Whole-genome duplication reshaped adaptive evolution in a relict plant species, Cyclocarya paliurus

Abstract

Cyclocarya paliurus is a relict plant species that survived the last Glacial period and shows a population expansion recently. Its leaves have been traditionally used to treat obesity and diabetes with the well-known active ingredient cyclocaric acid B. Here, we present three C. paliurus genomes from two diploids with different flower morphs and one haplotype-resolved tetraploid assembly. Comparative genomic analysis revealed two rounds of recent whole-genome duplication events and identified 691 genes with dosage-effect that likely contribute to adaptive evolution through enhanced photosynthesis and increased accumulation of triterpenoids. Re-sequencing analysis of 45 accessions uncovered two bottlenecks, consistent with the known events of environmental changes, and many selectively swept genes involved in critical biological functions, including plant defense and secondary metabolism biosynthesis. We also proposed the biosynthesis pathway of cyclocaric acid B based on multi-omics data and identified key genes, in particular gibberellin related genes, associated with heterodichogamy in the species. Our research sheds light on evolutionary history and provides genomics resources to study the medicinal herb.