CoPIs: Jean-Michel Ane (University of Wisconsin - Madison), Michael Udvardi (The Samuel Roberts Nobel Foundation) and Christopher A. Voigt (Massachusetts Institute of Technology)
Key Collaborators: Giles E. Oldroyd (John Innes Centre, UK) and Phillip S. Poole (John Innes Centre, Oxford University, UK)
Nitrogen is an essential element of biological molecules and life on earth. Lack of usable nitrogen limits growth of microbes, plants, and animals. Scarcity of nitrogen in agricultural soils limits plant production of food, feed, fiber and fuel. Nature solved the nitrogen limitation problem via evolution of biological nitrogen fixation in a type of bacteria, diazotrophs, that are able to reduce atmospheric N2 to NH3, which is readily assimilated into biological molecules. Biological nitrogen fixation is promoted by a complex metal containing enzyme called nitrogenase, whose oxygen-sensitivity may explain its restricted distribution amongst bacteria. Some plants, including most legumes and a few non-legumes form intimate, nitrogen-fixing symbioses with diazotrophs that provide the plants with ammonia. As a consequence, legumes have been an integral part of sustainable agricultural systems for thousands of years. Unfortunately, many important food species, including the grasses maize/corn, rice, and wheat cannot establish effective nitrogen-fixing symbioses with diazotrophs, making them dependent on nitrogenous fertilizers for high yield. Large-scale use of industrially-produced nitrogen-fertilizer has doubled the influx of nitrogen into the terrestrial biogeochemical nitrogen-cycle, with serious negative consequences for human health and the natural environment. Therefore, the long-term sustainability of massive nitrogen-fertilizer inputs in agriculture has come into question.
This project brings together an interdisciplinary team of investigators from the US and UK to solve the dual nitrogen problems of nitrogen-fertilizer over-use in developed countries and soil nitrogen-paucity in developing countries by developing effective endophytic (bacteria inside the root) and associative (bacteria attached outside the root) nitrogen-fixing symbioses in a model and a crop plant species. The overarching goal of the project is to develop effective N2-fixing symbioses between the model C4-grass, Setaria viridis, as well as the related crop species, Zea mays, with the endophytic bacterium, Rhizobium sp. IRBG74, as well as the associative bacterium, Pseudomonas fluorescenes Pf5. Successful deployment of biological nitrogen fixation in model or crop grass species will pave the way for a second Green Revolution to increase crop yields for resource-poor farmers and decrease the use and environmental-impact of industrial nitrogen-fertilizers by wealthier farmers.
This project will establish a powerful new model system for the study of plant-microbe interactions and demonstrate the power of synthetic biology in engineering new associative relationships and interdependencies that have the potential to be universal for all crop plants. It will test this potential in the important crop, maize. The integrated US-UK research partnership will provide a unique training opportunity for students and post-doctoral associates with active exchange of personnel between academic laboratories and research foundations in both countries. Data and materials generated in the study including plasmid constructs and genetically modified bacterial and plant species will be made available via websites maintained in the US and the UK. To broaden the impact of the work, traditional and non-traditional outreach strategies will be used to help K-12 teachers, students, and the public understand the fundamentals and benefits of interdisciplinary research and the implications of synthetic biology for the next generation of biotechnological solutions in agriculture.