The chromosome-level genome of Centella asiatica provides insights into triterpenoid biosynthesis

Centella asiatica is a well-known herbal plant that makes a significant contribution to the treatment of various chronic ailments. Triterpenoid saponins are the main active components extracted from C. asiatica, which have rich pharmacological activity. However, only a few studies have systematically elucidated the molecular mechanism underlying the biosynthesis of triterpenoid saponins in C. asiatica. Here, we report a chromosome-level reference genome of C. asiatica, by using Illumina, PacBio HiFi, and Hi-C technologies. The assembled genome exhibits high quality with a size of 455 Mb and a contig N50 of 36 Mb. A total of 26,479 protein-coding genes were predicted. Comparative genomic analysis revealed that the gene families involved in triterpenoid saponin biosynthesis, including squalene synthase (SS) and farnesyl diphosphate synthase (FPS), rapidly expanded in the C. asiatica genome. In particular, we have discovered two whole-genome duplication events in C. asiatica genomes. A further comprehensive analysis of the metabolome and transcriptome was performed using different tissues of C. asiatica in order to identify the key genes associated with triterpenoid saponin biosynthesis. Consequently, seven enzyme genes were considered to play important roles in triterpenoid biosynthesis. Subsequent functional characterization of CaOSC4 demonstrated that it is responsible for the biosynthesis of three ursane-type triterpenoids in C. asiatica. Our research establishes a genomic data platform that can be employed in the excavation of genes and precision breeding in C. asiatica. Additionally, the results offer new insights into the biosynthesis of triterpenoid saponins.