Chloranthus genome provides insights into the early diversification of angiosperms

Chloranthales remain the last major mesangiosperm lineage without a nuclear genome assembly. We therefore assemble a high-quality chromosome-level genome of Chloranthus spicatus to resolve enigmatic evolutionary relationships, as well as explore patterns of genome evolution among the major lineages of mesangiosperms (eudicots, monocots, magnoliids, Chloranthales, and Ceratophyllales). We find that synteny is highly conserved between genomic regions of Amborella, Vitis, and Chloranthus. We identify an ancient single whole-genome duplication (WGD) (kappa) prior to the divergence of extant Chloranthales. Phylogenetic inference shows Chloranthales as sister to magnoliids. Furthermore, our analyses indicate that ancient hybridization may account for the incongruent phylogenetic placement of Chloranthales + magnoliids relative to monocots and eudicots in nuclear and chloroplast trees. Long genes and long introns are found to be prevalent in both Chloranthales and magnoliids compared to other angiosperms. Overall, our findings provide an improved context for understanding mesangiosperm relationships and evolution and contribute a valuable genomic resource for future investigations. Chloranthales remain the last lineage of core angiosperms that lacks a nuclear genome assembly. Here, the authors report the genome assembly of Chloranthus spicatus and show its contribution to deepen our understanding on diversification, phylogeny, and genome evolution in angiosperms.

Automated summary

Chloranthales are the last major mesangiosperm lineage without a nuclear genome assembly, but a high-quality genome assembly of Chloranthus spicatus has now been achieved, providing insights into the evolutionary relationships and genome evolution of mesangiosperms. This study sheds light on the unique characteristics of Chloranthales and magnoliids compared to other angiosperms, and contributes to a better understanding of angiosperm diversification and phylogeny.