Showing papers on "Phytoalexin published in 2001"
TL;DR: The results showed that the hydroxyl group in 4′ position is not the sole determinant for antioxidant activity, and the presence of 4′-OH together with stereoisomery in the trans-conformation was absolutely required for inhibition of cell proliferation.
461 citations
TL;DR: The results suggest that IGS is of importance in the defense against bacterial pathogens and methyl jasmonate was able to trigger IGS accumulation in Arabidopsis.
Abstract: Elicitors from the plant pathogen Erwinia carotovora trigger coordinate induction of the tryptophan (Trp) biosynthesis pathway and Trp oxidizing genes in Arabidopsis. To elucidate the biological role of such pathogen-induced activation we characterized the production of secondary defense metabolites such as camalexin and indole glucosinolates derived from precursors of this pathway. Elicitor induction was followed by a specific increase in 3-indolylmethylglucosinolate (IGS) content, but only a barely detectable accumulation of the indole-derived phytoalexin camalexin. The response is mediated by jasmonic acid as shown by lack of IGS induction in the jasmonate-insensitive mutant coi1-1. In accordance with this, methyl jasmonate was able to trigger IGS accumulation in Arabidopsis. In contrast, ethylene and salicylic acid seem to play a minor role in the response. They did not trigger alterations in IGS levels, and methyl jasmonate- or elicitor-induced IGS accumulation in NahG and ethylene-insensitive ein2-1 mutant plants was similar as in the wild type. The breakdown products of IGS and other glucosinolates were able to inhibit growth of E. carotovora. The results suggest that IGS is of importance in the defense against bacterial pathogens.
308 citations
TL;DR: The possible role of phytoalexins in the resistance of rice plants against the fungus Pyricularia oryzae (= Magnaporthe grisea) is discussed, and the future prospects ofphy toalexin research are outlined.
257 citations
TL;DR: Results indicate that BcatrB is a determinant in sensitivity of B. cinerea to plant defense compounds and fungicides.
Abstract: During pathogenesis, fungal pathogens are exposed to a variety of fungitoxic compounds. This may be particularly relevant to Botrytis cinerea, a plant pathogen that has a broad host range and, consequently, is subjected to exposure to many plant defense compounds. In practice, the pathogen is controlled with fungicides belonging to different chemical groups. ATP-binding cassette (ABC) transporters might provide protection against plant defense compounds and fungicides by ATP-driven efflux mechanisms. To test this hypothesis, we cloned BcatrB, an ABC transporter-encoding gene from B. cinerea. This gene encodes a 1,439 amino acid protein with nucleotide binding fold (NBF) and transmembrane (TM) domains in a [NBF-TM6]2 topology. The amino acid sequence has 31 to 67% identity with ABC transporters from various fungi. The expression of BcatrB is up regulated by treatment of B. cinerea germlings with the grapevine phytoalexin resveratrol and the fungicide fenpiclonil. BcatrB replacement mutants are not affected in saprophytic growth on different media but are more sensitive to resveratrol and fenpiclonil than the parental isolate. Furthermore, virulence of deltaBcatrB mutants on grapevine leaves was slightly reduced. These results indicate that BcatrB is a determinant in sensitivity of B. cinerea to plant defense compounds and fungicides.
209 citations
TL;DR: Results were a good indication that the combination of a pathogen-inducible promoter and a defence gene may increase tolerance against fungi in grapevine.
Abstract: Resveratrol is a major phytoalexin in grapevine but its synthesis in response to phytopathogen attack decreases with grape berry ripening. A chimeric gene combining an alfalfa PR 10 promoter and Vst1 (Vitis stilbene synthase 1) gene was introduced into the genome of 41B rootstock. Transgenic plants were analysed for resveratrol production in leaves infected with Botrytis using an in vitro test. Among the 50 transgenic lines analysed, some exhibited a production lower than the non-transgenic control, but others accumulated resveratrol from 5-100-fold. Moreover, in the latter clones, symptoms were highly reduced in response to infection. These results were a good indication that the combination of a pathogen-inducible promoter and a defence gene may increase tolerance against fungi in grapevine. The efficacy of this approach should be further tested by experiments conducted in the vineyard.
