Transcription factor genes of Schizophyllum commune involved in regulation of mushroom formation

Mushrooms represent the most conspicuous structures of fungi. Their development is being studied in the model basidiomycete Schizophyllum commune. The genome of S. commune contains 472 genes encoding predicted transcription factors. Of these, fst3 and fst4 were shown to inhibit and induce mushroom development respectively. Here, we inactivated five additional transcription factor genes. This resulted in absence of mushroom development (in the case of deletion of bri1 and hom2), in arrested development at the stage of aggregate formation (in the case of c2h2) and in the formation of more but smaller mushrooms (in the case of hom1 and gat1). Moreover, strains in which hom2 and bri1 were inactivated formed symmetrical colonies instead of irregular colonies like the wild type. A genome-wide expression analysis identified several gene classes that were differentially expressed in the strains in which either hom2 or fst4 was inactivated. Among the genes that were downregulated in these strains were c2h2 and hom1. Based on these results, a regulatory model of mushroom development in S. commune is proposed. This model most likely also applies to other mushroom-forming fungi and will serve as a basis to understand mushroom formation in nature and to enable and improve commercial mushroom production.