Comparative and Phylogenetic Analyses of Complete Plastomes of Aucuba (Garryaceae)

Abstract Backgroud: Aucuba (Garryaceae), which includes approximately 10 evergreen woody species, is a genus endemic to East Asia. Their striking morphological features give Aucuba species remarkable ornamental value. Owing to high levels of morphological divergence and plasticity, species definition of Aucuba remains perplexing and problematic. Here, we sequenced and characterized the complete plastid genomes (plastomes) of three Aucuba species: Aucuba chlorascens, Aucuba eriobotryifolia, and Aucuba japonica. Results: Comparative analyses revealed that Aucuba plastomes are highly conserved in size, structure, gene content, and organization, and exhibit high levels of sequence similarity. We recommend 11 plastid DNA regions as potential DNA barcodes for species identification and genotyping of Aucuba germplasm. Phylogenetic reconstruction based on 71 plastid protein-coding genes from taxa encompassing a wide phylogenetic diversity in the lamiids strongly supported the sister relationship between Garryaceae and Eucommiaceae. Conclusion: Plastome tree revealed the monophyly of Garryales, offering plastid phylogenomic evidence for the acceptance of Garryales as outlined by the updated Angiosperm Phylogeny Group. Under a comparative framework within Garryales, we detected massive plastome arrangements between Aucuba and Eucommia. In summary, our study provides useful genomic resources for further study of the taxonomy, evolution, conservation, and exploitation of Aucuba species.