Showing papers on "Phytoalexin published in 1983"
TL;DR: Results indicate that an O 2 − -generating system may be activated in potato tissues during the incompatible interaction induced by invading fungi or fungal wall components, and also that the generation of O 1 − may be involved during hypersensitive cell death as a trigger of the sequence of resistance reactions.
Abstract: Potato tuber tissue discs, which were aged after wounding in order to acquire hypersensitive reactivity, reduced extracellular cytochrome c and nitroblue tetrazolium (NBT) following inoculation with an incompatible, but not compatible, race of Phytophthora infestans . The cytochrome c -reducing activity rapidly increased from l to 4 h after inoculation along with an increase in the percentage of hypersensitively dead cells, and then decreased from the time when most of the penetrated cells had died. A localized activation of NBT reduction around invading hyphae of the incompatible, but not those of the compatible, race was observed at early stages of penetration before cell death. The reductive activity of the discs was also elicited by treatment with a hypersensitivity-eliciting substance, hyphal wall components of the fungus. Superoxide dismutase (SOD), an enzyme catalysing the conversion of the superoxide anion (O 2 − ) to H 2 O 2 and O 2 inhibited the enhanced reducing activity of the discs when added to the assay solution, indicating that cytochrome c and NBT may be reduced by O 2 − generated from the discs. Pre-infectional, vacuum infiltration of the discs with a solution containing SOD significantly delayed the occurrence of hypersensitive cell death caused by infection with the incompatible race as well as the accumulation of phytoalexin. Application of SH-binding reagents and NADP + , but not respiratory inhibitors, inhibited the elicitation of the reducing activity caused by infection with the incompatible race. These results indicate that an O 2 − -generating system may be activated in potato tissues during the incompatible interaction induced by invading fungi or fungal wall components, and also that the generation of O 2 − may be involved during hypersensitive cell death as a trigger of the sequence of resistance reactions.
773 citations
TL;DR: 6-Methoxymellein was identified as a common phytoalexin produced by carrot roots irrespective of the species of challenging fungi and it was shown that cultured carrot cells produced 6-methoxcyellein when the culture was inoculated with fungi.
148 citations
TL;DR: Observations suggest that the membrane binding sites are mycolaminaran-specific receptors which are physiologically involved in the initiation of phytoalexin production in soybean cotyledons.
Abstract: Soybean membrane preparations specifically bound [14C]mycolaminaran, a branched β-1,3-glucan produced by Phytophthora sp. which elicits production of the phytoalexin glyceollin in soybean tissues. A Scatchard plot of the binding data disclosed the presence of a single affinity class of binding sites with a Kd value of 11.5 micromolar for the glucan. To assess the physiologic importance of mycolaminaran binding in phytoalexin elicitation, several derivatives of mycolaminaran were prepared. Reduced mycolaminaran had slightly greater elicitor activity and binding affinity than the native substance, while periodinated mycolaminaran was virtually devoid of either elicitor activity orbinding capability. Phosphorylated mycolaminaran, on the other hand, gave values for both elicitor activity and membrane binding which were intermediate between the native and periodinated preparations. No other tested carbohydrates competed with the binding of [14C]mycolaminaran. Soybean membrane preparations contained β-1,3-endoglucanase activity that degraded mycolaminaran and reduced both its efficiency as a phytoalexin elicitor and its membrane binding at temperatures above 0°C. Once [14C]mycolaminaran bound to membranes, however, it was not appreciably susceptible to glucanase attack and could not be displaced with excess unlabeled ligand. Taken collectively, the observations suggest that the membrane binding sites are mycolaminaran-specific receptors which are physiologically involved in the initiation of phytoalexin production in soybean cotyledons. Because the binding of mycolaminaran to membranes was abolished by heat and proteolytic enzymes, the receptor is probably a protein(s) or glycoprotein(s).
118 citations
TL;DR: The results suggest that certain abiotic and biotic compounds which induce responses similar to those induced in the authentic “resistance response” may be useful in investigating the mode by which these responses are induced.
