Lipopeptides from Bacillus velezensis YTQ3 inhibit Botrytis cinerea through cell wall and membrane disruption coupled with mitochondrial dysfunction

Postharvest gray mold, primarily caused by Botrytis cinerea , leads to significant economic losses in agriculture. This study elucidated the antifungal mechanisms of lipopeptides derived from Bacillus velezensis YTQ3 (YTQ3-LPs) against B. cinerea . In vitro assays demonstrated that YTQ3-LPs significantly inhibited mycelial growth and spore germination. Scanning electron microscopy revealed severe morphological damage to mycelia and spores. Further analysis showed that YTQ3-LPs disrupted fungal cell wall integrity, indicated by the leakage of alkaline phosphatase and a decrease in β-1,3-glucan and chitin content, followed by damage to the cell membrane, which resulted in a reduction in ergosterol and leakage of cellular contents. Fluorescence localization confirmed that YTQ3-LPs penetrated cell walls and cell membranes and accumulated intracellularly. This penetration induced severe oxidative stress, characterized by reactive oxygen species (ROS) accumulation, suppression of antioxidant enzymes (superoxide dismutase and catalase), and elevated hydrogen peroxide and malondialdehyde levels. Mitochondrial dysfunction was observed, including diminished membrane potential, reduced activities of succinate dehydrogenase, malate dehydrogenase, and ATPase, accompanied by ATP depletion. Additionally, YTQ3-LPs downregulated key virulence-related genes in B. cinerea , further supporting its antifungal efficacy. Notably, in vivo experiments demonstrated that YTQ3-LPs completely suppressed B. cinerea infection in grape berries. These findings demonstrate that YTQ3-LPs act as a promising biocontrol agent for postharvest disease management. Characteristics and antifungal mechanisms of lipopeptides produced by Bacillus velezensis YTQ3. • YTQ3-LPs significantly inhibit B. cinerea in vivo and in vitro . • YTQ3-LPs destroyed the morphology of mycelia and spores of B. cinerea . • YTQ3-LPs penetrate and disrupt B. cinerea cell walls and membranes • YTQ3-LPs cause damage to the mitochondrial function of B. cinerea . • YTQ3-LPs are a promising agent with multiple modes of antifungal action.