Complete chloroplast genome sequencing and phylogeny of wild Atractylodes lancea from Yuexi, Anhui province / 中国中药杂志

This study investigated the choroplast genome sequence of wild Atractylodes lancea from Yuexi in Anhui province by high-throughput sequencing, followed by characterization of the genome structure, which laid a foundation for the species identification, analysis of genetic diversity, and resource conservation of A. lancea. To be specific, the total genomic DNA was extracted from the leaves of A. lancea with the improved CTAB method. The chloroplast genome of A. lancea was sequenced by the high-throughput sequencing technology, followed by assembling by metaSPAdes and annotation by CPGAVAS2. Bioiformatics methods were employed for the analysis of simple sequence repeats(SSRs), inverted repeat(IR) border, codon bias, and phylogeny. The results showed that the whole chloroplast genome of A. lancea was 153 178 bp, with an 84 226 bp large single copy(LSC) and a 18 658 bp small single copy(SSC) separated by a pair of IRs(25 147 bp). The genome had the GC content of 37.7% and 124 genes: 87 protein-coding genes, 8 rRNA genes, and 29 tRNA genes. It had 26 287 codons and encoded 20 amino acids. Phylogenetic analysis showed that Atractylodes species clustered into one clade and that A. lancea had close genetic relationship with A. koreana. This study established a method for sequencing the chloroplast genome of A. lancea and enriched the genetic resources of Compositae. The findings are expected to lay a foundation for species identification, analysis of genetic diversity, and resource conservation of A. lancea.

Chloroplast genomic characterization and phylogenetic analysis of Castanopsis hystrix / 生物工程学报

The structure and size of the chloroplast genome of Castanopsis hystrix was determined by Illumina HiSeq 2500 sequencing platform to understand the difference between C. hystrix and the chloroplast genome of the same genus, and the evolutionary position of C. hystrix in the genus, so as to facilitate species identification, genetic diversity analysis and resource conservation of the genus. Bioinformatics analysis was used to perform sequence assembly, annotation and characteristic analysis. R, Python, MISA, CodonW and MEGA 6 bioinformatics software were used to analyze the genome structure and number, codon bias, sequence repeats, simple sequence repeat (SSR) loci and phylogeny. The genome size of C. hystrix chloroplast was 153 754 bp, showing tetrad structure. A total of 130 genes were identified, including 85 coding genes, 37 tRNA genes and 8 rRNA genes. According to codon bias analysis, the average number of effective codons was 55.5, indicating that the codons were highly random and low in bias. Forty-five repeats and 111 SSR loci were detected by SSR and long repeat fragment analysis. Compared with the related species, chloroplast genome sequences were highly conserved, especially the protein coding sequences. Phylogenetic analysis showed that C. hystrix is closely related to the Hainanese cone. In summary, we obtained the basic information and phylogenetic position of the chloroplast genome of red cone, which will provide a preliminary basis for species identification, genetic diversity of natural populations and functional genomics research of C. hystrix.

Analysis of the chloroplast genome of Incarvillea younghusbandii Sprague / 生物工程学报

Incarvillea younghusbandii Sprague is a traditional tonic herb. The roots are used as herbal medicine for nourishing and strengthening, as well as treating postpartum milk deficiency and weakness. In this study, the chloroplast genome of I. younghusbandii was sequenced and assembled by the high-throughput sequencing technology. The sequence characteristics, sequence repeats, codon usage bias, phylogenetic relationships and estimated divergence time of I. younghusbandii were analyzed. The 159 323 bp sequence contained a large single copy (80 197 bp), a small single copy (9 030 bp) and two inverted repeat sequences (35 048 bp). It contained 120 genes, including 77 protein coding genes, 8 ribosomal RNA genes and 35 transfer RNA genes. AAA was the most frequent codon in the chloroplast coding sequence of I. younghusbandii. A total of 42 simple sequence repeats were identified in the chloroplast genome. Phylogenetic analysis revealed I. younghusbandii was mostly like its taxonomically close relative Incarvillea compacta. The divergence between I. younghusbandii and I. compacta was dated to 4.66 million years ago. This study was significant for the scientific conservation and development of resources related to I. compacta. It also provides a basic genetic resource for the subsequent species identification of the genus Incarvillea, and the population genetic diversity study of Bignoniaceae.

Characteristics and phylogenetic analysis of chloroplast genome of a new type of fruit Rubus rosaefolius / 生物工程学报

The genomic DNA of Rubus rosaefolius was extracted and sequenced by Illumina NovaSeq platform to obtain the complete chloroplast genome sequence, and the sequence characteristics and phylogenetic analysis of chloroplast genes were carried out. The results showed that the complete chloroplast genome of the R. rosaefolius was 155 650 bp in length and had a typical tetrad structure, including two reverse repeats (25 748 bp each), a large copy region (85 443 bp) and a small copy region (18 711 bp). A total of 131 genes were identified in the whole genome of R. rosaefolius chloroplast, including 86 protein coding genes, 37 tRNA genes and 8 rRNA genes. The GC content of the whole genome was 36.9%. The genome of R. rosaefolius chloroplast contains 47 scattered repeats and 72 simple sequence repeating (SSR) loci. The codon preference is leucine codon, and the codon at the end of A/U is preferred. Phylogenetic analysis showed that R. rosaefolius had the closest relationship with R. taiwanicola, followed by R. rubraangustifolius and R. glandulosopunctatus. The chloroplast genome characteristics and phylogenetic analysis of R. rosaefolius provide a theoretical basis for its genetic diversity research and chloroplast development and utilization.