168 citations
TL;DR: Resistance of Arabidopsis against P. porri appears to depend on unknown defence mechanisms that are under the control of PAD2, which is similar to that seen in agronomically important diseases caused by Phytophthora species.
Abstract: 1These two authors have contributed equally to the work. Summary Arabidopsis accessions were screened with isolates of Phytophthora porri originally isolated from other crucifer species. The described Arabidopsis‐Phytophthora pathosystem shows the characteristics of a facultative biotrophic interaction similar to that seen in agronomically important diseases caused by Phytophthora species. In susceptible accessions, extensive colonization of the host tissue occurred and sexual and asexual spores were formed. In incompatible combinations, the plants reacted with a hypersensitive response (HR) and the formation of papillae at the sites of attempted penetration. Defence pathway mutants such as jar1 (jasmonic acid-insensitive), etr1 (ethylene receptor mutant) and ein2 (ethylene-insensitive) remained resistant towards P. porri. However, pad2, a mutant with reduced production of the phytoalexin camalexin, was hyper-susceptible. The accumulation of salicylic acid (SA) and PR1 protein was strongly reduced in pad2. Surprisingly, this lack of SA accumulation does not appear to be the cause of the hyper-susceptibility because interference with SA signalling in nahG plants or sid2 or npr1 mutants had only a minor effect on resistance. In addition, the functional SA analogue benzothiadiazol (BTH) did not induce resistance in susceptible plants including pad2. Similarly, the complete blockage of camalexin biosynthesis in pad3 did not cause susceptibility. Resistance of Arabidopsis against P. porri appears to depend on unknown defence mechanisms that are under the control of PAD2.
162 citations
TL;DR: It seems unlikely that any one of the infection-induced compounds identified so far has a decisive role in the resistance response to P. syringae, as well as the disease resistance phenotypes, were essentially the same for infected wild-type and tt4 (no kaempferol glycosides) or fah1 (no sinapoyl malate) mutant plants.
Abstract: The chemical structures and accumulation kinetics of several major soluble as well as wall-bound, alkali-hydrolyzable compounds induced upon infection of Arabidopsis thaliana leaves with Pseudomonas syringae pathovar tomato were established. All identified accumulating products were structurally related to tryptophan. Most prominent among the soluble substances were tryptophan, β-d-glucopyranosyl indole-3-carboxylic acid, 6-hydroxyindole-3-carboxylic acid 6-O-β-d-glucopyranoside, and the indolic phytoalexin camalexin. The single major accumulating wall component detectable under these conditions was indole-3-carboxylic acid. All of these compounds increased more rapidly, and camalexin as well as indole-3-carboxylic acid reached much higher levels, in the incompatible than in the compatible P. syringae/A. thaliana interaction. The only three prominent phenylpropanoid derivatives present in the soluble extract behaved differently. Two kaempferol glycosides remained largely unaffected, and sinapoyl malate decreased strongly upon bacterial infection with a time course inversely correlated with that of the accumulating tryptophan-related products. The accumulation patterns of both soluble and wall-bound compounds, as well as the disease resistance phenotypes, were essentially the same for infected wild-type and tt4 (no kaempferol glycosides) or fah1 (no sinapoyl malate) mutant plants. Largely different product combinations accumulated in wounded or senescing A. thaliana leaves. It seems unlikely that any one of the infection-induced compounds identified so far has a decisive role in the resistance response to P. syringae.
112 citations
TL;DR: It is proposed that IOMT colocalizes with the endoplasmic reticulum–associated is oflavone synthase cytochrome P450 to ensure rapid B-ring methylation of the unstable 2,4′,7-trihydroxyisoflavanone product of isoflavonoid synthase, thereby preventing its dehydration to daidzein and subsequent A- ring methylation by free IomT.
