Fusarium oxysporum f. sp. cubense Race 4 Effector, Foc4-305, Targets a Proline-Rich Protein in Banana and Contributes to Virulence

Fusarium oxysporum f. sp. cubense (Foc) ranks as the leading cause of banana wilt globally, devastating crops through the action of pathogen-secreted effectors. This study revealed Foc4-305 as a putative effector from isolate Foc4, identified via transcriptomics, and validated for its pivotal role in pathogenesis. Deletion of Foc4-305 impaired fungal growth, heightened sensitivity to oxidative stresses and cell wall disruptors, and diminished pathogenicity toward banana plants. Localization studies showed Foc4-305 primarily in the nuclei and cytoplasm of Nicotiana benthamiana cells, where it could inhibit BAX-triggered cell death. Interactions with a proline-rich protein (Ma-PRP) were confirmed through yeast two-hybrid, bimolecular fluorescence complementation and coimmunoprecipitation assays. Western blot analysis showed that Foc4-305 stabilized Ma-PRP proteins in vivo. Virus-induced gene silencing of Ma-PRP enhanced the resistance of bananas to wilt disease. Differentially expressed genes of wild-type Foc4 and effector Foc4-305 knockout mutants were revealed by RNA-seq analysis. GO and KEGG analyses highlighted some of these genes as associated with reproduction, DNA repair, and amino acid metabolism, underscoring the role of Foc4-305 role in enhancing virulence of Foc4 by modulating growth, response to stresses, and involvement in host immunity.