Identifizierung und Charakterisierung zweier für die Produktion extrazellulärer Glykolipide verantwortlichen Gencluster in U. maydis

Under conditions of nitrogen starvation Ustilago maydis produces large amounts of extracellular glycolipids, ustilagic acid and mannosylerythritollipids (ustilipids). In this work the biosynthesis pathways and the biological functions were characterized. Deletion mutant strains were generated, which showed a defect in glycolipid production. The glycosyltransferase Emt1, which is essential for ustilipid production, could be identified. Because of the specific induction of emt1 under conditions of nitrogen starvation a gene cluster could be identified by microarray-analysis, which is responsible for ustilipid biosynthesis. This gene cluster consists of five genes with predicted functions. For the acetyltransferase Mat1 the predicted function could be verified by enzyme-assay and mass spectrometric analysis. By microarray-analysis a ustilagic acid gene cluster and another glycosyltransferase (Hgt1) in this cluster could be identified. It could be shown that ustilagic acids are important for pheromone recognition, and that they show a toxic effect against other microorganisms. Ustilipids are surface active substances and show hemolytic activity.