We propose to modify nitrate reductase (NR) activity in Arabidopsis and follow the consequences of this modification through multiple levels of biological organization; cells to ecosystem. An overarching hypothesis of this project is that a single-enzyme change affecting an important biological process (i.e. nitrate assimilation) will translate across multiple levels of biological organization to produce detectable and predictable responses at the ecosystem level. A combination of hydroponic and soil-based mesocosms will allow us to establish mechanistic links between adjacent levels using tools of molecular biology, genomics, biochemistry, physiology, population genetics, microbiology, and ecology. Hydroponic systems will allow the source and concentration of nitrogen to be closely controlled. A soil-based system will also be used to address how mechanistic relationships at cellular and organismal levels influence population, community, and ecosystem-scale processes. A factorial study will involve wild type (WT) and transformed Arabidopsis, and mixtures of the two, exposed to ambient and elevated [CO2]. Elevated [CO2] treatments will help identify causal associations among levels of biological organization by accentuating interactions between the carbon and nitrogen cycles. As a secondary goal, we expect that this research will contribute to fundamental understanding of the linkages between NR activity and photosynthesis, and more generally to the importance of N metabolism in determining plant responses to elevated [CO2]. Results from these investigations will contribute to a more mechanistic description of how environmental change influences structure and function of terrestrial ecosystems; a primary goal of the DOE Program for Ecosystem Research.


Integration of Systems Biology and Ecology
A mesocosm-scale study designed to span the gene-ecosystem continuum
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