Showing papers on "Phytoalexin published in 1998"
TL;DR: Conclusive evidence is presented that silicon is involved in the increased resistance of cucumber to powdery mildew by enhancing the antifungal activity of infected leaves by activating low-molecular-weight metabolites.
Abstract: The controversial role of silicon in plant disease resistance, described mostly as a passive mechanical protection, has been addressed. Conclusive evidence is presented that silicon is involved in the increased resistance of cucumber to powdery mildew by enhancing the antifungal activity of infected leaves. This antifungal activity was attributable to the presence of low-molecular-weight metabolites. One of these metabolites, described here as a phytoalexin, was identified as a flavonol aglycone rhamnetin (3,5,3',4'-tetrahydroxy-7-O-methoxyflavone). This is the first report of a phytoalexin for this chemical group in the plant kingdom and of a flavonol phytoalexin in cucumber, a chemical defense long believed to be nonexistent in the family Cucurbitaceae. The antifungal activity of leaf extracts was better expressed after acid hydrolysis, extending to another plant species the concept that some phytoalexins are synthesized as glycosylated phytoalexins or their precursors.
398 citations
TL;DR: This study is the first to show that sphingolipids have elicitor activity in plants, and results indicate that the methyl group at C-9 and the 4E-double bond in the sphingoid base moiety of cerebrosides A and C are the key elements determining the elicitoractivity of these compounds.
165 citations
TL;DR: The results suggest that the plant represses less essential metabolic activities such as anthocyanin synthesis as a means of compensating for the immediate biochemical and physiological needs for the defense response.
Abstract: Sorghum (Sorghum bicolor L. Moench) accumulates the anthocyanin cyanidin 3-dimalonyl glucoside in etiolated mesocotyls in response to light. Inoculation with the nonpathogenic fungus Cochliobolus heterostrophus drastically reduced the light-induced accumulation of anthocyanin by repressing the transcription of the anthocyanin biosynthesis genes encoding flavanone 3-hydroxylase, dihydroflavonol 4-reductase, and anthocyanidin synthase. In contrast to these repression effects, fungal inoculation resulted in the synthesis of the four known 3-deoxyanthocyanidin phytoalexins and a corresponding activation of genes encoding the key branch-point enzymes in the phenylpropanoid pathway, phenylalanine ammonia-lyase and chalcone synthase. In addition, a gene encoding the pathogenesis-related protein PR-10 was strongly induced in response to inoculation. The accumulation of phytoalexins leveled off by 48 h after inoculation and was accompanied by a more rapid increase in the rate of anthocyanin accumulation. The results suggest that the plant represses less essential metabolic activities such as anthocyanin synthesis as a means of compensating for the immediate biochemical and physiological needs for the defense response.
146 citations
TL;DR: Defence-response gene transcripts in roots of nematode-resistant and susceptible alfalfa plants thus differed both constitutively and in inductive responses to nematodes infection.
Abstract: Alfalfa (Medicago sativa) varieties with antibiosis-based resistance to the root-lesion nematode (Pratylenchus penetrans), a migratory endoparasite of many crops, have been developed by recurrent selection. Individual plants from these varieties that support significantly lower nematode reproduction were identified for molecular and biochemical characterization of defense responses. Before nematode infection, RNA blot analysis revealed 1.3–1.8-fold higher phenylpropanoid pathway mRNA levels in roots of three resistant plants as compared to three susceptible alfalfa plants. The mRNAs encoded the first enzyme in the pathway (phenylalanine ammonia-lyase), the first in the pathway branch for flavonoid biosynthesis (chalcone synthase), a key enzyme in medicarpin biosynthesis (isoflavone reductase) and a key enzyme in the pathway branch for biosynthesis of lignin cell wall precursors (caffeic acid O-methyltransferase). After nematode infection, the mRNAs declined over 48 h in resistant roots but rose in susceptible plants during the first 12 h after-infection and then declined. Acidic β-1,3-glucanase mRNA levels were initially similar in both root types but accumulated more rapidly in resistant than in susceptible roots after nematode infection. Levels of a class I chitinase mRNA were similar in both root types. Histone H3.2 mRNA levels, initially 1.3-fold higher in resistant roots, declined over 6–12 h to levels found in susceptible roots and remained stable in both root types thereafter. Defense-response gene transcripts in roots of nematode-resistant and susceptible alfalfa plants thus differed both constitutively and in inductive responses to nematode infection. HPLC analysis of isoflavonoid-derived metabolites of the phenylpropanoid pathway revealed similar total constitutive levels, but varying relative proportions and types, in roots of the resistant and susceptible plants. Nematode infection had no effect on isoflavonoid levels. Constitutive levels of the phytoalexin medicarpin were highest in roots of the two most resistant plants. Medicarpin inhibited motility of P. penetrans in vitro.
