Showing papers on "Phytoalexin published in 2005"
TL;DR: ISR was blocked in Arabidopsis mutants npr1-1, eds5/sid1, and sid2, indicating that components of the pathway from isochorismate and a functional NPR1 play a crucial role in the K165-mediated ISR.
Abstract: The biocontrol bacterium Paenibacillus alvei K165 has the ability to protect Arabidopsis thaliana against Verticillium dahliae. A direct antagonistic action of strain K165 against V. dahliae was ruled out, making it likely that K165-mediated protection results from induced systemic resistance (ISR) in the host. K165-mediated protection was tested in various Arabidopsis mutants and transgenic plants impaired in defense signaling pathways, including NahG (transgenic line degrading salicylic acid [SA]), etr1-1 (insensitive to ethylene), jar1-1 (insensitive to jasmonate), npr1-1 (nonexpressing NPR1 protein), pad3-1 (phytoalexin deficient), pad4-1 (phytoalexin deficient), eds5/sid1 (enhanced disease susceptibility), and sid2 (SA-induction deficient). ISR was blocked in Arabidopsis mutants npr1-1, eds5/sid1, and sid2, indicating that components of the pathway from isochorismate and a functional NPR1 play a crucial role in the K165-mediated ISR. Furthermore, the concomitant activation and increased transient accumulation of the PR-1, PR-2, and PR-5 genes were observed in the treatment in which both the inducing bacterial strain and the challenging pathogen were present in the rhizosphere of the A. thaliana plants.
218 citations
TL;DR: Results tend to confirm that wheat plants fed with Si can produce phytoalexins in response to powdery mildew infection.
199 citations
TL;DR: The pathways used by plant pathogenic fungi to metabolize and detoxify phytoalexins are reviewed and prospects for application of recent findings are discussed.
166 citations
TL;DR: All vst and pss transgenic lines accumulated stilbene derivatives upon induction by UV light and the detected stilbenes showed a remarkable similarity to resveratrol and pinosylvin, however were found to be more hydrophilic than resver atrol andPinus sylvestris, and none of the four tested pss expressing lines showed a reduction in disease incidence.
79 citations
TL;DR: The results of this study support the idea that induced resistance in cucumber is largely correlated with rapid de novo biosynthesis of flavonoid phytoalexin compounds.
Abstract: In this study, cucumber plants (Cucumis sativus) expressing induced resistance against powdery mildew (caused by Podosphaera xanthii) were infiltrated with inhibitors of cinnamate 4-hydroxylase, 4-coumarate:CoA ligase (4CL), and chalcone synthase (CHS) to evaluate the role of flavonoid phytoalexin production in induced disease resistance. Light and transmission electron microscopy demonstrated ultrastructural changes in inhibited plants, and biochemical analyses determined levels of CHS and β-glucosidase enzyme activity and 4CL protein accumulation. Our results showed that elicited plants displayed a high level of induced resistance. In contrast, down regulation of CHS, a key enzyme of the flavonoid pathway, resulted in nearly complete suppression of induced resistance, and microscopy confirmed the development of healthy fungal haustoria within these plants. Inhibition of 4CL ligase, an enzyme largely responsible for channeling phenylpropanoid metabolites into the lignin pathway, had little effec...
65 citations
TL;DR: It is proposed that luteoforol is released upon pathogen attack from its cellular compartment and inhibits further disease development by destroying pathogen cells as well as by inducing a hypersensitive-like reaction in the host plant tissue.
Abstract: Treatments with prohexadione-calcium led to lowered incidence of fire blight, scab and other diseases in pome fruit trees and other crop plants. In addition to acting as a growth regulator, prohexadione-calcium interferes with flavonoid metabolism and induces the accumulation of the 3-deoxycatechin luteoliflavan in shoots of pome fruit trees. Luteoliflavan does not possess any remarkable antimicrobial activity. Therefore luteoforol, its unstable and highly reactive precursor, has been tested in vitro for its bactericidal and fungicidal activities. Luteoforol was found to be highly active against different strains of Erwinia amylovora, the causal agent of fire blight, and all other bacterial and fungal organisms tested. Phytotoxic effects were also observed in pear plantlets. The results obtained indicate that prohexadione-calcium induces luteoforol as an active principle with non-specific biocidal properties. It is proposed that luteoforol is released upon pathogen attack from its cellular compartment and inhibits further disease development by destroying pathogen cells as well as by inducing a hypersensitive-like reaction in the host plant tissue. This mechanism would be closely analogous to the one known for structurally related phytoalexins in sorghum.
