Chromosome-level genome of a leaf vegetable Glebionis coronaria provides insights into the biosynthesis of monoterpenoids contributing to its special aroma.

Glebionis coronaria is a popular vegetable with special aroma and a medical plant in East Asia and Mediterranean, but its biological studies and breeding have been hindered by the lack of reference genome. Here, we present a chromosome-level reference genome of G. coronaria, with assembled genome size of 6.8 Gb, which is the largest among all the published genomes of diploid Asteraceae species. The large genome size of G. coronaria is mainly caused by the recent widespread explosions of long-terminal-repeat retrotransposons. Analyses of macro-synteny and synonymous mutation rate distribution indicate that the G. coronaria genome experienced a whole-genome triplication at 40-45 million years ago, shared with all Asteraceae species. In subtribe Artemisiinae, Glebionis arose before the divergence of Chrysanthemum from Artemisia, and Glebionis species evolved much faster than Chrysanthemum and Artemisia species. In G. coronaria, the synthesis genes of monoterpenoids 8-oxocitronellyl enol and isopiperitenone were expanded, and the higher expressions of these expanded genes in leaves and stems may contribute to its special aroma. The G. coronaria genomic resources will promote the evolution studies of Asteraceae, the metabolism mechanism studies of bioactive compounds, and the breeding improvement of agronomic traits in G. coronaria.