Showing papers on "Phytoalexin published in 1982"
TL;DR: For two of the induced enzymes, phenylalanine ammonia-lyase and chalcone synthase, the changes in activity at stage I were shown to be preceded by large changes in their rates of synthesis, as determined by in vivo labelling with [35S] methionine and immunoprecipitation.
Abstract: The glucan elicitor from cell walls of the fungal pathogen, Phytophthora megasperma f. sp. glycinea, induced rapid but transient increases in enzyme activities of general phenylpropanoid metabolism (phenylalanine ammonia-lyase and 4-coumarate: CoA ligase) and of the flavonoid pathway (chalcone synthase) in cell suspension cultures of soybean (Glycine max). After transferring cells into fresh medium, two peaks of inducibility for the enzymes by elicitor were observed, one shortly after transfer (stage I), and one at the end of the linear growth phase (stage II). Only one of the two isoenzymes of 4-coumarate: CoA ligase (“isoenzyme 2”), for which a specific involvement in flavonoid biosynthesis has been postulated, was affected by the elicitor. For two of the induced enzymes, phenylalanine ammonia-lyase and chalcone synthase, the changes in activity at stage I were shown to be preceded by large changes in their rates of synthesis, as determined by in vivo labelling with [35S] methionine and immunoprecipitation.
59 citations
Journal Article•
TL;DR: Phytoalexins are antibiotic compounds synthesized in an infected plant in response to infection.
Abstract: Phytoalexins are antibiotic compounds synthesized in an infected plant in response to infection. Nematodes are capable of eliciting phytoalexins in resistant plants. Resistant lima bean (Phaseolus lunatus) infected by Pratylenchus penetrans produces the phytoalexin coumestrol; soybean (Glycine max) infected by Meloidogyne incognita produces glyceollin; cotton (Gossypium hirsuturn) infected by M. incognita produces terpenoid aldehydes.
53 citations
TL;DR: Patterns of phytoalexin accumulation have been studied in response to varying concentrations of the crude and fractionated elicitor; 5-hydroxy isoflavonoid accumulation is highly dependent upon elicitor concentration, the dose-response curves for kievitone accumulation showing maxima at around 1 μg glucose equivalents per cotyledon, minima at 2–3 μg equivalents and increasing induction at higher concentrations.
Abstract: In wounded cotyledons ofPhaseolus vulgaris L. the accumulation of the 5-hydroxy isoflavonoids kievitone and 2′-hydroxygenistein precedes the major increases in the levels of the 5-deoxy compounds phaseollin and coumestrol. Increased phytoalexin levels are preceded by transient increases in the extractable activities of L-phenylalanine ammonia-lyase (EC 4.3.1.5.), chalcone synthase and chalcone isomerase (EC 5.5.1.6.). Accumulation of phytoalexins, above wounded control levels, is observed following treatment of excised cotyledons or hypocotyls with crude or fractionated elicitor preparations heat-released from the cell walls ofColletotrichum lindemuthianum. Chalcone synthase levels are also induced in cotyledons, although crude elicitor and all fractions suppress L-phenylalanine ammonia-lyase activity in both tissues. Kievitone is the major phytoalexin induced in cotyledons, whereas in hypocotyls phaseollin predominates. Patterns of phytoalexin accumulation have been studied in response to varying concentrations of the crude and fractionated elicitor; 5-hydroxy isoflavonoid accumulation is highly dependent upon elicitor concentration, the dose-response curves for kievitone accumulation showing maxima at around 1 μg glucose equivalents per cotyledon, minima at 2–3 μg equivalents and increasing induction at higher concentrations. Similar patterns are observed for L-phenylalanine ammonia-lyase and chalcone synthase levels, although the overall extent of these changes is masked by the high wound response. Accumulation of 5-deoxy isoflavonoids above control levels requires high elicitor concentrations; no experimental conditions were found under which phaseollin accumulated to higher levels than kievitone in cotyledons during the first 48 h after elicitation.
