Showing papers on "Phytoalexin published in 1997"
TL;DR: In this article, the authors demonstrate a causal relationship between early and late reactions of parsley cells to the elicitor and indicate a sequence of signaling events from receptor-mediated activation of ion channels via ROS production and defense gene activation to phytoalexin synthesis.
Abstract: Fungal elicitor stimulates a multicomponent defense response in cultured parsley cells (Petroselinum crispum). Early elements of this receptor-mediated response are ion fluxes across the plasma membrane and the production of reactive oxygen species (ROS), sequentially followed by defense gene activation and phytoalexin accumulation. Omission of Ca2+ from the culture medium or inhibition of elicitor-stimulated ion fluxes by ion channel blockers prevented the latter three reactions, all of which were triggered in the absence of elicitor by amphotericin B-induced ion fluxes. Inhibition of elicitor-stimulated ROS production using diphenylene iodonium blocked defense gene activation and phytoalexin accumulation. O2− but not H2O2 stimulated phytoalexin accumulation, without inducing proton fluxes. These results demonstrate a causal relationship between early and late reactions of parsley cells to the elicitor and indicate a sequence of signaling events from receptor-mediated activation of ion channels via ROS production and defense gene activation to phytoalexin synthesis. Within this sequence, O2− rather than H2O2 appears to trigger the subsequent reactions.
558 citations
TL;DR: Proteins encoded by jasmonate-induced genes include enzymes of alkaloid and phytoalexin synthesis, storage proteins, cell wall constituents and stress protectants, and the wound-induced formation of proteinase inhibitors is a well-studied example.
535 citations
01 Jan 1997
TL;DR: A causal relationship between early and late reactions of parsley cells to the elicitor is demonstrated and a sequence of signaling events from receptor-mediated activation of ion channels via ROS production and defense gene activation to phytoalexin synthesis is indicated.
Abstract: Fungal elicitor stimulates am ulticomponent defense response in cultured parsley cells (Petroselinum crispum). Early elements of this receptor-mediated response are ion fluxes across the plasma membrane and the produc- tionofreactiveoxygenspecies(ROS),sequentiallyfollowedby defense gene activation and phytoalexin accumulation. Omis- sion of Ca 21 from the culture medium or inhibition of elicitor-stimulated ion fluxes by ion channel blockers pre- vented the latter three reactions, all of which were triggered in the absence of elicitor by amphotericin B-induced ion fluxes.Inhibitionofelicitor-stimulatedROSproductionusing diphenylene iodonium blocked defense gene activation and phytoalexin accumulation. O2 but not H2O2stimulated phy- toalexin accumulation, without inducing proton fluxes. These results demonstrate a causal relationship between early and late reactions of parsley cells to the elicitor and indicate a sequence of signaling events from receptor-mediated activa- tion of ion channels via ROS production and defense gene activation to phytoalexin synthesis. Within this sequence, O2 ratherthanH2O2appearstotriggerthesubsequentreactions.
513 citations
TL;DR: Interestingly, each combination of double mutants between pad1-1, pad2-1 and pad3-1 exhibited additive shifts to moderate or full susceptibility to most of the isolates, indicating that PAD4 has a regulatory function.
Abstract: We are working to determine the role of the Arabidopsis phytoalexin, camalexin, in protecting the plant from pathogen attack by isolating phytoalexin-deficient (pad) mutants in the accession Columbia (Col-0) and examining their response to pathogens. Mutations in PAD1, PAD2, and PAD4 caused enhanced susceptibility to the bacterial pathogen Pseudomonas syringae pv. maculicola strain ES4326 (PsmES4326), while mutations in PAD3 or PAD5 did not. Camalexin was not detected in any of the double mutants pad1-1 pad2-1, pad1-1 pad3-1 or pad2-1 pad3-1. Growth of PsmES4326 in pad1-1 pad2-1 was greater than that in pad1-1 or pad2-1 plants, while growth in pad1-1 pad3-1 and pad2-1 pad3-1 plants was similar to that in pad1-1 and pad2-1 plants, respectively. The pad4-1 mutation caused reduced camalexin synthesis in response to PsmES4326 infection, but not in response to Cochliobolus carbonum infection, indicating that PAD4 has a regulatory function. PAD1, PAD2, PAD3 and PAD4 are all required for resistance to the eukaryotic biotroph Peronospora parasitica. The pad4-1 mutation caused the most dramatic change, exhibiting full susceptibility to four of six Col-incompatible parasite isolates. Interestingly, each combination of double mutants between pad1-1, pad2-1 and pad3-1 exhibited additive shifts to moderate or full susceptibility to most of the isolates.
