The complete chloroplast genome of Waldheimia glabra

Abstract Waldheimia glabra (Decne.) Rgl. 1879 (family Asteraceae) is a perennial herb with high economic and medicinal values. In this study, we sequenced the complete chloroplast (cp) genome of W. glabra by high-throughput Illumina sequencing. The size of the W. glabra cp genome is 151,499 bp, with overall GC content of 37.3%. It contains a large single copy and a small single copy region of 83,078 bp and 18,457 bp, respectively, separated by a pair of inverted repeats regions of 24,982 bp. We also discovered 131 genes, including 86 protein-coding genes, 37 transfer RNA genes, and 8 ribosomal RNA genes in the genome. The maximum-likelihood phylogenetic tree demonstrated that W. glabra is closely related to Leucanthemella linearis.

Asteraceae; chloroplast genome; phylogenetic relationships; Waldheimia glabra Waldheimia glabra, a perennial herb (family Asteraceae), is mainly distributed in India, Nepal, Pakistan, Afghanistan, and China, growing on the stony slopes of the Himalayas at 4000 À 5400 m altitude. The plant is medicinally important and is often used to treat common infections, skin diseases, arthritis, and rheumatism in traditional medicine. It is also used as vermifuge, antiseptic paste, and incense (Bhatnagar et al. 2017). Although it has high economic and medicinal values, reports on the floristic study of this high-altitude plant species are limited. Consequently, germplasm resources are decreasing, and breeding and applications are restricted.
The study of the genetic variability of W. glabra to formulate appropriate conservation strategies and developing resistant fine cultivars requires immediate attention. The objectives of our study were to sequence and assemble the complete chloroplast genome (cp) of W. glabra using next generation sequencing (Du et al. 2015). We also analyzed its phylogenetic relationship with other members of the Asteraceae family for better understanding of their interspecific relationship. Our study facilitates the protection of W. glabra germplasm resources.
The plant material of W. glabra was collected from the Himalayan region of Burang County, Ngari Prefecture, Tibet, China (N 30 12 0 29.3 00 , E 81 37 0 22.3 00 ) and the specimen was deposited at Museum of Beijing Forestry University, Beijing, China (Huien Zhao, zhaohuien@bjfu.edu.cn, 20180829BJFU010). Total genomic DNA was extracted from fresh young leaves (Li et al. 2013;Xu et al. 2019) and conserved in Beijing Forestry University. The extracted DNA was subjected to paired-end libraries construction and sequencing on an Illumina Novaseq platform. The results were stored in the FASTQ file format.
Approximately 4.25 Gb of clean data were generated after filtering. The GetOrganelle (Jin et al. 2018) and SOAPdenovo software (Luo et al. 2012) assessed and assembled the paired-end reads. We used OGDRAW program to draw circular chloroplast genome map (Marc et al. 2013). The cp genome sequence of W. glabra has been submitted to GenBank (accession number: MW628520).
The cp DNA of W. glabra is 151,499 bp long, with an average sequencing depth of 467Â. It contains a large singlecopy (LSC) region of 83,078 bp and a small single-copy (SSC) region of 18,457 bp, which is separated by a pair of inverted repeats (IR) regions (24,982 bp). The overall GC content of the cp genome is 37.3%. We annotated a total of 131 functional genes, including 86 protein-coding genes, 8 ribosomal RNA (rRNA) genes, and 37 transfer RNA (tRNA) genes. Among them, 15 genes contain only one intron and 2 genes contain two introns. In addition, one ribosomal-protein gene has trans-splicing. Gene duplication was found in the IR regions, including one protein-coding gene, four tRNA genes, and four rRNA genes. Our result is consistent with those obtained from other Asteraceae species (Zhang et al. 2016).
Since reports on the floristic study of this high-altitude plant species are limited, its interspecific relationship with other members of the family Asteraceae is still unclear. A phylogenetic analysis compared the cp genome of W. glabra with those from 21 Asteraceae species, including Chrysanthemum, Artimisia, Crossostephium, Opisthopappus, and other genera. Arabidopsis thaliana was used as an outgroup for the study. The maximum-likelihood phylogenetic tree shows that W. glabra is most closely related to Leucanthemella linearis with high bootstrap values. It clusters with Stilpnolepis centiflora, Chrysahthemum, and Artimisia. Chrysanthemum and Artimisia are grouped together (Figure 1). Our result is consistent with previous studies on the phylogenetic relationship of Asteraceae species (Panero and Crozier 2016;Wang et al. 2020). Our research lays the foundation for the study of genetic diversity and phylogeny of W. glabra.

Disclosure statement
No potential conflict of interest was reported by the author(s).