The impact of a single gene change in nitrogen metabolism on the structure and function of a model ecosystem grown at current and elevated CO2

Ecological genomics is an emerging field of study in ecology and is founded on the presumption that genes, at some level, drive ecosystem processes. However, the extent to which a single gene can impact the structure and function of a terrestrial ecosystem is unclear. In an attempt to address this question, we have grown arabidopsis in model ecosystems to better understand the links between multiple levels of biological organization. Our approach was to modify the entry of carbon and nitrogen into the central metabolism of a model organism at two well defined points and then follow the impact of these changes from the level of the gene through to ecosystem structure and function. We grew wild type plants, and mutant plants that have a reduced nitrate reductase activity in 36 environmentally-controlled mesocosms. The plants were exposed to either ambient or elevated carbon dioxide concentration for multiple generations. In order to follow the impact of changes in carbon and nitrogen acquisition we measured gene expression, enzyme activity, metabolite levels, ecosystem gas exchange, growth and fecundity. Preliminary results suggest that wild type and mutant plants show distinct differences, both with respect to each other, and to the imposed carbon dioxide treatments. Here we present data from three generations of plants and discuss how a reduction in the expression of a single gene can translate through successive hierarchies of biological organization and lead to measurable impacts on the structure and function of our model ecosystem.