59 citations
TL;DR: The results seem to indicate that in carnation the concentration of some preformed antifungal flavonoids may be significantly increased by a fungal presence: owing to their fungitoxic properties, these molecules could cooperate, together with the unconstitutive and postinfectional anthranilic acid-derivative phytoalexins, to the plant defensive response against Fusarium attacks.
Abstract: The fungitoxic flavonol triglycoside, kaempferide 3-O-[2 G -β-D-glucopyranosyl]-β-rutinoside, is a constituent of the carnation cultivar 'Novada', known as one of the most resistant cultivar to Fusarium oxysporum f. sp. dianthi, causative agent of Fusarium wilt. Due to its constitutive presence within the carnation tissues, this antifungal flavonol should be considered as a phytoanticipin; its biosynthesis, however, is stimulated by the inoculation with F. oxysporum f. sp. dianthi, just as is the rule for a typical phytoalexin. The results seem to indicate that in carnation the concentration of some preformed antifungal flavonoids may be significantly increased by a fungal presence: owing to their fungitoxic properties, these molecules could cooperate, together with the unconstitutive and postinfectional anthranilic acid-derivative phytoalexins, to the plant defensive response against Fusarium attacks.
45 citations
TL;DR: An inability by “P” strains to induce high levels of phytoalexins in cotton, not only makes them ineffective as biocontrol agents, but renders them pathogenic to susceptible cultivar seed lots.
41 citations
TL;DR: In vitro experiments showed that resveratrol and its glucoside in fact could contribute to improving the pathogen resistance of apple leaves.
Abstract: Resveratrol is a phytoalexin produced in different unrelated plant species such as grapevine and peanut. The effect of resveratrol and its glucoside trans-resveratrol-3-O-β-d-glycopyranosid (piceid) against Venturia inaequalis, the causal agent of apple scab, was evaluated using a newly established test based on enzymatically isolated cuticular membranes (CMs) from apple (Malus domestica Borkh.) leaves. The test substances resveratrol and piceid were either sorbed to CMs before inoculation with spores or were applied simultaneously with the Venturia inaequalis spores to the CMs, and their effect on germination, appressoria formation, and penetration was examined. Resveratrol had no influence on spore germination but a significant inhibiting effect on penetration when applied simultaneously as well as before. A percentage inhibition of 89.7 ± 11.5 and 61.8 ± 35.1 was observed for simultaneous and preapplication, respectively. The resveratrol glucoside piceid had a significant inhibitory effect on germinati...
37 citations
TL;DR: This, the first report of induction of phytoalexin biosynthesis by an insect elicitor, suggests that Bruchin B not only stimulates neoplasm formation, but also activates other plant defence responses.
Abstract: Bruchins, mono and bis (3-hydroxypropanoate) esters of long chain alpha,omega-diols, are a recently discovered class of insect elicitors that stimulate cell division and neoplasm formation when applied to pods of peas and certain other legumes. Differential display analysis resulted in the identification of an mRNA whose level was increased by the application of Bruchin B to pea pods. The corresponding amplification product was cloned and sequenced and a full length cDNA sequence was obtained. This cDNA and the gene from which it was derived were assigned the name CYP93C18 based upon sequence similarities to the cytochrome P450 mono-oxygenase CYP93C subfamily, which contains isoflavone synthase genes from legumes. RNA gel blots and quantitative RT-PCR demonstrated that expression of CYP93C18 increased within 8 h of bruchin treatment to a maximum of 100-200-fold of the level in untreated pods, and then declined. The up-regulation of CYP93C18 was followed by an increase in the level of the isoflavone phytoalexin, pisatin. Pisatin was detectable in the bruchin-treated pods after 16 h and reached a maximum between 32 h and 64 h. This, the first report of induction of phytoalexin biosynthesis by an insect elicitor, suggests that Bruchin B not only stimulates neoplasm formation, but also activates other plant defence responses.
