell suspension cultures with compounds known as elicitors. These are often carbohydrates of fungal origin. In bean, transcriptional activation of the defence genes commences less than five minutes after elicitor addition, thus it is clearly a very rapid response implying few biochemical steps exist between elicitor interaction and the initiation of defence gene transcription. The induction of phytoalexin biosynthesis during incompatible interactions of bean with Colletotrichum lindemuthianum occurs rapidly during the initial contact between the host and pathogen. This appears to be a direct response to molecular recognition of the pathogen. In compatible interactions however, the pathogen grows biotrophically and phytoalexin biosynthesis is not triggered until lesions begin to form. Thus this may be a response to tissue damage rather than direct molecular recognition. Many bean defence genes, including those regulating key points in the phytoalexin biosynthetic pathway, exist in the genome as small multigene families. In some cases there is differential regulation within a family in response to developmental and environmental signals. The analysis of the cis-acting sequences involved in the regulation of chalcone synthase has been facilitated by the use of electroporated protoplasts as a transient assay system. This work and the use of DNA footprinting and gel-retardation assays will help identify the corresponding trans-acting factors involved in the regulation of these genes. While progress is being made in understanding the mechanisms of transcriptional activation of defence genes little is known of how plants recognize pathogens and elicitors or how this signal is transduced to the nucleus.
69 citations
TL;DR: The results show that the preformed cyanogenic glycoside, dhurrin, is not the only source of resistance of sorghum seedlings to fungal infection, and it is proposed that synthesis of the pigment complex constitutes a defense response in the juvenile Sorghum leaf.
58 citations
TL;DR: Triterpenoid synthesis was markedly reduced just prior to the onset of phytoalexin accumulation, and this apparent lack of any regulatory control of the incorporation of MVA into the three triterpenoids and into phy toalexins is presumably the principal reason for the need to bring about the rapid and complete inhibition of squalene synthetase activity in the cells of inoculated cultures.
56 citations
TL;DR: Soybean and parsley cells not only perceive different signals from cell walls of Phytophthora megasperma f.
Abstract: Different components of a crude cell-wall preparation from the phytopathogenic fungus, Phytophthora megasperma f. sp. glycinea, act as elicitors of phytoalexin accumulation in parsley (Petroselinum crispum) and soybean (Glycine max). Treatments of cultured parsley cells and protoplasts or soybean cells and cotyledons with proteinase-digested or deglycosylated elicitor preparations identify proteinaceous constituents as active eliciting compounds in parsley, which are inactive in soybean. The proteinase-treated elicitor as well as a defined heptaglucan are active in soybean but do not stimulate phytoalexin synthesis in parsley. Soybean and parsley cells therefore not only perceive different signals from cell walls of Phytophthora megasperma f. sp. glycinea, but are unable to respond to the fungal compounds primarily recognized by the other plant.
56 citations
TL;DR: PG-II and PG-IV released heat-stable elicitors from purified soybean cell walls supporting the evidence that uronides are intermediate inducers in elicitation by endo-PGs.
TL;DR: The data indicate that infection hyphase of C. lindemuthianum remain viable at HR sites on P. vulgaris, and support the conclusion that phytoalexin accumulation is a major feature of HR and a determinant of resistance in this host-parasite system.
TL;DR: Leaf and stem tissues of Brassica napus accumulated two phytoalexins following inoculation with pycnidiospore suspension of a non-aggressive isolate of Leptosphaeria maculans, which were identified as methoxybrassinin and cyclobrassinin based on UV, IR, NMR and mass spectral analysis.
TL;DR: A new enzyme activity is induced which catalyses the conversion of the 2′‐hydroxyisoflavanone vestitone to the pterocarpan medicarpin in chickpea cell suspension cultures.
TL;DR: It is proposed that the hydrocarbon 4- epi -eremophila-9,11-diene is a common intermediate in the biosynthesis of all the named compounds and further that 8-hydroxydebneyol is the direct precursor of the phytoalexin cyclodebneyol.
TL;DR: Elicitor treatment of intact fruits to protect against rot development by B. cinerea was achieved without the fruits sustaining unsightly damage.