Abstract: The bioactive isoflavonoids of the Leguminosae often are methylated on the 4'-position of their B-rings. Paradoxically, reverse genetic evidence implicates alfalfa isoflavone O-methyltransferase (IOMT) in the biosynthesis of 4'-O-methylated isoflavonoids such as the phytoalexin medicarpin in vivo, whereas biochemical studies indicate that IOMT has strict specificity for methylation of the A-ring 7-hydroxyl of daidzein, the presumed substrate for O-methylation, in vitro. Radiolabeling and isotope dilution studies now confirm that daidzein is not an intermediate in isoflavonoid phytoalexin biosynthesis in alfalfa. Furthermore, protein gel blot analysis and confocal microscopy of a transiently expressed IOMT-green fluorescent protein fusion in alfalfa leaves show that the operationally soluble IOMT localizes to endomembranes after elicitation of the isoflavonoid pathway. We propose that IOMT colocalizes with the endoplasmic reticulum-associated isoflavone synthase cytochrome P450 to ensure rapid B-ring methylation of the unstable 2,4',7-trihydroxyisoflavanone product of isoflavone synthase, thereby preventing its dehydration to daidzein and subsequent A-ring methylation by free IOMT. In this way, metabolic channeling at the entry point into isoflavonoid phytoalexin biosynthesis protects an unstable intermediate from an unproductive metabolic conversion.
99 citations
TL;DR: The results suggest that theAnti-invasive activity of resveratrol is independent of the anti-proliferative activity, and that the antioxidative property of res veratrol may be involved in its anti- invasive action.
88 citations
TL;DR: It is established that a blackspot-resistant species (Sinapis alba) metabolized destruxin B to a less toxic product substantially faster than any of the susceptible species and appears to be a unique example of phytotoxin detoxification and simultaneous phytoalexin elicitation by the detoxification product.
Abstract: To facilitate plant colonization, some pathogenic fungi produce phytotoxic metabolites that damage tissues; plants may be resistant to a particular pathogen if they produce an enzyme(s) that catalyzes detoxification of this metabolite(s). Alternaria blackspot is one of the most damaging and significant fungal diseases of brassica crops, with no source of resistance known within the Brassica species. Destruxin B is the major phytotoxin produced by the blackspot-causing fungus, Alternaria brassicae (Berkley) Saccardo. We have established that a blackspot-resistant species (Sinapis alba) metabolized 14C-labeled destruxin B to a less toxic product substantially faster than any of the susceptible species. The first metabolite, hydroxydestruxin B (14C-labeled), was further biotransformed to the β-d-glucosyl derivative at a slower rate. The structures of hydroxydestruxin B and β-d-glucosyl hydroxydestruxin B were deduced from their spectroscopic data [NMR, high resolution (HR)-MS, Fourier transform infrared (FTIR)] and confirmed by total chemical synthesis. Although these hydroxylation and glucosylation reactions occurred in both resistant (S. alba) and susceptible (Brassica napus, Brassica juncea, and Brassica rapa) species, hydroxylation was the rate limiting step in the susceptible species, whereas glucosylation was the rate limiting step in the resistant species. Remarkably, it was observed that the hydroxydestruxin B induced the biosynthesis of phytoalexins in blackspot-resistant species but not in susceptible species. This appears to be a unique example of phytotoxin detoxification and simultaneous phytoalexin elicitation by the detoxification product. Our studies suggest that S. alba can overcome the fungal invader through detoxification of destruxin B coupled with production of phytoalexins.
74 citations
TL;DR: A direct role for protein phosphorylation/ dephosphorylation events in the activation of defense responses in rice, in particular on the accumulation of antifungal phytoalexins and the PBZ proteins is indicated.
Abstract: The protein phosphatase inhibitor cantharidin activates defense responses in rice leaves when applied exogenously at concentrations ranging from 100 to 500 μM. Responses include the accumulation of the major rice phenolic phytoalexin sakuranetin and the lactone phytoalexin momilactone A. Accumulation of sakuranetin was preceded by an induction of phenylalanine ammonia lyase (PAL) activity and an increase in the activity of naringenin 7-O-methyltransferase (NOMT), the key enzyme in sakuranetin biosynthesis. Cantharidin also strongly induced accumulation of the probenazole (PBZ)-inducible protein (PBZ1) and two novel, related proteins named PBZ2 and PBZ3. Endothall, a herbicide and potent protein phosphatase inhibitor, but not its inactive analog (1,4-dimethylendothall) also induced sakuranetin accumulation, increased activity of NOMT and accumulation of the 3 PBZ proteins. In contrast, two other protein phosphatase inhibitors, calyculin A and microcystin LR, did not activate these defense responses. Induction of NOMT and PAL activity, and sakuranetin accumulation, was completely blocked by cycloheximide. Leaf segments treated with cantharidin and endothall showed brownish and orange colored lesions, respectively, similar to the lesion mimic mutants of rice. These results indicate a direct role for protein phosphorylation/ dephosphorylation events in the activation of defense responses in rice, in particular on the accumulation of antifungal phytoalexins and the PBZ proteins.
