Role of the Gene tri14 in Biosynthesis of the Trichothecene Toxin Harzianum A in Trichoderma arundinaceum

Trichothecenes are a family of toxic metabolites produced by multiple fungal species. All trichothecene analogs include an epoxide-containing tricyclic structure known as 12,13-epoxytrichothec-9-ene (EPT) but differ by the presence, absence and types of substituents attached to EPT. Among the 21 known genes associated with trichothecene biosynthesis, <i>tri14</i> is one of only three that are universally found in all trichothecene-producing fungi. Recent studies have revealed that the <i>tri14</i>-encoded protein, Tri14, enhances the biosynthetic reaction that forms EPT, a reaction previously thought to occur spontaneously. In our study, we assessed the impact of <i>tri14</i> deletion on the biology of <i>Trichoderma arundinaceum</i>, a producer of the trichothecene harzianum A (HA). The results revealed that <i>tri14</i> deletion reduced HA production by 69%, an outcome that was associated with diminished antifungal activity. To our knowledge, this is the first study showing that <i>tri14</i> is required for wild-type production of a trichothecene analog by a fungal organism. <i>tri14</i> deletion also had moderate effects on the expression of some other trichothecene biosynthetic genes, as well as in the production of metabolites beyond HA. These results suggest that Tri14 plays a crucial role in EPT formation, leading to diverse downstream effects on the biology of <i>T. arundinaceum</i>.