Abstract
Fusaric acid (FSA) is a mycotoxin produced by pathogenic Fusarium species that inhibits the growth of various beneficial microbes. In this study, we investigated the molecular mechanisms by which Trichoderma harzianum NJAU4742 (Th), a beneficial fungus, responds to FSA-induced stress. Here, by combining a transcriptome analysis, a gene knockout, and physiological data measurements, our study investigated the molecular mechanisms underlying the response of Trichoderma harzianum NJAU4742 (Th) to FSA stress. The results showed that FSA can induce severe oxidative stress in Th, and an aldehyde dehydrogenase (Thaldh3) in Th plays a critical role in alleviating FSA stress. Deleting Thaldh3 significantly decreased the γ-aminobutyrate (GABA) content, causing more severe oxidative damage in Th. Furthermore, we also provide evidence demonstrating that Thaldh3 alleviates FSA stress by enhancing the activities of key enzymes involved in the tricarboxylic acid cycle and ATP content. A pot experiment showed that an enhanced tolerance to FSA increased the Th biomass, strengthening its antagonistic capacity against pathogens and reducing the disease index in tomatoes. In conclusion, these observations provide new insight into the role of beneficial microbes in promoting plant health.