Designing Nitrogen Fixing Ability in Oxygenic Photosynthetic Cells

INTELLECTUAL MERIT

The overall goal in this project is to develop the design principles to establish nitrogen fixing ability in the unicellular cyanobacterium, Synechocystis 6803, an oxygenic photosynthetic organism. Nitrogen is an essential nutrient for plant growth. While a few plants acquire fixed nitrogen via symbioses with microorganisms, most plants obtain nitrogen through uptake of nitrogenous compounds from the soil. The application of nitrogen-containing fertilizers is widely used to enhance plant growth. However, artificial fertilizers are expensive and have serious negative environmental effects, including degradation of soil quality and runoff and contamination of water sources. A solution to the problem of nitrogen availability to crop plants is to engineer plant cells with the ability to fix atmospheric nitrogen into usable compounds. Presently, a major challenge in developing such a system is the fact that photosynthesis in chloroplasts generates oxygen, a potent inhibitor of nitrogenase, the key enzyme for nitrogen fixation. Interestingly, a number of cyanobacterial strains have the ability to perform both nitrogen fixation and oxygenic photosynthesis, using ingenious strategies that separate these two processes temporally. This project uses synthetic biology tools to engineer a non-diazotrophic cyanobacterium to fix nitrogen, thereby defining the minimum requirements for nitrogen fixation to occur in photosynthetic cells including those in crop plants. If successful, this effort will usher a new paradigm for integrating seemingly incompatible metabolic functions in a photosynthetic cell.

BROADER IMPACTS

Enhanced production of crop plants is an urgent need for the production of food, feed and fuel for an ever-increasing human population on this planet, and efficient use of nitrogen is a key factor to meet such a need. The knowledgebase created in this project will be directly applicable to engineer nitrogen-fixing crop plants, and will thus have enormous potentials for societal benefits. The project team has broad expertise in cyanobacterial systems biology, computational modeling, and synthetic biology, and plans to develop innovative interdisciplinary educational programs focused on the application of such approaches to photosynthetic organisms. In particular, emphasis will be placed on (1) Development of an inter-institutional iGEM (International Genetically Engineered Machine) training program for undergraduate students; and (2) Engagement of international partners at two academic institutions in India. Both set of activities will be intimately linked to the research goals of this project, and will be aimed at providing hands on training opportunities for students in Science, Technology, Engineering and Mathematics (STEM).