Decoding the Genetic Basis of Aromatic Terpene Metabolism in Rosemary:
Ancient Whole-Genome Duplications and Ancestral Karyotypes Shed Light on
Evolutionary Signatures
Abstract
Salvia rosmarinus, a commonly known aromatic plant
belonging to the Salvia genus, is valued for its medicinal
properties, derived primarily from the terpenoids present in its leaves.
We have successfully created a chromosome-level genome assembly of
S. rosmarinus, covering 1.24 Gb, with a scaffold N50 value of
107.45 Mb and 61,717 annotated protein-coding genes. Our analysis
highlights a recent whole genome duplication (WGD) event as the primary
driver of genomic rearrangement and fusion following speciation. As a
result of the WGD, key genes involved in monoterpene biosynthesis, such
as HMGR, 1,8-cineole synthase, and limonene synthase, underwent
tandem duplication and double punctuation. Limonene synthase experienced
a nonpolar mutation that favored structural diversity in monoterpene
biosynthesis, while 1,8-cineole synthase underwent a polar mutation that
favored 1,8-cineole(eucalyptol) accumulation. In addition, our analysis
revealed differences in the mechanisms of diterpene biosynthesis between
S. rosmarinus and S. miltiorrhiza, as evidenced by the
tandem duplication, covariance, and high-level expression of genes
essential for carnosol biosynthesis, specifically CYP76AK6–8.
These findings no punctuation for understanding the molecular-level
diversity of terpenoids in S. rosmarinus and will facilitate
molecular breeding and quality improvement efforts for this economically
important plant.