97 citations
TL;DR: In this paper, a laccase-like stilbene-oxidase of Botrytis cinerea, the causal organism for grey mould, is characterized as a resveratrol dehydrodimer.
80 citations
TL;DR: Barley F1-OMT, apigenin 7-O-methyltransferase, is suggested to be involved in the production of a methylated flavonoid phytoalexin.
Abstract: We have shown previously that transcripts corresponding to the cDNA clone pBH72-F1, with similarities to O-methyltransferases (OMT), accumulated in barley leaves in response to attack by the pathogenic fungus Blumeria graminis (Plant Mol Biol 26 (1994) 1797) To investigate the accumulation pattern in the defence response and the organ localization of the pBH72-F1-encoded polypeptide (F1-OMT), an antiserum was raised against Escherichia coli expressed F1-OMT The 43 kDa protein was absent in normal leaves but accumulated strongly in response to pathogen attack The F1-OMT protein accumulated faster in barley lines inoculated with an avirulent B graminis isolates compared to a virulent isolate Additionally, F1-OMT related proteins were detected in developing kernels F1-OMT was expressed as a functional enzyme in E coli and the substrate specificity was investigated The enzyme exhibited OMT activity towards flavonoid aglycones with the highest activity against apigenin (4',5,7-trihydroxyflavone) In contrast, caffeic acid did not serve as substrate for F1-OMT The product of F1-OMT was analyzed by HPLC and GC-MS and found to be genkwanin (4',5-dihydroxy-7-methoxyflavone) Initial velocity data were best represented by a sequential bi-bi mechanism, and kinetic parameters of KSAM = 109 microM, Kapigenin = 46 microM and a specific activity of 045 mukat/g were obtained Barley F1-OMT, apigenin 7-O-methyltransferase, is suggested to be involved in the production of a methylated flavonoid phytoalexin
74 citations
TL;DR: Observation of particular intravacuolar spherical vesicles and of granular material deposits along the tonoplast are likely to be related to the oxidation of resveratrol by an intracellular laccase-like stilbene oxidase of B. cinerea.
Abstract: Observations using light microscopy showed that approximately 30% of Botrytis cinerea conidia treated with semi-lethal concentrations (i.e., 60 mug/ml) of the grapevine phytoalexin resveratrol possessed intracellular brown coloration. This coloration was never observed in the absence of resveratrol or in conidia treated with resveratrol together with sulfur dioxide (antioxidant compound) or sodium diethyldithiocarbamate (inhibitor of laccase action), suggesting that discoloration resulted from the laccase-mediated oxidation of resveratrol. Further studies using transmission electron microscopy enabled the observation of particular intravacuolar spherical vesicles and of granular material deposits along the tonoplast. These observations are likely to be related to the oxidation of resveratrol by an intracellular laccase-like stilbene oxidase of B. cinerea.
71 citations
TL;DR: Studies of plant-microorganism interactions yielded the first evidence that oligosaccharides could serve as biological signals, and this research focused on the synthesis and accumulation of antimicrobial phytoalexins in response to microbial attack.
Abstract: Studies of plant-microorganism interactions yielded the first evidence that oligosaccharides could serve as biological signals Much of this research focused on the synthesis and accumulation of antimicrobial phytoalexins in response to microbial attack Phytoalexin synthesis and accumulation are observed not only after microbial infection, but also after treatment of plant tissue with cell-free extracts of microbial origin
69 citations
TL;DR: A bacterial strain, isolated from soil, belonging to the genus Bacillus was found to be an antagonist of this disease causing fungus, which can be used as a potential biological control agent as well as a biological elicitor of resveratrol.
