Chemical genetic analysis of cell separation in the basidiomycetes Ustilago maydis

• Applicant: Dr. Björn Sandrock
• Subject Area: General Genetics and Functional Genome Biology
• Term: from 2008 to 2013
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 70878402

During its haploid phase, the dimorphic fungus Ustilago maydis grows as elongated, cigar-shaped cells, which multiply vegetatively by budding. The budding process in U. maydis involves the sequential formation of two distinct septa that delimit a fragmentation zone, at which separation of mother and daughter cells occurs. We have identified a Cdc42 signalling module that is essential for initiation of the secondary septum during cytokinesis. We have demonstrated that the Rho-GEF Don1 is required to activate Cdc42 during cell separation. By chemical genetic analysis we could show that Cdc42 and the germinal centre protein kinase Don3 act independently in triggering secondary septum formation. The aim of this project is to identify downstream effectors of Cdc42 and Don3 in this process and to elucidate the molecular mechanism of septum initiation during cytokinesis. Preliminary data indicate that the diaphanous related formins Dia1 and Dia2 act as direct targets of Cdc42. We will investigate, whether these two proteins have partially overlapping or distinct functions during cell separation in U. maydis. We want to characterize the interaction of the formin proteins with Cdc42 and other GTP binding proteins of the Rho/Rac family GTPases. In addition, we will use the chemical genetic approach to investigate, which steps of the cell separation process depend on the kinase activity of Don3. We will use a candidate approach to search for potential kinase targets and we plan to establish an in vivo phospho-proteomics approach to identify novel kinase targets.

• DFG Programme: Research Grants