The F‐box protein Fbp1 functions in the invasive growth and cell wall integrity mitogen‐activated protein kinase (MAPK) pathways in Fusarium oxysporum

Summary F ‐box proteins determine substrate specificity of the ubiquitin–proteasome system. Previous work has demonstrated that the F ‐box protein F bp1, a component of the SCF Fbp1 E 3 ligase complex, is essential for invasive growth and virulence of the fungal plant pathogen F usarium oxysporum . Here, we show that, in addition to invasive growth, F bp1 also contributes to vegetative hyphal fusion and fungal adhesion to tomato roots. All of these functions have been shown previously to require the mitogen‐activated protein kinase ( MAPK ) F mk1. We found that F bp1 is required for full phosphorylation of F mk1, indicating that F bp1 regulates virulence and invasive growth via the F mk1 pathway. Moreover, the Δ fbp1 mutant is hypersensitive to sodium dodecylsulfate ( SDS ) and calcofluor white ( CFW ) and shows reduced phosphorylation levels of the cell wall integrity MAPK M pk1 after SDS treatment. Collectively, these results suggest that F bp1 contributes to both the invasive growth and cell wall integrity MAPK pathways of F . oxysporum .