Cytokinins synthesized by the biotrophic fungus Claviceps purpurea are essential for a compatible rye-fungus interaction
J. HINSCH (1), S. Kind (2), P. Galuszka (3), P. Tudzynski (2) (1) University of Duesseldorf, Germany; (2) University of Muenster, Germany; (3) Centre of Molecular Biology and Genetics of the Palacký University, Czech Republic

The ergot fungus Claviceps purpurea is a biotrophic phytopathogen with a broad host range including economically important crops causing harvest intoxication upon infection. Its infection process is restricted to unfertilized ovaries without causing macroscopic defense symptoms. Thus, sophisticated host manipulation strategies are implicated. The plant hormone cytokinins (CKs) are known to regulate diverse plant cell processes and several plant pathogens alter CK levels during infection. However, CK biosynthesis pathways were unknown in fungi, so far. For the first time, we could show that C. purpurea synthesizes CKs via two mechanisms: The fungus contains a de novo biosynthesis pathway mainly based on a novel bifunctional enzyme “Ipt-Log” which directly synthesizes the highly active isopentenyladenine. Its functionality was confirmed by enzyme activity assays. Additionally, similar to plants, a second pathway involving degradation of modified tRNAs contributes to the CK pool of the fungus and knockout approaches prove a redundancy of both pathways. In order to assess the role of CKs in the Claviceps-rye interaction, CK levels were measured in planta and expression profiles of CK associated genes were determined. Taken together, we could show that fungus-derived CKs influence the host-pathogen interaction and are required for the infection of rye by C. purpurea. Our work proves that C. purpurea synthesizes and depends on CKs to establish a compatible biotrophic interaction.

Abstract Number: P9-268
Session Type: Poster