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, CHI family genes are not well understood in Dracaena cambodiana Pierre ex Gagnep, an important source plant of dragon’s blood. In this study, 11 CHI family genes were identified from D. cambodiana, and they were classified into three types. Evolutionary and transcriptional profiling analysis revealed that DcCHI1 and DcCHI4 might be involved in flavonoid production. Both DcCHI1 and DcCHI4 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 Escherichia coli and purified by His-Bind resin chromatography. Enzyme activity assay indicated that DcCHI1 catalyzed the formation of naringenin from naringenin chalcone, while DcCHI4 lacked this catalytic activity. Overexpression of DcCHI1 or DcCHI4 enhanced the flavonoid production in D. cambodiana and tobacco. These findings implied that DcCHI1 and DcCHI4 play important roles in flavonoid production. Thus, our study will not only contribute to better understand the function and expression regulation of CHI family genes involved in flavonoid production in D. cambodiana but also lay the foundation for developing the effective inducer of dragon’s blood.

Biochemical and Molecular Characterization of the Rice Chalcone Isomerase Family

“…In plants, the CHI families consist of several genes [ 13 , 14 , 38 ]. Soybean contains 12 CHI members [ 14 ], and five genes comprise the CHI family in Arabidopsis [ 13 ].…”

“…Soybean contains 12 CHI members [ 14 ], and five genes comprise the CHI family in Arabidopsis [ 13 ]. Eleven CHI family genes were identified from Dracaena cambodiana [ 38 ]. Likewise, seven OsCHI genes were found in the rice genome and were classified into three types, types I, III, and IV ( Table 1 and Figure 1 ).…”

“…Likewise, seven OsCHI genes were found in the rice genome and were classified into three types, types I, III, and IV ( Table 1 and Figure 1 ). Among family members, a few genes encode bona fide type I and type II CHIs [ 12 , 14 , 38 ]. In Arabidopsis, only one of five CHI members appears to be a bona fide type I CHI [ 13 , 39 ].…”

The Flavonoid Biosynthesis Network in Plants

“…In general, CHIs can be classified into two types in plants according to the substrate utilized [ 52 ]. Type I CHIs, ubiquitous in vascular plants, are responsible for the conversion of THC into naringenin [ 53 ]. Type II CHIs are found primarily in leguminous plants and can utilize either THC or isoliquiritigenin to generate naringenin and liquiritigenin [ 1 ].…”

“…The expression level of CHI was found to be positively correlated with flavonoid content in A. thaliana [ 55 ]. In both Dracaena cambodiana and tobacco, the overexpression of DcCHI1 or DcCHI4 leads to increased flavonoid accumulation [ 53 ]. In transgenic tobacco plants, RNAi-mediated suppression of CHI enhances the level of chalcone in pollen [ 56 ].…”