Abstract

Anthocyanins are flavonoids and possess extensive bioactivities and pharmacological properties. Chalcone isomerase (CHI; EC 5.5.1.6) is an essential enzyme of the anthocyanins biosynthetic pathway, which catalyzes the intramolecular cyclization of bicyclic chalcones into tricyclic (S)-flavanones. In order to investigate the role of chalcone isomerase in anthocyanins biosynthesis in sweetpotato, we cloned and characterized the chalcone isomerase gene from purple-fleshed sweetpotato (Ipomoea batatas (L.) Lam) cultivar Yuzi 263, which was designated as IbCHI (Genbank accession number: JN083840). The full-length cDNA of IbCHI was 890-bp long and contained a 732-bp coding sequence encoding a polypeptide of 243-amino acids. A phylogenetic tree of CHIs was constructed from different organisms including plants and algae, which showed that IbCHI had high similarities with other plant CHIs. Tissue expression pattern analysis indicated that IbCHI was expressed constitutively in all sweetpotato tissues including roots, stems, young leaves, old leaves and petiole with highest expression in roots, and at the same time the anthocyanin content in the tissues coincided with the gene expression pattern. The cloning and characterization of IbCHI will be helpful in the understanding of the role of CHI involved in the anthocyanins biosynthesis at the molecular level and provide a candidate gene for metabolic engineering of the anthocyanins biosynthesis in sweetpotato.

Key words: Purple-fleshed sweetpotato, chalcone isomerase, anthocyanin, expression profile.