Das Projekt "Ammoniumtransport in Pflanzen: strategisches Modell fuer die Stickstoffeffektivitaet (EURATINE)" wird vom Umweltbundesamt gefördert und von Universität Tübingen, Fakultät für Biologie, Botanisches Institut durchgeführt. Current agriculture requires high inputs of nitrogen fertilizers, causes many secondary problems like nitrate leaching, contamination of the ground water, and the accumulation of nitrate in edible plant parts up to human-toxic concentrations. Therefore, an important future development in agroindustry will be identification or development of plants that are able to efficiently use low nitrogen levels in soils by maintaining high crop yield and quality. NH4+ transporters must play a strategic role in plant nitrogen efficiency. Despite their importance, the first ammonium transporters were cloned just recently, from the yeast Sacchraromyces cerevisiae and the plant Arabidopsis thaliana, by two participants of this project. The two proteins (MEP1/AMT1) are highly similar in sequence and define a new family of transporters also conserved in bacteria and animals. Preferential expression of plant NH4+ transporters in root hairs is strongly indicative of a pivotal role in nitrogen nutrition. EURATINE's objective is to use this recently acquired knowledge to perform an exhaustive molecular analysis of NH4+ transport proteins in the model plant Arabidopsis thailiana and to characterise their role in uptake of NH4+ from the soil and/or from symbiotic bacteria. Ammonium uptake into and efflux from nitrogen-fixing bacteria will also be analyzed with respect to their propensity to modulate legumes. In parallels, a targeted analysis of NH4+ transporters will be carried out in the yeast Saccharomyces cerevisiae, which will be used both as an essential tool to characterise plant transporters and as a model to study regulatory mechanisms in NH4+ transport.