369 citations
TL;DR: Results provide the first direct evidence that cucumber plants produce elevated levels of phytoalexins in response to an eliciting treatment after infection, and are likely liberated from conjugated phenolics by enzymatic hydrolysis in planta.
Abstract: Phenolic compounds extracted from cucumber (Cucumis sativus L) leaves were separated and analyzed for their differential presence and fungitoxicity in relation to a prophylactic treatment with Milsana (Compo, Munster, Germany) against powdery mildew (Sphaerotheca fuliginea) Based on our extraction and purification procedures, at least eight separate phenolic compounds with antifungal activity were identified as intrinsic components of cucumber plants Of these compounds, six displayed a significant increase in concentration as a result of elicitation with Milsana, this being particularly evident when the plant was stressed by the pathogen The combined amounts of these antifungal compounds in treated plants was nearly five times the level found in control plants One week after Milsana application, some of the antifungal compounds obtained through hydrolysis of their glycosidic links were also detected in their free form, indicating that they are likely liberated from conjugated phenolics by enzymatic hydrolysis in planta To our knowledge, these results provide the first direct evidence that cucumber plants produce elevated levels of phytoalexins in response to an eliciting treatment after infection
192 citations
TL;DR: The accumulation of the phytoalexin trans-resveratrol, the product of stilbene synthase, was detectable shortly after fungal inoculation, resulting in a significant increase in the resistance of transgenic tomato to Phytophthora infestans.
156 citations
TL;DR: This result, together with earlier results, suggests that the hydroxyl group at the C-1 position is the main functional moiety for the high antifungal activity of phytocassane E.
100 citations
TL;DR: A natural free radical scavenger, ascorbic acid (AsA) shows both counteractive and enhancing effects on JA‐inducible phytoalexin production, depending on its concentration, which suggests that active oxygen species (AOS) may play important roles in phy toalex in production by JA in rice leaves.
94 citations
TL;DR: The data imply for the first time that the expression of phenylpropanoid genes in grapevine is induced by SAR activators without phenotypic consequences and suggest a role for CCoAOMT and stilbene synthase in the disease-resistance response leading beyond the level of pathogenesis-related proteins as markers of the SAR.
Abstract: Cell-suspension cultures of Vitis vinifera L cv Pinot Noir accumulated resveratrol upon fungal elicitation, and the activity of S-adenosyI-L-methionine:trans-caffeoyl-coenzyme A 3-O-methyl-transferase (CCoAOMT), yielding feruloyl-CoA, increased to a transient maximum at 12 to 15 h CCoAOMT cDNA was cloned from the elicited cells and was shown to encode a polypeptide highly homologous to CCoAOMTs from cells of Petroselinum species or Zinnia species The expression of the cDNA in Escherichia coli revealed that grapevine CCoAOMT methylates both caffeoyl-and 5-hydroxyferuloyl-coenzyme A and is probably involved in phenolic esterification and lignification Commercial plant activators induce the disease-resistance response of test plants and are considered to mimic the action of salicylic acid Among these chemicals, 2,6-dichloroisonicotinic acid and benzo(1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester provoke systemic acquired resistance (SAR) and were also shown to induce the expression of class III chitinase in grapevine The SAR response is classified by an unchanged phenotype of tissues, but the mechanistic basis is unknown Treatment of the cultured V vinifera cells with either fungal elicitor or low concentrations of salicylic acid and 2,6-dichloroisonicotinic acid, respectively, raised the CCoAOMT or stilbene synthase transcript abundance, suggesting that grapevine is capable of the SAR response, whereas benzo(1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester was ineffective The data imply for the first time (to our knowledge) that the expression of phenylpropanoid genes in grapevine is induced by SAR activators without phenotypic consequences and suggest a role for CCoAOMT and stilbene synthase in the disease-resistance response leading beyond the level of pathogenesis-related proteins as markers of the SAR
90 citations
TL;DR: A negative correlation was found between the potential for resveratrol accumulation in different cultivars and their susceptibility to decay caused by R. stolonifer, coinciding with their increased susceptibility.
