Location: Plant Genetics Research
2013 Annual Report
The research is focused on improving the understanding of central carbon metabolism that leads to altered oil production in plant tissues. This work addresses the parent project plan objective: To improve our understanding of carbon, energy, and redox source and sink partitioning within plants through explorations of primary metabolism by labeling investigations, and by making use of systems biology methods including flux analysis.
The goal of this project is to characterize molecular phenotypes by quantifying the impact of transgenic modifications at the biochemical level as compared to the wild type. To increase the productivity of Camelina, ARS scientists in St. Louis, MO explored transgenics, where targeted genes have been inserted to increase photosynthetic efficiency including carbon fixation, and raise the net energy of the seeds by increased oil content. We anticipated that attempts to engineer Camelina would generate mixed results and therefore we compared different transgenic lines to the wild type to better understand metabolism. Camelina is not a well-domesticated or well-studied crop; therefore initial investigations focused on characterizing the metabolic phenotype of the different tissues that provide important benchmark data for comparison to transgenic lines. Products of metabolism for different aged plants were measured including growth, oil, protein, and starch production.
Isotopic labeling methods, using stable or radioactive isotopes of carbon and nitrogen, were developed to probe camelina embryo and leaf metabolism. Camelina embryos were grown in culture media formulated to reflect the composition of liquid endosperm of seeds. The media contained sucrose, glucose, fructose, glutamine and alanine, each of which can be labeled. Using this procedure a developmental time course of isotopic enrichment of primary metabolites was obtained.
We developed a chamber suitable for gaseous isotopic labeling of leaves and were able to track the carbon fixed by photosynthesis into leaf sugars and amino acids. To complete the analysis, methods for the measurement of net photosynthesis, transpiration, stomatal conductance and intracellular carbon dioxide concentration were adapted and used to examine leaves of difference age, size and location on the plant.