The Clausena lansium genome provides new insights into alkaloid diversity and the evolution of the methyltransferase family

Wampee () is an important evergreen fruit tree native to southern China that has a long history of use for medicinal purposes. Here, a chromosome-level genome of was constructed with a genome size of 282.9 Mb and scaffold N50 of 30.75 Mb. The assembled genome contains 48.70% repetitive elements and 24,381 protein-coding genes. Comparative genomic analysis showed that diverged from Aurantioideae 15.91–24.95 million years ago. Additionally, some expansive and specific gene families related to methyltransferase activity and -adenosylmethionine-dependent methyltransferase activity were also identified. Further analysis indicated that -methyltransferase (NMT) is mainly involved in alkaloid biosynthesis and -methyltransferase (OMT) participates in the regulation of coumarin accumulation in wampee. This suggested that wampee's richness in alkaloids and coumarins might be due to the gene expansions of NMT and OMT. The tandem repeat event was one of the major reasons for the NMT expansion. Hence, the reference genome of will facilitate the identification of some useful medicinal compounds from wampee resources and reveal their biosynthetic pathways.