Abstract: Botrytis cinerea Pers was found to be highly pathogenic to the grapevine plant, producing the characteristic grey mould symptoms within 7 days of inoculation on vitroplants A bacterial strain, isolated from soil, belonging to the genus Bacillus was found to be an antagonist of this disease causing fungus The fungal attack on the grapevine acts as an elicitor to the production of phytoalexines like resveratrol This compound was also formed when the leaves of the grapevine vitroplants were inoculated with the bacteria alone, and this activity was enhanced when a mixture of the pathogen and the antagonist bacteria was applied Since resveratrol in wine is considered to be beneficial to human health provided moderate consumption, this bacteria can be used as a potential biological control agent as well as a biological elicitor of resveratrol The article includes the details of the fungal parasite, its biological control and resveratrol elicitation
61 citations
TL;DR: An antifungal test on the phytoalexins showed that a phenolic hydroxyl group was essential for the activity.
Abstract: Fourteen phenylphenalenone-type phytoalexins (1-14), including three new compounds, were isolated from the peel of unripe Musa acuminata [AAA] cv. Bungulan fruit which had been injured and then inoculated with conidia of Colletotrichum musae. These new phytoalexins were identified as (+)-cis-2,3-dihydro-2,3-dihydroxy-4-(4'-hydroxyphenyl)phenalen-1-one (12), 9-(3',4'-dimethoxyphenyl)-2-methoxyphenalen-1-one (13) and 9-(4'-hydroxyphenyl)-2-methoxyphenalen-1-one (14). The ratios of the relative intensities of the [M](+)/[M-H](+) ions or [M-H2O](+)/[M-H2O-H](+) ions in the EI mass spectra were applied to discriminate between 4- and 9-phenylphenalenones. An antifungal test on the phytoalexins showed that a phenolic hydroxyl group was essential for the activity.
57 citations
TL;DR: It is concluded that active oxygen species from the oxidative burst are necessary but not sufficient for inducing isoflavonoid phytoalexin accumulation in soybean cells.
Abstract: Treatment of soybean ( Glycine max L. cv Williams 82) cell-suspension cultures with Pseudomonas syringae pv glycinea ( Psg ) harboring an avirulence gene ( avrA ) or with yeast elicitor resulted in an oxidative burst characterized by the accumulation of H 2 O 2 . This burst, and the resultant induction of glutathione S -transferase transcripts, occurred more rapidly and was more prolonged if cells were simultaneously treated with serine protease inhibitors such as phenylmethylsulfonyl fluoride (PMSF) or diisopropylfluorophosphate. PMSF and diisopropylfluorophosphate potentiate a large oxidative burst in cells exposed to Psg harboring the avrC avirulence gene, which is not recognized by the soybean cultivar used in this study. The potentiated burst was inhibited by diphenylene iodonium, an inhibitor of NADPH oxidase, and by the protein kinase inhibitor K252a. PMSF treatment of elicited cells or cells exposed to Psg:avrA caused a large increase in the accumulation of the isoflavonoid phytoalexin glyceollin; however, this was not associated with increased levels of transcripts encoding key phytoalexin biosynthetic enzymes. Glyceollin accumulation was inhibited by diphenylene iodonium; however, the oxidative burst in cells treated with Psg:avrC and PMSF was not followed by phytoalexin accumulation. We conclude that active oxygen species from the oxidative burst are necessary but not sufficient for inducing isoflavonoid phytoalexin accumulation in soybean cells.
TL;DR: The injection of the elicitor into the leaves of intact carrot plants confirmed the results obtained with cell cultures with regard to the induction of the hypersensitive response, and purification of the active compound revealed a 25-kDa protein which triggers both cell death and 4-HBA synthesis.
