Two genes specifically expressed in fruiting dikaryons of Schizophyllum commune: homologies with a gene not regulated by mating-type genes

The nucleotide (nt) sequences of the Sc3 and Sc4 genes of the filamentous fungus Schizophyllum commune, and the deduced amino acid (aa) sequences, were determined; moreover, the previously published sequence for the ScI gene Dons et al., EMBO J. 3 (1984) 2101–2106] was corrected. All three independently isolated genes were found to have similar structures and nt sequences of their coding regions. At the aa level the homology is 43–62% (63–69% in the C-terminal parts of the proteins), the hydrophobic aa predominate and the hydrophobicity patterns are similar. All three proteins contain leader sequences and eight cysteines among about 110 aa, conserved at the same positions. Yet these genes are differentially regulated: Sc1 and Sc4 are only expressed at high levels in fruiting dikaryons, whereas Sc3 is highly expressed in both monokaryons and dikaryons, independent from fruiting.