Plant pathogenic fungi colonizing living plant tissue secrete a cocktail of novel effector proteins to suppress plant immunity and reprogram host cells. Although many of these effectors function inside host cells, delivery systems used by pathogenic bacteria to translocate effectors into host cells have not been detected in fungi. During the course of studying such novel effectors in Ustilago maydis, a biotrophic fungus causing smut disease in corn, we have identified five unrelated effectors and two membrane proteins which form a stable protein complex. The corresponding genes appear co-regulated and are only expressed during colonization. Single mutants in any of these seven genes arrest in the epidermal layer, fail to suppress host defense responses and fail to induce non-host resistance, two reactions likely depending on translocated effectors. The complex is anchored in the fungal membrane, protrudes into host cells and contacts channel forming plant plasma membrane proteins, suggesting that we identified a translocation system. The system could be reconstituted in a surface-exposed form in cultured U. maydis cells. As orthologs of the complex-forming proteins are conserved in smut fungi, the complex may become an interesting fungicide target.
Regine Kahmann studied biology at the Georg August University in Göttingen. She did her doctorate from 1972 to 1974 at the Max Planck Institute for Molecular Genetics and the Free University of Berlin. From 1980 to 1982 she worked as a research assistant at the Max Planck Institute for Biochemistry in Martinsried. In 1982 she started an independent research group at the Max Planck Institute for Molecular Genetics in Berlin. Between 1992 and 2001 she was Professor for Genetics at the Ludwig Maximilians University in Munich. Regine Kahmann was Director and Head of the Department of Organismic Interactions at the Max Planck Institute for Terrestrial Microbiology in Marburg from 2000-2019.
Moderation: Professorin Dr. Ulla Bonas