E 1 - Alfred Batschauer

Sensing of light by the biotrophic fungus Ustilago maydis in the maize phyllosphere








Prof. Dr. Alfred Batschauer

Philipps-Universität Marburg, Faculty of Biology

Karl-von-Frisch-Straße 8, 35043 Marburg

+49 - 6421 - 2827064




Research summary:

The biotrophic fungus Ustilago maydis causes corn smut disease and is a well-established fungal model organism to study important aspects of environmental response and host-pathogen interaction. The effect of light on host-pathogen interactions is an emerging topic. However, at the commencement of this project, the photobiology of U. maydis was unexplored. Based on homology search we identified ten putative light sensors or photoreceptors in the genome of U. maydis. In the first funding period within CRC 987 we focussed on the functional, biochemical and spectroscopic characterization of six of these proteins predicted to bind a flavin chromophore. Among them are four members of the cryptochrome/photolyase family (CPF), one white collar 1 homolog (Wco1) and one BLUF-domain protein (Blf1).

With the exception of Wco1, we successfully characterized these blue light receptors in vitro by showing their flavin binding and functional photochemistry. Based on transcriptome analysis we showed that Wco1 is the dominant blue light sensor in U. maydis. This does not preclude the presence of other photoreceptors active in the same spectral range as Wco1. Furthermore, we have preliminary data showing that some photoreceptors in U. maydis operate under green light (3 opsins). The function of the only phytochrome present in U. maydis, which should sense red and far-red light remains to be investigated.

Future work in the second funding period will address the question on the role of these photoreceptors in particular on interaction with the host plant maize and pathogenesis. For this purpose, we will study the effect of light under defined polychromatic and monochromatic light conditions on filamentation, appressoria formation, penetration into plant tissue and pathogenicity. These studies will be performed with wild-type and photoreceptor mutant strains which have been generated in the first funding period. We have made mutants not only for the solopathogenic strain SG200 but likewise for FB1 and FB2 haploid strains. With the latter strains of compatible mating loci we intend to study effects of various light sources on mating behaviour. The influence of light and the role of photoreceptors on growth and formation of secondary metabolites will also be investigated under saprophytic conditions. In addition, we aim to elucidate selected light signalling pathways by identification of interaction partners and cis-acting elements in light-controlled genes. In summary, this project addresses important aspects how light controls fungal development and pathogenicity.