Fungal warfare: Unravelling the defence mechanisms of mushroom-forming fungi

Abstract

Mushroom-forming fungi such as button and oyster mushrooms are economically important for food production but face serious threats from pathogens and pests in commercial cultivation, leading to significant yield losses. Understanding how these fungi defend themselves against microbial and animal threats is essential for improving the resilience of cultivated strains and contributing to more sustainable mushroom production. This research presents the first comparative gene expression analysis of conserved defence responses across mushroom-forming fungi and identified a core set of 562 gene families that were consistently activated during interactions with antagonists. These include genes involved in transport, detoxification, redox regulation, secondary metabolism, and the production of secreted proteins, providing a focused set of targets for further investigation. To better understand individual defence components, the mushroom-forming fungus Schizophyllum commune was used as a model species. During interactions with other microorganisms, a large group of genes encoding small secreted proteins was strongly induced. Ten of these proteins were further characterised, seven of which inhibited the growth of other microorganisms. Tip8, an enzyme of the AA7 family, showed oxidative activity that produced antimicrobial hydrogen peroxide and preferentially oxidised N-acetylglucosamine, suggesting a new defensive role for this enzyme family. Several other Tip proteins also affected microbial growth in a more species-specific manner, supporting their role as effectors in fungal defence. Genes related to secondary metabolism were also upregulated during interactions, although additional experiments did not reveal a clear functional role. By combining gene expression data with experimental validation, this study uncovered new weapons in the arsenal of mushroom-forming fungi. These findings form a foundation for future studies and may ultimately support the development of disease-resistant and sustainably cultivated mushrooms.