Cloning and Functional Analysis of the Arabidopsis lut1 Locus: A Noval Activity Required for Hydroxylation of Epsilon Ring Carotenoids in Plants

植物合成两大类胡萝卜素：胡萝卜素，它是环化或非环化的碳氢化合物(如番茄红素和β胡萝卜素)，以及叶黄素，它是胡萝卜素的各种含氧衍生物(如叶黄素和玉米黄质)。胡萝卜素羟基酶(OHase)在环状胡萝卜素的环上添加羟基，是植物合成全叶黄素所必需的。该方案通过分离定义特定胡萝卜素羟基酶的基因，并通过突变分析改变一种或多种活性的表达，对植物组织中的胡萝卜素羟基酶进行了详细的分析。这些修饰对光合作用组织中类胡萝卜素和叶黄素的合成和组成的影响，将为深入了解每个酶在该途径中的作用以及粮食作物途径工程的后果提供重要的见解。鉴于胡萝卜素作为抗氧化剂在人类饮食中的重要性，以及类胡萝卜素在降低全球人口某些亚群中黄斑变性、各种癌症和维生素A缺乏症的发生率和进展中的作用(S)，进一步了解参与类胡萝卜素和叶黄素合成的酶可能对人口的整体健康产生有益影响。

Plants synthesize two major groups of carotenoids: carotenes, which arecyclized or uncyclized hydrocarbons (e.g. lycopene and beta carotene), andxanthophylls, which are variously oxygenated derivatives of carotenes (e.g.lutein and zeaxanthin). Carotene hydroxylases (OHases) add hydroxyl groupsto the rings of cyclic carotenes and are essential for the synthesis of allxanthophylls in plants. This proposal performs a detailed analysis ofcarotene hydroxylases in plant tissues by isolating genes defining specificcarotene hydroxylases and modifying the expression of one or more activityby mutant analysis. The consequences of such modifications on carotenoidand xanthophyll synthesis and composition in photosynthetic tissues willprovide important insights into the role of each enzyme in the pathway andthe consequences of pathway engineering in food crops. Given the importanceof carotenes as antioxidants in the human diet and the role(s) ofcarotenoids in decreasing the incidence and progression of maculardegeneration, various cancers and vitamin A deficiency in certain subgroupsof the global population, a further understanding of the enzymes involvedin carotenoid and xanthophyll synthesis may have beneficial impacts on theoverall health of the population.