Identification and Characterization of Chalcone Isomerase Genes Involved in Flavonoid Production in Dracaena cambodiana

Abstract

Dragon's blood is a traditional medicine in which flavonoids are the main bioactive compounds; however, the underlying formation mechanism of dragon's blood remains largely poorly understood. Chalcone isomerase (CHI) is the key enzyme in the flavonoid biosynthesis pathway. However, <i>CHI</i> family genes are not well understood in <i>Dracaena cambodiana</i> Pierre ex Gagnep, an important source plant of dragon's blood. In this study, 11 <i>CHI</i> family genes were identified from <i>D. cambodiana</i>, and they were classified into three types. Evolutionary and transcriptional profiling analysis revealed that <i>DcCHI1</i> and <i>DcCHI4</i> might be involved in flavonoid production. Both <i>DcCHI1</i> and <i>DcCHI4</i> displayed low expression levels in stem under normal growth conditions and were induced by methyl jasmonate (MeJA), 6-benzyl aminopurine (6-BA, synthetic cytokinin), ultraviolet-B (UV-B), and wounding. The recombinant proteins DcCHI1 and DcCHI4 were expressed in <i>Escherichia coli</i> and purified by His-Bind resin chromatography. Enzyme activity assay indicated that <i>DcCHI1</i> catalyzed the formation of naringenin from naringenin chalcone, while DcCHI4 lacked this catalytic activity. Overexpression of <i>DcCHI1</i> or <i>DcCHI4</i> enhanced the flavonoid production in <i>D. cambodiana</i> and tobacco. These findings implied that <i>DcCHI1</i> and <i>DcCHI4</i> play important roles in flavonoid production. Thus, our study will not only contribute to better understand the function and expression regulation of <i>CHI</i> family genes involved in flavonoid production in <i>D. cambodiana</i> but also lay the foundation for developing the effective inducer of dragon's blood.