Plastome characteristics and species identification of Chinese medicinal wintergreens (Gaultheria, Ericaceae)

Wintergreen oil is a folk medicine widely used in foods, pesticides, cosmetics and drugs. In China, nine out of 47 species within Gaultheria (Ericaceae) are traditionally used as Chinese medicinal wintergreens, although discriminating accurately among these species remain poorly resolved based on a multiple-gene approach. In this study, we sequenced and characterized plastomes from nine Chinese wintergreen species and identified candidate DNA barcoding regions for Gaultheria . Each Gaultheria plastome contained 110 unique genes (76 protein-coding, 30 tRNA, and four rRNA genes), and all plastomes lacked ycf1 and ycf2 genes. Gaultheria plastomes shared substantially contracted SSC regions that contained only the ndhF gene. Moreover, plastomes of G. leucocarpa var. yunnanensis contained an inversion and IR expansion. Gene duplications were detected in trnfM , rps14 , and rpl23 , which likely generated long repeats of up to 1,700 bp. Multiple rearrangement events apparently occurred between the Gaultheria plastomes and those from several previously reported families in Ericales. Our phylogenetic reconstruction using 42 plastomes revealed supported relationships within all nine Gaultheria species. Additionally, seven mutational hotspot regions were identified as potential DNA barcodes for Chinese medicinal wintergreens. Our study is the first to describe the structural variation of completed plastomes from species in the complicated genus Gaultheria. In addition, our findings provide important resources for identification of Chinese medicinal wintergreens. • The study was the first to analyze the structural variation of the plastome genomes of the genus Gaultheria from Ericaceae. • In this study, we found some unique structural variations that differ from those of most angiosperms or even other related taxa within Ericales. • This work brings new perspectives for us to understand the dynamics of angiosperm plastomes, and also provides a substantial genetic foundation for further studies on the active ingredients of these Chinese herbs.