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 pseudogenes. 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.

Complete chloroplast genome sequence of Heteroplexis sericophylla (Asteraceae), a rare and vulnerable species endemic to China

Heteroplexis sericophylla (Asteraceae) is a rare and vulnerable species endemic to China. Here, we report and characterize the complete chloroplast genome sequence of H. sericophylla based on Illumina paired-end sequencing data. The complete plastid genome was 152,629 bp in length, which contained two inverted repeats (IRs) of 24,954 bp separated by a large single-copy (LSC) and a small single-copy (SSC) of 84,427 bp and 18,294 bp, respectively. The cpDNA contains 131 genes, comprising 85 protein-coding genes, 37 tRNA genes, 8 rRNA genes and one processed pseudogene. The overall GC content of the plastome is 37.3%. The phylogenetic analysis of 17 selected chloroplast genomes demonstrated that H. sericophylla was close to congeneric species H. incana.