Transcriptomics reveals the regulation of the immune system of the mushroom-forming fungus Schizophyllum commune during interaction with four competitors.

Mushroom-forming fungi frequently encounter competitors during their lifecycle, but their defense mechanisms remain largely unexplored. We studied the response of the mushroom-forming fungus Schizophyllum commune during interaction with the fungal competitors Trichoderma harzianum, Trichoderma aggressivum and Purpureocillium lilacinum and the bacterial competitor Serratia quinivorans. Transcriptomics revealed 632 up-regulated genes in the direct interaction zone, which were enriched in small secreted proteins and transporters. A set of 26 genes were up-regulated during all interactions, indicating a core transcriptomic defense response. In the non-interacting edge of the mycelium of S. commune, there were 154 up-regulated genes, suggesting that there is a systemic response due to a signal that reaches unaffected areas. The GATA zinc finger transcription factor gene gat1 was up-regulated during interaction and a Δgat1 strain displayed increased colonization by T. harzianum. Previously linked to mushroom development, this transcription factor apparently has a dual role. Moreover, 138 genes were up-regulated during both interaction and mushroom development, indicating priming of the defense response during development to prepare the fruiting body for future interactions. Overall, we unveiled a defensive response of S. commune during interaction with fungal and bacterial competitors and identified a regulator of this response.