Chalcone Isomerase a Key Enzyme for Anthocyanin Biosynthesis in .

Anthocyanins are distributed ubiquitously to terrestrial plants and chalcone isomerase (CHI) catalyzes the stereospecific isomerization of chalcones - a committed step in the anthocyanin biosynthesis pathway. In this study, one gene encoding CHI was isolated from and designated as . Multiple sequence alignments and phylogenetic analysis revealed that OjCHI had the conserved CHI active site residues and was classified into type I CHI group. In order to better understand the mechanisms of anthocyanin synthesis in , integrative analysis between metabolites and expression was conducted. The results showed expression matched the accumulation patterns of anthocyanins not only in different tissues but also during the flower developmental stages, suggesting the potential roles of in the biosynthesis of anthocyanin. Then biochemical analysis indicated that recombinant OjCHI protein exhibited a typical type I CHI activity which catalyzed the production of naringenin from naringenin chalcone. Moreover, expressing in Arabidopsis mutant restored the anthocyanins and flavonols phenotype of hypocotyl, cotyledon and seed coat, indicating its function as a chalcone isomerase . In summary, our findings reveal the as well as functions of OjCHI and provide a resource to understand the mechanism of anthocyanin biosynthesis in .