Stage-Specific Genetic Interaction between FgYCK1 and FgBNI4 during Vegetative Growth and Conidiation in Fusarium graminearum .

CK1 casein kinases are well conserved in filamentous fungi. However, their functions are not well characterized in plant pathogens. In Fusarium graminearum , deletion of FgYCK1 caused severe growth defects and loss of conidiation, fertility, and pathogenicity. Interestingly, the Fgyck1 mutant was not stable and often produced fast-growing spontaneous suppressors. Suppressor mutations were frequently identified in the FgBNI4 gene by sequencing analyses. Deletion of the entire FgBNI4 or disruptions of its conserved C-terminal region could suppress the defects of Fgyck1 in hyphal growth and conidiation, indicating the genetic relationship between FgYCK1 and FgBNI4 . Furthermore, the Fgyck1 mutant showed defects in polarized growth, cell wall integrity, internalization of FgRho1 and vacuole fusion, which were all partially suppressed by deletion of FgBNI4 . Overall, our results indicate a stage-specific functional relationship between FgYCK1 and FgBNI4 , possibly via FgRho1 signaling for regulating polarized hyphal growth and cell wall integrity.