Characterization of the complete chloroplast genome sequence of Daphne retusa Hemsl. (Thymelaeaceae), a rare alpine plant species in northwestern China

Daphne retusa Hemsl. (Thymelaeaceae) is an evergreen shrub plant. First, we characterized the complete nucleotide sequence of chloroplast (cp) genome of D. retusa. The total length of cp genome was found to be 170,553 bp, including a large single copy (LSC) region of 84,886 bp, a small single copy (SSC) region of 2,437 bp, and a pair of inverted repeats (IRs) of 41,617 bp. The cp genome of Daphne retusa Hemsl. contains 134 genes, including 90 protein-coding genes (75 PCG species), 37 transfer RNA genes (29 tRNA species), and 6 rRNA genes (3 RNA species). A total of 13 genes (trnK-UUU, trnS-CGA, atpF, rpoC1, trnL-UAA, trnC-ACA, petD, rpl16, rpl2, ndhB, trnE-UUC, ndhA, and trnA-UGC) contain a single intron, and one gene (ycf3) contains two introns. The GC content in whole cp genome, LSC region, SSC region, and IR region was 36.75%, 34.83%, 28.19%, and 38.96% respectively, like other Thymelaeaceae plants. Phylogenetic analysis suggested that D. retusa has a close relationship with congeneric Daphne tangutica.