Nitrate signaling in fungi

Background and state of research Ecologically, nitrate (NO3-) plays a central role in the global nitrogen cycle because it is a stable end product of the biological mineralization process and the major source of nutrients for plants and algae. However, leaching of nitrate from intensive agricultural production systems into inland waters, oceans, and local groundwater also causes major ecological problems and economic losses. Fungi are one of the most essential components of global soil nutrient cycling, and they can temporarily store nitrate in the soil by converting it to fungal biomass (known as nitrate assimilation), provided enough usable carbon is available there. Fungi therefore play a major role in preventing nitrogen losses in soils. In general, the conversion of nitrate to fungal biomass is already well studied, but it is not yet clear which cellular signals are responsible for the activation of the corresponding genetic network that ultimately controls the assimilation process from nitrate to biomass. Planned work and collaborations Based on our previous data, we propose that a key regulator (the transcription factor NirA) is activated by direct allosteric effects of nitrate and not, as in plants or bacteria, by an indirect signal transduction pathway involving nitrate transporters or receptors. In the present project proposal, genetic, molecular genetic and biochemical experiments are planned, which should clarify the signal transduction issue in nitrate transformation in a typical soil fungus (Aspergills nidulans). In this project, the applicant group of Prof. Joseph Strauss, head of the Institute of Microbial Genetics at the BOKU Campus Tulln, plans an international cooperation with Prof. Papageorgiou from the Turku Bioscience Centre in Finland, who is specialized in protein structure elucidation and should apply these methods to a regulatory protein of nitrate utilization. Scientific and societal relevance of the expected results. The results of the project will have both basic science and application-oriented relevance. On the one hand, our understanding of the ecological function of fungi in the conversion of nitrate to biomass will be improved and, on the other hand, this may help to reduce nitrate problems in water pollution. Furthermore, with the associated reduction of nitrogen loss from the soil, the nitrogen balance and thus the sustainability and economic viability of agricultural production will be improved.