Comparative effect of the fungicide Prochloraz-Mnon Agaricus bisporus vegetative-mycelium and fruit-body cell walls / Estudios comparativos del efecto del fungicida Prochloraz-Mn sobre las paredes celulares del micelio vegetativo y de los cuerpos fructíferos de Agaricus bisporus

Fungicides to control mycopathogens of commercial Agaricus bisporus, a mushroom cultivated for human consumption, are a major field of study, since these chemicals are toxic to both the host and its fungal parasites. The fungicide Prochloraz-Mn, used at its LD50 for A. bisporus, partially inhibited protein biosynthesis in the vegetative my celial cell walls of this mushroom and caused significant changes in cell-wall polysaccharide structure, as deduced by methylation analysis and gas liquid chromatography-mass spectrometry (GLC-MS).Furthermore, the aggregated my celial walls showed distinct alterations in their overall chemical composition following the administration of Prochloraz-Mn at the LD50 and the LD50 ×1000. As expected, GLC-MS studies indicated that the latter dose caused more appreciable differences in polysaccharide structure. The decrease in mushroom crop yields obtained from industrial cultures treated with Prochloraz-Mn to control V. fungicola infection depended on the dose of the fungicide employed, whereas fruit-body morphology was only slightly affected at the highest Prochloraz-Mn concentration used (AU)

Los fungicidas para el control de micopatógenos de Agaricusbisporus, un hongo de cultivo comercial para consumo humano, representan un importante tema de estudio debido a que son tóxicos tanto para el huésped como para sus parásitos fúngicos. El fungicida Prochloraz-Mn, empleado a su LD50 para A. bisporus, inhibe parcialmente la biosíntesis de proteínas en las pared celular del micelio vegetativo de este hongo y provoca cambios significativos en la estructura polisacárida de la pared celular, tal como se observa mediante el análisis de metilación y la cromatografía líquida de gases-espectrometría de masa (GLC-MS). Además, las paredes agregadas del micelio presentan diferentes alteraciones en la composición química global después de la administración de Prochloraz-Mn a la LD50 y LD50×1000. Como cabría esperar, los estudios de GLC-MS, indican que la última dosis causa más diferencias apreciables en la estructura polisacárida. La disminución en la producción del hongo en los cultivos industriales tratados con Prochloraz-Mn para controlar la infección por V. fungicola, dependía de la dosis de fungicida empleada, mientras que la morfología del cuerpo fructífero sólo resulta ligeramente afectada a la concentración de Prochloraz-Mnmás elevada (AU)

Comparative effect of the fungicide Prochloraz-Mn on Agaricus bisporus vegetative-mycelium and fruit-body cell walls.

Fungicides to control mycopathogens of commercial Agaricus bisporus, a mushroom cultivated for human consumption, are a major field of study, since these chemicals are toxic to both the host and its fungal parasites. The fungicide Prochloraz-Mn, used at its LD50 for A. bisporus, partially inhibited protein biosynthesis in the vegetative mycelial cell walls of this mushroom and caused significant changes in cell-wall polysaccharide structure, as deduced by methylation analysis and gas liquid chromatography-mass spectrometry (GLC-MS). Furthermore, the aggregated mycelial walls showed distinct alterations in their overall chemical composition following the administration of Prochloraz-Mn at the LD50 and the LD50 x1000. As expected, GLC-MS studies indicated that the latter dose caused more appreciable differences in polysaccharide structure. The decrease in mushroom crop yields obtained from industrial cultures treated with Prochloraz-Mn to control V. fungicola infection depended on the dose of the fungicide employed, whereas fruit-body morphology was only slightly affected at the highest Prochloraz-Mn concentration used.

Verticillium disease or "dry bubble" of cultivated mushrooms: the Agaricus bisporus lectin recognizes and binds the Verticillium fungicola cell wall glucogalactomannan.

The step of recognition and (or) binding for the development of the disease of the cultivated mushroom Agaricus bisporus by the mycoparasite Verticillium fungicola was studied by several approaches: agglutination of V. fungicola germinated spores by an A. bisporus extract from fruit body cell walls, immunofluorescence microscopy of A. bisporus hyphae from fruit bodies and vegetative mycelia pretreated with purified V. fungicola cell wall glucogalactomannan, and finally, by hemagglutination experiments carried out with an A. bisporus fruit body lectin in the presence and absence of the same glucogalactomannan. Hemagglutinating activity of the purified A. bisporus fruit body lectin was clearly inhibited by the V. fungicola glucogalactomannan, whereas in the A. bisporus vegetative mycelium such lectin was not encountered. All the results obtained make evident the recognition and binding of the A. bisporus fruit body lectin to the V. fungicola cell wall glucogalactomannan, clarifying why the mushrooms, but not the vegetative mycelium, become diseased.

Properties of a hydrophobin isolated from the mycoparasitic fungus Verticillium fungicola.

Verticillium fungicola, isolated from Agaricus bisporus (commercial mushroom), produced significant extracellular hydrophobin when grown for 7 days in a static liquid culture of synthetic minimal medium. The hydrophobin was purified by precipitation with ammonium sulphate (80% saturation), Sephadex G-100 gel filtration, and hydroxyapatite column chromatography. The purified protein yielded a single band in polyacrylamide gel electrophoresis under native conditions, with an apparent molecular mass of 70 +/- 4 kDa, and also another single band in SDS-PAGE, with a molecular mass of 7 +/- 3 kDa. Molecular mass determined with matrix-assisted laser desorption ionization-mass spectrometry (MALDI-MS) resulted in 7563.9 m/z. The same protein was extracted from the V. fungicola mycelium. Analysis of the amino acid composition revealed the presence of about 50% hydrophobic residues, detecting at least six cysteines, evaluated as cystines, and no free sulfhydryl groups. The protein did not show any glycosylation. On the basis of similarities in hydropathy patterns and solubility characteristics, V. fungicola hydrophobin can be included as a new member of Class II hydrophobins.