Antioxidant metabolism in Chlamydomonas

描述(申请人提供)：几种由植物合成的抗氧化剂小分子是人类饮食中必不可少的维生素。这些营养素，包括维生素A前体(类胡萝卜素)、维生素E(生育酚)和维生素C(抗坏血酸)，在猝灭和清除活性氧方面具有关键作用，而活性氧是从细菌到动植物的所有需氧生物体中不可避免的代谢副产物。尽管抗氧化维生素对人类健康很重要，但关于它们的功能和生物合成的调节，许多基本问题仍然没有得到回答。这项建议使用分子遗传学、基因组和生理学方法在一种易驯化的单细胞绿藻--莱茵衣藻中解决了其中的几个问题。衣藻是研究植物体内抗氧化剂代谢的一种强大的真核模式生物，就像萌芽酵母酿酒酵母被用作动物模型一样。这项建议的具体目标是(1)完成衣藻类胡萝卜素生物合成的分子和遗传分析，(2)产生一系列影响生育酚组成的突变体，以便在体内测试不同生育酚的抗氧化功能，(3)研究类胡萝卜素和生育酚在多不饱和脂膜中作为抗氧化剂的功能重叠，以及(4)对环境因素(如光照强度)如何调节细胞中类胡萝卜素和生育酚水平进行基因组和遗传学分析。这项研究将为脂溶抗氧化剂在预防人类黄斑变性等与年龄相关的疾病中的作用提供新的见解，并将为合理修改植物中类胡萝卜素和生育酚的组成和含量以利于人类营养和健康提供基础。

DESCRIPTION (provided by applicant): Several antioxidant small molecules that are synthesized by plants are essential vitamins in the human diet. These nutrients, including vitamin A precursors (carotenoids), vitamin E (tocopherols), and vitamin C (ascorbate), have critical functions in quenching and scavenging reactive oxygen species that are inevitable byproducts of metabolism in all aerobic organisms, from bacteria to plants and animals. Despite the importance of antioxidant vitamins for human health, many fundamental questions remain unanswered about their function and the regulation of their biosynthesis. This proposal addresses several of these questions using molecular genetic, genomic, and physiological approaches in a tractable, unicellular green alga, Chlamydomonas reinhardti. Chlamydomonas represents a powerful eukaryotic model organism for studying antioxidant metabolism in plants, much like the budding yeast Saccharomyces cerevisiae is used as a model for animals. The specific aims of this proposal are (1) to complete a molecular and genetic analysis of carotenoid biosynthesis in Chlamydomonas, (2) to generate a series of mutants affecting tocopherol composition in order to test the antioxidant function of different tocopherols in vivo, (3) to examine functional overlap between carotenoids and tocopherols as antioxidants in polyunsaturated lipid membranes, and (4) to perform genomic and genetic analyses of how carotenoid and tocopherol levels are regulated in cells by environmental factors, such as light intensity. This investigation will provide new insights into the roles of lipid-soluble antioxidants in preventing age-related diseases such as macular degeneration in humans and will provide a foundation for rational modification of carotenoid and tocopherol composition and content in plants to benefit human nutrition and health.