TL;DR: Results indicate that GSH elicits the formation not only of the pterocarpan phytoalexins medicarpin and maackiain, but also that of the constitutive isoflavones biochanin A and formononetin and, in seedlings older than 4 d, that ofthe isoflavanones homoferreirin and cicerin.
TL;DR: Seven phytoalexins (1-7), including a new compound, were isolated from the peel of unripe kiwi fruit (Actinidia deliciosa cv. Golden King) that had been wounded and inoculated with Colletotrichum musae.
Abstract: Seven phytoalexins (1-7), including a new compound, were isolated from the peel of unripe kiwi fruit (Actinidia deliciosa cv. Golden King) that had been wounded and inoculated with Colletotrichum musae. The new phytoalexin (1) was identified as 2α,3β,23-trihydroxy-12,20(30)-ursadien-28-oic acid, and named actinidic acid. Phytoalexins 2-6 are known triterpenes but have not previously been described as phytoalexins. Phytoalexin 7 is the same triterpene as the phytoalexin of nectarine fruit.
TL;DR: The results lend support to the view of ozone as an abiotic elicitor of plant defence responses by suggesting that proneness to develop visible ozone symptoms might rest on a sequence of molecular events similar to that leading to the hypersensitive response during plant–pathogen incompatible interactions.
Abstract: On exposure to a realistic ozone dose, an enhanced mRNA accumulation for phenyalanine ammonia-lyase (EC 4.3.1.5), naringenin–chalcone synthase [malonyl–CoA:4-coumaroyl–CoA malonyltransferase (cyclising); EC 2.3.1.74] and chalcone isomerase [flavanone lyase (decyclising); EC 5.5.1.6] genes, whose products are involved in the biosynthesis of phenylpropanoid molecules, flavonoid pigments and isoflavonoid phytoalexins, was observed in primary leaves of the bean (Phaseolus vulgaris L.) cv. Pinto. This cultivar was previously known to be ozone-sensitive on the basis of the appearance of macroscopic foliar injury, but not in coeval leaves of the bean cv. Groffy, known to be ozone-resistant on the basis of the aforementioned criterion. Distinct time patterns were observed in Pinto leaves for the ozone-dependent enhanced mRNA accumulation for the aforementioned genes, which in all cases largely preceded the appearance of visible injury symptoms. These results lend support to the view of ozone as an abiotic elicitor of plant defence responses. By analogy with other case studies, it is also suggested that proneness to develop visible ozone symptoms might rest on a sequence of molecular events similar to that leading to the hypersensitive response during plant–pathogen incompatible interactions.
TL;DR: Yi et al. as discussed by the authors isolated a full-length cDNA clone encoding ACL from hot pepper leaves inoculated with Xanthomonas campestris pv. glycines8ra.
TL;DR: Data indicate that the inhibition of the plasma membrane H + -ATPase, and more specifically the proton efflux, may be a key step in the signalling pathway leading to the activation of phytoalexin and isoflavone excretion in chickpea seedlings.
TL;DR: Trans-resveratrol inhibited lipoxygenase activity more effectively than other lip oxygengenase inhibitors, including propyl gallate, ibuprofen, ursolic acid, acetylsalicylic acid, and salicylhydroxamic acid.
Abstract: Trans-resveratrol, a phytoalexin produced by a variety of plants, has been shown to inhibit oxidative enzymes in an animal cell system. Its effect on several oxidative and antioxidative enzymes from plants was investigated using in vitro assays. Trans-resveratrol inhibited superoxide dismutase, lipoxygenase, catalase, peroxi- dase, polyphenol oxidase, and 1-aminocyclopropane-1-carboxylic acid oxidase with apparent K I 's of 10, 90, 100, 255, 305, and 350 M, respectively. Trans-resveratrol inhibited lipoxygenase activity more effectively than other lipoxygenase inhibitors, including propyl gallate, ibuprofen, ursolic acid, acetylsalicylic acid, and salicylhydroxamic acid.
