STRIPAK Dependent and Independent Phosphorylation of the SIN Kinase DBF2 Controls Fruiting Body Development and Cytokinesis during Septation and Ascospore Formation in .

The supramolecular striatin-interacting phosphatases and kinases (STRIPAK) complex is highly conserved in eukaryotes and controls diverse developmental processes in fungi. STRIPAK is genetically and physically linked to the Hippo-related septation initiation network (SIN), which signals through a chain of three kinases, including the terminal nuclear Dbf2-related (NDR) family kinase DBF2. Here, we provide evidence for the function of DBF2 during sexual development and vegetative growth of the homothallic ascomycetous model fungus . Using mutants with a deleted gene and complemented strains carrying different variants of , we demonstrate that is essential for fruiting body formation, as well as septum formation of vegetative hyphae. Furthermore, we constructed mutants carrying phospho-mimetic and phospho-deficient codons for two conserved phosphorylation sites. Growth tests of the phosphorylation mutants showed that coordinated phosphorylation is crucial for controlling vegetative growth rates and maintaining proper septum distances. Finally, we investigated the function of DBF2 by overexpressing the gene. The corresponding transformants showed disturbed cytokinesis during ascospore formation. Thus, regulated phosphorylation of DBF2 and precise expression of the gene are essential for accurate septation in vegetative hyphae and coordinated cell division during septation and sexual spore formation.