Systematic Identification and Characterization of -Methyltransferase Gene Family Members Involved in Flavonoid Biosynthesis in L.

L. capitulum is an enriched source of flavonoids with broad-ranging biological activities, mainly due to their anti-inflammatory, anti-cancer, immune regulation, anti-microbial activity, hepatoprotective, and neuroprotective effects. The -methylation of various secondary metabolites has previously been demonstrated to be mainly catalyzed by -adenosyl-L-methionine-dependent -methyltransferase (OMT) proteins encoded by the gene family. However, limited comprehensive study was published on the gene family, especially the subfamily, involved in the -methylation of flavonoids in Chrysanthemum. Here, we analyzed the spatiotemporal expression patterns of . genes in leaf and flower at different developmental stages. Transcriptome sequencing and qRT-PCR analysis showed that s were mainly highly expressed in capitulum, especially in full bloom, while s were mainly highly expressed in leaves. Correlation analysis of gene expression and flavonoids accumulation revealed that four s (, , , and ) were putatively involved in most methylated flavonoids biosynthesis in the capitulum. Furthermore, we identified a true CCoAOMT enzyme, CiCCoAOMT1, and found that it catalyzed -methylation of quercetin and luteolin at the 3'-OH position. In summary, this work provides an important theoretical basis for further research on the biological functions of s in . .