Abstract: Pea endocarps were treated with optimal concentrations of biotic and abiotic compounds which are potent inducers of phytoalexin production and of certain disease resistance responses. Total cell mRNA which accumulated during induction was translated in vitro with a rabbit reticulocyte protein synthesizing system. Both the synthesis of phenylalanine ammonia lyase (PAL) and the two-dimensional separations of total labelled proteins from the various inducer treatments were compared. The increases in the synthesis of the observed specific proteins, induced by the DNA-specific compounds, result from the increased translation activity of mRNAs within the pea tissue. The induction of PAL and other specific proteins by chitosan, a glucosamine polymer in fungal walls, resembled the patterns induced by Fusarium solani f. sp. phaseoli macroconidia. There were only minor differences in protein induction by the F. solani f. sp. phaseoli macroconidia, actinomycin D, 4,5′8-trimethylpsoralen plus 366 nm UV light, and 260 nm UV light. Major shifts in the protein synthesis patterns were found in proteins translated from the RNA from CdCl 2 and quinacrine-treated tissue. Our results suggest that certain abiotic and biotic compounds which induce responses similar to those induced in the authentic “resistance response” may be useful in investigating the mode by which these responses are induced.
67 citations
TL;DR: Previous suggestions that a low molecular weight, diffusible factor of host plant origin is involved (in French bean) in the intercellular transmission of the elicitation response to abiotic elicitors are extended.
Abstract: Treatment of hypocotyl sections or cell suspension cultures of dwarf French bean (Phaseolus vulgaris L.) with an abiotic elicitor (denatured ribonuclease A) resulted in increased extractable activity of the enzyme l-phenylalanine ammonia-lyase. This induction could be transmitted from treated cells through a dialysis membrane to cells which were not in direct contact with the elicitor. In hypocotyl sections, induction of isoflavonoid phytoalexin accumulation was also transmitted across a dialysis membrane, although levels of insoluble, lignin-like phenolic material remained unchanged in elicitor-treated and control sections. In bean cell suspension cultures, the induction of phenylalanine ammonia-lyase in cells separated from ribonuclease-treated cells by a dialysis membrane was also accompanied by increases in the activities of chalcone synthase and chalcone isomerase, two enzymes previously implicated in the phytoalexin defense response. Such intercellular transmission of elicitation did not occur in experiments with cells treated with a biotic elicitor preparation heat-released from the cell walls of the bean pathogen Colletotrichum lindemuthianum. The results confirm and extend previous suggestions that a low molecular weight, diffusible factor of host plant origin is involved (in French bean) in the intercellular transmission of the elicitation response to abiotic elicitors.
64 citations
TL;DR: Under the experimental conditions glyceollin had no significant effect on the growth, development, or subsequent survival of the larvae, indicating that the phytoalexins may be a mild digestibility-reducing factor for the loopers.
Abstract: Effects of soybean phytoalexins on the feeding of the soybean looper and Mexican bean beetle were investigated to test the hypothesis that phytoalexins might be a defense mechanism of plants against insects as well as against pathogens. Short-term behavioral responses to the phytoalexins were analyzed using dual-choice tests with phytoalexin-rich and phytoalexin-poor (control) tissues. Phytoalexin production was elicited with ultraviolet radiation. Results from the dual-choice tests indicated that 6th instar soybean looper larvae fed equally on the control and phytoalexin-rich tissues. Feeding by adult and 4th instar Mexican bean beetles, however, was strongly deterred by the phytoalexins as evidenced by “single-bite” mandible scars on the phytoalexin-rich cotyledon discs. Nutritional effects of the isoflavonoid phytoalexin glyceollin on early instar soybean looper larvae were tested by incorporating the phytoalexin into an artificial medium at a level of 1% dry weight (0.15% fresh weight). The larvae were reared for 7 days from emergence on diets of control and glyceollin-containing media. Although survival on the glyceollin diets was initially less than on the control diets, under the experimental conditions glyceollin had no significant effect on the growth, development, or subsequent survival of the larvae. Efficiency of food utilization (ECI) was reduced, indicating that the phytoalexins may be a mild digestibility-reducing factor for the loopers. Implications of the results for host-plant resistance are discussed.
61 citations
TL;DR: Leaves of Sophora japonica produced the pterocarpanoid phytoalexins medicarpin and maackiain in response to inoculation with the fungus Helminthosporium carbonum and this appears to be the first case in which (+) enantiomers of 6aH pterOCarpans have been reported as phy toalexin samples.
41 citations
TL;DR: In this article, the sesquiterpenoid phytoalexins lubimin, rishitin and solavetivone were found to be present in the cells and the medium.
