Thaldh3-Dependent GABA Metabolism Modulates Response of Trichoderma to Fusaric Acid-Induced Oxidative Stress

Fusaric acid (FSA) is a mycotoxin produced by pathogenicFusariumspecies that inhibits the growth of various beneficial microbes. In this study, we investigated the molecular mechanisms by whichTrichoderma harzianumNJAU4742 (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 ofTrichoderma harzianumNJAU4742 (Th) to FSA stress. The results showed that FSA can induce severe oxidative stress inTh, and an aldehyde dehydrogenase (Thaldh3) inThplays a critical role in alleviating FSA stress. DeletingThaldh3significantly decreased the γ-aminobutyrate (GABA) content, causing more severe oxidative damage inTh. Furthermore, we also provide evidence demonstrating thatThaldh3alleviates 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 theThbiomass, 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.