31 citations
TL;DR: The non-host penetration resistance to A. alternata was clearly associated with activation of the jasmonate- and ethylene-signalling pathways and analysis using histochemical staining of GUS activity suggests that defence reactions in non- host penetration resistance are activated locally.
Abstract: SUMMARY When challenged with the necrotrophic fungal pathogen Alternaria alternata Japanese pear pathotype, all tested ecotypes of Arabidopsis plants failed to show hypersensitive cell death, accumulation of detectable levels of reactive oxygen species or accumulation of phytoalexin. We operationally define A. alternata as a non-host pathogen for Arabidopsis plants and show that the protection against A. alternata demonstrated in this study is a non-host penetration resistance. To characterize non-host penetration resistance, we examined the expression patterns of c. 7000 genes by cDNA microarray analysis in Arabidopsis Col-0 plants after inoculation with A. alternata. After inoculation with A. alternata, the transcript levels of 48 genes increased in Col-0 plants. The expression of genes associated with hypersensitive reaction was induced in the non-host penetration resistance to A. alternata, despite the fact that A. alternata had no visible effect on the plants. The non-host penetration resistance to A. alternata was clearly associated with activation of the jasmonate- and ethylene-signalling pathways. In addition, analysis using histochemical staining of GUS activity suggests that defence reactions in non-host penetration resistance are activated locally. The characterization of non-host pathosystem involving Arabidopsis and A. alternata offers an overview of non-host penetration resistance.
TL;DR: The results suggest that apoptosis of NB4 cells induced by resveratrol requires caspase-3 activation and is related to the mitochondrial transmembrane potential, which may be useful in treating acute promyelocytic leukemia.
Journal Article•
TL;DR: Phytoal- exin, an antibiotic compound produced by plants infected with pathogens, can be employed for pathogen con- trol and the natural secondary metabolites for pest control might be one of the alternatives for environmentally friendly agriculture.
Abstract: Pathogens, insects and weeds have significantly reduced agricultural productivity. Thus, to increase the pro- ductivity, synthetic agricultural chemicals have been overused. However, these synthetic compounds that are different from natural products cannot be broken down easily in natural systems, causing the destruction of soil quality and agricultural environments and the gradually difficulty in continuous agriculture. Now agricul- ture is faced with the various problems of minimizing the damage in agricultural environments, securing the safety of human health, while simultaneously increasing agricultural productivity. Meanwhile, plants produce secondary metabolites to protect themselves from external invaders and to secure their region for survival. Plants infected with pathogens produce antibiotics phytoalexin; monocotyledonous plants produce flavonoids and diterpenoids phytoalexins, and dicotylodoneous plant, despite of infected pathogens, produce family-spe- cific phytoalexin such as flavonoids in Leguminosae, indole derivatives in Cruciferae, sesquitepenoids in Solan- aceae, coumarins in Umbelliferae, making the plant resistant to specific pathogen. Growth inhibitor or antifeedant substances to insects are terpenoids pyrethrin, azadirachtin, limonin, cedrelanoid, toosendanin and fraxinellone/dictamnine, and terpenoid-alkaloid mixed compounds sesquiterpene pyridine and norditerpenoids, and azepine-, amide-, loline-, stemofoline-, pyrrolizidine-alkaloids and so on. Also plants produces the sub- stances to inhibit other plant growths to secure the regions for plant itself, which is including terpenoids essen- tial oil and sesquiterpene lactone, and additionally, benzoxazinoids, glucosinolate, quassinoid, cyanogenic glycoside, saponin, sorgolennone, juglone and lots of other different of secondary metabolites. Hence, phytoal- exin, an antibiotic compound produced by plants infected with pathogens, can be employed for pathogen con- trol. Terpenoids and alkaloids inhibiting insect growth can be utilized for insect control. Allelochemicals, a compound released from a certain plant to hinder the growth of other plants for their survival, can be also used directly as a herbicides for weed control as well. Therefore, the use of the natural secondary metabolites for pest control might be one of the alternatives for environmentally friendly agriculture. However, the natural substances are destroyed easily causing low the pest-control efficacy, and also there is the limitation to pro- ducing the substances using plant cell. In the future, effects should be made to try to find the secondary metabolites with good pest-control effect and no harmful to human health. Also the biosynthetic pathways of secondary metabolites have to be elucidated continuously, and the metabolic engineering should be applied to improve transgenics having the resistance to specific pest.
