Showing papers on "Phytoalexin published in 1990"
TL;DR: This site-restricted synthesis suggests that the phytoalexin response occurs initially in the first cells that come under fungal attack and is not simply a response of cells that surround the original infection site.
Abstract: Sorghum produces phytoalexins that are 3-deoxyanthocyanidin flavonoids. The compounds inhibit the growth of phytopathogenic fungi in vitro. The phytoalexins appear to be synthesized in subcellular inclusions within a host epidermal cell that is about to be penetrated by a fungus. This site-restricted synthesis suggests that the phytoalexin response occurs initially in the first cells that come under fungal attack and is not simply a response of cells that surround the original infection site.
330 citations
TL;DR: In this paper, the major phytoalexin of oat leaves is not the 4-H-3,1-benzoxazin-4 one previously reported, but the corresponding amide.
198 citations
TL;DR: Analysis of soybean membranes suggested that the putative glucan‐elicitor receptors bind a basic structural determinant present in all elicitor‐active glucans from the soybean pathogen P. megasperma.
110 citations
TL;DR: Fosetyl-Al does not enhance sesquiterpenoid phytoalexin biosynthesis in cv.
89 citations
TL;DR: The data draw attention to the involvement of isoflavone hydroxylases during the constitutive and elicitor-induced accumulation of is oflavonoids and their conjugates in alfalfa cell cultures.
Abstract: The isoflavonoid conjugates medicarpin-3-O-glucoside-6″-O-malonate (MGM), afrormosin-7-O-glucoside (AG), and afrormosin-7-O-glucoside-6″-O-malonate (AGM) were isolated and characterized from cell suspension cultures of alfalfa (Medicago sativa L.), where they were the major constitutive secondary metabolites. They were also found in alfalfa roots but not in other parts of the plant. The phytoalexin medicarpin accumulated rapidly in suspension cultured cells treated with elicitor from Colletotrichum lindemuthianum, and this was subsequently accompanied by an increase in the levels of MGM. In contrast, net accumulation of afrormosin conjugates was not affected by elicitor treatment. Labeling studies with [14C]phenylalanine indicated that afrormosin conjugates were the major de novo synthesized isoflavonoid products in unelicited cells. During elicitation, [14C]phenylalanine was incorporated predominantly into medicarpin, although a significant proportion of the newly synthesized medicarpin was also conjugated. Treatment of 14C-labeled, elicited cells with l-α-aminooxy-β-phenylpropionic acid, a potent inhibitor of PAL activity in vivo, resulted in the initial appearance of labeled medicarpin of very low specific activity, suggesting that the phytoalexin could be released from a preformed conjugate under these conditions. Our data draw attention to the involvement of isoflavone hydroxylases during the constitutive and elicitor-induced accumulation of isoflavonoids and their conjugates in alfalfa cell cultures.
87 citations
TL;DR: Comparison of the fungitoxicity of the compound with that of two phytoalexins identified previously showed that all three of the compounds exhibited toxicity to C. graminicola at concentrations of less than 10 μ m.
78 citations
TL;DR: The pterocarpan biosynthetic pathway in chickpea cells represents a suitable model for investigations of differential gene activation in connection with the expression of antimicrobial defence reactions.
Abstract: Cell-suspension cultures of Ascochyta rabiei-resistant (ILC 3279) and -susceptible (ILC 1929) chickpea (Cicer arietinum L.) cultivars were compared with regard to their elicitor-induced accumulation of pterocarpan phytoalexins and increases in the activities of biosynthetic enzymes. The growth performances and protein patterns of the two cell-culture lines were essentially identical. Treatment of cell cultures with a polysaccharide elicitor from A. rabiei induced fivefold-higher amounts of the phytoalexins medicarpin and maackiain in the cells of the resistant than in the susceptible cultivar. Glucose 6-phosphate dehydrogenase and eight enzymes representing the general phenylpropanoid pathway, the flavonoid-forming steps and the pterocarpanspecific branch of phytoalexin biosynthesis were found to be elicitor-induced. Phenylalanine ammonia-lyase and chalcone synthase reached sharp, transient optima some 8 h after elicitor application in the cells of both cultivars. The activities of isoflavone 2′- and 3′-hydroxylases were only induced in cells of the resistant cultivar with a maximum after 8 h. Cinnamic acid 4-hydroxylase, chalcone isomerase, 2′-hydroxyisoflavone reductase and pterocarpan synthase showed a later or no sharp optimum. The isoflavone-specific 7-O-glucosyltransferase was not induced in either cell-culture line. Cells of the susceptible cultivar failed to induce significant activities of isoflavone 2′-hydroxylase and these cells produced only very low amounts of phytoalexins. Isoflavone 2′-hydroxylase is postulated to be the main limiting enzyme for pterocarpan biosynthesis in cells of the susceptible cultivar. The pterocarpan biosynthetic pathway in chickpea cells represents a suitable model for investigations of differential gene activation in connection with the expression of antimicrobial defence reactions.
