Filamentous fungi are known as producers of a large array of diverse secondary metabolites (SMs) that aid in securing their environmental niche. Here, we demonstrated that the SMs have an additional role in fungal defence against other fungi: Trichoderma guizhouense, a mycoparasite, is able to antagonize Fusarium oxysporum f. sp. cubense race 4 (Foc4) by forming aerial hyphae that kill the host with hydrogen peroxide. At the same time, a gene cluster comprising two polyketide synthases is strongly expressed. Using functional genetics, we characterized this cluster and identified its products as azaphilones (termed as trigazaphilones). The trigazaphilones were found lacking of antifungal toxicity but exhibited high radical scavenging activities. The antioxidant property of trigazaphilones was in vivo functional under various tested conditions of oxidative stress. Thus, we conclude that the biosynthesis of trigazaphilones serves as a complementary antioxidant mechanism and defends T. guizhouense against the hydrogen peroxide that it produces to combat other fungi like Foc4.

中文翻译：

---

Azaphilones的生物合成补充了贵州木霉抗氧化应激的防御机制

丝状真菌被称为各种多样的次级代谢产物（SM）的生产者，这些代谢产物有助于确保其环境利基。在这里，我们证明了SM在对抗其他真菌的真菌防御中还有其他作用：真菌木霉贵州木霉（Trichoderma guizhouense）能够拮抗尖孢镰刀菌（Fusarium oxysporum f）。sp。立方体通过形成气生菌丝，用过氧化氢杀死宿主，从而使第4种族（Foc4）死亡。同时，强烈表达了包含两个聚酮化合物合酶的基因簇。利用功能遗传学，我们对该簇进行了表征，并将其产物鉴定为氮杂苯甲酮（称为三氮杂苯甲酮）。发现曲格苯酮缺乏抗真菌毒性，但表现出高自由基清除活性。在各种测试的氧化应激条件下，trigazaphilones的抗氧化特性在体内均具有功能。因此，我们得出的结论是，trigazaphilones的生物合成是一种互补的抗氧化剂机制，可以保护T. guizhouense抵御它产生的过氧化氢，以对抗Foc4等其他真菌。