Complete plastid genome characterization and phylogenetic analysis of Pentasachme caudatum Wallich ex Wight (Gentianales: Apocynaceae) from Guangdong, China

Pentasachme caudatum Wallich ex Wight is considered as one of the Asian enigmatic genera classified in the Asclepiadoideae (Apocynaceae). To determine its evolutionary relationship in the family, we sequenced and characterized the complete chloroplast genome of P. caudatum. The plastid genome of P. caudatum is 158,487 bp in length, containing a large single-copy (90,380 bp), a small single-copy (18,585 bp), and a pair of inverted repeats (24,761 bp). It has 127 annotated genes, consisting of 83 protein-coding, eight rRNA and 36 tRNA genes. Phylogenetic analysis using 76 protein-coding regions of the plastid genomes of related taxa showed that P. caudatum was resolved in a fully supported clade with Orthanthera albida. The newly sequenced P. caudatum provides essential genetic information that is useful for future phylogenetic studies in the family Apocynaceae.