Abstract: Suspension-cultured carrot cells and intact leaves respond to crude and purified protein elicitors from the non-host fungus Pythium aphanidermatum by activating the general phenylpropanoid pathway and incorporating de-novo-synthesized 4-hydroxybenzoic acid (4-HBA) into the cell wall. The cultured cells undergo a very rapid elicitor-induced cell death. Both reactions are directly correlated in their time course and their dose dependency. Cell death in elicitor-treated protoplasts resulted in early membrane damage and the digestion of DNA into oligonucleosomal fragments. The same pattern of DNA degradation could be induced in protoplasts by the G-protein activators Mas-7 or mastoparan. In cell cultures, both activators induced a rapid loss of viability without the activation of the general phenylpropanoid pathway. The elicitor-induced reactions, the loss of viability and the induction of 4-HBA biosynthesis were blocked by the calcium-channel blocker nifedipine. Neomycin and U73122, two inhibitors of phospholipase C, blocked the induction of 4-HBA biosynthesis but did not affect the loss in viability. The injection of the elicitor into the leaves of intact carrot plants confirmed the results obtained with cell cultures with regard to the induction of the hypersensitive response. The purification of the active compound revealed a 25-kDa protein which triggers both cell death and 4-HBA synthesis. The signalling pathways to both reactions could be independently blocked or induced.
TL;DR: The treatment of hairy roots of Hyoscyamus albus with copper sulfate (Cu2+) and methyl jasmonate (JAMe) produced several phytoalexins having the vetispyrane skeleton, including lubimin and solavetivone.
Abstract: The treatment of hairy roots of Hyoscyamus albus with copper sulfate (Cu 2+ ) and methyljasmonate (JAMe) produced several phytoalexins having the vetispyrane skeleton. Lubimin and solavetivone were isolated after treatment with Cu 2+ . Seven sesquiterpenoid phytoalexins were isolated from the culture medium after treatment with JAMe, including lubimin, solavetivone, 3-hydroxysolavetivone and four new compounds (1-4). Structures of the new compounds were elucidated to be (3R,4S,5R,7S,9R))-3-hydroxy-9-tigloyloxysolavetivone (1), (3R,4S,5R,7S, 9R)-3-hydroxy-9-(3-methylbutenoyloxy)-solavetivone (2), (3R,4S, 5R, 7S,9R)-3-hydroxy-9-isobutanoyloxysolavetivone (3); and (3R,4S, 5R, 7S,9R)-3,9-dihydroxyso-lavetivone (4). The induction pattern of phytoalexins in hairy roots treated with JAMe was different in those treated with Cu 2+ , and co-treatment with JAMe and Cu 2+ gave only solavetivone.
TL;DR: The glycoprotein elicitor should prove useful in identifying second messengers leading to induction of phytoalexin biosynthesis in cotton cell suspension cultures, indicating that only protein components are responsible for the elicitation ofphy toalexins in cotton cells.
TL;DR: Cell suspension cultures of three cultivars of Capsicum annuum L., with different degrees of sensibility to the fungus Phytophthora capsici, responded to elicitation by both lyophilized mycelium and fungus filtrate, showing properties of a multicomponent dynamic system in which different protective mechanisms play complementary roles in the overall expression of the defence reaction.
Abstract: Cell suspension cultures of three cultivars of Capsicum annuum L., with different degrees of sensibility to the fungus Phytophthora capsici, responded to elicitation by both lyophilized mycelium and fungus filtrate. They showed conductivity changes, browning, production of the phytoalexin capsidiol and synthesis or accumulation of pathogenesis-related (PR) proteins with glucanase (EC 3.2.1.39) and chitinase (EC 3.2.1.14) activities. The cultivation medium was optimised for growth of both the plant and the fungus in order to avoid any stress during their combination. The resistant cv. Smith-5, showed a more rapid and intense response to the elicitor preparations than the sensitive cvs Americano and Yolo Wonder. This was particularly evident when the cell suspensions were elicited with the filtrate, when differences became clearly visible after only 6 h incubation. The greatest rate of capsidiol accumulation occurred after 18 h in the mycelium-elicited cells and after 12 h in those elicited with the filtrate. These times are the optimal for capsidiol accumulation, and the phytoalexin is produced much more rapidly than it can be excreted into the extracellular medium. The inhibition threshold of fungal growth (300 μg capsidiol [g dry weight] -1 ) was reached only in the resistant cultivar. The induction of an intracellular glucanase (pI 8.9 and R f 0.18) and an extracellular chitinase (pl 5.4 and R f 0.70) only in the resistant cultivar 24 h after elicitation suggests that these enzymes are involved in the resistance to Phytophthora capsici, while other hydrolases common to all three cultivars form part of a more general defence. The results indicate that elicitation of pepper cell suspension cultures by signal molecules from P. capsici exhibits properties of a multicomponent dynamic system in which different protective mechanisms play complementary roles in the overall expression of the defence reaction. We confirm that the differential responses of resistant and susceptible pepper cultivars to P. capsici previously seen in plant stem sections are retained in suspension culture.
