The rice blast fungus expresses a pathogenicity gene, MPG1, during appressorium formation, disease symptom development, and conidiation. The MPG1 gene sequence predicts a small protein belonging to a family of fungal proteins designated hydrophobins. Using random ascospore analysis and genetic complementation, we showed that MPG1 is necessary for infection-related development of Magnaporthe grisea on rice leaves and for full pathogenicity toward susceptible rice cultivars. The protein product of MPG1 appears to interact with hydrophobic surfaces, where it may act as a developmental sensor for appressorium formation. Ultrastructural studies revealed that MPG1 directs formation of a rodlet layer on conidia composed of interwoven ~5-nm rodlets, which contributes to their surface hydrophobicity. Using combined genetic and biochemical approaches, we identified a 15-kD secreted protein with characteristics that establish it as a class I hydrophobin. The protein is able to form detergent-insoluble high molecular mass complexes, is soluble in trifluoroacetic acid, and exhibits mobility shifts after treatment with performic acid. The production of this protein is directed by MPG1.

Two monokaryons of Schizophyllum commune can form a fertile dikaryon when the mating-type genes differ. Monokaryons form sterile aerial hyphae, while dikaryons also form fruiting bodies that function in sexual reproduction. The SC3 hydrophobin gene is expressed both in monokaryons and in dikaryons. The SC4 hydrophobin is dikaryon specific. In the monokaryon, SC3 lowers the water surface tension, coats aerial hyphae with a hydrophobic layer and mediates attachment of hyphae to hydrophobic surfaces. The SC4 protein lines gas channels within fruiting bodies with a hydrophobic membrane. Using gene disruptions, in this study, we show that in dikaryons SC3 fulfils the same roles as in monokaryons. SC4, on the other hand, has a role within fruiting bodies. In contrast to gas channels in fruiting bodies of the wild type, those of a DeltaSC4 strain easily filled with water. Thus, SC4 prevents gas channels filling with water under wet conditions, probably serving uninterrupted gas exchange. Other dikaryon-specific hydrophobin genes, SC1 and SC6, apparently do not substitute for the SC4 gene. In addition, by expressing the SC4 gene behind the SC3 promoter in a DeltaSC3 monokaryon, it was shown that SC4 cannot fully substitute for SC3, indicating that both hydrophobins evolved to fulfil specific functions.

GPD genes encoding glyceraldehyde-3-phosphate dehydrogenase were isolated from the homobasidiomycetes Schizophyllum commune, Phanerochaete chrysosporium and Agaricus bisporus. All three species contain one transcriptionally active GPD gene, but A. bisporus also contains an inactive GPD gene (tandemly linked to the active gene). These genes contain 5-9 introns located at conserved positions, differing (except in one case) from intron positions in ascomycetous GPD genes. The predicted amino-acid sequences of the proteins encoded by the three active GPD genes are highly homologous. A comparison with protein sequences from filamentous ascomycetes shows a clear distinction, whereas the GPD genes from ascomycetous yeasts are quite distinct from both the filamentous ascomycetes and basidiomycetes. Promoter regions of ascomycetous GPD genes do not correspond to those of the GPD genes of basidiomycetes which may (partly) explain poor expression in basidiomycetes of introduced genes driven by an ascomycete GPD promoter.

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In Saccharomyces cerevisiae, Neurospora crassa, Aspergillus nidulans and Coprinus cinereus most of the alkali-insoluble (1 leads to 3)-beta-D/(1 leads to 6)-beta-D-glucan of the wall can be extracted with dimethyl sulphoxide. The same fraction, and in Saccharomyces cerevisiae a small additional fraction, can be extracted by a destructive procedure involving 40% NaOH at 100 degrees C. The small fraction of the glucan which resists this treatment becomes soluble after a subsequent treatment with HNO2 indicating that it is covalently linked to chitin in the wall. In contrast, in Schizophyllum commune and Agaricus bisporus, nearly all the (1 leads to 3)-beta-D/(1 leads to 6)-beta-D-glucan appears to be held insoluble by linkage to chitin.