Comparative and phylogenetic analysis based on chloroplast genome of Heteroplexis (Compositae), a protected rare genus

Background: Heteroplexis Chang is an endangered genus endemic to China with important ecological and medicinal value. However, due to the lack of genetic data, our conservation strategies have repeatedly been delayed by controversial phylogenetic (molecular) relationships within the genera. In this study, we reported three new Heteroplexis chloroplast (cp.) genomes (H. vernonioides, H. impressinervia and H. microcephala) to clarify phylogenetic relationships between species allocated in this genus and other related Compositae.Results: All three new cp. genomes were highly conserved, showing the classic four regions. Size ranged from 152,984 - 153,221 bp and contained 130 genes (85 protein-coding genes, 37 tRNA, eight rRNA) and two pseudo genes. By comparative genomic and phylogenetic analyses, we found a large-scale inversion of the entire large single-copy (LSC) region in H. vernonioides, H. impressinervia and H. microcephala, being experimentally verified by PCR. The inverted repeat (IR) regions showed high similarity within the five Heteroplexis plastomes, showing small size contractions. Phylogenetic analyses did not support the monophyly of Heteroplexis genus, whereas clustered the five species within two differentiated clades within Aster genus. These phylogenetic analyses suggested that the five Heteroplexis species might be subsumed into the Aster genus.Conclusion: Our results enrich the data on the cp. genomes of the genus Heteroplexis, providing valuable genetic resources for future studies on the taxonomy, phylogeny, and evolution of Aster genus.

Automated summary

This study reported three new Heteroplexis chloroplast genomes, which showed high conservation and provided valuable genetic resources for future studies on the taxonomy, phylogeny, and evolution of the Aster genus. Phylogenetic analyses did not support the monophyly of the Heteroplexis genus, suggesting that the five species might be subsumed into the Aster genus.