Abstract:

Celery（Apium graveolens L.）is an important vegetable in Apiaceae family，with excellent source of carotenoid. Lycopene epsilon cyclase is a key enzyme in the pathway of carotenoid biosynthesis. Here，the AgLCYE gene encoding lycopene epsilon cyclase was cloned from A. graveolens‘Jinnan Shiqin’. The sequences of AgLCYE gene contained an open reading frame with the length of 1 590 bp，which encoded 529 amino acids. Multiple alignments of the AgLCYE amino acid sequences from celery and other different plants showed a homology of 77.68%. The homology of LCYE was up to 98.07%  between celery and carrot. Phylogenetic tree analysis showed that the LCYE proteins were conserved. The physicochemical property analysis showed that AgLCYE belonged to hydrophilic protein. There were 9 alpha helices and 18 beta folds in the predicted tertiary structure of the protein. The results of disordered analysis showed that the amino acid sequence of AgLCYE protein had four disorder regions. The contents of lutein and α-carotene of celery leaves in different growth stages（30，45，and 60 d）were determined by UPLC. The peak of lutein content was detected at 30 d. The lowest content of lutein was observed in 45 d. There was no significant difference between 45 d and 60 d. The lutein content in leaf blade was higher than that in petiole of celery. The presences of α-carotene were not detected in leaf blade and petiole of celery，respectively. The expression levels of AgLCYE gene in celery were detected by quantitative real-time PCR. In leaf blade，the relative expression levels of AgLCYE gene increased gradually over the process of celery growth and development. On the contrary，the relative expression levels of AgLCYE gene decreased in petiole.

Key words: celery, carotenoid, AgLCYE gene, lutein, α-carotene