Synergistic transcriptional modules in Trichoderma asperellum enhance glutathione detoxification to counteract fungal pathogen toxins.

Abstract

Trichoderma fungi are potent biocontrol agents. However, their defence mechanisms against pathogen-derived toxins remain poorly understood. We identified two synergistic transcription factor modules in T. asperellum that orchestrate the detoxification of cytotoxic secondary metabolites from the poplar blight pathogen Alternaria alternata. Overexpression of the central regulator TasMYB46 reduced disease lesion area by approximately 22% and was associated with decreased pathogen-induced reactive oxygen species (ROS) accumulation. Mechanistically, TasMYB46 directly activates the glutathione S-transferases TasGST61.1 and TasGST56.1 through distinct promoter binding sites (G-box/as-1/MBS), forming dedicated detoxification modules. Crucially, we identified urolithin C as the most abundant phytotoxin in A. alternata metabolites, which is efficiently detoxified through the TasMYB46-TasGST61.1 module. The transcription enhancer TasbHLH53.8 amplifies this system by binding to TasMYB46, boosting TasGST expression and enhancing glutathione-dependent detoxification capacity. This coordinated response elevates glutathione pools and antioxidant enzyme activities (GST/GPx), conferring increased oxidative stress resistance. This study reveals a novel defence mechanism in Trichoderma in which MYB-bHLH-GST modules enable biocontrol agents to neutralise pathogen-derived toxins. Given that Alternaria toxins threaten crops globally (tomatoes, potatoes, citrus), the discovered regulatory synergy represents a strategic advance in developing next-generation biocontrol solutions against toxin-producing plant pathogens.