Fruit body development in basidiomycetes is normally
initiated in heterokaryotic mycelium upon induction by
environmental stimuli. In heterothallic species such as
Schizophyllum commune and Coprinus cinereus, fruiting competence
is under control of mating type genes and analysis of
the mating type loci has been the subject of many studies
(Griffin, 1994). In a number of basidiomycetes, however, fruit
body development also occurs in homokaryotic strains (Elliott,
1985a). The structures of homokaryotic fruits may vary from
slightly differentiated tissue to fully differentiated fruit bodies
and this suggests that especially in the latter case the
expression of genes controlling fruit body development are
not strictly controlled by the mating type loci.