Antimicrobial peptaibols from Trichoderma pseudokoningii induce programmed cell death in plant fungal pathogens

Antibiosis is one of the widespread strategies used by Trichoderma spp. against plant fungal pathogens, the mechanism of which, however, remains poorly understood. Peptaibols are a large family of antimicrobial peptides produced by Trichoderma spp. Our previous study showed that trichokonins, a type of peptaibol from Trichoderma pseudokoningii SMF2, exhibited antibiotic activities against plant fungal pathogens. In this study, we first demonstrated that trichokonin VI (TK VI) induced extensive apoptotic programmed cell death in plant fungal pathogens. For a deeper insight into the apoptotic mechanism involved in the action of TK VI, Fusarium oxysporum was used as a model. Cells of F. oxysporum treated with TK VI showed apoptotic hallmarks, such as exposure of phosphatidylserine, the appearance of reactive oxygen species and fragmentation of nuclear DNA. Moreover, TK VI-treated cells exhibited an accumulation of cytoplasmic vacuoles with loss of the mitochondrial transmembrane potential, and this process was independent of metacaspases. Therefore, TK VI induces metacaspase-independent apoptotic cell death in F oxysporum. This represents what is believed to be the first report to reveal the antibiotic mechanism of peptaibols against plant fungal pathogens.