Research on the Pathogenic Mechanism of Effector FvCfem7 in Fusarium verticillioides

Fusarium verticillioides, a hemibiotrophic pathogen, infects a range of important crops and contaminates grains with fumonisin B1 (FB1) toxins, posing serious threats to yield, quality, and food safety. Secreted proteins containing Common Fungal Extracellular Membrane (CFEM) domains are known to contribute to the pathogenicity of several fungi, yet their functions in F. verticillioides remain poorly understood. In this study, we first identified the truncated protein FvCfem7ΔSP without signal-peptide-triggered host immune responses in tobacco. The knockout mutant ΔFvcfem7 exhibited significantly enhanced virulence, while the constitutive overexpression of the FvCFEM7-OE strain showed reduced pathogenicity. Notably, foliar spraying of recombinant FvCfemΔSP protein suppressed fungal infection. FvCfem7 accumulated specifically in haustorium-like structures during early infection of maize leaves and onion. However, heterologous expression of FvCfemΔSP in Nicotiana benthamiana leaves and maize protoplasts can be localized in their cytoplasm and nucleus, although its potential transport mechanism remains to be elucidated. Further analysis revealed that FvCfem7 interacts with specific members of ZmPR5, as well as ZmPR1 and ZmPR4. The ΔFvcfem7 mutant suppressed ZmPR1 induction while enhancing ZmPR5 expression at 24 hpi, which suggests that FvCfem7 modulates the expression of PR proteins at the early invasion stage. In summary, FvCfem7 was identified as a CFEM effector that is recognized and hijacked by PR proteins, thereby triggering immune defenses, while its host-targeting function was also characterized.