GENE-EXPRESSION DURING FRUITING IN SCHIZOPHYLLUM-COMMUNE

Fruiting in the basidiomycete Schizophyllum commune is accompanied by transcription of a small number of specific genes that produce abundant mRNAs. These fruiting genes are regulated by the mating-type genes MATA and MATB, as well as by other genes such as FBF and THN, but also by the developmental stage of the mycelium. The developmentally regulated genes characterized thus far belong to gene families and code for excreted proteins. One gene family encodes hydrophobins, small hydrophobic cysteine-rich proteins which are excreted into the culture medium by submerged hyphae but accumulate in the walls of emergent hyphae where they form highly-insoluble complexes. The genes Sc1 and Sc4 of this family are only active in the dikaryon and the encoded hydrophobins typically accumulate in hyphal walls of developing fruit bodies. Another member of this family, Sc3, is also expressed in monokaryons and the encoded hydrophobin accumulates in walls of individually growing aerial hyphae. The effects of mutations in the FBF and THN genes indicate that these differentially regulated hydrophobins may play a key role in the emergence of aerial structures while different hydrophobins may determine specific hyphal-surface properties.