Submitted to: American Society of Plant Biologists Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 7/5/2006
Publication Date: 8/5/2006
Citation: Lu, S., Lopez, A.B., Li, L. 2006. Identification of or as a novel regulatory gene controlling high-level of b-carotene accumulation in cauliflower. [abstract] American Society of Plant Biologists Annual Meeting. p. 226.
Technical Abstract: Carotenoids are indispensable to plants and play a critical role in human nutrition and health. In spite of recent significant progress in our understanding of carotenoid biosynthesis in plants, the overall control mechanisms remain largely unknown. The high-b-carotene Or (Orange) gene mutation in cauliflower provides an ideal model to divulge the regulatory mechanisms because it turns on carotenogenesis in tissues where carotenoid accumulation is normally repressed. By using a map-based cloning strategy, a single gene coding for Or has been identified and successfully verified by phenotypic complementation in the wild type cauliflower and Arabidopsis "cauliflower" mutant. The wild type Or gene consists of 8 exons and encodes a protein of 33 kDa with a putative transit peptide and two transmembrane domains. The Or gene appears to be plant-specific and shares high sequence identity with orthologs from Arabidopsis, tomato, potato, maize, and rice. The mutant Or allele contains a large retrotransposon insertion in exon 3. Northern analysis showed that the Or transcript was most abundant in curd, very young leaf, and flower tissues. Western analysis revealed a similar pattern of OR protein expression. The tissue-specific expression of endogenous Or gene was further confirmed by examining the expression of Proor:GUS in transgenic Arabidopsis plants. Subcellular localization study indicated that the OR-GFP fusion protein was targeted to leucoplasts in the epidermal cells of young leaves. It was localized to a division site of plastids as observed in the developing seeds. Experiments are under way to decipher the control mechanism by which Or induces carotenogenesis.