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

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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.