ARTICLES

Cell Research (2006)16: 731-739
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Tissue differential expression of lycopene β-cyclase gene in papaya

Rachel L Skelton, Qingyi Yu, Rajeswari Srinivasan, Richard Manshardt, Paul H Moore, Ray Ming,

Correspondence: Ray Ming Fax: +1-217-244-1336; E-mail: rming@life.uiuc.edu Received 1 Feb 2006; revised 24 Feb 2006; accepted 27 Mar 2006; published online 27 Jun 2006

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Carotene pigments in flowers and fruits are distinct features related to fitness advantages such as attracting insects for pollination and birds for seed dispersal. In papaya, the flesh color of the fruit is considered a quality trait that correlates with nutritional value and is linked to shelf-life of the fruit. To elucidate the carotenoid biosynthesis pathway in papaya, we took a candidate gene approach to clone the lycopene β-cyclase gene, LCY-B. A papaya LCY-B ortholog, cpLCY-B, was successfully identified from both cDNA and bacterial artificial chromosome (BAC) libraries and complete genomic sequence was obtained from the positive BAC including the promoter region. This cpLCY-B shared 80% amino acid identity with citrus LCY-B. However, full genomic sequences from both yellow- and red-fleshed papaya were identical. Quantitative real-time PCR (qPCR) revealed similar levels of expression at six different maturing stages of fruits for both yellow- and red-fleshed genotypes. Further expression analyses of cpLCY-B showed that its expression levels were seven- and three-fold higher in leaves and, respectively, flowers than in fruits, suggesting that cpLCY-B is down-regulated during the fruit ripening process.

Cell Research (2006) 16:731-739. doi:10.1038/sj.cr.7310081; published online 27 June 2006

Keywords: Carica papaya, fruit flesh color, lycopene ¦Â-cyclase