Whole-genome, transcriptome, and methylome analyses provide insights into the evolution of platycoside biosynthesis in , a medicinal plant.

Triterpenoid saponins (TSs) are common plant defense phytochemicals with potential pharmaceutical properties. (Campanulaceae) has been traditionally used to treat bronchitis and asthma in East Asia. The oleanane-type TSs, platycosides, are a major component of the root extract. Recent studies show that platycosides exhibit anti-inflammatory, antiobesity, anticancer, antiviral, and antiallergy properties. However, the evolutionary history of platycoside biosynthesis genes remains unknown. In this study, we sequenced the genome of and investigated the genes involved in platycoside biosynthesis. The draft genome of is 680.1 Mb long and contains 40,017 protein-coding genes. Genomic analysis revealed that the family genes play a major role in platycoside oxidation. The gene family of was much larger than that of other Asterid species. Orthologous gene annotation also revealed the expansion of () in , which was confirmed by tissue-specific gene expression. In these expanded gene families, we identified key genes showing preferential expression in roots and association with platycoside biosynthesis. In addition, whole-genome bisulfite sequencing showed that and genes are hypomethylated in , suggesting that epigenetic modification of these two gene families affects platycoside biosynthesis. Thus whole-genome, transcriptome, and methylome data of provide novel insights into the regulation of platycoside biosynthesis by and gene families.