The arbuscular mycorrhizal symbiosis, a close interaction between plant roots and soil fungi, is essential for the nutrient uptake of approximately 80 % of all known plant species. The arbuscular mycorrhizal fungus with its extraradical mycelium takes up nutrients such as phosphate and nitrogen for the plant, and is supplied in exchange with carbohydrates from the plant. However, our knowledge of the metabolic pathways involved in nitrogen uptake and transfer to the host plant and about the regulation of nutrient exchange between the symbiotic partners is still limited. The goal of this project is to understand the exchange of nutrients in the arbuscular mycorrhizal symbiosis, which is also key to applying arbuscular mycorrhizal fungi as "biofertilizers" in sustainable agriculture. The experimental approach we plan includes stable and radioactive isotope labeling, protein quantification and enzymatic assays, gene expression studies and protein and elemental localization techniques such as immunohistochemistry and energy dispersive X-ray microanalysis. This project will tell us how nitrogen is handled in the arbuscular mycorrhizal symbiosis, and how the flux of nitrogen in the symbiosis is regulated. The trainees, including a postdoc, a graduate student and undergraduates will learn an unusually broad range of modern biological techniques and will gain insights into the arbuscular mycorrhizal symbiosis and its importance for the nutrient acquisition of plants.