34 citations
TL;DR: The biosynthesis of isoflavonoid phytoalexins and the incorporation of sodium [1,2-(13)C2] acetate into phaseollin and kievitone were discussed in this article.
Abstract: Article on the biosynthesis of isoflavonoid phytoalexins and the incorporation of sodium [1,2-(13)C2] acetate into phaseollin and kievitone.
25 citations
TL;DR: Most fungitoxic compounds had not more than one or two polar substituents and methylation of all of these groups removed activity.
Abstract: Three hydroxyflavan phytoalexins and 23 other flavonoid compounds variously substituted in their homocyclic rings were assessed for antifungal activity against Botrytis cinerea and Cladosporium herbarum using sporeling and TLC plate bioassays. The pairs of optical isomers of two of the phytoalexins possessed similar activity. The isoflavan analogue of the phytoalexin 7-hydroxyflavan was active. Most fungitoxic compounds had not more than one or two polar substituents and methylation of all of these groups removed activity. The basis of the antifungal activity of flavonoids is discussed.
25 citations
TL;DR: Using the cotyledon phytoalexin elicitor assay, maximum heatlabile elicitor activity was obtained when soybean stems were extracted with acetate buffer at pH 6.0 and addition of 1 millimolar CaCl(2) increased apparent heat-labile elicit activity.
Abstract: An extract of frozen and thawed soybean (Glycine max L. Merr. cv. Wayne) stems is active, in wounded soybean cotyledons, as a heat-labile elicitor of phytoalexins. The elicitor activity of the extract is destroyed by heating to 95°C for 10 minutes. The fraction that contains heat-labile elicitor activity releases heat-stable elicitor-active molecules from purified soybean cell walls. Heat-labile elicitor activity voids a Bio-Gel P-6 column and can be absorbed onto and eluted from a DEAE Sephadex ion exchange column. Using the cotyledon phytoalexin elicitor assay, maximum heatlabile elicitor activity was obtained when soybean stems were extracted with acetate buffer at pH 6.0. Addition of 1 millimolar CaCl2 increased apparent heat-labile elicitor activity. The heat-labile elicitor stimulated maximum phytoalexin accumulation when applied to cotyledons immediately after the cotyledons were cut. Partially purified stem extracts lost heat-labile elicitor activity during storage for several days at 3°C. The possible role of a heat-labile elicitor in stimulation of phytoalexin accumulation by both abiotic and biotic elicitors is discussed.
23 citations
TL;DR: The results indicated that the degree of resistance among resistant cultivars depended primarily on the rate of occurrence of hypersensitivity and the associated accumulation of rishitin.
Abstract: Using 12 potato cultivars having various R -genes and apparently different degrees of resistance to an incompatible race of Phytophthora infestans , relationships were investigated between (1) the percentage of cells reacting hypersensitively, (2) the number of dead and brown cells at late stages of infection, (3) the accumulation of rishitin and (4) the restriction of fungal growth. The number of invaded and browned cells of aged tuber discs 2 days after inoculation was lower than that of fresh tuber discs and, within each cultivar, was negatively correlated with the percentage of hypersensitive cells observed 7 h after inoculation. Hypersensitivity within 7 h after inoculation evidently contributed to the localization of the invading fungi in the hypersensitive cells by stimulating the accumulation of phytoalexin in these cells to an inhibitory level at 12 h after inoculation, when invading fungi were about to grow through the invaded cells to the other cells. In less resistant cultivars, the percentage of hypersensitive cells after 7 h was low and hyphae grew into deeper layers of cells, some of which became brown. More rishtin accumulated in these cultivars: the amount being related to the number of brown cells 24 h after inoculation but not with the number at later times. These results indicated that the degree of resistance among resistant cultivars depended primarily on the rate of occurrence of hypersensitivity and the associated accumulation of rishitin.
