Extracellular proteins in fungi: a cytological and molecular perspective

Mapping the Secretome and Its N-Linked Glycosylation of Pleurotus eryngii and Pleurotus ostreatus Grown on Hemp Stalks

Our previous research showed that Pleurotus eryngii and Pleurotus ostreatus were effective fungi for pretreatment of industrial hemp stalks to improve enzymatic saccharification. The secretomes of these two fungi were analyzed to search for the effective enzyme cocktails degrading hemp lignin during the pretreatment process. In total, 169 and 155 proteins were identified in Pleurotus eryngii and Pleurotus ostreatus, respectively, and 50% of the proteins involved in lignocellulose degradation were CAZymes. Because most of the extracellular proteins secreted by fungi are glycosylated proteins, the N-linked glycosylation of enzymes could be mapped. In total, 27 and 24 N-glycosylated peptides were detected in Pleurotus eryngii and Pleurotus ostreatus secretomes, respectively. N-Glycosylated peptides of laccase, GH92, exoglucanase, phenol oxidase, α-galactosidase, carboxylic ester hydrolase, and pectin lyase were identified. Deglycosylation could decrease enzymatic saccharification of hemp stalks. The activities of laccase, α-galactosidase, and phenol oxidase and the thermal stability of laccase were reduced after deglycosylation.

Protein glycosylation in the phytopathogen Ustilago maydis: From core oligosaccharide synthesis to the ER glycoprotein quality control system, a genomic analysis

The corn smut fungus Ustilago maydis has, over recent decades, become established as a robust pathogenic model for studying fungi-plant relationships. This use of U. maydis can be attributed to its biotrophic host interaction, easy culture and genetic manipulation in the laboratory, and the severe disease symptoms it induces in infected maize. Recent studies have shown that normal protein glycosylation is essential for pathogenic development, but dispensable for the saprophytic growth or mating. Given the relevance of protein glycosylation for U. maydis virulence, and consequently its role in the plant pathogenesis, here we review the main actors and events implicated in protein glycosylation. Furthermore, we describe the results of an in silico search, where we identify all the conserved members of the N- and O-glycosylation pathways in U. maydis at each stage: core oligosaccharide synthesis, addition of the core oligosaccharide to nascent target proteins, maturation and extension of the core oligosaccharide, and the quality control system used by the cell to avoid the presence of unfolded glycoproteins. Finally, we discuss how these genes could affect U. maydis virulence and their biotechnological implications.

Sensitivity of different zygomycetes to the Penicillium chrysogenum antifungal protein (PAF)

The effects of the Penicillium. chrysogenum low molecular mass antifungal protein (PAF) on selected fungal species belonging in the Zygomycetes were investigated. A total of 21 fungal isolates from 15 different genera (Absidia, Actinomucor, Cokeromyces, Gilbertella, Micromucor, Mortierella, Mucor, Mycotypha, Rhizomucor, Rhizopus, Saksenaea, Syncephalastrum, Thamnostylum, Umbelopsis and Zygorhynchus) were tested. The inhibitory potentials of PAF at 50 microg ml(-1) on the germination of the sporangiospores and at 6.25-50 microg ml(-1) on the hyphal extension were examined on different culture media. From among the fungi regarded as opportunistic human and/or animal pathogens, PAF exhibited inhibitory effects against Absidia, Mortierella, Rhizomucor and Rhizopus species.