TL;DR: In this article, a saprobe capable of inducing phytoalexin production in soybean cotyledons and in the leaves of tropical Rubiaceae on whose surface it has been found was partially purified and the activity compared to that of a glucan elicitor isolated from Phytophthora sojae.
Abstract: Plants accumulate antimicrobial compounds (phytoalexins) in response to a wide variety of microorganisms. Mucor ramosissimus Samutsevitsch is a saprobe capable of inducing phytoalexin production in soybean cotyledons and in the leaves of tropical Rubiaceae on whose surface it has been found. In the present study, the elicitor from M. ramosissimus was partially purified and the activity compared to that of a glucan elicitor isolated from Phytophthora sojae. Optimal isolation of the elicitor (based on fungal growth, yield of spores and elicitor activity) was achieved by autoclaving spores obtained from nine day-old cultures of the fungus. The elicitor was precipitated with ethanol and purified by chromatography on an anion exchange column, which retained the elicitor, and a Concanavalin A-affinity matrix, to which the elicitor did not bind. The purification resulted in a considerable increase (six-fold) in the specific activity of the elicitor. Neutral sugar composition, analyzed by HPLC, revealed the predominance of mannose, followed by glucose and galactose, whereas colorimetric quantification showed the presence of uronic acids. GC-MS analysis of the elicitor revealed the predominance of glucuronic acid and mannose. These results suggest that fragments of mucoran-type polysaccharides are the phytoalexin elicitors present in the spores of the saprobe M. ramosissimus. Our results also indicate for the first time that soybean cotyledon tissues can recognize fragments of glucuronic-acid heteropolymers as phytoalexin elicitors.
Journal Article•
TL;DR: The accumulation of isoflavonoids has been associated with a incompatible response of soybean roots to infection by the root-knot nematode, and the phytoalexin accumulated in soybean tissues in response to nematodes infection is glyceollin, which is derived from the is oflavonoid precursor daidzein.
Abstract: The accumulation of isoflavonoids has been associated with a incompatible response of soybean roots to infection by the root-knot nematode. Soybean isoflavonoids have been proposed to have many effects on host-pathogen interactions. The phytoalexin accumulated in soybean tissues in response to nematode infection is glyceollin, which is derived from the isoflavonoid precursor daidzein. Accumulation of the isoflavonoids genistin and daidzin and their aglycones genistein and daidzein in soybean roots following inoculation with Meloidogyne incognita race 3 was determined in the whole root system by high performance liquid chromatography (HPLC). The roots were harvested from controls and nematode-inoculated seedlings 1, 3, and 10 days after inoculation. Extractions were made from roots with ethanol and the extracts were analyzed for isoflavonoids by HPLC. There was no significant difference between susceptible cultivar Pickett 71 and the resistant cultivar FT-Cometa one day after inoculation for all isoflavonoids. Daidzein and genistein were detected for all evaluated cultivars inoculated and non-inoculated. The resistant cultivar FT-Cometa showed a higher concentration of daidzein than the Pickett 71 cultivar ten days after inoculation, which ranged from 0.181/100g of root at the first day after inoculation to 1.025 mg/100g of root at tem days after inoculation.
TL;DR: The results suggest that stress induced resistance and accumulation of phytoalexin of plant is required for the adhesion of plant cell wall-plasma membrane.
01 Oct 2005
TL;DR: In vitro pathogen inhibition assays showed that Resveratrol inhibited fungal pathogens of papaya, and lines produced with increased resistance to diseases became available for crossing with SunUp to produce hybrids that have resistance to both virus and fungal diseases.
Abstract: Phytoalexins have been shown to be important natural components in the defense of plants against fungal infection. Resveratrol is a major phytoalexin in grapevine. We conducted in vitro pathogen inhibition assays to show that Resveratrol inhibited fungal pathogens of papaya. Resveratrol at 1.0 mM in V8 agar culture medium inhibited mycelia growth of P. palmivora up to 50% of control. The compound was active against P. palmivora as low as 100 μM. Resveratrol was not as effective against the anthracnose pathogen, Colletotrichum gloeosporiodes. We transformed papaya embryogenic cultures with the stilbene synthase gene cloned from grapevine and driven by its own inducible promoter along with the hygromycin resistance or kanamycin resistance gene under the control of a CaMV35S promoter. The presence of transgenes was confirmed by PCR and Southern blot. Twenty lines of transgenic plants were propagated from tissue cultures for greenhouse assays. Transgenic papaya plants were challenged with oomycete pathogen in greenhouse conditions. Data from greenhouse studies showed that the disease level in transgenic plants was reduced to 35% of the disease level in non-transformed control plants. Papaya lines produced with increased resistance to diseases became available for crossing with SunUp to produce hybrids that have resistance to both virus and fungal diseases.
