Antibiosis and transcriptomic analysis of inhibitory effect of the endophytic fungus Simplicillium lamellicola against phytopathogenic fungi

Endophytic fungus such as Simplicillium lamellicola exhibit pronounced antagonistic activity against a broad spectrum of plant pathogens. However, the molecular mechanisms underlying their fungal–fungal interactions remain insufficiently understood. In this study, we investigated the antagonistic effects of S. lamellicola against two necrotrophic pathogens, Thielaviopsis paradoxa and Heterobasidion annosum , through dual-culture assays integrated with comparative transcriptomic analyses. S. lamellicola significantly inhibited by antibiosis the growth of both pathogens, inducing conspicuous morphological alterations including hyphal distortion, hyperbranching, and cellular lysis at the interaction interfaces. Transcriptomic profiling revealed extensive transcriptional reprogramming, identifying 1336 differentially expressed genes (DEGs) in T. paradoxa (TpSl) and 441 in H. annosum (HaSl), with a predominance of downregulated genes (66.2 % and 56.2 %, respectively). Functional annotation indicated shared stress-adaptive responses encompassing oxidative stress defense, detoxification processes, and nutrient competition, accompanied by distinct species-specific strategies: T. paradoxa exhibited enhanced membrane restructuring, efflux-mediated transport, and structural reinforcement, whereas H. annosum activated chemically mediated defense pathways and oxidative stress mitigation mechanisms. Collectively, these findings demonstrate that S. lamellicola functions as a potent mycoparasitic biocontrol agent capable of eliciting complex defense responses in phytopathogenic fungi, thereby providing a molecular framework for its application in sustainable plant disease management. • Simplicillium lamellicola showed strong antibiosis against phytopathogens Thielaviopsis paradoxa and Heterobasidion annosum . • Dual culture assays revealed severe pathogen hyphal distortion and cell lysis. • Comparative transcriptomics uncovered extensive pathogen transcriptional reprogramming. • Pathogens showed both shared and species-specific stress adaptation mechanisms. • Results highlight S. lamellicola as a promising candidate for sustainable biocontrol.