Carbon partitioning between starch and oil in Avena sativa (oat) and Arabidopsis thaliana

In recent years, the demand for plant-derived oils as renewable alternatives to fossil oil has increased due to the rising cost of petroleum and the increased concern about the environment. However, the supply of vegetable oils today relies upon only a few crops with low potential for further increases in oil yields. Redirection of carbon flux from starch to oil in the cereal seed can provide for new high-yielding oil crops as a sustainable alternative to fossil oil to meet the increased need for plant oils. Increased knowledge of oil biochemistry and the regulation of carbon partitioning between different storage compounds in seeds is therefore of crucial importance for the development of such novel oil crops in the future. In a study to determine if the future environment with elevated atmospheric CO2 can be expected to alter the partitioning of carbon into oil in seeds, it was found that elevated CO2 induced a much higher starch accumulation in leaves of A. thaliana whereas seed oil content was unaffected. However, leaf lipid metabolism was altered in an elevated CO2 environment and changes were targeted to the lipids in the photosynthetic membranes of the chloroplasts. Among the cereals, oat is unique in storing high amounts of oil in the endosperm. The deposition of storage compounds during seed development and their mobilization during germination was investigated. There were large differences in partitioning of carbon between oil and carbohydrate reserves between oat cultivars having different oil content, both during seed development and germination. The data suggests that oat is suitable as a model plant for oil synthesis in the cereal endosperm to find the metabolic switches for carbon partitioning between starch and oil. An in vitro liquid culture for oat seeds on detached panicles was established to mimic seed development and cultivar differences in storage accumulation from anthesis to maturity in planta. The in vitro system was used in preliminary stable radioactive isotope labeling experiments that confirmed the cultivar differences in carbon partitioning into oil observed in planta.