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Volatile and gaseous metabolites released by germinating seeds of lentil and maize cultivars with different susceptibilities to fusariosis and smut.

The effect of volatile and gaseous metabolites released by germinating seeds of lentil cultivars more and less susceptible to fusariosis on the germination of spores of Mucor racemosus, Trichoderma viride, Verticillium dahliae and Botrytis cinerea was found to depend rather on the fungal genus than on the lentil cultivar. However, spores of Fusarium oxysporum reacted more sensitively during germination to the presence of exudates of both cultivars, when the more susceptible lentil displayed a stimulation, the less susceptible one an inhibition of spore germination. The greatest difference in the effect of exudates was observed in the more and less susceptible maize cultivars with respect to the germination of chlamydospores of Ustilago maydis, especially during the first hours of seed germination. Analysis of the exudates of germinating seeds showed the release of a greater amount of ethanol and methanol with acetaldehyde by the more susceptible cultivars of lentil and particularly maize.

Ethanol↗

Residues of dicloran in clingstone peaches after pre- and postharvest application.

Trials were carried out over a period of several years in order to test the efficacy of pre- and postharvest treatments against fungi causing postharvest rots of stored clingstone peaches destined to canning. Among the fungicides tested, dicloran (2, 6-dichloro-4-nitroaniline) was applied against Botrytis cinerea, Monilia cinerea and Rhizopus stolonifer. The purpose of this work was to determine the residues of this fungicide in fresh, washed, peeled and canned fruits. No relevant data are reported in the open literature to our knowledge. Some residue data, most of them produced by the manufacturer of the compound, were evaluated by the FAO/WHO Joint Meeting on Pesticide Residues (JMPR) and are summarized in the 1974 and 1977 monographs (FAO/WHO 1975 and 1978).

Agriculture↗

Protection of oilseed rape (Brassica napus) toward fungal pathogens by strains of plant-associated Bacillus amyloliquefaciens.

In this report, four Bacillus strains were tested for effects on plant fitness and disease protection of oilseed rape (Brassica napus). The strains belonged to newly discovered plant-associated Bacillus amyloliquefaciens and a recently proposed species, Bacillus endophyticus. The fungal pathogens tested represented different infection strategies and included Alternaria brassicae, Botrytis cinerea, Leptosphaeria maculans, and Verticillium longisporum. The B. amyloliquefaciens strains showed no or a weak plant growth promoting activity, whereas the B. endophyticus strain had negative effects on the plant as revealed by phenological analysis. On the other hand, two of the B. amyloliquefaciens strains conferred protection of oilseed rape toward all pathogens tested. In vitro experiments studying the effects of Bacillus exudates on fungal growth showed clear growth inhibition in several but not all cases. The protective effects of Bacillus can therefore, at least in part, be explained by production of antibiotic substances, but other mechanisms must also be involved probably as a result of intricate plant-bacteria interaction. The protective effects observed for certain Bacillus strains make them highly interesting for further studies as biocontrol agents in Brassica cultivation.

Bacillus↗

Biotransformation of 6,7-epoxygeraniol by fungi.

The biotransformation of 6,7-epoxygeraniol by resting cells of selected fungi was investigated. The main product obtained from the transformation in Rhodotorula glutinis and R. marina cultures was 6,7-epoxynerol (5-48% of chloroform extracts), whereas Saccharomyces cerevisiae, Candida parapsilosis and C. kefyr reduced this substrate to 6,7-epoxycitronellol (30-33% of chloroform extracts). Cultures of Yarrowia lipolytica, Botrytis cinerea and S. cerevisiae promoted the cyclisation of 6,7-epoxygeraniol to 2-methyl-2-(2-hydroxyethyl)-5-(2-hydroxyprop-2-yl)tetrahydrofuran (11-99% of chloroform extracts). The biotransformation of 6,7-epoxynerol was also investigated. However, none of the tested micro-organisms converted this compound.

Acyclic Monoterpenes↗

Antimicrobial activity of resin acid derivatives.