39 citations
28 citations
TL;DR: The elicitor activity of sucrose was abolished by actinomycin D, puromycin, and cycloheximide at a concentration of 10 micrograms per milliliter or greater, suggesting that gene derepression is required for expression of the phytoalexin response.
Abstract: Extracts of seeds and leaves of the tropical legume Cajanus cajan (L.) Millsp. (the pigeon pea) elicited the accumulation of three phytoalexins when applied as droplets to superficially wounded leaves of the plant. The active component was purified and identified as sucrose. Phytoalexin accumulation was proportional to the logarithm of the concentration of sucrose applied, with maxima ranging from 338 to 455 micrograms per gram (fresh weight) of leaf tissue. The sucrose concentrations required to elicit half these amounts ranged from 20 to 35 micrograms per milliliter, but other sugars had little effect even at 1000 micrograms per milliliter. The elicitor activity of sucrose was abolished by actinomycin D, puromycin, and cycloheximide at a concentration of 10 micrograms per milliliter or greater, suggesting that gene derepression is required for expression of the phytoalexin response.
23 citations
TL;DR: The glucan elicitor from cell walls o f the fungal pathogen, Phytophthora megasperma f.
Abstract: Abstract The glucan elicitor from cell walls o f the fungal pathogen, Phytophthora megasperma f. sp. glycinea, caused a decrease in activity of 3-hydroxy-3-methylglutaryl coenzyme A reductase in wounded soybean cotyledons, whereas wounding alone led to an increase in the activity of this enzyme. A decrease o f HMG -CoA reductase activity after elicitor treatment was also found in soybean hypocotyls and soybean cell cultures. In contrast to the activity o f HMG -CoA reductase, the activity of dimethylallylpyrophosphate: 3,6a,9-trihydroxypterocarpan dimethylallyltransferase increases after elicitor challenge of soybean cell cultures and after inoculation of soybean hypocotyls (cv Amsoy 71) with mycelium of either race 1 (incompatible) or race 3 (compatible) of P. megasperma.
TL;DR: The P. vulgaris enzyme showed similarities to the enzyme recently purified from cell cultures of Petroselinum hortense with respect to molecular weight, pH optimum, ability to catalyse 14 CO 2 exchange between NaH 14 CO 3 and malonyl-CoA, and overall response of naringenin formation to varying thiol concentration, but appeared much less stable.
TL;DR: Three isoflavonoid phytoalexins of Phaseolus vulgaris, phaseollin, kievitone and phaseollinisoflavan, were concurrently metabolized by Fusarium solani f.
Abstract: Three isoflavonoid phytoalexins of Phaseolus vulgaris , phaseollin, kievitone and phaseollinisoflavan, were concurrently metabolized by Fusarium solani f. sp. phaseoli . The products of these reactions were the known metabolites la-hydroxyphaseollone and kievitone hydrate, from phaseollin and kievitone respectively, as well as a not yet fully characterized compound—designated metabolite-1—from phaseollinisoflavan. In liquid cultures, although all three phytoalexins (each at 7·5 μg ml −1 ) had disappeared c. 30 h after their addition to the medium, loss of kievitone, and the concomitant appearance of kievitone hydrate, were most rapid. Triple metabolism of the phytoalexins also occurred when F. solani f. sp. phaseoli grew on agar impregnated with the three compounds. All three products appeared to be less toxic than their parent compounds. When cell-free filtrates were prepared from liquid cultures of the fungus, whether or not induction had been attempted by prior addition of small amounts of the phytoalexins, only kievitone was transformed.
TL;DR: Eight phytoalexins have been isolated from Phaseolus aureus (mung bean) seedlings after treatment with aqueous CuCl2 and the antifungal activities against Cladosporium cucumerinum were determined.
Abstract: Abstract Eight phytoalexins have been isolated from Phaseolus aureus (mung bean) seedlings after treatment with aqueous CuCl2. These compounds include three isoflavones: genistein, 2′-hydroxygenistein and a compound tentatively identified as 2,3-dehydrokievitone, four isoflavanones: dalbergioidin, kievitone, cyclokievitone and 5-deoxykievitone, and the pterocarpan phaseollidin. The antifungal activities against Cladosporium cucumerinum were determined.
