ABSTRACT
Disruption of the SC3 gene in the basidiomycete Schizophyllum commune affected not only formation of aerial hyphae but also attachment to hydrophobic surfaces. However, these processes were not completely abolished, indicating involvement of other molecules. We here show that the SC15 protein mediates formation of aerial hyphae and attachment in the absence of SC3. SC15 is a secreted protein of 191 aa with a hydrophilic N-terminal half and a highly hydrophobic C-terminal half. It is not a hydrophobin as it lacks the eight conserved cysteine residues found in these proteins. Besides being secreted into the medium, SC15 was localized in the cell wall and the mucilage that binds aerial hyphae together. In a strain in which the SC15 gene was deleted (DeltaSC15) formation of aerial hyphae and attachment were not affected. However, these processes were almost completely abolished when the SC15 gene was deleted in the DeltaSC3 background. The absence of aerial hyphae in the DeltaSC3DeltaSC15 strain can be explained by the inability of the strain to lower the water surface tension and to make aerial hyphae hydrophobic.
Subject(s)
Cell Adhesion , Fungal Proteins/genetics , Fungal Proteins/physiology , Hyphae/growth & development , Schizophyllum/metabolism , Schizophyllum/physiology , Amino Acid Sequence , Cell Wall/chemistry , Fungal Proteins/metabolism , Gene Deletion , Genes, Fungal , Hydrophobic and Hydrophilic Interactions , Hyphae/genetics , Molecular Sequence Data , Morphogenesis , Mutagenesis, Insertional , Sequence Alignment , Sequence Analysis, Protein , Sequence Homology, Amino AcidABSTRACT
⢠The immunolocalization of one of the hydrophobins of Pisolithustinctorius (HYDPt-1) is reported. Hydrophobin proteins play key roles in adhesion and aggregation of fungal hyphae, and it is already known that formation of ectomycorrhizas on eucalypt roots enhances the accumulation of hydrophobin mRNAs in the mycelium of Pisolithus tinctorius. ⢠Purification of SDS-insoluble proteins from the mycelium of P. tinctorius showed the presence of a 13 kDa polypeptide with properties of class I hydrophobin. ⢠Polyconal antibodies were raised against a recombinant HYDPt-1 polypeptide, and these were used for immunofluorescence-coupled transmission electron microscopy. ⢠HYDPt-1 is a cell wall protein located at the surface of the hyphae with no preferential accumulation in the fungal cells of the different tissues of the ectomycorrhiza (i.e. extraradical hyphae, mantle or Hartig net).