01 Dec 2005
TL;DR: In this article, the authors studied the mechanism of resistance to Fusarium oxysporum f.sp.vasinfectum induced by some chitosan derivatives in susceptible cotton plants.
Abstract: The present investigation studied the mechanism of resistance to Fusarium oxysporum f.sp.vasinfectum induced by some chitosan derivatives in susceptible cotton plants. Pretreating cotton seeds with chitosan markedly increased cotton resistance to vascular wilt caused by Fusarium oxysporum f.sp. vasinfectum. The five chitosan derivatives tested repressed the pathogen mycelial growth. Chitosans 3, 4 and 8 had a disease score of 0.5:tO.02, 0.6:tO.5 and 0.0 respectively, indicating that the host plants were free from visual symptoms and that these chitosans were the most effective in controlling Fusarium wilt disease. Phytoalexin (gossypol) production was greatly increased with a maximum of 1.16 mg/5gmfresh root tissue in chitosan-treated plants. The level of gossypol was higher in the roots than in the stems and the maximum production of gossypol was achieved in cotton plants treated with the chitosan 3, 4 and 8 and inoculated with the pathogen spores as compared with uninoculated plants.
TL;DR: Metabolic flux analysis by the distribution ratio of common substrate showed that UV-irradiation of etiolated rice seedlings decreased the flux for primary metabolism of gibberellins biosynthesis by half and geranylgeranyl pyrophosphate was used for induction of pimaradiene intermediate as the major phytoalexin.
Abstract: Relative transcript levels of eight rice diterpene cyclases at the branch points of gibberellins and phytoalexins biosynthesis pathway were measured by reverse transcription quantitative PCR. Metabolic flux analysis by the distribution ratio of common substrate showed that UV-irradiation of etiolated rice seedlings decreased the flux for primary metabolism of gibberellins biosynthesis by half (from 62 to 27%) and 41% of geranylgeranyl pyrophosphate was used for induction of pimaradiene intermediate as the major phytoalexin. In comparison, light-illumination used almost all geranylgeranyl pyrophosphate (96%) for gibberellin biosynthesis to stimulate the plant growth and strongly repressed the metabolic flux for phytoalexins biosynthesis.
Journal Article•
TL;DR: Pinosylvin, a natural stilbenoid, might be a new candidate for a potential cancer chemopreventive agent.
Abstract: 748 Pinosylvin (3,5-dihydroxy- trans -stilbene), one of the naturally occurring resveratrol analog found in heartwood and leaves of Pinus species, is a phytoalexin with antioxidant, antifungal, algicidal and nematocidal activities. Based on anti-inflammatory and chemopreventive activities of resveratrol, we have evaluated the effects of pinosylvin on cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) activities in lipopolysaccharide (LPS)-stimulated RAW 264.7 mouse macrophage cells by measuring the production of prostaglandin E 2 (PGE 2 ) and nitric oxide (NO). As a result, pinosylvin exhibited the inhibitory activities in both PGE 2 and NO productions in a dose dependent manner. To elucidate the inhibitory mechanism of pinosylvin on COX-2 and iNOS expression, Western blot analysis and reverse transcription-polymerase chain reaction (RT-PCR) were performed. Pinosylvin suppressed COX-2 and iNOS protein and gene expression. Further study revealed that pinosylvin inhibited NF-κB-DNA binding via the inhibition of IκB-α degradation. In addition, the growth inhibitory effects of pinosylvin against human cancer cells were investigated. Pinosylvin inhibited the growth of HCT116 human colon cancer cells with an IC 50 value of 60 μM by MTT assay at 72 hr incubation. Cell cycle distribution treated by pinosylvin (60 μM) exhibited G 0 /G 1 phase arrest. Checkpoint proteins of cyclin D1, cdk4 and proliferating cell nuclear antigen (PCNA) related to G 0 /G 1 phase were down-regulated by pinosylvin. Taken together, pinosylvin, a natural stilbenoid, might be a new candidate for a potential cancer chemopreventive agent.
