A frequently occurring mutation that blocks the expression of fruiting genes in Schizophyllum commune

Summary Fruiting in the basidiomycete Schizophyllum commune readily occurs in a homokaryon with constitutive mutations in both the A and B mating-type genes. Such a homokaryon frequently expresses a mutation, fbf, which completely blocks fruiting and leads to a somewhat faster growth rate. The mutation is unlinked to the A and B genes, frequently reverts to its wild-type allele, and is recessive with respect to fruiting in matings with wild-type homokaryons. The mutation suppresses the accumulation of a number of mRNAs which are regulated by the mating-types genes and are specific for fruiting. The expression of the Sc-3 gene, structurally related to two of the fruiting genes (Sc-1 and Sc-4) but not regulated by the mating-type genes, is unaffected.