Abstract
Euonymus maackii Rupr. is a small deciduous tree belonging to family Celastraceae. It is an important ornamental tree and a potential medicinal plant resource. Here, we assembled and annotated the chloroplast (cp) genome of E. maackii. By combining this genome with seven available cp genomes from Euonymus species, we performed plastome variation analysis of E. maackii and Euonymus. Furthermore, we reconstructed a phylogenetic tree and estimated the differentiation time of E. maackii. The newly assembled cp genome of E. maackii was 157,551 bp in size and had a typical quadripartite structure, which consisted of one large single-copy (LSC 86,524 bp) region, one small single-copy (SSC 18,337 bp) region, and a pair of inverted repeat regions (26,345 bp). A total of 652 single nucleotide polymorphisms (SNPs) and 65 insertions/deletions (indels) were detected between the two cp genomes of E. maackii, with overall genetic variation of 4.1 SNPs per kb or a π value of 0.00443, reflecting a high level of intraspecific variation. Some coding and noncoding regions with higher variation were identified, including trnV-UAC, petN, ycf1-ndhF, trnM-CAU-atpE, rpl2-rpl23, psbZ-trnG-GCC, trnY-GUA-trnE-UUC, trnW-CCA-trnP-UGG, rps16-trnQ-UUG, and psbC-trnS-UGA. The hypervariable coding and noncoding regions in E. maackii were not the same as those in Euonymus. The phylogenetic tree and divergence time based on the whole cp genomes showed that the seven Euonymus species formed a clade, which was sister to that formed with Catha edulis and Maytenus guangxiensis, and they separated 24.74 million years ago. E. maackii and E. hamiltonianus were most closely related, having separated from each other only approximately 2.68 million years ago. Our study provides important genetic information for further studies of E. maackii, such as studies on its phylogeography, population genetics and molecular ecology, and provides new insights into the evolution of the cp genome in Euonymus.
Highlights
Introduction published maps and institutional affilEuonymus maackii Rupr. is a small deciduous tree belonging to the family Celastraceae
The cp genome assembled (E. maackii 1) in this study was 157,551 bp in length and had a typical quadripartite structure, which consisted of one LSC region (86,525 bp), one SSC
Our results revealed that there was a high level of cp genome variation in E. maackii
Summary
Introduction published maps and institutional affilEuonymus maackii Rupr. (synonym: Euonymus bungeanus) is a small deciduous tree belonging to the family Celastraceae. (synonym: Euonymus bungeanus) is a small deciduous tree belonging to the family Celastraceae. It is native to northern China and has the characteristics of cold resistance, drought resistance, salt and alkali resistance, few diseases and insect pests, and strong germination [1,2]; it is widely distributed in most areas from Heilongjiang Province to the Yangtze River Basin and further extends to a wider area, including the Ussuri Region, southern Siberia, and the Korean Peninsula [3]. In autumn, its leaves turn red, and its dehiscent fruit turns orange; it has high ornamental value and has been cultivated as a horticultural tree for more than 20 years in China [2,4,5]. A series of cultivars of E. maackii with colorful leaves have been obtained through artificial cultivation. In addition to the common characteristics of E. maackii, iations
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