Genetic Analysis and Regulation of Carotenoid Biosynthesis

TL;DRAbstract

Carotenoids comprise a large class of natural pigments that are ubiquitous in photosynthetic organisms and are essential for photooxidative protection. A large collection of anoxygenic photosynthetic bacterial carotenoid biosynthesis mutants with novel color phenotypes have been isolated over the past 40 years. Genes involved in carotenoid biosynthesis have recently been mapped, cloned and sequenced. Seven clustered genes (crtA, crtB, crtC, crtD, crtE, crtF, crtI) are required for carotenoid biosynthesis in Rhodobacter (Rb.) capsulatus and Rb. sphaeroides. The crt gene products participate in reactions that convert FPP to spheroidene/spheroidenone. The proposed requirement for the products of Rb. capsulatus ORF160 and ORF 469 in carotenoid biosynthesis conflicts with experiments using their respective Rb. sphaeroides homologs. Nucleotide sequences have been determined for all of the Rb. capsulatus crt genes and for crtD, crtI, crtB and a portion of crtC in Rb. sphaeroides. The Rb. caps

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