Genome-Wide Identification, Characterization, and Expression Analysis of CHS Gene Family Members in Chrysanthemum nankingense

The chalcone synthase (CHS) gene family catalyzes the first committed step in the biosynthesis of flavonoids and plays key roles in various biological processes in plants. However, systematic studies of the CHS gene family in chrysanthemum remain unknown to date. In this study, 16 CnCHS genes were identified by searching the complete genome sequence of Chrysanthemum nankingense. Most contained two exons and one intron with Chal-sti-synt_N and Chal-sti-synt_C domains. A phylogenetic tree of CnCHSs indicated divergence into three major groups, including I, II, and III. Analyses of the genes and promoters of these genes indicated that there are many cis-acting elements that respond to light, phytohormones, stress, and developmental stages. The CnCHS genes have extensive patterns of expression in various tissues and stages of flower development. Tandemly repeated and segmental repeat genes were expressed at higher levels in different tissues than most of the CnCHS genes that have been identified. CnCHS10 is expressed at higher levels in various flower organs than in vegetative tissues, particularly in disc floret petals and pistils. Our study provides valuable information for the systematic analysis of the CnCHS gene family, which also contributes to further research on flavonoid synthesis and petal colors of chrysanthemum.