Antifungal activity and biochemical characteristics of natamycin against Fusarium graminearum

Fusarium head blight (FHB) caused by Fusarium graminearum is a destructive fungal disease of wheat. Natamycin is a natural polyene macrolide antifungal compound exhibiting broad-spectrum antifungal activity, but its efficacy and mechanism against F. graminearum remain unclear. In this study, the sensitivity of 47 F. graminearum strains from different regions of China to natamycin was determined. The results showed that natamycin had a good inhibitory effect with the EC50 value ranging from 0.93 to 4.04 μg/mL and a mean EC50 value of 2.20 ± 0.59 μg/mL. No resistance association was found between natamycin and five commonly used fungicides, and no synergistic effect was observed with tebuconazole or metconazole. Natamycin also enhanced wheat disease resistance by triggering ROS bursts and activating defense-related genes. DON is a key virulence factor of F. graminearum. Importantly, natamycin significantly reduced DON production by downregulating the expression of DON biosynthesis gene FgTRI5 and transporter gene FgTRI12. Moreover, natamycin affected ergosterol content and lipid droplet accumulation, triggering stress responses. Metabolomics and activity-based protein profiling (ABPP) analyses further revealed that natamycin disrupts core metabolic and protein networks, supporting a multi-target regulatory pattern. Exogenous metabolite supplementation excluded metabolic interference, whereas ergosterol addition restored mycelial growth in a dose-dependent manner, confirming ergosterol as the primary target. Molecular dynamics simulation verified that natamycin inserts into the phospholipid bilayer and specifically binds ergosterol. Collectively, this study clarifies the membrane-targeting mechanism of natamycin and supports its application as a green agent for FHB control and detoxification.