Fimbriae of coprinus cinereus, schizophyllum commune and ustilago violacea = structural aspects and a role in conjugation

摘要

Surface fibrils (fimbriae) have been observed on fungi from every majorgroup. Fimbriae are thought to be involved in the following cell to cellinteractions: conjugation, flocculation and adhesion. Several higher fungiexibit two other types of interactions: hyphal fusion (anastomosis) andclamp connection formation. As a prelude to examining the role offimbriae in these processes, the fimbriae of two fungi that undergo thesefusion events were examined.Electron microscopy studies revealed that Coprinus cinereus andSchizophyllum commune are fimbriated. C. cinereus fimbriae were 5 nmin diameter and 0.5 to 20 11m in length. Fimbriae of C. cinereus oidia weremore numerous and longer than those of the hyphal stage. S. communefimbriae were also 5 nm in diameter, but were only 0.5 to 2 11m in length.There was an unequal distribution of fimbriae on the hyphal surfaces of S.commune . Fimbriae were sparsely distributed over the entire hyphalsurface, with higher densities of fibrils present on the side growths of thehyphae found in the older sections of the mycelium.Antiserum raised against Ustilago violacea fimbrial protein (AU) crossreactedstrongly with 37 and 39 kd C. cinereus mycelial proteins. Incontrast, AU bound very weakly to 89 and 92 kd S. commune mycelialproteins. Since AU cross-reacted poorly with S. commune fimbrialproteins, it was impossible to further characterize the fimbriae of thisspecIes. The 37 and 39 kd C. cinereus proteins, were isolated byelectroelution and were shown to be able to form fibrils the same diameteras oidial fimbriae. The 37 kd protein was shown to be composed of severalproteins with isoelectric points ranging from pH 6.1 to 7.63. Furthermore,the 37 kd protein was found to be multimeric, while the 39 kd protein wasnot. These results strongly suggested that the 37 kd protein is thestructural fimbrial protein of C. cine reus .Finally, a series of experiments were designed to determine whetherfimbriae are required for conjugation in U. violacea Conjugation wasinhibited significantly with AU, but not with pre-immune serum or AUpreincubated with purified fimbrial protein. Thus, it was concluded thatfimbriae play a central role in mating in this organism.