Global expression profiling of the corn smut fungus reveals unprecedented insights into how its metabolism and effectors are used in the plant environment.
D. LANVER (1), A. Müller (1), G. Schweizer (1), N. Ludwig (1), F. Haas (2), J. Altmüller (3), S. Rensing (2) (1) Max-Planck-Institute for Terrestrial Microbiology, Germany; (2) Philipps University Marburg, Germany; (3) Cologne Center for Genomics, Germany

The biotrophic fungus Ustilago maydis causes smut disease in corn plants and induces tumors as most conspicuous disease symptoms. Here, we resolve the infection process by using deep RNA sequencing. We follow the stages of appressorium formation, penetration, establishment of biotrophy, as well as tumor and spore formation. We observed dramatic changes in the U. maydis transcriptome, with more than 80% of the genes being differentially regulated. Our expression data indicates that the switch from initial growth on the plant surface to biotrophic growth is accompanied by an increased translation and energy metabolism. However, already at the onset of tumor formation, i.e. before massive proliferation occurs, this metabolism is down-regulated, and instead genes involved in lipid breakdown and autophagy are induced. The metabolic regulation indicates a starvation response early during fungal development and could constitute an infection strategy to maximize nutrient supply. During plant penetration U. maydis secretes an array of effectors. We classified the effectors according to their expression profile, leading to the identification of expression waves that coincide with the establishment of biotrophy and the induction of tumors. Interestingly, many of the early induced effectors including those that play a crucial role for the establishment of biotrophy are successively down-regulated during later stages of infection. We will discuss implications of these expression patterns.

Abstract Number: P9-275
Session Type: Poster