Transcription factors Fst8, Ftr3 and Gat1 are regulators of the immune system of the mushroom Schizophyllum commune

Mushroom-forming fungi encounter numerous competitors during their lifecycle and have developed strategies to defend themselves. However, the regulation of this fungal immune system is largely unknown. We studied the role of transcription factors Fst8, Ftr3 and Gat1 during the interaction between the mushroom-forming fungus Schizophyllum commune and the ascomycete mycoparasites Trichoderma harzianum and Trichoderma aggressivum. These proteins are conserved to varying degrees in basidiomycetes, with a high degree of conservation in Agaricales. We showed that the regulators Fst8 and Ftr3 play a role in regulating the immune system, similar to Gat1 which we previously identified. Deletion of the fst8 and ftr3 genes led to varying degrees of defensive impairment in S. commune. A Δgat1Δfst8 double knockout strain was most affected, indicating that these regulators are likely involved in different pathways. We identified putative (direct or indirect) targets of these transcription factors using a transcriptomics approach. These genes include small secreted proteins and transporters. Combining data from the single deletion strains, we identified a core group of 18 putative targets, including thaumatins, cell wall modifiers, and detoxifiers. Combined, we identified the regulatory network initiated by the regulators Fst8, Ftr3 and Gat1 during interaction with fungal competitors.