Jiangsu Provincial Key Lab for Organic Solid Waste Utilization, Nanjing Agricultural University, Nanjing, Jiangsu, 210095, China.
National Engineering Research Center for Organic-Based Fertilizers, Nanjing Agricultural University, Nanjing, Jiangsu, 210095, China.
Environ Microbiol. 2020 Nov;22(11):4808-4824. doi: 10.1111/1462-2920.15246. Epub 2020 Oct 19.
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.
丝状真菌被称为产生大量不同次级代谢产物（SMs）的生产者，这些代谢产物有助于它们在环境中立足。在这里，我们证明了这些 SMs 在真菌防御其他真菌方面具有额外的作用：木霉属真菌是一种真菌寄生菌，能够通过形成气生菌丝来对抗尖孢镰刀菌古巴专化型 4 号（Foc4），气生菌丝利用过氧化氢杀死宿主。与此同时，一个包含两个聚酮合酶的基因簇被强烈表达。我们利用功能遗传学对这个基因簇进行了表征，并鉴定出其产物为氮杂菲酮（称为三氮菲酮）。三氮菲酮没有抗真菌毒性，但表现出很高的自由基清除活性。在各种测试的氧化应激条件下，三氮菲酮的抗氧化特性在体内具有功能。因此，我们得出结论，三氮菲酮的生物合成作为一种补充抗氧化机制，防御木霉属真菌产生的过氧化氢，以对抗像 Foc4 这样的其他真菌。