The wide potential of resin acids as bioactive agents gave rise to a growing effort in the search for new applications of the natural forms and their derivatives. In some of these compounds, the antimicrobial activity is associated to the presence in the molecules of functional groups such as the hydroxyl, aldehyde, and ketone or to their cis or trans configurations. The resin acid family covers a spectrum of antimicrobial activities against several microorganisms, from bacteria to fungi, in which the mode of action was studied by electron microscopy. The morphological alterations are consistent with an unspecific mode of action causing inhibition of the fungal growth or damaging the fungal cells in parallel with a mechanism of resistance based on the retention of the compound by the lipid accumulation. The sterol composition of phytopathogenic fungi Botrytis cinerea and Lophodermium seditiosum treated with methyl cis-7-oxo-deisopropyldehydroabietate revealed the presence of ergosterol (M+ 396) and dihydroergosterol (M+ 398) in both cultures showing that this compound did not interfere with the ergosterol metabolic pathway of both fungi.

Anti-Bacterial Agents↗

Improved antifungal activity of a mutant of Trichoderma harzianum CECT 2413 which produces more extracellular proteins.

Trichoderma harzianum is a well-known biological control agent against fungal plant diseases. In order to select improved biocontrol strains from Trichoderma harzianum CECT 2413, a mutant has been isolated for its ability to produce wider haloes than the wild type, when hydrolysing pustulan, a polymer of beta-1,6-glucan. The mutant possesses between two and four times more chitinase, beta-1,3- and beta-1,6-glucanase activities than the wild type, produces about three times more extracellular proteins and secretes higher amounts of a yellow pigment (alpha-pyrone). This mutant performed better than the wild type during in vitro experiments, overgrowing and sporulating on Rhizoctonia solani earlier, killing this pathogen faster and exerting better protection on grapes against Botrytis cinerea.

Antifungal Agents↗

Molecular characterization and in planta detection of Sclerotinia sclerotiorum endopolygalacturonase genes.

Sclerotinia sclerotiorum, a plant pathogenic ascomycete, secretes multiple pectinolytic enzymes that facilitate penetration, colonization, and maceration of the plant tissues. Molecular analysis has previously revealed that the pectinolytic system of the fungus is organized as a multigene family, among which a subfamily of three members encoding for neutral endopolygalacturonase (endoPG) isoforms has been characterized. Here we describe the isolation and characterization of three additional endoPG-encoding genes ( pg5, pg6, and pg7) that belong to distinct phylogenetic groups. Pairwise sequence comparison between the known endoPGs from S. sclerotiorum revealed 43% to 97% identity, and the genomic organization of the pectinolytic system showed a great similarity to that of the related necrotroph Botrytis cinerea. During plant pathogenesis, a sequential expression of the endoPG-encoding genes was shown.

Ascomycota↗

Proteomic response of the biological control fungus Trichoderma atroviride to growth on the cell walls of Rhizoctonia solani.

Trichoderma atroviride has a natural ability to parasitise phytopathogenic fungi such as Rhizoctonia solani and Botrytis cinerea, therefore providing an environmentally sound alternative to chemical fungicides in the management of these pathogens. Two-dimensional electrophoresis was used to display cellular protein patterns of T. atroviride (T. harzianum P1) grown on media containing either glucose or R. solani cell walls. Protein profiles were compared to identify T. atroviride proteins up-regulated in the presence of the R. solani cell walls. Twenty-four protein spots were identified using matrix-assisted laser desorption ionisation mass spectrometry, liquid chromatography mass spectrometry and N-terminal sequencing. Identified up-regulated proteins include known fungal cell wall-degrading enzymes such as N-acetyl-beta-D: -glucosaminidase and 42-kDa endochitinase. Three novel proteases of T. atroviride were identified, containing sequence similarity to vacuolar serine protease, vacuolar protease A and a trypsin-like protease from known fungal proteins. Eukaryotic initiation factor 4a, superoxide dismutase and a hypothetical protein from Neurospora crassa were also up-regulated as a response to R. solani cell walls. Several cell wall-degrading enzymes were identified from the T. atroviride culture supernatant, providing further evidence that a cellular response indicative of biological control had occurred.

Cell Wall↗

Molecular cloning and expression of the nag1 gene (N-acetyl-beta-D-glucosaminidase-encoding gene) from Trichoderma harzianum P1.

