Gene networks of Sinorhizobium meliloti

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Legumes, like pulses (e.g., chickpeas, lentils) and soybean, are major crops in Canada. Canada is the world-leader in production of lentils and peas, while pulses and soybean account for 20% the value of Canada's agricultural commodity exports. It is crucial to develop sustainable agricultural practices maximizing legume crop yields while minimizing the costs and environmental impacts of modern farming. These needs can be addressed by improving the relationship between legumes and their bacterial partners, the rhizobia. These soil bacteria enter into endosymbiotic relationships with legumes, during which they convert N2 gas into ammonium thereby allowing the plants to thrive in nitrogen-deficient soils without nitrogen fertilizers. Optimizing this process would increase crop yield while reducing the use of toxic fertilizers. Nitrogen fixation by rhizobia also plays an important role in improving soil quality during crop rotations. The long-term goal of my research is to understand how rhizobia fix nitrogen in symbiosis with legumes in order to engineer strains with improved plant growth promoting abilities. To achieve this goal, it is necessary to first develop a better functional understanding of the genome of rhizobia and which biological activities determine the effectiveness of the symbiotic interaction. We will: i) use state-of-the-art methods to uncover the functions of rhizobium genes in a high-throughput manner, ii) test the role of stress tolerance in optimizing the ability of rhizobia to interact with legumes, and iii) build and use novel tools to study the roles of genes throughout the interaction with legumes. We will accomplish these tasks with a multi-disciplinary approach integrating current methodologies in molecular genetics, functional genomics, microbial physiology, plant-microbe interactions, comparative genomics, and in silico metabolic modelling. Through this research program, we will generate new knowledge of rhizobium legume symbioses, whose eventual translation into applied outcomes will benefit Canadian legume farmers and the global environment. Additionally, the multi-disciplinary nature of the research program will provide an outstanding environment for the broad training of HQP, providing them with expertise in emerging technologies and professional competencies. A poor functional understanding of gene function is not specific to rhizobia but is an enduring issue within prokaryotic (and eukaryotic) genomics. These functional knowledge gaps can impair the ability of synthetic biologists to engineer bacteria with improved phenotypes. This research program will provide a significant advance in the functional annotation of the genome of Sinorhizobium meliloti, a model Alphaproteobacterium that is closely related to numerous bacteria relevant to biotechnological applications such as bioremediation and biofuel production. As such, our research will also benefit Canada's budding biotechnology sector.