89 citations
TL;DR: Genetic differences in phytoalexin response between rice cultivars are likely to play an important role among the many factors that determine differences in blast resistance between different rice genotypes.
TL;DR: Amino acid conjugates of jasmonic acid are found to elicit production of the flavonoid phytoalexin, sakuranetin in rice leaves and are speculated to be the later component in the signaling transduction chain in stressed rice plants.
TL;DR: The isolation and synthesis of 4-hydroxy-benzylisothiocyanate, the major antifungal component isolated from extracts of white mustard, and optimized conditions for the isolation of the phytotoxin destruxin B are described.
TL;DR: An ecological role for tolytoxin as an inducible chemical defense agent (phytoalexin) capable of protecting S. ocellatum against fungal invasion is suggested.
Abstract: The addition of fungal cell-wall homogenates of Penicillium notatum and Cylindrocladium spathiphylli markedly stimulated the accumulation of tolytoxin, an antifungal secondary metabolite, in cultures of the cyanobacterium Scytonema ocellatum Lyngbye ex Bornet et Flahault. Evaluation of polysaccharides, proteins, and other polymers established that a limited range of polysaccharides, especially chitin and carboxymthylcellulose, selectively elicited enhanced tolytoxin accumulation in S. ocellatum. The elicitor activity of fungal cell-wall preparations could be correlated with the chitin content of the preparation. Polymeric chitin was half-maximally effective at a concentration (EC50) of 19 mg.L-1, whereas chitin oligoments were more effective (EC50= 3.3 mg.L-1) in eliciting enhanced tolytoxin accumulation. The elicitor activity of either purified chitin or an elicitor-active fungal cell-wall preparation could be destroyed by treatment with chitinase. The results suggest an ecological role for tolytoxin as an inducible chemical defense agent (phytoalexin) capable of protecting S. ocellatum against fungal invasion.
TL;DR: In soybean H2O2 and O2− may not be directly responsible for phytoalexin production, but may be an independent defence response, as indicated by inhibitor studies.
TL;DR: The major compound produced by scab-resistant cells in response to the challenge has been identified as the 2,4-methoxy-3-hydroxy-9-O-beta-D-glucosyloxydibenzofuran by UV, mass spectrometry, (1)H-nuclear magnetic resonance (NMR), and (13)C-NMR spectroscopy and the trivial name malusfuran is suggested.
Abstract: Cell suspension cultures of the scab-resistant apple (Malus × domestica) cultivar Liberty were challenged with yeast extract to mimic the effect of biological stress such as fungal invasion. The cells responded to the challenge by production of novel compounds. Suspension cultures of the scab-susceptible cultivar McIntosh, when similarly challenged, showed no detectable response. The major compound produced by scab-resistant cells in response to the challenge has been identified as the 2,4-methoxy-3-hydroxy-9-O-β-D-glucosyloxydibenzofuran by UV, mass spectrometry, 1H-nuclear magnetic resonance (NMR), and 13C-NMR spectroscopy. We suggest the trivial name malusfuran for the compound. Malusfuran production was initiated approximately 24 h after being challenged. Malusfuran inhibited spore germination and growth of Venturia inaequalis at millimolar concentrations, indicating its role as a possible phytoalexin. The aglycone of malusfuran, 2,4-methoxy-3,9-hydroxy-dibenzofuran, showed higher toxicity to...
TL;DR: Results indicate that 2,6-dimethyl-3-hydroxy-4H-pyran-4-one (DHP) is a novel exogenous low molecular weight neurotrophic substance without apparent cytotoxicity and may be a useful prototype leading chemical for developing therapeutic and/or prophylactic drugs for neurodegenerative disorders.
TL;DR: A new phytoalexin was induced and isolated from papaya fruit slices treated with copper salts and showed high antifungal activity against Colletotrichum gloesporioides, a pathogenic fungus of papaya.
TL;DR: Assessment of phytoalexin production by the host during defense responses cannot replace monitoring of external symptoms as a resistance test, but assessment of fungal growth, whether by reisolations above the compartmentalization area or by measurement of PG activity, provides a both rapid and reliable prediction of disease development.