TL;DR: Salicylic acid was applied to eight-week-old pea plants to determine if it could induce the synthesis of pisatin, the pea phytoalexin, and there was an increase in the phenylalanine ammonia-lyase activity and phenolic contents in plants treated with SA and spores of E. polygoni.
Abstract: Accumulation of phytoalexin is a host defense mechanism against invading pathogens. It is not clear if phytoalexins can be produced in sufficient quantity by exogenous treatment of plants with elicitors. Salicylic acid (SA) was applied at 1, or 3 or 5 mM concentrations to eight-week-old pea plants to determine if it could induce the synthesis of pisatin, the pea phytoalexin. Other plants were inoculated with Erysiphe polygoni. There was an increase in the phenylalanine ammonia-lyase activity and phenolic contents in plants treated with SA and spores of E. polygoni. Plants treated with 1 and 3 mM SA showed minor variations in phenylalanine ammonia-lyase activity and phenolic contents and did not accumulate detectable amounts of pisatin. Treatment with 5 mM SA increased pisatin and phenolic contents in susceptible pea plants.
TL;DR: It was found that the transduction of physical signal and the chemical signal in the plant depended on the adhesion between cell wall and plasma and active oxidative species producted by stimulation.
DOI•
08 Apr 2005
TL;DR: In this paper, the role of phytoalexins accumulated in potato tuber slices inoculated with Fusarium solani caused the potato dry rot on disease resistance or susceptibility.
Abstract: The present investigation was aimed to study the role of phytoalexins accumulated in potato tuber slices inoculated with Fusarium solani caused the potato dry rot on disease resistance or susceptibility. Potato tuber slices inoculated with F. solani were incubated at two different regimes of temperature i.e., 16oC or 25oC. Disease severity on slices incubated at 25oC was very higher than that found on slices incubated at 16oC. This observation was opposite to phytoalexins accumulated at 16oC whereas the intensity of phytoalexin spots separated by TLC was very intensive than that accumulated at 25oC. The role of phytoalexins accumulated in potato tuber slices inoculated with F. solani incubated at 16oC was studied by inhibiting of biosynthesis of them in inoculated slices by HMG-CoA reductase (3-hydroxy-3-methylglutaryl-CoA reductase) inhibitor. This treatment led to increase disease severity of Fusarium infection accompanied by disappearance of phytoalexin spots on TLC and benzene extracts of such slices…
Journal Article•
TL;DR: The phenylalanine and leucine conjugates were highly effective in causing necrotic symptoms, enhanced levels of naringenin 7-0-methyltamsferase activity and subsequent phytoalexin sakuranetin production, and changes in protein profiles.
Abstract: Jasmonic acid (JA) is an essential and important component of the rice ( Oryza sativa L.) plant self-defense response. Oh the other hand, its amino acid (aa) conjugates are suggested to play some role in the stressed tissues. Here we examined and compared in detail the effects of exogenously applied JA and JAaa conjugates on symptoms, phytoalexin production and protein profiles, in the leaves of young rice seedlings, using techniques in liquid chromatography and two-dimensional electrophoresis. Results revealed that among the four JAaa conjugates examined in this study, the phenylalanine and leucine conjugates were highly effective in causing necrotic symptoms, enhanced levels of naringenin 7-0-methyltamsferase activity and subsequent phytoalexin sakuranetin production, and changes in protein profiles. These results suggest that like the critical signalling molecule JA, the JAaa conjugates, especially the phenylalanine and leucine conjugates, might also be important endogenous components of the rice plant defense/stress response pathways.
TL;DR: The 1α,11-Dihydroxy-4α,5α,7β,10β (H)-eremophilane 6 has been examined as a phytoalexin analogue and shown to be a powerful inhibitor of the growth of the plant pathogen, Botrytis cinerea as discussed by the authors.
Abstract: 1α,11-Dihydroxy-4α,5α,7β,10β (H)-eremophilane 6 has been examined as a phytoalexin analogue and shown to be a powerful inhibitor of the growth of the plant pathogen, Botrytis cinerea. Its metabolit...