Plant Storage Lipid Biosynthesis

点击翻译按钮获取中文摘要

Rising incomes, population growth, and an urgent need for renewable liquid fuels are driving an unprecedented global demand for seed oils. This year it is estimated that Canada will produce about 16 million metric tonnes of canola generating about $19 billion in economic activity for the nation (Canola Council of Canada). The overall goal of my research program is to understand how seed oil formation is controlled as a basis for developing canola with increased seed oil content and oil that can be designated as “zero saturate” to increase both the competitiveness and marketability of the oil. In general, increased consumption of saturated fats tends to be associated with increased prevalence of cardiovascular disease. During seed development, a series of oil-building enzymes (biological catalysts) drive the formation of oil. The action of these enzymes can influence both the quantity of oil formed and the composition and properties of the oil. The proposed research program focuses on two types of enzymes that drive reactions in the oil-building pathway. One of these enzymes (abbreviated DGAT) drives the final step in oil formation whereas the other enzyme (abbreviated LACS) drives the formation of building blocks for use in the final oil-building step. Recombinant DNA technology will be used to modify canola DGAT and the resulting modified forms of the enzyme will undergo biochemical testing. Enzyme modification will involve removing sections from the enzyme or making specific changes within the enzyme. This type of probing should provide some insight into how the enzyme operates and is able to accommodate certain oil-building blocks. High throughput methods will be used to generate a multitude of enzyme variants, some of which may have the characteristics sought. Production and identification of functional DGAT variants will be conducted using a yeast system whereas a bacterial system will be used for this purpose in the case of LACS. DGAT variants which drive the formation of oils reduced in saturation will be selected for further biochemical testing. In the case of LACS, enzyme variants will be selected which drive the formation of oil-building blocks with reduced saturation. Promising DGAT or LACS variants will then be introduced into a model oilseed plant (thale cress), via genetic engineering, to see if the degree of saturation is reduced in the oil. Enzyme variants which reduce saturation in thale cress seed oil will then be evaluated for their ability to reduce saturation in canola oil. We will also attempt to purify, crystallize and determine the detailed structure of canola DGAT in order to find out what really “makes it tick”. If this high risk component of our work is successful, it will complement our work on DGAT modification. Currently, there is no detailed structural information available on this enzyme. Detailed information on the structure and action of this key oil-building enzyme will lead to the development of other strategies for modifying seed oil production. This plant oil formation research will rely on methods from numerous disciplines including plant biochemistry, structural biology, molecular breeding, molecular biology and genetic-engineering. The proposed research program will also contribute to the training of highly qualified personnel in the burgeoning area of plant oils research.