Abstract: Carnation cultivars with different levels of partial resistance were inoculated with race 2 of Fusarium oxysporum f.sp. dianthi and monitored for accumulation of host phytoalexins, fungal escape from compartmentalization, production of fungal pectin-degrading enzymes and development of external disease symptoms. Accumulation of phytoalexins, assessed after 10 days in the first 5 cm above the inoculation site, was weakly (methoxydianthramide S) or not (hydroxydianthalexin B) correlated with resistance levels after 12 weeks. Fungal escape from compartmentalization, assessed after 3 weeks as percentages colonized plants at 8 cm above the inoculation site, was highly correlated with expression of susceptibility after 12 weeks. Polygalacturonase (PG) activity, assessed after 4 weeks in the first 5 cm above the inoculation site, was highly correlated to final disease development. Linear increases in disease severity were accompanied by quadratic increases in PG activity. In contrast to water-treated plants, that lacked any PG activity, inoculated plants contained two main groups of fungal PGs, the dominant forms of which had estimated pI values of 7.0 and minimally 9.5, respectively. Compared to those of the first group, enzymes of the second group were produced only in trace amounts in liquid media containing pectin or polygalacturonate as sole source of carbon. On these media, the fungus also produced a pectin methyl esterase (PME) with an estimated pI of 9.3. Besides PMEs of host origin, inoculated plants of susceptible cultivars contained the fungal PME while no more than traces were found in resistant ones.
TL;DR: In this paper, the biotransformation of three methyl benzyldithiocarbamates by the blackleg fungus (Leptosphaeriamaculans (Desm.) Ces. et de Not., asexual stage Phomalingam (Tode ex Fr.) Desm) was investigated.
Abstract: The biotransformation of three methyl benzyldithiocarbamates by the blackleg fungus (Leptosphaeriamaculans (Desm.) Ces. et de Not., asexual stage Phomalingam (Tode ex Fr.) Desm) was investigated. The main biotransformation products were isolated and their chemical structures were determined by spectroscopic methods. Similarly to our previous studies with the phytoalexin brassinin, these results suggest that virulent blackleg isolates are significantly more effective in metabolizing benzyldithiocarbamates than the related avirulent isolates. Keywords: benzyldithiocarbamates, brassinin, Leptosphaeriamaculans, Phomalingam, phytoalexins.
Journal Article•
TL;DR: It is proposed that in L. albus simple isoflavones - and not pterocarpans - are major stress metabolites, possibly fulfilling the role of lupin's phytoalexins.
TL;DR: Cell components were extracted and purified from cells of compatible and incompatible isolates of Xanthomonas campestris pv.
Abstract: Cell components (lipopolysaccharide (LPS), exopolysaccharide (EPS), capsular glycoproteins and the cell envelope) were extracted and purified from cells of compatible and incompatible isolates of Xanthomonas campestris pv. vesicatoria and infiltrated into pepper leaves in an attempt to protect them against a compatible isolate. All cell components induced protection but only EPS and the cell envelope elicited phytoalexins. Therefore, resistance mechanisms other than phytoalexins may exist in pepper leaves and appear to be more effective than phytoalexins.
Patent•
21 Apr 1997
TL;DR: In this paper, a method of screening an elicitor inducing the production of a phytoalexin in rice is proposed, which involves using a young rice plant as a test plant, treating an appropriate part of the young rice plants with a test sample and screening an elicit by using the phythealexins thus formed in the plant as an indication.
Abstract: A method of screening an elicitor inducing the production of a phytoalexin in rice which comprises using a young rice plant as a test plant, treating an appropriate part of the young rice plant with a test sample and screening an elicitor by using the phytoalexin thus formed in the plant as an indication; and a rice disease controlling agent containing as the active ingredient a specific compound capable of inducing the production of a phytoalexin in rice.
TL;DR: It is concluded that low functional compatibility of AM, with respect to P supply and plant growth stimulation by the fungus, is not associated with a defence-like response (glyceollin I) by the plant.
TL;DR: Evidence is presented that the primary metabolite (-)6a-OH-maackiain is subsequently hydroxylated at carbon 6, a step resulting in a compound that is increased in polarity and decreased in toxicity relative to the parent compound and (-)7-trihydroxy-8,9,methylenedioxy-pterocarpan.
