A Coumarin Compound Derived From <i>Zanthoxylum avicennae</i> Reduces the Pathogenicity of <i>Fusarium verticillioides</i> by Directly Binding to and Inhibiting Glycoside Hydrolase 3 Activity

The cell wall serves as a critical barrier in plant defence against pathogen infection, whereas various Fusarium fungi secrete cell wall-degrading enzymes (CWDEs) to facilitate hyphal infection. In this study, luvangetin, a coumarin compound isolated and identified from the root of Zanthoxylum avicennae, was found to affect the cell wall degradation capacity and pathogenicity of Fusarium verticillioides on maize. Enzymatic activity assays of secreted enzymes from F. verticillioides demonstrated that luvangetin significantly inhibited the activity of the fungal crude enzyme extract, with the highest inhibition (13.5%) observed on cellulase activity. It also impaired the enzymatic hydrolysis to straw, wheat bran and bagasse. Integrated transcriptomic, proteomic and in vitro activity analyses collectively revealed that luvangetin binds to three critical sites (Y193, D571 and E575) of the glycoside hydrolase 3 family (GH3) β-glucosidase in Fusarium species. Gene knockout and overexpression mutants were generated to further demonstrate that FvBgls3 plays a critical role in the pathogenicity of F. verticillioides and that it is an important target of luvangetin. Luvangetin directly binds to the catalytic active centre of FvBgls3, thereby suppressing the activity of CWDEs in F. verticillioides and ultimately reducing its pathogenicity. This study is the first to report that a coumarin small molecule directly binds to and inhibit the activity of GH3 family enzymes, revealing the molecular mechanism by which luvangetin directly inhibits cell wall degradation capacity, providing novel targets and strategies for future control of F. verticillioides.