66 citations
TL;DR: The results suggest that A. majus cells are particularly suitable for biosynthetic studies on various coumarins as well as for regulatory studies of the inhibition of coumarin phytoalexin accumulation.
50 citations
TL;DR: In this article, a sesquiterpenoid phytoalexin, cichoralesin, was isolated from Cichorium intybus inoculated with Pseudomonas cichorexin and its structure was elucidated by spectroscopic methods.
47 citations
01 May 1990
TL;DR: The genotype/strain specific occurrence of the hypersensitive response in root nodules resembles the race/cultivar specific incompatibility of several plant-pathogen interactions and points out the close physiological relationship between the late stages of the root nodule symbiosis and a plant/pathogen interaction.
Abstract: Three Glycine genotypes, G. max cv. Williams, G. soja PI 468397, and G. soja PI 342434 in combination with the two rhizobial strains Bradyrhizobium japonicum USDA 123 and Rhizobium fredii USDA 193 were analysed for phytoalexin concentration in the nodules. In the nodules of PI 468397/B. japonicum USDA 123 a very strong glyceollin I accumulation occurred around 30 d.p.i. Ultrastructural analysis of these nodules revealed several symptoms of a severe plant defense response associated with plant cell death (hypersensitive reaction): The cytoplasm of the infected cells was degraded and organelles had vanished. The cell walls of the infected cells showed remarkable thickening. This plant defense response could only be observed in this strain/genotype interaction. The same strain did not elicit a phytoalexin accumulation in the other plant genotypes tested, indicating that this response occurs at the genotype-specific level. This special character of G. soja PI 468397 is heritable as indicated by glyceollin I analysis of the nodules formed by F1 hybrids of PI 468397xWilliams inoculated with B. japonicum USDA 123. The genotype/strain specific occurrence of the hypersensitive response in root nodules resembles the race/cultivar specific incompatibility of several plant-pathogen interactions. This specificity, together with the phenomenon of the HR itself, points out the close physiological relationship between the late stages of the root nodule symbiosis and a plant/pathogen interaction.
45 citations
TL;DR: The fact that phosphonate improves fungal cells in vitro to overproduce compound(s) which elicits a resistance response, support the hypothesis that the toxophore may act indirectly in vivo interfering with the processes of pathogenicity.
TL;DR: An endogenous elicitor of the phytoalexin of soybean, was synthesized by way of highly stereoselective glycosylations that involved Glycosyl fluorides as the donors and oxidation of the twelve primary hydroxyl groups in the alpha-(1----4)-linked galactododecaoside derivative.
TL;DR: Xylem from susceptible ‘Lena’ suffering degradation was characterized by a loss of syringyl groups from the lignin and by demethylation of pectin in an early stage of infection.
Abstract: Minute pieces of xylem and other tissues from stems of healthy and fungus-infected plants of two carnation cultivars Novada and Lena were investigated for lignification (lignin/polysaccharide ratios) and lignin composition by means of pyrolysis mass spectrometry and pyrolysis gas chromatography mass spectrometry. This technique proved also very effective for the localization of dianthramide phytoalexins which accumulate in carnation after infection withFusarium oxysporum f.sp.dianthi. The composition of healthy tissues from both cultivars was practically the same. In the resistant cultivar Novada, infection induced a change from guaiacyl-syringyl lignin into a mainly guaiacyl lignin in the gum-occluded parts of the xylem. Considerable amounts of the phenolic amide dianthalexin and of other dianthramide phytoalexins were present in occluded xylem, but not in adjacent phloem, medulla or unoccluded xylem. Xylem from susceptible ‘Lena’ suffering degradation was characterized by a loss of syringyl groups from the lignin and by demethylation of pectin in an early stage of infection. Small quantities of dianthalexin and other dianthramide phytoalexins were found in ‘Lena’ when local defense responses (particularly occlusion) had occurred. In both cultivars evidence for degradation of hemicellulose was found.
TL;DR: Inoculation of white cabbage heads with Pseudomonas cichorii resulted in induction of a new phytoalexin, 4-methoxybrassinin, whose structure was elucidated on the basis of spectroscopic methods.