A 72-kDa N-acetyl-beta-D-glucosaminidase was purified from the mycoparasitic fungus Trichoderma harzianum P1; antibodies were raised against it, and aa-sequences were obtained. The antibody reacted with a single 72-kDa protein band in culture filtrates of T. harzianum grown on chitin, and was subsequently used to clone the corresponding nag1 gene from a lambdagt11 cDNA expression library. It was interrupted by two short introns and encoded a protein of 580 amino acids. The deduced protein sequence contained aa-sequence areas of high similarity to N-acetyl-glucosaminidases from other eukaryotes such as Candida albicans, and invertebrate and vertebrate animal tissues. The highest similarity was observed with the corresponding gene from the silkworm. The aa-sequence of a tryptic fragment of purified N-acetyl-beta-D-glucosaminidase from T. harzianum corresponded to a deduced aa sequence from a portion of the cloned gene, thus verifying that the protein is encoded by nag 1. Southern analysis showed that nag 1 is present as a single-copy gene in T. harzianum. Expression of nag1-mRNA was strongly induced upon growth on chitin, N-acetyl-glucosamine and the cell walls of Botrytis cinerea used as a carbon source. The appearance of the corresponding N-acetyl-beta-D-glucosaminidase protein, as determined by Western analysis, paralleled the pattern of nag 1 expression, thereby suggesting that its formation is regulated at the level of transcription.

Acetylglucosaminidase↗

Identification of pathogen-responsive regions in the promoter of a pepper lipid transfer protein gene (CALTPI) and the enhanced resistance of the CALTPI transgenic Arabidopsis against pathogen and environmental stresses.

The 5' flanking region of the CALTPI gene, which encodes a basic lipid transfer protein, was isolated and characterized from the genomic DNA of Capsicum annuum. Four different regions of the promoter sequence of the CALTPI gene were fused to the beta-glucuronidase (GUS) coding region. In an Agrobacterium-mediated transient expression assay, the transcriptional activations of the promoter deletions were examined in tobacco leaves after infection with Pseudomonas syringae pv. tabaci, and treatment with ethylene and salicylic acid. The -808 bp region of the CALTPI gene promoter sequence exhibited full promoter activity. The W-box and ERE-box elements, which are essential for induction by all signals, were localized in the region between -555 bp and -391 bp upstream of the translation initiation site. A CALTPI transgene was then introduced under the control of the 35S promoter into the Arabidopsis ecotype Col-0. Transgenic Arabidopsis lines expressing the CALTPI gene developed rapidly compared to the wild-type plants, indicating that CALTPI may be involved in plant development. Overexpression of the CALTPI gene enhanced the resistance against infection by P. syringae pv. tomato and Botrytis cinerea. The transgenic plants expressing the CALTPI gene also showed high levels of tolerance to NaCl and drought stresses at various vegetative growth stages. No transcription of the PR-1, PR-2, PR-5, thionin, and RD29A genes was observed in untreated leaf tissues of the transgenic plants. The enhanced resistance to pathogen and environmental stresses in transgenic Arabidopsis correlated with the enhanced expression of the CALTPI gene.

Adaptation, Physiological↗

Desiccation and osmotic stress increase the abundance of mRNA of the tonoplast aquaporin BobTIP26-1 in cauliflower cells.

Changes in vacuolar structure and the expression at the RNA level of a tonoplast aquaporin (BobTIP26-1) were examined in cauliflower (Brassicaoleracea L. var. botrytis) under water-stress conditions. Gradual drying out of slices of cauliflower floret tissue caused its collapse, with a shrinkage in tissue and cell volumes and an apparent vesiculation of the central vacuole, whereas osmotic stress resulted in plasmolysis with a collapse of the cytoplasm and the central vacuole within. Osmotic stress caused a rapid and substantial increase in BobTIP26 mRNA in slices of floret tissue. Exposure of tissue slices to a regime of desiccation showed a slower but equally large rise in BobTIP26 mRNA followed by a rapid decline upon rehydration. In situ hybridization showed that BobTIP26-2 mRNA is expressed most highly in meristematic and expanding cells of the cauliflower florets and that desiccation strongly increased the expression in those cells and in differentiated cells near the xylem vessels. These data indicate that under water-deficit conditions, expression of the tonoplast aquaporin gene in cauliflower is subject to a precise regulation that can be correlated with important cytological changes in the cells.