Characteristics of the chloroplast genome of Dracaena marginata and phylogenetic analysis / 生物工程学报

Dracaena marginata is a widely cultivated horticultural plant in the world, which has high ornamental and medicinal value. In this study, the whole genome of leaves from D. marginata was sequenced by Illumina HiSeq 4000 platform. The chloroplast genome were assembled for functional annotation, sequence characteristics and phylogenetic analysis. The results showed that the chloroplast genome of D. marginata composed of four regions with a size of 154 926 bp, which was the smallest chloroplast genome reported for Dracaena species to date. A total of 132 genes were identified, including 86 coding genes, 38 tRNA genes and 8 rRNA genes. Codon bias analysis found that the codon usage bias was weak and there was a bias for using A/U base endings. 46 simple sequence repeat and 54 repeats loci were detected in the chloroplast genome, with the maximum detection rate in the large single copy region and inverted repeat region, respectively. The inverted repeats boundaries of D. marginata and Dracaena were highly conserved, whereas gene location differences occurred. Phylogenetic analysis revealed that D. serrulata and D. cinnabari form a monophyletic clade, which was the closest relationship and conformed to the morphological classification characteristics. The analysis of the chloroplast genome of D. marginata provides important data basis for species identification, genetic diversity and chloroplast genome engineering of Dracaena.

Chloroplast genomic characterization and phylogenetic analysis of Pellionia scabra / 生物工程学报

Pellionia scabra belongs to the genus Pellionia in the family of Urticaceae, and is a high-quality wild vegetables with high nutritional value. In this study, high-throughput techniques were used to sequence, assemble and annotate the chloroplast genome. We also analyzed its structure, and construct the phylogenetic trees from the P. scabra to further study the chloroplast genome characteristics. The results showed that the chloroplast genome size was 153 220 bp, and the GC content was 36.4%, which belonged to the typical tetrad structure in P. scabra. The chloroplast genome encodes 130 genes, including 85 protein-coding genes, 37 tRNA genes, and 8 rRNA genes in P. scabra. Among them, 15 genes contained 1 intron, 2 genes contained 2 introns, and rps12 had trans-splicing, respectively. In P. scabra, chloroplast genomes could be divided into four categories, including 43 photosynthesis, 64 self-replication, other 7 coding proteins, and 4 unknown functions. A total of 51 073 codons were detected in the chloroplast genome, among which the codon encoding leucine (Leu) accounted for the largest proportion, and the codon preferred to use A and U bases. There were 72 simple sequence repeats (SSRs) in the chloroplast genome of P. scabra, containing 58 single nucleotides, 12 dinucleotides, 1 trinucleotide, and 1 tetranucleotide. The ycf1 gene expansion was present at the IRb/SSC boundary. The phylogenetic trees showed that P. scabra (OL800583) was most closely related to Elatostema stewardii (MZ292972), Elatostema dissectum (MK227819) and Elatostema laevissimum var. laevissimum (MN189961). Taken together, our results provide worthwhile information for understanding the identification, genetic evolution, and genomics research of P. scabra species.

Complete chloroplast genome of Ligustrum lucidum and highly variable marker identification for Ligustrum / 中国中药杂志

Ligustri Lucidi Fructus, the sun-dried mature fruit of Ligustrum lucidum, is cool, plain, sweet, and bitter, which can be used as both food and medicine, with the effects of improving vision, blacking hair, and tonifying liver and kidney. It takes effect slowly. However, little is known about the genetic information of the medicinal plant and it is still a challenge to distinguish Ligustrum species. In this study, the complete chloroplast genome of L. lucidum was obtained by genome skimming and then compared with that of five other Ligustrum species, which had been reported. This study aims to evaluate the interspecific variation of chloroplast genome within the genus and develop molecular markers for species identification of the genus. The result showed that the chloroplast genome of L. lucidum was 162 162 bp with a circular quadripartite structure of two single-copy regions separated by a pair of inverted repeats. The Ligustrum chloroplast genomes were conserved with small interspecific difference. Comparative analysis of six Ligustrum chloroplast genomes revealed three variable regions(rbcL-accD, ycf1a, and ycf1b), and ycf1a and ycf1b can be used as the species-specific DNA barcode for Ligustrum. Phylogeny analysis provided the best resolution of Ligustrum and supported that L. lucidum was sister to L. gracile. This study clarified the genetic diversity of L. lucidum from provenance, which can serve as a reference for further analysis of pharmacological differences and breeding of excellent varieties with stable drug effects.