TL;DR: Capsidiol accumulation, not 5-epi-aristolochene synthase gene expression or total sesquiterpene cyclase enzyme activity, appears to be a good marker for the HR of tobacco.
Abstract: The induction of sesquiterpene cyclase, a key phytoalexin biosynthetic enzyme, and the accumulation of phytoalexins in relation to the induction of a hypersensitive response (HR) and cell necrosis in tobacco (Nicotiana tabacum L.) were investigated. When tobacco leaves were inoculated with virulent or avirulent isolates of Ralstonia solanacearum, steady-state levels of mRNA complementary to cDNA of the sensitivity-related (sts) gene str319 were dramatically induced. This cDNA clone is greater than 90% homologous with a gene coding for 5-epi-aristolochene synthase (EAS), previously described as a branch-point enzyme regulating the synthesis of capsidiol, the major sesquiterpenoid phytoalexin found in tobacco. Accumulation of EAS transcripts in leaves after inoculation with virulent and avirulent strains of R. solanacearum, or after treatment with necrotizing or non-necrotizing elicitins was rapid but transient, and restricted to the site of infiltration. Two highly similar sesquiterpene cyclase activities, 5-epi-aristolochene synthase and a vetispiradiene synthase-like activity, were found in extracts of elicitin-challenged and R. solanacearum-inoculated tobacco. Under all conditions tested, the induction of cyclase activity was closely correlated with induction of the cyclase mRNA level. In contrast, high levels of capsidiol were found only after treatment with the necrosis-inducing elicitin cryptogein, or after infiltration with HR-inducing bacterial strains. Low levels of capsidiol did accumulate after application of capsicein, an elicitin that induces little or no necrosis on tobacco, or after infection with a virulent bacterium. Hence, capsidiol accumulation, not 5-epi-aristolochene synthase gene expression or total sesquiterpene cyclase enzyme activity, appears to be a good marker for the HR of tobacco.
TL;DR: The possible involvement of the GP 66 elicitor from the canker stain agent of the plane tree in the activation of the phenolic metabolism of the plant is discussed.
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TL;DR: Differences in the cell wall polysaccharide composition of Alibertia myrcifolia and Rudgea jasminoides leaves are reported on to discuss the possible involvement of these pecticpolysaccharides with the capacity of elicitation of phytoalexin in R. jasmine and not in A. myRCifolia.
Abstract: Previous analysis of phytoalexin induction in tropical Rubiaceae revealed that species of Rudgea are capable of synthesizing phytoalexins in response to fungal inducers whereas species of Alibertia showed negative phytoalexin response even when different fungi were used. In the present work we report on differences in the cell wall polysaccharide composition of Alibertia myrcifolia and Rudgea jasminoides leaves. The cell walls of the phytoalexin-producing species R. jasminoides were more labile to Driselase and endopolygalacturonase treatment and contained higher relative amounts of pectins which were richer in acidic polysaccharides than the cell walls of A. myrcifolia. In contrast, a considerably higher proportion of arabinose was detected in pectic polysaccharides of A. myrcifolia. The results are discussed in terms of the possible involvement of these pectic polysaccharides with the capacity of elicitation of phytoalexin in R. jasminoides and not in A. myrcifolia. Additional index terms: Alibertia myrcifolia, hemicelluloses, pectins, Rudgea jasminoides.
TL;DR: Dose experiments showed that 60 μg/mL 4′‐aminomethyl‐4,5′,8‐trimethylpsoralen followed by 18 J/cm2 UV365 was sufficient to produce an accumulation of pisatin similar to that produced in response to the fungus.
