9406466 Ohlrogge Plant fatty acids are essential for the structure and function of all cell membranes and in addition are the major form of carbon storage in seeds of many species. The long range objective of this research project is to answer the question: What determines how much fatty acid is produced by a plant cell? Precise control over primary metabolic pathways is frequently obtained by a complex network of interlocking mechanisms which include both short term biochemical regulation over enzyme specific activity and longer term modifications in enzyme expression. This project will examine both types of control of plant fatty acid synthesis and will focus on the following areas: I. results from prior NSF support of this project have provided clear in vivo evidence that acetyl-CoA carboxylase activity is a major determinant of flux through the fatty acid synthesis pathway. However, it is not known how plant cells regulate the activity of this enzyme. Preliminary information indicates that acetyl-CoA carboxylase is regulated by feedback inhibition. Therefore, one goal of this project will be to determine which metabolites, regulatory molecules, or other mechanisms are involved in controlling the activity of acetyl-CoA carboxylase. II. Longer term control over the activity of the fatty acid synthesis pathway may be determined at the level of gene expression. We have developed a tobacco cell suspension system in which the cellular demand for fatty acid production can be either up or down regulated. We will determine if there is a direct relationship between expression of genes for several enzymes of fatty acid synthesis and the cell's supply of demand for fatty acid production. III. Several cDNA and genomic clones for acetyl-CoA carboxylase have recently been isolated which may encode both cytoplasmic and plastidial isozymes. The relationship between the structure of these different genes. Their regulation in different tissues, and their involvement in fatty acid synthesis in the plastid and cytoplasm will be determined. %%% Plant oils have gradually replaced animal fats and thus, are a major and growing source of calories in American diets. In addition, plant oils are used in a number of industrial application such as the manufacture of soaps and detergents, lubricants and plastics. World production of plant oils is approximately 60 million tons with a value of over 25 billion dollars. Genetic engineering of plant oils has the potential to produce new oils with improved nutritional or industrial value. To optimize the production of plant oils for either food or non-food uses it is important to understand how plants control the synthesis of storage oils in their seeds. Therefore, the long range objective of this research project is to answer the question: What determines how much fatty acid (oil) is produced by a plant cell? We have identified acetyl-CoA carboxylase as a regulatory enzyme which controls, at least in part, the flux of carbon into the lipid biosynthetic pathway. This project will determine which metabolites, regulatory molecules or other mechanisms are involved in controlling the activity of acetyl-CoA carboxylase. In addition we will determine if there is a direct relationship between expression of genes for enzymes of fatty acid synthesis (including acetyl-CoA carboxylase) and the cellular demand for fatty acid production. Information obtained from this analysis from this analysis of how plants control fatty acid synthesis will be used to genetically engineer improved oilseed crops. ***