TL;DR: In this paper, a cassane-type diterpene, designated phytocassane E, was isolated and identified as 1β-hydroxy-12,15-cassadien-3,11-dione.
Abstract: Large amounts of phytoalexins were produced in suspension-cultured rice cells by treatment with a mycelial extract of the potato pathogenic fungus Phytophthora infestans. Among them, a new cassane-type diterpene, designated phytocassane E, was isolated and identified as 1β-hydroxy-12,15-cassadien-3,11-dione. The ED50 values of phytocassane E in the prevention of spore germination and germ tube growth of the rice pathogenic fungus Magnaporthe grisea were 6 and 2 μg ml−1, respectively. This result, together with earlier results, suggests that the hydroxyl group at the C-1 position is the main functional moiety for the high antifungal activity of phytocassane E.
TL;DR: It is suggested that the methylation inhibitor tubericidin selectively inhibits the accumulation of isoflavones, with the flavone and licodione accumulating as alternative phytoalexins.
TL;DR: Treatment of cell suspension cultures of soybean, alfalfa, or tobacco with macromolecular elicitors resulted in the release of low molecular mass endogenous elicitors that could pass through a dialysis membrane into the surrounding culture medium.
TL;DR: Comparisons were made between two breeding lines of faba bean, following inoculation of leaf material with Botrytis cinerea and the more aggressive B. fabae, suggesting that differential levels of abscission are a consequence of differences in the biosynthesis of ethylene in the two lines rather than in their responses to ethylene.
Abstract: Comparisons were made between two breeding lines of faba bean (designated 224 and 335), following inoculation of leaf material with Botrytis cinerea and the more aggressive B. fabae. Line 335 exhibited greater initial resistance to infection, in terms of retarded lesion development and higher rates of phytoalexin production. However, in whole plant inoculation experiments line 335 abscinded its leaflets more readily after infection. The role of the gaseous plant hormone ethylene in this reaction was analysed. Both lines exhibited a similar abscission response to exogenous ethylene, applied at a concentration of 10 μL L−1. However, there were significant differences in the ability of the lines to produce ethylene. In response to inoculation with B. fabae, line 335 liberated ethylene at a higher concentration and for a longer period. These results suggest that the differential levels of abscission are a consequence of differences in the biosynthesis of ethylene in the two lines rather than in their responses to ethylene.
TL;DR: It is concluded that the increased activity of the activated methyl cycle during defence interactions in alfalfa is required to support phytoalexin synthesis and cell wall modifications.
Abstract: In order to determine why the activated methyl cycle is up-regulated in plants undergoing defence responses to fungal pathogens we have monitored the utilisation of methyl groups derived from methionine in cell-suspension cultures of alfalfa (Medicago sativa L.) treated for various times with fungal elicitor, by carrying out a parallel labelling study with [35S]methionine and [methyl-3H]methionine. The distribution of the two radiolabels among the medium, soluble cellular components and cell wall was then determined. In the absence of elicitor the utilisation of the two radiolabels was similar. However, in the presence of the elicitor the total incorporation of radioactivity from [methyl-3H]methionine into metabolites was far greater than from [35S]methionine, indicating that the methyl label had been utilised in methylation reactions. Elicitor treatment resulted in up to a sixfold increase in the use of 3H-methyl groups in the methylation of hydrophobic metabolites. In the period 0–24 h after elicitor treatment, increased methylation was directed largely into the synthesis of the isoflavonoid phytoalexin medicarpin and related metabolites. Newly synthesized phytoalexins were exported into the medium, while a significant proportion of the medicarpin accumulating in the cell in the early stages of elicitation was derived from the hydrolysis of its respective conjugate. Elicitor treatment also modified the incorporation of 3H-methyl groups into the cell wall. Between 0 and 24 h after elicitor treatment the methylation of pectin in the cell wall declined. After 24 h, pectin methylation recovered and was associated with an increase in the methylation of other wall-bound polysaccharide components. Since no other major metabolic sink for the increased methylation was determined we conclude that the increased activity of the activated methyl cycle during defence interactions in alfalfa is required to support phytoalexin synthesis and cell wall modifications.