Abstract: In the pea plant (Pisum sativum), compounds that intercalate into DNA induce the production of ∼20 major proteins similar to the pattern induced during nonhost disease resistance to the bean fungal pathogen, Fusarium solani f.sp. phaseoli. The pea phytoalexin, pisatin, as well as RNA homologous to several disease-resistance response (DRR) genes accumulate following treatment with these compounds. Psoralen was chosen to characterize this interaction further because it intercalates into DNA and, following irradiation with 365 nm UV light (UV365), forms covalent bonds with pyrimidines on either or both strands of DNA. This produces monoadducts or cross-links, respectively. Dose experiments showed that 60 μg/mL 4′-aminomethyl-4,5′,8-trimethylpsoralen followed by 18 J/cm2 UV365 was sufficient to produce an accumulation of pisatin similar to that produced in response to the fungus. Under these inducing conditions, there was an average of 0.19 adducts per kb of pea genomic DNA. The accumulation of pisatin and the RNA of several DRR genes by psoralen required photoactivation, which suggests that covalent binding to DNA was necessary for induction. As the promoters of several putative fungal-induced pea genes contain long stretches of d(AT)n, which is the preferred psoralen photobinding site, restriction fragments spanning DRR genes were examined after in vivo psoralen treatment. The rate of crosslinking was compared between fungal-induced and noninduced genes using a modified Southern blot analysis. Implications of the induction of the DRR due to psoralen binding are discussed.
TL;DR: In time-course experiments, the amounts of phytoalexin in hypocotyls of the resistant bean cultivar Flor de Mayo were determined after infection with Colletotrichum lindemuthianum andphaseollin and phaseollidin accumulated as a defence response.
Abstract: In time-course experiments, the amounts of phytoalexin in hypocotyls of the resistant bean cultivar Flor de Mayo were determined after infection with Colletotrichum lindemuthianum. Phaseollin and phaseollidin accumulated as a defence response. However, phaseollidin accumulated earlier than phaseollin and at greater concentrations (155 + 14 compared with 120 + 9 μg g−1 fresh weight). Phaseollidin was found conjugated as a glucoside in the tissue. Fungal treatment apparently led to a decline of approximately 50% in phaseollidin conjugate after only 7 h after infection. Isolation of vacuoles confirmed the presence of phaseollidin glucosides in this organelle. Treatment of the tissue or isolated protoplasts with a fungal elicitor also produced a decrease, by half, of phaseollidin conjugate concentrations from vacuoles isolated from both sources. The contribution of pre-existing pools of phaseollidin glycoside to the accumulation of this phytoalexin is discussed.
TL;DR: A new bioassay for measuring elicitor activity in rice plants is developed by cultivating rice plants under conditions of low temperature, high light intensity and high humidity, which induced the accumulation of the rice phytoalexins, momilactones and phytocassanes.
Abstract: When plants interact with pathogens, they protect themselves with various chemical and physical barriers. Some barriers, such as phytoalexin production, are induced by molecules called elicitors that are produced by pathogens. Although bioassays for measuring elicitor activity in suspension-cultured rice cells have been established, a bioassay for measuring elicitor activity in rice plants has been lacking. Phytoalexin accumulation in rice leaves in response to elicitor treatment is highly dependent on environmental conditions, establishing the right combination of conditions has been difficult. We have succeeded in developing a new bioassay by cultivating rice plants under conditions of low temperature (22°C), high light intensity (30, 000lux) and high humidity (80%). When the fifth leaves of rice plants cultivated under these conditions were fully expanded, the treatment of the fourth leaves with mycelial extracts of Magnaporthe grisea or Phytophthora infestans induced the accumulation of the rice phytoalexins, momilactones and phytocassanes.
TL;DR: Bioassays of HBQ and its hydroquinone established that the quinone is considerably more toxic to V. dahliae than is the Hydroquinone, which apparently represents a detoxification mechanism employed by the pathogen.
Abstract: o-Hibiscanone (HBQ) is a phytoalexin produced by kenaf in response to infection by the wilt pathogen Verticillium dahliae In several bioassays utilizing both conidia and mycelia of V dahliae, HBQ
TL;DR: 2,2,3,4-tetrahydro-6,7-dihydroxy-1-(4'-hydroxycinnamyliden)naphthalen-2-one were found as new phytoalexins of banana fruits, which are probably a biosynthetic intermediate of phenylphenalenones in banana fruits.