Animals↗

Plate assay for determining the time of production of protease, cellulase, and pectinases by germinating fungal spores.

A new method for detecting enzymes produced by fungal spores during germination is described here. With this method, the production of enzymes such as protease, cellulase, or pectinase can be correlated with the extent of spore germination. Germination is studied in vitro on agar-based media containing protein, cellulose, or pectin. The spores are immobilized on a permeable membrane mounted on the substrate-containing medium. At various times after inoculation the membrane-bound spores are removed and the medium is stained. The extent of germination is assessed by microscopic examination of the spores and the presence of active hydrolytic enzymes is revealed by the staining. The staining methods are sensitive; detection limits are 1 X 10(-3) unit of cellulase; 2 X 10(-4) unit of protease; 3 X 10(-3) unit of pectin lyase; 3.5 units of polygalacturonase; 2 X 10(-3) unit of pectin methyl esterase. The method has been demonstrated by studying the production of enzymes by germinating conidia of Botrytis cinerea. Cellulase and protease were present before any spores germinated. Pectin lyase was first observed when at least 80% of the spores had germinated. Pectin methyl esterase and polygalacturonase were not produced by the spores.

Cellulase↗

Plant pyruvate dehydrogenase complex purification, characterization and regulation by metabolites and phosphorylation.

The pyruvate dehydrogenase complex was purified from mitochondria of cauliflower, Brassica oleracea var. botrytis floral buds to a specific activity of 5.4 mumol of NADH/min per mg of protein. The pyruvate dehydrogenase complex required CoASH, NAD+, thiamine pyrophosphate and Mg2+ for the oxidative decarboxylation of pyruvate. The kinetic analysis of the complex gave a series of parallel lines for all substrates. Product interaction patterns showed that NADH is competitive with NAD+; acetyl-CoA is competitive with CoASH; and NADH and acetyl-CoA uncompetitive with pyruvate. These kinetic patterns suggest a multisite ping-pong mechanism as described by Cleveland ((1973) J. Biol. Chem 248, 8353). The noncompetitive inhibition of NADH versus CoASH, and acetyl-CoASH versus NAD are not predicted by this mechanism. Regulation of the complex was more sensitive to the NADH/NAD+ ratio than acetyl-CoA/CoASH ratio. Hydroxypyruvate and glyoxylate inhibited the complex noncompetitively versus pyruvate. The pyruvate dehydrogenase complex was inactivated and phosphorylated by ATP. The ATP dependent inactivation is believed to be enzyme catalyzed by a pyruvate dehydrogenase complex kinase. However, no evidence was found for a plant pyruvate dehydrogenase complex phosphatase. The results suggest that the cauliflower pyruvate dehydrogenase complex is regulated by a phosphorylation-dephosphorylation mechanism.

Adenosine Triphosphate↗

Large-scale purification and subunit structure of DNA-dependent RNA polymerase II from cauliflower inflorescence.

DNA-dependent RNA polymerase II (nucleosidetriphosphate:RNA nucleotidyltransferase, EC 2.7.7.6) from cauliflower inflorescence (Brassica oleracae, var. botrytis) was highly purified by polyethyleneimine treatment on a large scale. The solubilized enzyme was partially purified by polyethyleneimine fractionation and subjected to chromatography on DEAE-Sephadex and phosphocellulose, and subsequently to sedimentation in a glycerol gradient. The specific activity (231 nmol/mg per 10 min) of this enzyme was comparable to that reported for other purified eukaryotic RNA polymerases. Analysis of the purified RNA polymerase II by polyacrylamide gel electrophoresis under nondenaturing conditions revealed a single band. The subunit composition of the enzyme was analyzed by electrophoresis under denaturing conditions. The RNA polymerase II contained subunits with molecular weights and molar ratios (in parentheses) of 180 000(1), 130 000(2), 48 000(2), 25 000(4), and 19 500(4).

Centrifugation, Density Gradient↗

Pine stilbene synthase cDNA, a tool for probing environmental stress.

