FgNup2 regulates nuclear import of the histone H2B monoubiquitination enzyme by stabilizing the FgImpα-FgBre1 complex to mediate pathogenicity in Fusarium graminearum

Fusarium head blight caused by Fusarium graminearum threatens global wheat production. The pathogenicity of this fungus depends on histone H2B monoubiquitination (H2Bub1), yet the nuclear import mechanism of its key enzyme, FgBre1, remains unclear. In this study, we identified 24 nucleoporins in F. graminearum and found that FgNup2 is essential for fungal growth, toxin biosynthesis, and virulence. FgNup2 positively regulates H2Bub1 levels by facilitating the nuclear import of FgBre1, thereby influencing pathogenic development. The nuclear import of FgBre1 relies on the importin receptor FgImpα, and these two proteins interact. FgNup2, through a critical phenylalanine residue (F981) within its FG-repeat domain, promotes and stabilizes the FgImpα-FgBre1 complex, driving the assembly of the tripartite FgNup2-FgImpα-FgBre1 complex. This ultimately mediates the rapid nuclear translocation of FgBre1 under induction by the trichothecene biosynthesis-inducing medium. Our findings reveal a mechanism by which a nucleoporin regulates the nuclear entry of a histone-modifying enzyme via stabilizing the importin-cargo complex, advancing the understanding of non-canonical roles of the nuclear pore complex in pathogen adaptation.