Biological Function Analysis Of FgAP-2 Complex In Fusarium Graminearum

AP-2 complex is widely distributed in eukaryotes in the form of heterotetramer that functions in the uptake of membrane proteins during mammalian/plant clathrin-mediated endocytosis.However,its biological function remains mysterious in pathogenic fungi.In this study,the wheat scab fungus,Fusarium graminearum,was used to characterize the biological function of the AP-2 complex.Our study shows that FgAP-2complex plays a critical role in the maintenance of hyphal polarity.Lack of any subunit(FgAP2^α,FgAP2^β,FgAP2^σand FgAP2^mu)of the FgAP-2complex significantly affects the fungal vegetative growth,conidial morphology and germination.Remarkably,FgAP-2 complex is important for the fungal pathogenicity,especially during colonization and extension after infecting the host.The FgAP-2 complex is expressed ubiquitously at all developmental stage but having more concentrated protein distribution at the sub-apical collar and septa in young growing hyphae.Although FgAP-2 complex displays similar dynamic behavior to the actin patch components and accumulates at endocytic sites,it is dispensable for general endocytosis.We further demonstrated that FgAP-2 complex is essential for polar localization of the lipid flippases FgDnfA and FgDnfB which led to the proposal that FgAP-2 functions as a cargo-specific adaptor that promotes polar growth and colonizing ability of F.graminearum.