Stilbene synthase cDNAs were isolated from a pine (Pinus sylvestris) cDNA library. Poly(A)+RNA required for the preparation was obtained from young seedlings challenged with Botrytis cinerea. A full-length cDNA encoding pinosylvin-forming stilbene synthase was sequenced, and the deduced amino acid sequence was compared with sequences of resveratrol-forming stilbene synthases. The cDNA coding for the key enzyme of pinosylvin formation is a valuable tool for detecting early effects of environmental stress in pine needles.

Acyltransferases↗

Direct injection into the HPLC column for monitoring the behaviour of xenobiotics in biological media. II. Behaviour of cymoxanil in fungus and locust and of E-destruxin in locust.

Multidimensional chromatographies (MDC) implying either a single column with an unique packing designed for providing several separation modes such as internal surface reversed-phase (ISRP), or C1 large pores particles, or multi-column switching technique using the previous supports as guard columns, allow fast and easy direct monitoring of pesticides into plant or animal biological media. In such a way, the comparative study of the agricultural fungicide cymoxanil in two strains of Botrytis cinerea of different sensitivities gave concordant conclusions with the previous work using radiolabelled cymoxanil and TLC. Moreover, as a comparison, a study of the metabolism of this xenobiotic was also followed in animal biological fluids likely to contain peptidases. In locust or lobster haemolymph, an unusual isomerization into a cyclic compound was thus demonstrated accompanying the classical peptidase-depending metabolism generally observed in plants. The same chromatographic approaches were tested and compared for monitoring the metabolism of the natural insecticide toxin E-destruxin in insects. A detoxication process leading to the less toxic E-diol destruxin was evidenced in the organs or haemolymph of the locust Locusta migratoria chosen as a model of non-target insects.

Acetamides↗

The effect of zeolite on the toxicity of lead to fungi.

In order to determine whether clinoptilolite, a naturally occurring zeolite, had any ameliorative effect on lead (Pb) toxicity to fungi, a series of growth experiments were performed. Three fungi, Aspergillus niger, Botrytis cinerea, and Fusarium culmorum, were grown on appropriately amended solid agar media, and their linear extension rates determined. B. cinerea was 25% inhibited, as compared to a control, at 100 mg dm(-3) Pb, and completely inhibited at 1000 mg dm(-3) Pb. F. culmorum was completely inhibited, and A. niger 97% inhibited at 1000 mg dm(-3) Pb. The addition of 3% clinoptilolite partially removed this inhibition in the case of A. niger and B. cinerea and almost completely removed it for F. culmorum. At a constant 500 mg dm(-3) Pb, increasing concentrations of clinoptilolite increased the linear extension rate of F. culmorum and B. cinerea, close to the rates achieved by the untreated controls. A. niger was not inhibited markedly at this Pb concentration. The evidence suggests that the Pb is adsorbed by the clinoptilolite which reduces the availability, and hence toxicity, of the metal to the fungi.

Journal Article↗

Stimulation of de novo synthesis of L-phenylalanine ammonia-lyase in relation to phytoalexin accumulation in Colletotrichum lindemuthianum elicitor-treated cell suspension cultures of french bean (Phaseolus vulgaris).

(1) The regulation of the accumulation of the isoflavonoid-derived phytoalexin phaseollin in cell suspension cultures of Dwarf French Bean (Phaseolus vulgaris/ has been investigated. (2) An elicitor preparation from cell walls of Colletotrichum lindemuthianum, the causal agent of anthracnose disease of French bean, caused a marked accumulation of phaseollin in the cultures. The elicitor induced phaseollin accumulation to a level of 60% that obtained with the artificial elicitor autoclaved ribonuclease A and was maximally active at a concentration (weight basis) of at least 50 times lower than required for maximal response to ribonuclease. (3) Elicitor preparations from cell walls of Phytophthora megasperma var. sojae, a fungal pathogen of soybean, and Botrytis cinerea, the common grey mould, were much less effective than the C. lindemuthianum wall-released elicitor. (4) There was a marked but transient increase in the extractable activity of phenylalanine ammonia-lyase, the enzyme catalysing the first reaction in the biosynthesis of phaseollin from L-phenylalanine, in response to the elicitor from C. lindemuthianum. (5) Comparative density labelling with 2H from 2H2O indicated that the elicitor stimulates de novo synthesis of phenylalanine ammonie findings provide the basis of a scheme for elicitor induction of phytoalexin accumulation.

Ammonia-Lyases↗