Characterization and Phylogenetic Analysis of the Complete Chloroplast Genome of Xanthopappus subacaulis (Asteraceae), an Endemic Species from the Qinghai-Tibet Plateau in China

Xanthopappus subacaulis (Asteraceae) is a medicinal plant endemic to the alpine meadows from the middle east region of the Qinghai-Tibet Plateau in China. In this study, we sequenced and analyzed its whole chloroplast (cp) genome using Next Generation Sequencing techniques, representing the first complete cp genome for the genus Xanthopappus . Our results show that the cp genome of X. subacaulis contains 153 297 base pairs (bp) with a relatively high A + T content (62.28%) and has a standard quadripartite structure, where the large (LSC, 84 142 bp) and small (SSC, 18 769 bp) single copy regions are separated by two copies of inverted repeats (IRs, 25 193 bp each). The cp genome encoded a total of 131 genes of which 87 are protein-coding genes, 36 are tRNA genes and eight are rRNA genes. The majority (85) of these genes occur within the LSC region. When comparing these results with the previously published cp genome of a related taxon from Asteraceae (genus Arctium ), both species share similar number and type of genes, and A + T content. In addition, a Maximum Likelihood and Maximum Parsimony phylogenetic analyses based on 33 chloroplast genomes of Asteraceae suggested that X. subacaulis forms an independent and well supported clade paraphyletic to all the other members within tribes Carduinae, Carlininae and Centaureinae of Asteraceae.