Molecular Regulation and Transport of Sterols in Plants

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Plant sterols represent a complex array of chemical compounds that areessential for many facets of plant growth and development, and are ofconsiderable importance for their nutritional contributions to animals andman. Hence, it is not surprising that the biochemistry and molecularbiology of the sterol biosynthetic pathway has been intensively studied.Nonetheless, very little is actually known about the regulation of thisbiochemical pathway in plants. One goal of our long-term research in sterolmetabolism has been focussed on the regulation of squalene synthase, a keyenzyme in sterol biosynthetic enzyme. Our recent results suggest thatsqualene synthase gene expression and enzyme activity are localized toshoot meristems. In attempting to reconcile these results with thosealready reported in the literature, the most logical interpretation is thatsterol biosynthesis itself is localized to this tissue. This interpretationimplies that regulation of sterol biosynthesis occurs in the shootmeristem, a tissue that has not been evaluated as such before, and that asterol transport system for the movement of sterol from the apical meristemthroughout the plant must exist. Experiments to test these predictions areproposed and include: 1, an evaluation if sterol biosynthesis localized tothe shoot meristem is regulated; 2, the development of a test for longdistance transport of sterol within plants; and 3, a determination if NPC1,a highly conserved protein involved in cholesterol uptake and intracellulartrafficking, plays a similar role in plants as in animals. The proposedwork, which will involve undergraduate and graduate students and apostdoctoral associate, should provide important insights into how thispathway might be engineered for enhanced value using emerging technologies.