Antioxidant metabolism in Chlamydomonas

描述（由申请人提供）：由植物合成的几种抗氧化小分子是人类饮食中的必需维生素。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），在淬灭和清除活性氧方面具有关键作用，活性氧是所有有氧生物体（从细菌到植物和动物）代谢的不可避免的副产物。尽管抗氧化维生素对人类健康的重要性，但关于其功能和生物合成调节的许多基本问题仍未得到解答。该提案使用分子遗传学、基因组学和生理学方法在易处理的单细胞绿色藻类莱茵衣藻中解决了其中的几个问题。衣原体是研究植物抗氧化代谢的一种强大的真核生物模式生物，就像芽殖酵母酿酒酵母被用作动物模型一样。该提议的具体目的是（1）完成衣原体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）检查类胡萝卜素和生育酚作为多不饱和脂膜中的抗氧化剂之间的功能重叠，和（4）进行细胞中类胡萝卜素和生育酚水平如何受环境因素如光强度调节的基因组和遗传分析。这项研究将为脂溶性抗氧化剂在预防人类黄斑变性等年龄相关疾病中的作用提供新的见解，并将为合理修饰植物中类胡萝卜素和生育酚的组成和含量以有益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.