TL;DR: Analysis of the total in-vitro-translated proteins by two-dimensional gel electrophoresis showed that the constitutively expressed patterns of mRNA activities in the cell cultures of the two cultivars were identical, and considerably more translatable mRNAs were induced in the cells of cultivar ILC 3279.
Abstract: Cell-suspension cultures of two chickpea (Cicer arietinum L.) cultivars, resistant (ILC 3279) and susceptible (ILC 1929) to the fungus Ascochyta rabiei (Pass.) Lab., showed differential accumulation of the phytoalexins medicarpin and maackiain, and transient induction of related enzyme activities after application of an A. rabiei-derived elicitor. The chalcone-synthase (CHS) activity (EC 2.3.1.74) which is involved in the first part of phytoalexin biosynthesis exhibited a maximum 8-12 h after elicitation in the cells of both cultivars. Concomitant with the fivefold-higher phytoalexin accumulation, CHS activity increased twofold in the cells of the resistant cultivar. The maximum of the elicitor-induced CHS-mRNA activity was determined 4 h after onset of induction in the cultures of both cultivars, although in cells of cultivar ILC 3279 this mRNA activity was induced at a level twofold higher than that in cells of the susceptible race ILC 1929. Investigations of CHS isoenzymes by two-dimensional gel electrophoresis of immunoprecipitated in-vitro-translated protein indicated the presence of five proteins. In the cells of both cultivars only two of the isoenzymes were induced after elicitor treatment. Analysis of the total in-vitro-translated proteins by two-dimensional gel electrophoresis showed that the constitutively expressed patterns of mRNA activities in the cell cultures of the two cultivars were identical. After elicitation, considerably more translatable mRNAs were induced in the cells of cultivar ILC 3279. The few induced proteins, and their respective mRNA activities, which could be detected in the cells of the susceptible cultivar, all existed in the cells of the resistant cultivar, too. One highly induced protein (Mr 18 kDa) found in the cells of cultivar ILC 3279 reached its maximum mRNA activity 6 h after elicitor application. The amount of this protein was hardly increased in the cells of the susceptible cultivar. This protein appears to be excreted from the cells into the growth medium.
TL;DR: In this article, conidia and the conidial mucilage of Colletotrichum graminicola contained materials that elicited the accumulation of deoxyanthocyanidin phyto-alexins in sorghum mesocotyls and juvenile Sorghum leaves.
TL;DR: With both methods, higher inoculum dosages led to higher wilting rates and higher phytoalexin concentrations, and injection appears the most promising technique for the development of routine screening methods for resistance based on phy toaleXin accumulation.
Abstract: Five methods of stem inoculation of carnations with conidial suspensions ofFusarium oxysporum f.sp.dianthi were compared for uptake of the suspension, induction of phytoalexin accumulation and wilt development. Inoculation was performed by incision of the stem across droplets of inoculum placed on leaves, or by injection of droplets into the stem. With both methods, higher inoculum dosages led to higher wilting rates and higher phytoalexin concentrations. Injection was more effective than incision since a lower inoculum dosage was required to obtain the same phytoalexin levels. Injection therefore appears the most promising technique for the development of routine screening methods for resistance based on phytoalexin accumulation.
TL;DR: This paper found that Mandarin cell suspension cultures did not give a typical hypersensitive response (HR) when challenged with a fungal elicitor or an incompatible strain of the soybean leaf pathogen Pseudomonas syringae cv. glycinea (Psg).
TL;DR: Changes in pH values at the moment of elicitation of carrot cell suspension cultures influenced the amounts of both phytoalexins synthesized.
TL;DR: The two phytoalexins accumulated in limited lesions (resistant reaction) in plant tissue in response to inoculation with B. cinerea at the same time as the growth of infection hyphae was restricted within the lesions, reaching 300–400 μg g −1 dry wt of tissue.
Journal Article•
TL;DR: Low concentrations of the plant hormones augmented the response of Phaseolus vulgaris to limiting concentrations of cell wall elicitors of Colletotrichum lindemuthianum, as measured by changes in the activity of enzymes of the flavonoid pathway.
Abstract: The effect of IAA and 2,4-D on the response of Phaseolus vulgaris to limiting concentrations of cell wall elicitors of Colletotrichum lindemuthianum was investigated in attached leaves of both the susceptible, Pinto, and resistant, Kievit, cultivars. Low concentrations of the plant hormones augmented the response, as measured by changes in the activity of enzymes of the flavonoid pathway (phenylalanine ammonia-lyase (PAL) and ρ-coumaric acid coenzyme-A ligase (ρ-CL)) and phytoalexin concentration, both cultivars. (...)
