摘要
Carotene pigments in flowers and fruits are distinct features related to fitness advantages such as attracting insects forpollination and birds for seed dispersal.In papaya,the flesh color of the fruit is considered a quality trait that correlateswith 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 genomicsequence was obtained from the positive BAC including the promoter region.This cpLCY-B shared 80% amino acididentity 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 forboth yellow-and red-fleshed genotypes.Further expression analyses of cpLCY-B showed that its expression levels wereseven- and three-fold higher in leaves and,respectively,flowers than in fruits,suggesting that cpLCY-B is down-regulatedduring the fruit ripening process.