TL;DR: Two trinorcadalene phytoalexins, hibiscanal (2,8-dihydroxy-4,7-dimethoxy-6-methyl-1-naphthaldehyde) and o -hibiscanone (3, 8-dimethyl-1,2-Naphthoquinone), were isolated and identified from stem stele of kenaf ( Hibiscus cannabinus ) inoculated with the fungal pathogen Verticillium dahliae.
TL;DR: Two different isolates of the phytopathogen Phoma lingam metabolized and phyto-alexin cyclobrassinin 3 to the PHYtoalexins dioxibrassinin 5 and brassilexin 9; both 5 and 9 were further metabolized by each fungal isolate as discussed by the authors.
TL;DR: The cruciferous phytoalexin brassilexin 3 has been synthesized in four steps from indoline-2-thione via 3-(aminomethylene)indole-2 -thione 2, a metabolic intermediate of the detoxification pathway of the phy ToALxin cyclobrassinin 1.
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Journal Article•
TL;DR: Preliminary results indicated that the stilbene synthase gene could enhance the resistance of transgenic plants and their progenies to both pathogens.
Abstract: Immature embryos, mature embryos and embryogenic calli of 6 rice (Oryza sativa L) materials were transformed with particle bombardment The plasmids pSSVstl and pVE5+ were used, both containing the phytoalexin gene from grapevine coding for stilbene synthase, but driven by 35S and its own promoter respectively Through resistance selection for G418 (100 to 150 mg/L) or hygromycin (50 mg/L), 54 independent transgenic plants were isolated and further assessed by PCR, Southern blot and Dot blot analyses The transgenic plants and their progenies were tested for resistance to blast ( Pyricularia oryzae ) and bacterial blight of rice ( Xanthomonas oryzae ) Preliminary results indicated that the stilbene synthase gene could enhance the resistance of transgenic plants and their progenies to both pathogens
01 Jan 1998
TL;DR: The results suggest that the distinct behavior of the two species in relation to phytoalexin production could be related to differences in the pectin composition leading to the release of oligosaccharins of distinct composition.
Abstract: Leaves of Alibertia myrcifolia and Rudgea jasminoides, two tropical Rubiaceae species with different behavior toward phytoalexin induction, were analyzed in relation to the presence of oligosaccharins in their cell wall polysaccharides. Fragments active on soybean cotyledons were liberated from cell walls of both species through autoclaving or Driselase treatment. The oligosaccharins isolated from R. jasminoides were more stable and more active as phytoalexin elicitors than the ones isolated from A. myrcifolia. The results suggest that the distinct behavior of the two species in relation to phytoalexin production could be related to differences in the pectin composition leading to the release of oligosaccharins of distinct composition. Additional index terms: Alibertia myrcifolia, defensive responses, Rudgea jasminoides.
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TL;DR: In potato dextrose broth, the growth of A. niger showed a steady increase up to 32 hr while it was significantly inhibited with P1 in microtiter plates, and P2, P3 and P4 had significantly less antifungal activity as compared to P1.
Abstract: Phytoalexins from four different treatments viz. control, AF 1-treated, A. niger-treated, and dual inoculated were separated by TLC showed that one phytoalexin with an Rf value of 0.628 (P1) appeared on 2nd day only in dual-inoculated seeds of groundnut (A. hypogaea). By 3rd day three additional phytoalexins were visualized in response to A. niger-treatment with lower Rf values 0.485 (P2), 0.388 (P3) and 0.314 (P4) as compared to P1. In dual inoculated seedlings, P1 and P3 could be visualized while only P1 appeared in response to AF 1 on 3rd day. All the compounds lost fluorescence on exposure to light, got converted to pale yellow colour. In all the treatments no phytoalexin accumulation was observed after 3rd day. All the four phytoalexins had a major peak between 338 and 339.5 nm. In potato dextrose broth, the growth of A. niger showed a steady increase up to 32 hr while it was significantly inhibited with P1 in microtiter plates. P2, P3 and P4 (in the same order) had significantly less antifungal activity as compared to P1. The antifungal activity of the phytoalexins decreased with decrease in their Rf value.