TL;DR: In this article, the α and β races of Colletotrichum lindemuthianum and citrus pectic fragments had synergistic effects on the accumulation of phenolics and phyto-alexins in cotyledons of bean, Phaseolus vulgaris.
TL;DR: Metabolites and viable cells of Pseudomonas corrugata from liquid culture medium elicited biosynthesis of the phytoalexin medicarpin in ladino white clover leaflets and callus.
Abstract: Metabolites and viable cells of Pseudomonas corrugata from liquid culture medium elicited biosynthesis of the phytoalexin medicarpin in ladino white clover (Trifolium repens) leaflets and callus. The biologically active elicitor components were soluble in 80% ethanol. They were partially purified by removing components greater than 3,500 Da by dialysis and fractionating by preparative reversed-phase high-performance liquid chromatogrpahy (HPLC). None of the four fractions separated by HPLC elicited appreciable quantities of medicarpin in callus, but fraction 1 combined with fraction 4 elicited high concentrations of medicarpin (...)
TL;DR: Phytoalexins were elicited in the peanut by wounding (by slicing) and incubating the seed slices at 25 °C in the dark and Chromatographic analysis of the purified extract from 4-day incubated seed slices showed the presence of seven phy toalexin compounds.
TL;DR: The results suggest that phytoalexins do not control VAM development and emphasize the fact that the use of biocides can modify the physiological state of the root system and the plant-VAM fungus interaction.
01 Jan 1990
TL;DR: It is well documented that molecules from plant pathogenic fungi have the ability to induce both hypersensitive-type cell necrosis and/or phytoalexin accumulation in plant cells.
Abstract: Active defense of plants against fungal or bacterial pathogens often involves the rapid death of cells in intimate contact with the invading microorganism. Accompanying this so-called hypersensitive response (HR) are rapid localized changes in host metabolism which lead to the synthesis of potential defensive barriers; these include the accumulation of low Mr antimicrobial compounds termed phytoalexins, the deposition of phenolic material and hydroxyproline-rich glycoproteins (HRGPs) in the host cell wall, and the synthesis of hydrolytic enzymes. The exact relationship between the HR and phytoalexin accumulation is still somewhat vague; in some systems, hypersensitive cell death appears to be a pre-requisite for induction and accumulation of phytoalexins in neighboring healthy cells (Bailey 1982), whereas phytoalexin synthesis can be initiated in suspension cultured cells in the absence of serious effects on cell viability (Hamdan and Dixon 1986). It is, however, well documented that molecules from plant pathogenic fungi have the ability to induce both hypersensitive-type cell necrosis and/or phytoalexin accumulation in plant cells. These so-called elicitors often originate from the fungal cell wall.
TL;DR: Roots of intact soybean plants released 50–60% of stress metabolites synthesized into the medium after induction with an abiotic elicitor, or following infection with zoospores of Phytophthora megasperma f.
Journal Article•
TL;DR: In a separate experiment, the concentrations of the same elicited phytoalexins were measured in cotton leaves treated with the fungal elicitor and maintained at different levels of plant moisture stress.
TL;DR: Results suggested that the two components of the purified suppressor could hardly exhibit race specific activity, and that the specific suppressor activity occurred when the other components (of the glucan) existed.
Abstract: A glucan, hypersensitivity-suppressor, was isolated from fungal homogenates of Phytophthora infestans (Mont.) de Bary, and purified by using high performance liquid chromatography (HPLC). The active glucan fraction from both compatible and incompatible races consists of two components with Mr of 4, 700 and 280. Suppressor activity was analyzed by the phytoalexin accumulation as a biochemical marker of the hypersensitive reaction of potato tuber cells. The partially purified preparations showed an activity of the suppressor at 25-50μg/disks (14mm in diameter), whereas the purified components with Mr of 4, 700 and 280 from the two races showed little significant difference to inhibit the phytoalexin accumulation at the same concentration. The HPLC analysis of germinating fluid of the fungus demonstrated that the fungus produced the suppressor glucan with Mr of 280 and 30, 000 at the early infection period. These results suggested that the two components of the purified suppressor could hardly exhibit race specific activity, and that the specific suppressor activity occurred when the other components (of the glucan) existed. It was shown that the suppressor component with Mr of 280 had a close Rf value to glucose monomer in thin-layer chromatography assay.