Molecular Regulation and Transport of Sterols in Plants

植物甾醇代表了一系列复杂的化合物，它们对于植物生长和发育的许多方面都是必需的，并且对于它们对动物和人类的营养贡献具有相当重要的意义。因此，甾醇生物合成途径的生物化学和分子生物学得到深入研究也就不足为奇了。尽管如此，人们对植物中这一生化途径的调控实际上知之甚少。我们在甾醇代谢方面的长期研究的一个目标是集中于角鲨烯合酶的调节，角鲨烯合酶是甾醇生物合成酶的关键酶。我们最近的结果表明角鲨烯合酶基因表达和酶活性定位于分生组织。在试图将这些结果与文献中已经报道的结果相一致时，最合乎逻辑的解释是甾醇生物合成本身局限于该组织。这种解释意味着甾醇生物合成的调节发生在芽分生组织中，这是一种以前没有被评估过的组织，并且必须存在用于将甾醇从顶端分生组织移动到整个植物的甾醇运输系统。提出了测试这些预测的实验，包括： 1、评估位于茎分生组织的甾醇生物合成是否受到调节； 2、开发植物内甾醇长距离运输的测试方法； 3、确定NPC1（一种参与胆固醇摄取和细胞内运输的高度保守的蛋白质）是否在植物中发挥与动物中相似的作用。拟议的工作将涉及本科生、研究生和博士后助理，应该为如何利用新兴技术设计这条途径以提高价值提供重要的见解。

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.