AUTHOR=Sun Wei , Shen Huan , Xu Hui , Tang Xiaoxin , Tang Ming , Ju Zhigang , Yi Yin 

TITLE=Chalcone Isomerase a Key Enzyme for Anthocyanin Biosynthesis in Ophiorrhiza japonica

JOURNAL=Frontiers in Plant Science

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2019.00865

DOI=10.3389/fpls.2019.00865

ISSN=1664-462X

ABSTRACT=<p>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 <italic>Ophiorrhiza japonica</italic> and designated as <italic>OjCHI</italic>. 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 <italic>O. japonica</italic>, integrative analysis between metabolites and <italic>OjCHI</italic> expression was conducted. The results showed <italic>OjCHI</italic> expression matched the accumulation patterns of anthocyanins not only in different tissues but also during the flower developmental stages, suggesting the potential roles of <italic>OjCHI</italic> 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 <italic>OjCHI</italic> in Arabidopsis <italic>tt5</italic> mutant restored the anthocyanins and flavonols phenotype of hypocotyl, cotyledon and seed coat, indicating its function as a chalcone isomerase <italic>in vivo</italic>. In summary, our findings reveal the <italic>in vitro</italic> as well as <italic>in vivo</italic> functions of OjCHI and provide a resource to understand the mechanism of anthocyanin biosynthesis in <italic>O. japonica</italic>.</p>