23 citations
TL;DR: Inoculation of suspension cultures of a recently initiated cell line of Glycine max (L.) Merr.
15 citations
TL;DR: A new phytoalexin (apiocarpin) isolated from the fungus-inoculated leaflets of Apios tuberosa has been identified by chemical and spectroscopic analysis.
14 citations
TL;DR: It is suggested that the amounts of phytoalexin which accumulate depend on the different biochemical and physiological activities of the living tissues with which adjacent necrotic tissues interact.
Abstract: The phytoalexins, phaseollin, phaseollidin, phaseollinisoflavan and kievitone, were isolated from bean hypocotyls bearing TNV-induced necrotic lesions. Phaseollin was the predominant phytoalexin and was localized within the necrotic tissues. Highest yields of phaseollin (more than 450 μg g −1 fresh wt) were obtained from dark-grown infected bean seedlings brought into light. The production of each phytoalexin was reduced when cotyledons were removed. Growth and incubation in total darkness completely prevented the production of any phaseollinisoflavan. The total amount of virus produced was not greatly affected by these treatments. It is suggested that the amounts of phytoalexin which accumulate depend on the different biochemical and physiological activities of the living tissues with which adjacent necrotic tissues interact.
13 citations
TL;DR: Deposition of reaction material (papillae) and phytoalexin accumulation were detected in narcissus bulb scales undergoing resistant reactions following inoculation with conidia of Botrytis cinerea or B. narcissicola, and it was suggested that reaction material contained lignin and callose and that surrounding cell walls were also lignified.
Abstract: Deposition of reaction material (papillae) and phytoalexin accumulation were detected in narcissus bulb scales undergoing resistant reactions following inoculation with conidia of Botrytis cinerea or B. narcissicola, or mycelium of B. cinerea. Histochemical staining and micro-autoradiography suggested that reaction material contained lignin and callose and that surrounding cell walls were also lignified. Twelve phytoalexins were isolated from tissue bearing limited lesions and found to comprise two groups of structurally related compounds. The smoulder pathogen B. narcissicola was as sensitive to the inhibitors as non-pathogenic species of Botrytis. Neither phytoalexin accumulation nor lignification were detected in bulb tissue during the formation of spreading lesions caused by B. narcissicola. The role of lignification and phytoalexin accumulation in the resistance of narcissus bulbs to Botrytis is discussed.
TL;DR: Phytoalexin production and host cell death in lucerne leaves were investigated following inoculation with either a virulent or an avirulent isolate of Verticillum albo-atrum and the progress of the pathogen was not halted.
Abstract: Phytoalexin production and host cell death in lucerne ( Medicago sativa ) leaves were investigated following inoculation with either a virulent or an avirulent isolate of Verticillum albo-atrum . Attempted penetration in the incompatible interaction leads to rapid host cell death and to the rapid accumulation of medicarpin and sativan. High concentrations of both these phytoalexins were maintained throughout the incubation period and hyphal growth on the leaf surface was restricted. In the compatible interaction, only low levels of phytoalexins were produced over the first few days but the virulent isolate was not restricted and colonization of the leaf tissue continued. Later, even when high levels of medicarpin and sativan were produced in association with gross tissue damage, the progress of the pathogen was not halted.
TL;DR: After treatment with the fungus Helminthosporium carbonum or aqueous copper sulphate, excised Lathyrus sativus leaflets produce pisatin and a second isoflavonoid phytoalexin (lathycarpin) identified as (+)-6aR; 11aR-2,3-dimethoxy-6a-hydroxy-8,9-methylenedioxypterocarpan.
Abstract: After treatment with the fungus Helminthosporium carbonum or aqueous copper sulphate, excised Lathyrus sativus leaflets produce pisatin and a second isoflavonoid phytoalexin (lathycarpin) identified as (+)-6aR; 11aR-2,3-dimethoxy-6a-hydroxy-8,9-methylenedioxypterocarpan.