Abstract: Using the mRNA from the fruit of Citrus sinensis Osbeck cv. Cara Cara as the template, we amplified and cloned the cDNA of lycopene β-cyclase gene by reverse transcription polymerse chain reactin（RT-PCR）. Sequence analysis indicated that the cDNA was 1654 bp long with two transcripts Lcyb1 and Lcyb2, which had an open reading frame of 1512 bp and encoded a protein of 504 amino acids respectively. The full-length coding region of Lcyb1 and Lcyb2 cDNA were cloned using PCR and further subcloned into pET-28a(+), resulting in the prokaryotic expression vector pET-CitLcyb1 and pET-CitLcyb2. The results of color complementation demonstrated fusion protein 6×His-Lcyb1 and 6×His-Lcyb2 could catalyse lycopene to form β-carotene respectively.

Key words: citrus, lycopene β-cyclase, gene, clone, functional expression