01 Nov 1983
01 Jan 1983
TL;DR: This chapter deals with recent studies on the biochemistry of disease resistance expression in Phaseolus vulgaris L., paying particular attention to the regulation of phytoalexin accumulation, with strong evidence that the differential accumulation of the isoflavonoid derivative phaseollin and other structurally related phy toalexins plays a crucial role in the specificity of host resistance.
Abstract: This chapter deals with recent studies on the biochemistry of disease resistance expression in Phaseolus vulgaris L., paying particular attention to the regulation of phytoalexin accumulation. Advantages of this system for biochemical studies are: (a) The disease resistance profile of P vulgaris has been characterised genetically to some extent (Meiners, 1981) and physiologically (Bailey, 1981). In particular, different cultivars (eg. Kievit, Immuna, Red Kidney) undergo highly specific interactions with physiological races of Colletotrichum lindemuthianum (eg. β,δ,γ) the causal agent of anthracnose disease of P. vulgaris. (b) The physiology of this interaction has been extensively studied using hypocotyls, the organ which together with leaves is the natural site of attack by C. lindemuthianum. There is strong evidence that the differential accumulation of the isoflavonoid derivative phaseollin and other structurally related phytoalexins such as phaseollidin, phaseollinisoflavan and kievitone in resistant and susceptible interactions plays a crucial role in the specificity of host resistance (Bailey, 1981). (c) Detailed study of the effects of phytoalexin inducing agents on phenylpropanoid metabolism in P. vulgaris hypocotyls indicates that accumulation of phytoalexins is a specific event, and the levels of most other phenylpropanoid products (eg. hydroxycinnamic acids) remain roughly constant relative to untreated control tissue (Rathmell and Bendall, 1971).
Journal Article•
01 Jan 1983
TL;DR: Parsley suspension culture cells are treated with a cell wall preparation of Phytophthora megasperma var.
Abstract: In the present study, parsley suspension culture cells are treated with a cell wall preparation of Phytophthora megasperma var. glycinia and this interaction is considered as a model system for plant-fungal pathogen interactions with respect to phytoalexin biosynthesis. The relevance of this system for these studies can best be understood by a general discussion of phytoalexins and their biosynthesis in more intensively researched plant families, such as the Leguminosae.
TL;DR: Lathyrus sativus was investigated for the nature of its phytoalexin response with the result that leaflets, immature pods, and seeds were induced to produce 6a-hydroxy- 3-methoxy-8,9-methylenedioxypterocarpan (pisatin).
Abstract: Lathyrus sativus was investigated for the nature of its phytoalexin response with the result that leaflets, immature pods, and seeds were induced to produce 6a-hydroxy- 3-methoxy-8,9-methylenedioxypterocarpan (pisatin). Evidence is presented for the metabolism of pisatin, by the wound pathogen Botrytis cinerea, to a phenolic congener, 3,6a-hydroxy-8,9-methylenedioxypterocarpan
TL;DR: Antibacterial substances were produced in the citrus leaves inoculated with Pseudomonas sp.
Abstract: Antibacterial substances were produced in the citrus leaves inoculated with Pseudomonas sp. which was known as a bacterium antagonistic to the symptom development of citrus canker. The crude extracts from the leaves inoculated with cell suspension of Pseudomonas sp. (A-ex), or mixture of Pseudomonas sp. and Xanthomonas campestris pv. citri (AX-ex) remarkably inhibited the growth of X. campestris pv. citri, whereas the crude extract from the leaves inoculated with X. campestris pv. citri alone (Xex) showed week inhibition. Several fractions of A-ex by thin layer chromatography (TLC) on a silica gel plate markedly inhibited the growth of X. campestris pv. citri. From these fractions, two inhibitory substances, CLP-3 and CLP-5, were isolated by TLC with two developing solvent systems. The concentrations of these two substances were extremely high in A-ex and AX-ex, but very low in X-ex. The substances showed higher antibacterial activity against Pseuomonas sp. than X. campestris pv. citri. It suggests that these substances might be phytoalexins. These antibacterial substanes produced by inoculation of Pseudomonas sp. are considered to play some important roles in the mechanisms of the inhibition toward development of citrus canker. (Received May 30, 1983) Key Word: antagonistic bacterium, phytopalexin, X. campestris pv. citri.