Life history and developmental processes in the basidiomycete Coprinus cinereus

Coprinus cinereus has two main types of mycelia, the asexual monokaryon ant i the sexual dikaryon, formed by fusion of compatible monokaryons. Syngamy (plasmogamy) and karyogamy are spatially and temporally separated which is typical for basidiomycetous fungi. This property of the dikaryon enables an easy exchange of nuclear partners in further dikaryotic-monokaryotic and d ikaryotic-dikaryotic mycelial fusions. Fruiting bodies normally develop on the dikaryon, and the cytological process of fruiting-body development has been described in its principles. Within the specialized basidia, present w ithin the gills of the fruiting bodies, karyogamy occurs in a synchronized manner It is directly followed by meiosis and by the production of the meio tic basidiospores. The synchrony of karyogamy and meiosis has made the fung us a classical object to study meiotic cytology and recombination. Several genes involving in these processes have been identified. Both monokaryons a nd dikaryons can form multicellular resting bodies (sclerotia) and differen t types of mitotic spores, the small uninucleate aerial oidia, and, within submerged mycelium, the large thick-walled chlamydospores. The decision abo ut whether a structure will be formed is made on the basis of environment s ignals (light, temperature, humidity, and nutrients). Of the intrinsic fact ors that control development, the products of the two mating type loci are most important. Mutant complementation and PCR approaches identified furthe r genes which possibly link the two mating-type pathways with each other an d with nutritional regulation, for example with the cAMP signaling pathway. Among genes specifically expressed within the fruiting body are those for two galectins, beta-galactoside binding lectins that probably act in hyphal aggregation. These genes serve as molecular markers to study development i n wild type and mutant strains. The isolation of genes for potential non-DN A methyltransferases, needed for tissue formation within the fruiting body, promises the discovery of new signaling pathways, possibly involving secon dary fungal metabolites.