The type II phosphoinositide 4-kinase FgLsb6 is important for the development and virulence of Fusarium graminearum

Fusarium graminearum is the main pathogenic fungus causing Fusarium head blight (FHB), which is a wheat disease with a worldwide prevalence. In eukaryotes, phosphatidylinositol 4-phosphate (PI4P), which participates in many physiological processes, is located primarily in different organelles, including the trans-Golgi network (TGN), plasma membrane and endosomes. Type II phosphatidylinositol 4-kinases (PI4Ks) are involved in regulating the production of PI4P in yeast, plants and mammalian cells. However, the role of these proteins in phytopathogenic fungi is not well understood. In this study, we characterized the type II PI4K protein FgLsb6 in F. graminearum, a homolog of Lsb6 in Saccharomyces cerevisiae. Unlike Lsb6, FgLsb6 localizes to the vacuoles and endosomes. The Delta Fglsb6 mutant displayed defects in vegetative growth, deoxynivalenol (DON) production and pathogenicity. Furthermore, the Delta Fglsb6 deletion mutant also exhibited increased resistance to osmotic, oxidative and cell wall stresses. Further analyses of the Delta Fglsb6 mutant showed that it was defective in the generation of PI4P on endosomes and endocytosis. Collectively, our data suggest that the decreased vegetative growth and pathogenicity of Delta Fglsb6 was due to the conservative roles of FgLsb6 in the generation of PI4P on endosomes and endocytosis.