The complete chloroplast genome sequence of Styrax serrulatus Roxburgh (Styracaceae)

Abstract Styrax serrulatus Roxburgh (William Roxburgh 1832), which plays an important role in ecology and economy, is a deciduous species of Styracaceae. In this paper, we sequenced, assembled, and annotated the chloroplast (cp) genome of S. serrulatus by using the sequencing data from Illumina Novaseq platform (Illumina, San Diego, CA). The complete cp genome of S. serrulatus is 157,929 base pairs (bp) in length, containing a pair of inverted repeat regions (IRs) of 26,048 bp each, a large single-copy (LSC) region of 87,552 bp, and a small single-copy (SSC) region of 18,281 bp. It contains 133 genes, including 8 rRNA genes, 37 tRNA genes, 87 protein-coding genes, and 1 pseudo gene. The GC content of S. serrulatus cp genome is 36.96%. The phylogenetic analysis suggests that S. serrulatus is a sister species to Styrax agrestis in Styracaceae.

Styrax serrulatus Roxburgh is a prominent species of Styracaceae, around 4-12 m tall, and 9-25 cm diameter of trunk at breast height, which mainly distribute in sparse forests at an altitude of 500-1700 m in the south and southwest (S Guangdong, S Guangxi, Hainan, Taiwan, SE Xizang and S Yunnan) of China and in the Bhutan, India, Laos, W Malaysia, Myanmar, Nepal, Thailand and Vietnam (Huang and Grimes 2003). It possesses high value for ornamental, timber, and medicinal purposes. However, there has been little progress on its complete chloroplast genome. In this work, we characterized the complete cp genome sequence of S. serrulatus (GeneBank accession number: MZ152917) based on Illumina pair-end sequencing data to provide a valuable complete cp genomic resource.
The fresh leaves of S. serrulatus were collected from Xishuangbanna Tropical Botanical Garden ( ÃÃ latitude ÃÃ 21.6833 and ÃÃ longitude ÃÃ 101.4667) in Jinghong, Yunnan, China. A specimen was deposited at the herbarium of Nanjing Forestry University (contact person: xuehongma@ njfu.edu.cn) under the voucher number NF2021019.
By using ultrasound to break DNA, the fragments of DNA were passivated, repaired and bonded. After the genomic DNA of the sample was qualified, the DNA was fragmented by a mechanical interruption method (ultrasound), and then the fragmented DNA was separately purified, while the end repaired, A was added at 3 0 -end, and the sequencing adapter was connected. The DNA fragments were selected by agarose gel electrophoresis. The sample of genome sequencing library was formed by PCR amplification, which was carried out on Illumina Novaseq 6000 system (Illumina, San Diego, CA) with PE150 reads by Nanjing Genepioneer Biotechnologies Inc. (Nanjing, China).
The original reads was filtered by fastp (version 0.20.0), and the clean data were assembled into chloroplast genome with SPAdes (Bankevich et al. 2012). Then, the reference sequence (Genebank accession number: NC041127.1) was used for quality control after assembly. The assembled genome was annotated using CpGAVAS (Liu et al. 2012). To examine the phylogenetic position of S. serrulatus, a multiple sequence alignment (MSA) analyses was performed using MAFFT (Rozewicki et al. 2019). Finally, a maximum-likelihood (ML) tree was deduced by IQ-Tree (Gao et al. 2018).
To reveal the phylogenetic evolution of S. serrulatus, we constructed a ML phylogenetic tree based on 40 cp genomes from Styracaceae and 5 cp genomes as outgroups from 3 taxa (Ebenaceae, Symplocaceae, Theaceae). We found that S. serrulatus was clustered with other families of Styracaceae with 100% bootstrap values (Figure 1). In addition, S. serrulatus was highly supported to be a sister species to Styrax agrestis in Styracaceae.

Disclosure statement
The authors report no conflict of interest.

Data availability statement
The genome sequence data that support the findings of this study are openly available in GenBank of NCBI at https://www.ncbi.nlm.nih.gov under the accession no. MZ152917. The associated BioProject, SRA, and Bio-Sample numbers are PRJNA739084, SRR14861495, and SAMN19771193, respectively.