Over-expression of StLCYb increases β-carotene accumulation in potato tubers

Lycopene b-cyclase (LCYb) is involved in the first step of the β-branch synthetic pathway of carotenoids from lycopene in plants. In this study, to explore the possibility of regulating β-carotene synthesis via the β-branch-specific pathway in potato, StLCYb gene was first isolated from potato cultivar Désirée, and its open reading frame was 1503 bp long without intron. The protein sequence of StLCYb showed high similarity with that of LCYbs in other species such as SlLCYb1, CaLCYb, NtLCYb and ApLCYb. StLCYb was expressed in all tissues and the highest level was observed in tubers followed in flowers, and the lowest level was in roots. HPLC detected an about 1.5–1.9 times increase in β-carotene content of transgenic potato tubers, in which the gene StLCYb was overexpressed, compared with the wild-type control. Besides, the expression levels of carotenoid-related genes StPSY , StPDS , StZDS , StCHYb and StZEP transcripts in the transgenic lines were significantly higher than in the wild-type control, which implied a positive regulation in promoting carotenoid synthesis. All these results suggest that β-carotene content in potato tubers could be regulated by modulating StLCYb expression.