FgSPF1 regulates DON biosynthesis and fungicide sensitivity in fusarium graminearum by regulating toxisome formation and membrane permeability

Fusarium graminearum, which causes Fusarium head blight (FHB), reduces crop yield and compromises wheat quality by producing mycotoxins such as deoxynivalenol (DON). While SPF1 is well studied for preserving ER membrane integrity and ensuring transmembrane protein quality in yeast, its role in agriculturally important plant-pathogenic fungi like F. graminearum remains largely unexplored. Here, we demonstrate that FgSPF1, the ortholog of yeast SPF1 in F. graminearum, plays a pivotal role in regulating DON biosynthesis and fungicide sensitivity. ΔFgSPF1 mutants exhibited reduced virulence on wheat and significantly decreased DON production, which was directly attributed to the disruption of toxisome structure. Notably, ΔFgSPF1 mutants exhibited decreased sensitivity to seven types fungicides with distinct target site. Mechanistically, LC-MS analysis, conductivity measurements, and ultrastructural observations revealed that ΔFgSPF1 strains had enhanced cell membrane compactness and reduced membrane permeability, leading to decreased fungicide absorption and thus increased multi-fungicide resistance. Additionally, disruption of FgSPF1 impaired vegetative growth, reduced asexual sporulation, and abolished sexual reproduction due to actin polarity disruption and hyphal morphological changes. Collectively, this study identified a novel regulatory mechanism of FgSPF1 in pathogenicity and fungicides sensitivity of F. graminearum.