Comparative chloroplast genome and phylogenetic analyses of Chinese Polyspora

Polyspora Sweet (Theaceae) are winter ornamental landscape plants native to southern and southeastern Asia, some of which have medicinal value. The chloroplast (cp) genome data of Polyspora are scarce, and the gene evolution and interspecific relationship are still unclear. In this study, we sequenced and annotated Polyspora chrysandra cp genome and combined it with previously published genomes for other Chinese Polyspora species. The results showed that cp genomes of six Chinese Polyspora varied in length between 156,452 bp (P. chrysandra) and 157,066 bp (P. speciosa), but all contained 132 genes, with GC content of 37.3%, and highly similar genes distribution and codon usage. A total of eleven intergenic spacer regions were found having the highest levels of divergence, and eight divergence hotspots were identified as molecular markers for Phylogeography and genetic diversity studies in Polyspora. Gene selection pressure suggested that five genes were subjected to positive selection. Phylogenetic relationships among Polyspora species based on the complete cp genomes were supported strongly, indicating that the cp genomes have the potential to be used as super barcodes for further analysis of the phylogeny of the entire genus. The cp genomes of Chinese Polyspora species will provide valuable information for species identification, molecular breeding and evolutionary analysis of genus Polyspora.