Abstract: Immature Capsicum annuum fruits treated at wound-sites with glucans from the hyphal walls of Glomerella cingulata and incubated for 24 h or longer accumulated levels of capsicannol phytoalexins sufficient to inhibit rot development by Botrytis cinerea. Elicitor application to intact fruits induced the accumulation of relatively low levels of capsicannol compounds but further phytoalexin accumulation in fruits after wound-inoculation with B. cinerea was much more rapid than in untreated fruits and rot development was suppressed.
Capsicannol phytoalexins were produced in the live cells of the epidermis and little or no necrosis was associated with quantities produced in intact tissues. Elicitor treatment of intact fruits to protect against rot development by B. cinerea was achieved without the fruits sustaining unsightly damage.
TL;DR: Activity of the O‐methyltransferase was not found in fresh carrot roots but increased when they were treated with either type of elicitor in parallel with the increase in 6‐methoxymellein content.
TL;DR: Induction of stress metabolites in the suspension cultured cells of eggplant (Solanum melongena L.) was examined and elicitation of these compounds was closely correlated with cellular damage in terms of the decrease of growth rate and was inhibited by 10 micromolar cycloheximide.
Abstract: Induction of stress metabolites in the suspension cultured cells of eggplant (Solanum melongena L.) was examined. When autoclaved RNase A or nigeran, both of which are nonspecific phytoalexin elicitors in bean cells, were added to the cell culture of eggplant, greatly enhanced levels of three compounds were observed. One of them was cis-pentadeca-6-ene-1,3-diyne-5,15-diol, a novel diacetylenic compound. This compound has considerable fungitoxic activity. Also identified was falcarindiol, another fungitoxic diacetylenic compound previously reported as one of the phytoalexins in infected tomato fruits and leaves. Elicited compounds preferentially accumulated in the culture medium rather than in the cells and decreased to original levels during prolonged culturing. The elicitation of these compounds was closely correlated with cellular damage in terms of the decrease of growth rate and was inhibited by 10 micromolar cycloheximide.
TL;DR: Two phytoalexins, previously isolated from carnation infected by Phytophthora parasitica D, were synthesized: 2-phenyl-7-hydroxy-4H-3,l-benzoxazin-4-one (Dianthalexin) and 2-(2-hydroxbenzoyl)-amino-4methoxybenzoic acid (DIANTHramide A).
TL;DR: The data indicate that the toxic effect of arachidonic acid on potato tuber cells is unrelated to its ability to induce phytoalexin accumulation, and indicates that protoplasts may still be useful in this host-pathogen interaction since both Potato tuber cells and protoplast react similarly to elicitor treatments.
TL;DR: Callus cultures of various cultivars of Vicia faba were studied for regeneration and a black tissue was often observed correlated with an autolysis of some cells, which inhibited callus growth and regeneration of plants.
Abstract: Callus cultures of various cultivars of Vicia faba were studied for regeneration. During callus growth on agar or in liquid medium a black tissue was often observed correlated with an autolysis of some cells. With those tissues callus growth and regeneration of plants was inhibited. In black callus the phytoalexin synthesis is induced without infection by microorganism. The main phytoalexins in the callus tissue are wyerol and wyerone, with some wyeronic acid and dihydrowyerone. Wyerol was found especially in the cultivar Troy at a high concentration. In four cultivars the pooled phytoalexin concentration varied between 10 and 150 μg · g⁻¹ fresh weight.
TL;DR: The 3-ethylchromone phytoalexin lathodoratin from cupric sulphate-induced pods of sweet pea (Lathyrus odoratus) has a polyketide origin this paper.
TL;DR: A contribution of defense reactions to the determination of host specificity of the pathogenic strains of the Agrobacterium genus has been proposed.
Abstract: Agrobacterium radiobacter was tested for the ability to induce the accumulation of phytoalexins and hypersensitive necrotic reaction in pea, bean and potato. A live bacterial suspension with a cell concentration of 1/pL and a solution of a crude polysaccharide produced by the bacteria caused the hypersensitive reaction in potato and bean and the production of phytoalexins in all three species of plants. The results obtained are discussed in connection with the previously found protective effect of the studied strain ofA. radiobacter against soil phytopathogenic fungi. A contribution of defense reactions to the determination of host specificity of the pathogenic strains of theAgrobacterium genus has been proposed.