TL;DR: H2O2 production is an inducible defence response which may contribute to DED resistance by delaying the growth of the pathogen at the earliest stages of infection.
Abstract: The Dutch elm disease (DED) pathogen Ophiostoma novo-ulmi Buissm. elicited the production of H2O2 in cell suspension cultures of the resistant species Ulmus pumila L. This response was not observed in suspensions of the susceptible elm U. campestris Mill. H2O2 production started after a lag time of 30-40 min following inoculation, peaked between 4 and 6 h and lasted up to 24 h. Treatment of the suspensions with exogenously added H2O2 did not cause accumulation of the sesquiterpene phytoalexins mansonones nor of the coumarin scopoletin. Spore germination and growth of O. novo-ulmi were significantly delayed with different amounts of H2O2 (0.1-1 mM). These results suggest that H2O2 production is an inducible defence response which may contribute to DED resistance by delaying the growth of the pathogen at the earliest stages of infection. Whether H2O2 is involved in other elm defence responses to the pathogen is presently unknown, but its production seems to be an independent event from phytoalexin formation.
TL;DR: Investigation of the nitrogen-fixing soybean symbiont Bradyrhizobium japonicum found mutants defective in the biosynthesis of cyclic β-(1→3)-(1→6)-glucans showed higher susceptibility to both phytoalexin and H2O2.
Abstract: Susceptibility of the nitrogen-fixing soybean symbiont Bradyrhizobium japonicum to inducible plant defense metabolites such as phytoalexin and H2O2, was investigated. On the wild-type strain USDA 110 the soybean phytoalexin, glyceollin, showed bacteriostatic activity. Viable bacteria isolated from intact nodules were adapted to glyceollin. H2O2 in physiological concentrations did not affect wild-type bacteria. B. japonicum mutants defective in the biosynthesis of cyclic beta-(1-->3)-(1-->6)-glucans showed higher susceptibility to both phytoalexin and H2O2.
Journal Article•
TL;DR: In this article, the authors investigated the induction of enzymes and the accumulation of their end products associated with self-defense mechanism in rice and found that p-coumaric acid in rice leaves was closely correlated with self defense or allelopathic potential against barnyardgrass.
Abstract: The induction of enzymes and the accumulation of their end products associated with self-defense mechanism in rice were investigated When rice leaves were irradiated with UV light, activities of diterpene cyclase, phenylalanine ammonia-lyase (PAL), and cinnamic acid 4-hydroxylase (CA4H) were induced and rice phytoalexin, momilactone A was accumulated The content of p-coumaric acid in rice leaves was closely correlated with self-defense or allelopathic potential against barnyardgrass UV-challenged rice leaves gave rise to the inhibition of barnyardgrass growth
TL;DR: Allixin, a phytoalexin isolated from garlic, was induced by irradiating fresh garlic cloves with sunlight or UV light, and the accumulated amounts of allixin were 3.1-6.3 microg/g under experimental conditions.
Abstract: Allixin, a phytoalexin isolated from garlic, was induced by irradiating fresh garlic cloves with sunlight or UV light. Induced allixin was analyzed by HPLC, and the accumulated amounts of allixin were 3.1—6.3 μg/g under experimental conditions.
19 Apr 2001
TL;DR: Based on available evidence, available evidence is consistent with both phytoanticipins and phy toalexins being important in defence in some disease interactions.
Abstract: Plants produce many antimicrobial secondary metabolites. Two major classes with a demonstrated or proposed role in resistance to plant pathogens are phytoanticipins, or preformed inhibitors, which are present constitutively in plants, and phytoalexins, which are synthesized only in response to pathogen attack. Available evidence is consistent with both phytoanticipins and phytoalexins being important in defence in some disease interactions.
Keywords:
phytoalexin;
phytoanticipin;
plant disease;
inducible defence;
elicitor
TL;DR: These studies demonstrate that identification of mutants deficient in a phytoalexin (a useful tool for studying the role of phy toalexins in disease resistance) requires consideration of phalangexin accumulation kinetics, inoculum concentration, relative distribution of phYtoaleXin in leaves and spore droplet diffusates, and type of pathogen.