Plastome structure and phylogenetic relationships of Styracaceae (Ericales).

BACKGROUND: The Styracaceae are a woody, dicotyledonous family containing 12 genera and an estimated 160 species. Recent studies have shown that Styrax and Sinojackia are monophyletic, Alniphyllum and Bruinsmia cluster into a clade with an approximately 20-kb inversion in the Large Single-Copy (LSC) region. Halesia and Pterostyrax are not supported as monophyletic, while Melliodendron and Changiostyrax always form sister clades. Perkinsiodendron and Changiostyrax are newly established genera of Styracaceae. However, the phylogenetic relationship of Styracaceae at the generic level needs further research. RESULTS: We collected 28 complete plastomes of Styracaceae, including 12 sequences newly reported here and 16 publicly available sequences, comprising 11 of the 12 genera of Styracaceae. All species possessed the typical quadripartite structure of angiosperm plastomes, with sequence differences being minor, except for a large 20-kb (14 genes) inversion found in Alniphyllum and Bruinsmia. Seven coding sequences (rps4, rpl23, accD, rpoC1, psaA, rpoA and ndhH) were identified to possess positively selected sites. Phylogenetic reconstructions based on seven data sets (i.e., LSC, SSC, IR, Coding, Non-coding, combination of LSC + SSC and concatenation of LSC + SSC + one IR) produced similar topologies. In our analyses, all genera were strongly supported as monophyletic. Styrax was sister to the remaining genera. Alniphyllum and Bruinsmia form a clade. Halesia diptera does not cluster with Perkinsiodendron, while Perkinsiodendron and Rehderodendron form a clade. Changiostyrax is sister to a clade of Pterostyrax and Sinojackia. CONCLUSION: Overall, our results demonstrate the power of plastid phylogenomics in improving estimates of phylogenetic relationships among genera. This study also provides insight into plastome evolution across Styracaceae.

Complete plastome sequence of Changiostyrax dolichocarpa (Styracaeae): An endangered (EN) plant species endemic to China.

Changiostyrax dolichocarpa is a critically endangered plant species occurring in central and southeastern China. Although the systematic position of Changiostyrax was still unclear, morphological characters, plastid and nSSR evidence supported that C. dolichocarpa should be separated from Sinojackia (Styracaceae). Here, we report and characterize the complete plastid genome sequence of C. dolichocarpa in an effort to provide genomic resources useful for promoting its conservation. The complete plastome is 158,821 bp in length and contains the typical structure and gene content of angiosperm plastome, including two inverted repeat (IR) regions of 26,000 bp, a large single copy (LSC) region of 88,038 bp and a small single copy (SSC) region of 18,784 bp. The plastome contains 120 genes, consisting of 83 unique protein-coding genes, 37 unique tRNA gene, and eight unique rRNA genes. The overall A/T content in the plastome of C. dolichocarpa is 62.70%. The complete plastome sequence of C. dolichocarpa will provide a useful resource for the conservation genetics of this species as well as for the phylogenetic studies for Changiostyrax.