Louis Chavant

Xerocomus chrysenteron lectin: identification of a new pesticidal protein.

Xerocomus chrysenteron is an edible mushroom with insecticidal properties. In an earlier work, we found that proteins are responsible for this toxicity. Here we describe the purification of a approximately 15 kDa lectin, named XCL, from the mushroom. Its cDNA and gDNA were cloned by PCR strategies and a recombinant form was expressed in Escherichia coli. Sequence alignments and sugar specificity showed that this protein is the third member of a new saline-soluble lectin family present in fungi. This protein, either purified from mushroom or expressed in vitro in E. coli, was found to be toxic to some insects, such as the dipteran Drosophila melanogaster and the hemipteran, Acyrthosiphon pisum. The lectin possesses a high insecticidal activity compared to lectin isolated from leguminosae (Lathyrus ochrus) or from the snowdrop (Galanthus nivalis).

A water-soluble β-D-glucan from Boletus erythropus

Abstract The main component of a water extract of Boletus erythropus fruiting bodies is a M r 10 6 glucan. The use of classical structural analysis and HMQC (heteronuclear multiple quantum coherence) NMR experiments indicates a (1 → 3) linked β- d -glucan structure with a single glucose residue attached to O-6 of the main chain and a branching frequency of 1/3.

Proteins as Active Compounds Involved in Insecticidal Activity of Mushroom Fruitbodies

Abstract Many mushrooms are toxic to insects. To identify the chemicals involved in insecticidal activity, the toxicity of 14 species has been studied for water solubility, thermolability, and dialysis. The data strongly suggest that proteins are responsible for most of the insecticidal activity of mushroom fruitbodies and may be a source of genes available for plant protection against insects. Among proteins, lectins and hemolysins were good insecticide candidates because the toxicities were not affected by protease.

Insecticidal properties of mushroom and toadstool carpophores

In order to find compounds with insecticidal or antifeedant properties from mushrooms and toadstools, a wide screening was undertaken using the non-mycophagous Drosophila melanogaster as a model insect. Powdered fruit bodies of edible and poisonous mushrooms were incorporated with the Drosophilas rearing medium, and their development was observed. Among the 175 different species of fungi tested, 79 were found to inhibit insect development, hence making the isolation of new compounds look hopeful.

A fluorimetric method for measuring lipase activity based on umbelliferyl esters.

A new fluorimetric method for measuring lipase activity is described. The fluorescent compound umbelliferone (UMB) was esterified with various unsaturated and saturated fatty acids of different carbon chain lengths, and the non-fluorescent esters were used as substrates for measuring the activity of two lipases purified fromRhizopus delemar andCandida cylindracea. The fluorescence intensity of UMB liberated by hydrolysis of the substrates gives an indication of the lipase activity towards the respective esters. UMB was found to be somewhat more sensitive and stable than 4-methylumbelliferone (4-MU), which has been used previously. The highly sensitive method (nmoles UMB/mL/hr) described here was tested on five different esters. The method has the advantage of not requiring extraction of the lipolysis products. It also can be carried out quickly, in two to three minutes, and thus lends itself to the screening of lipase-producing micro-organisms. The method offers an interesting alternative or can be complementary to assays based on the use of 4-methylumbelliferone esters as substrates.

Modulation of a lectin insecticidal activity by carbohydrates

Lectins from plants present an insecticidal activity most probably through their carbohydrate binding properties; as a consequence, their toxicity should vary with the presence of a competitive sugar in the ingested food. In order to test this hypothesis, we performed competition experiments between insecticidal activity and carbohydrate binding. For this purpose, we used a lectin from Lathyrus ochrus and the specific carbohydrate for this protein, glucose. In toxicological tests with Drosophila melanogaster, we observed a decrease of lectin toxicity when glucose was added to the larva-rearing medium. This result suggests that the toxicity of the lectin is correlated to its ability to bind sugar in the insect digestive tract and stresses the importance of sugar composition of the nutriment used for toxicological testing of lectins or in genetically modified plants.

Applicability of API ZYM for screening enzyme activity of thermophilic moulds

The extracellular and intracellular activities of nineteen enzymes of thermophilic fungi were studied by API ZYM, which is a simple and rapid system. More enzymes were recorded in the intracellular pool than in the extracellular pool. Trypsin, β-glucuronidase and α-fucosidase enzymes were absent in both pools. α-Mannosidase and chymotrypsin occurred only in the intracellular pool, whereas acid and alkaline phosphatases, phosphoamidase, esterases, α- and β-glucosidases, and β-glucosaminidase were found in both pools.

Purification and characterization of a novel phospholipid transfer protein from filamentous fungi

1. We have isolated from mycelia of Mucor mucedo, a filamentous fungus, a phospholipid transfer protein. 2. The purification steps were gel filtration, hydroxyapatite chromatography, blue affinity column and fast protein liquid chromatography on anion exchanger. 3. A purified protein was obtained with a molecular mass of 24 kDa and a pI of 5.05 and its N-terminal sequence was established. 4. This protein transfers phosphatidylinositol, as well as phosphatidylcholine and phosphatidylethanolamine.

Water-soluble polysaccharides excreted by mycelium of higher fungi: relationship with taxonomy and physiology

Abstract Production of water-soluble polysaccharides from mycelium was determined in 347 species of higher fungi belonging to a variety of taxonomic groups. All strains were grown under identical conditions. The presence or absence of polysaccharides was related to habitat and taxonomie position of the various strains and species. In the Basidiomycetes, production of polysaccharides appeared to be a feature of the lignicolous species, whereas the soil-saprophytes and mycorrhizal taxa generally do not produce polysaccharides. This trait could be of taxonomic value in some groups, especially Polyporus and Collybia and for the Sarcoscyphaceae in the Discomycetes. In other cases (Stereaceae, Strophariaceae, Amanitaceae for example) this trait may also have some taxonomic value. Further studies on a larger number of species will be needed to confirm or improve these first results.

Lipid composition of thermophilic moulds Acremonium alabamensis and Thermomucor indicae-seudaticae

The total lipid content of Acremonium alabamensis and Thermomucor indicae-seudaticae ranged 2.6–7.3 and 8.5–13.0% of dry mycelium, respectively during development. Neutral lipid fraction increased during growth while polar and phospholipids declined. Both moulds contained palmitic, oleic, linoleic and palmitoleic acids as major fatty acid components in lipids. Degree of unsaturation of lipids of A. alabamensis was greater than that of T. indicae-seudaticae. Neutral lipids were more unsaturated than the polar lipids. The ratio of unsaturation index of polar lipids to neutral lipids was either one or less than one. The principal phospholipids of these moulds were phosphatidyl choline, phosphatidyl ethanolamine and phosphatidic acid. However, phosphatidic acid was not found in very high amounts as observed in Humicola grisea var. thermoidea.