Complete plastome sequence of Hydnocarpus hainanensis Merr (Achariaceae): an endemic 'vulnerable' tree in South China

Hydnocarpus hainanensis Merr. is an evergreen tree with a height of 6-12 m and a diameter at breast height of 50 cm. It is distributed in Guangxi, Guizhou, Hainan, South of Yunnan Province of China. Here, we report and characterize the complete plastid genome sequence of H. hainanensis in an effort to provide genomic resources useful for promoting its conservation and systematics research. The plastome of H. hainanensis is found to possess a total length 163,330bp with the typical quadripartite structure of angiosperms, containing two inverted repeats (IRs) of 26,870 bp, a large single copy (LSC) region of 91,510 bp and a small single copy (SSC) region of 18,080 bp. The plastome contains 111 genes, consisting of 78 unique protein-coding genes (seven of which are duplicated in the IR: rps12, rps7, ndhB, ycf2, rpl23, rpl2, and rps19), 29 unique tRNA genes (seven of which are duplicated in the IR, i.e. trnN(GUU), trnR(ACG), trnA(UGC), trnl(GAU), trnV(GAC), trnL(CAA), and trnl(CAU)) and four unique rRNA genes (5S rRNA, 4.55S rRNA, 23S rRNA, and 16S rRNA). The overall A/T content in the plastome of H. hainanensis is 63.70%. The phylogenetic analysis indicated that H. hainanensis is close to Salix rorida within Malpighiales. The complete plastome sequence of H. hainanensis will provide a useful resource for the conservation genetics of the one species as well as for the phylogenetic studies of Achariaceae.