A high-quality genome assembly of the tetraploid Teucrium chamaedrys unveils a recent whole-genome duplication and a large biosynthetic gene cluster for diterpenoid metabolism.

Abstract

Teucrium chamaedrys, commonly known as wall germander, is a small woody shrub native to the Mediterranean region. Its name is derived from the Greek words meaning "ground oak," as its tiny leaves resemble those of an oak tree. Teucrium species are prolific producers of diterpenes, endowing them with valuable properties widely utilized in traditional and modern medicine. Sequencing and assembly of the 3-Gbp tetraploid T. chamaedrys genome revealed 74 diterpene synthase genes, with a substantial number of these genes clustered at four synteny genomic loci, each harboring a copy of a large diterpene biosynthetic gene cluster. Comparative genomics revealed that this cluster is conserved in the closely related species Teucrium marum. Along with the presence of several cytochrome p450 sequences, this region is among the largest biosynthetic gene clusters identified. Teucrium is well known for accumulating clerodane-type diterpenoids, which are produced from a kolavenyl diphosphate precursor. To elucidate the complex biosynthetic pathways of these medicinal compounds, we identified and functionally characterized several kolavenyl diphosphate synthases from T. chamaedrys. The remarkable chemical diversity and tetraploid nature of T. chamaedrys make it a valuable model for studying genomic evolution and adaptation in plants.