Fruiting-body development in fungi – complementation of developmental mutants

By complementing fruiting-body mutants of S. macrospora we were able to isolate genes which are important for this process. The focus of our group is the conserved development protein PRO11, a homolog of proteins of the mammalian striatin family. In mammals, striatin proteins have been identified as central scaffolding proteins of the “striatin interacting phosphatase and kinase” (STRIPAK) complex. Striatin proteins are regulatory subunits of the phosphatase PP2A and link phosphatase PP2A to kinases of the germinal center (GC) III family and additional conserved proteins. Apparently, the STRIPAK complex regulates the phosphorylation and de-phosphorylation of target proteins which are involved in signal transduction pathways required for hyphal fusion and fruiting-body development. The striatin homolog PRO11 together with other previously identified developmental proteins is a central component of a STRIPAK complex in S. macrospora. This includes SmMOB3, a putative kinase activator, PRO22, a striatin interacting protein, and PP2AA, the scaffolding subunit of protein phosphatase 2A. In mammals, the cellular function of the STRIPAK complex is unknown. In contrast, functional analysis using knockout mutants with distinct developmental defects revealed a role of the fungal STRIPAK complex during hyphal fusion and fruiting-body development. We identified new interaction partners of the complex and our aim is the functional characterization of these interaction partners to define their role during hyphal fusion and fruiting-body development. This will give us crucial insights to understand conserved mechanisms for cell fusion and multicellular differentiation not only in fungi but also in higher eukaryotes.