Improving symbiotic performance for enhanced plant nutrition

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A central goal of sustainable agricultural practice is to provide nutritious food and plant products while minimizing the impact on the environment. Legume plants are a key component of sustainable agriculture since they form a symbiosis with nitrogen-fixing soil bacteria (rhizobia), reducing our reliance upon applied nitrogen fertilizers. The production of synthetic nitrogen fertilizers consumes vast quantities of fossil fuels and their application leads to negative environmental outcomes (e.g., greenhouse gas emissions, contamination of water resources). Rhizobia belong to a class of bacteria termed diazotrophs, organisms which can generate useable forms of nitrogen from inert atmospheric nitrogen gas. The atmosphere contains 78% nitrogen gas, yet the essential nitrogen element cannot be directly accessed by plants. Rhizobia enter into legume roots and colonize cells within a specialized organ called a root nodule. Rhizobia then provide nitrogen to the plant by converting nitrogen gas to ammonia (nitrogen fixation) in exchange for nutrients. Prior work has demonstrated that the rate of nitrogen fixation is limited by both the supply of nutrients to the bacteria as well as the rate of fixed nitrogen export out of the nodule. Therefore, there is an opportunity to explore novel strategies to increase symbiotic nitrogen fixation performance. The long-term goal of my program is to understand the molecular, biochemical, and genetic mechanisms that underlie the legume-rhizobial symbiosis. This will provide the knowledge base for strategies aimed at improving the value of legume plants in agriculture. In the short term, the proposed program aims to identify mechanisms which control the exchange of nutrients (metabolites and ions) between symbiotic partners. Improving the exchange of nutrients is hypothesized to enhance the rates of nitrogen fixation and the nutritive value of legumes. Increasing the rate of nitrogen fixation has long been a goal of researchers in the field and remains a promising opportunity. Collectively, the multi-disciplinary research program will address key unresolved questions in the field of legume research and provide advanced training opportunities for the next generation of scientists. As the demand for plant protein is steadily increasing, legumes are positioned to fulfill the need due to their low environmental impact and protein-rich seeds. This pivotal research is both timely and essential as we move towards a future of more environmentally responsible farming practices in Canada.