Genome structure and variation of Reynoutria japonica Houtt. chloroplast genome / 生物工程学报

Reynoutria japonica Houtt., belonging to Polygoneae of Polygonaceae, is a Chinese medicinal herb with the functions of draining dampness and relieving jaundice, clearing heat and detoxifying, dispersing blood stasis and relieving pain, and relieving cough and resolving phlegm. In this study, we carried out high-throughput sequencing for the chloroplast genome sequences of five cultivars of R. japonica and analyzed the genome structure and variations. The chloroplast genomes of the five R. japonica cultivars had two sizes (163 376 bp and 163 371 bp) and a typical circular tetrad structure composed of a large single-copy (LSC) region of 85 784 bp, a small single-copy (SSC) region of 18 616 bp, and a pair of inverted repeat (IR) regions (IRa/IRb) which are spaced apart. A total of 161 genes were obtained by annotation, which consisted of 106 protein-coding genes, 10 rRNA-coding genes, and 45 tRNA-coding genes. The total GC content was 36.7%. Specifically, the GC content in the LSC, SSC, and IR regions were 34.8%, 30.7%, and 42.7%, respectively. Comparison of the whole chloroplast genome among the five cultivars showed that trnk-UUU, rpoC1, petD, rpl16, ndhA, and rpl12 in coding regions had sequence variations. In the phylogenetic tree constructed for the 11 samples of Polygoneae, the five cultivars of R. japonica clustered into one clade near the root and was a sister group of Fallopia multiflora (Thunb.).

Chloroplast genome phylogeny and codon preference of Docynia longiunguis / 生物工程学报

Docynia longiunguis is a plant uniquely present in China and is of high edible and medicinal value. The analysis of its chloroplast genome will help clarify the phylogenetic relationship among Docynia and facilitate the development and utilization of D. longiunguis resources. Based on the alignment of chloroplast genome sequences of related species, the phylogeny and codon preference were analyzed. The total length of D. longiunguis chloroplast genome sequence was 158 914 bp (GenBank accession number is MW367027), with an average GC content of 36.7%. The length of the large single-copy (LSC), the small single-copy (SSC), and inverted repeats (IRs) are 87 020 bp, 19 156 bp, and 26 369 bp, respectively. A total of 102 functional genes were annotated, including 72 protein-coding genes, 26 tRNA genes, and 4 rRNA genes. The best model for constructing phylogenetic tree was TVM+F+R2. D. longiunguis and Docynia indica were clustered into a single group, while Docynia and Malus were clustered into a single group. Comparison of the chloroplast genome sequences of D. longiunguis and its five related species revealed that trnY (GUA)-psbD, ndhC-trnV (UAC), accD-psaI, psbZ-trnfM (CAU), ndhF-trnL gene regions varied greatly. The nucleic acid diversity analysis showed that there were 11 high variation areas with nucleotide variability > 0.01, all were located in the LSC and SSC regions. Except for D. longiunguis, the trnH genes in other sequences were located at the IRs/LSC junction and did not cross the boundary. Codon preference analysis showed that D. longiunguis chloroplast genome has the largest number of isoleucine (Ile) codons, up to 1 205. D. longiunguis has the closest genetic relationship with Malus baccata, Malus sieboldii, Malus hupehensis and Chaenomeles sinensis. Its chloroplast genome codon prefers to end with A/T. The chloroplast genome of D. longiunguis and other Rosaceae chloroplast genomes showed great differences in gene distribution in four boundary regions, while relatively small differences from the chloroplast genomes of Docynia delavayi and D. indica of the same genus were observed. The genome annotation, phylogenetic analysis and sequence alignment of chloroplast genome of D. longiunguis may facilitate the identification, development and utilization of this species.

DNA super-barcoding of several medicinal species in Gentiana from Yunnan province / 中国中药杂志

Gentiana is an important but complicated group in Gentianaceae. The genus covers numerous medicinal plants which are difficult to be identified. In the present study, several medicinal species in Gentiana from Yunnan province, including G. rigescens, G.rhodantha, and G. delavayi, were sequenced using the Illumina HiSeq 2500 system. Three complete chloroplast genome sequences were obtained after assembly and annotation. According to several published genome sequences of G. crassicaulis, the DNA super-barcoding of species in Gentiana was preliminarily carried out. The results revealed that chloroplast genomes of the three species were conservative with short lengths(146 944, 148 992, and 148 796 bp, respectively). The genomes encoded 114 genes, including 78 protein-coding genes, 30 tRNA genes, 4 rRNA genes, and 2 pseudogenes. Furthermore, these medicinal species in Yunnan province were identified using DNA super-barcoding based on chloroplast genomes. The results showed that the Gentiana species could be gathered into monophyletic branches with a high support value(100%). It indicated that DNA super-barcoding possessed obvious advantages in discriminating species in complicated genera. This study is expected to provide a scientific basis for the identification, utilization, and conservation of Gentiana species.

Transient expression of a green fluorescent protein in tobacco and maize chloroplast

BACKGROUND: Maize is one of the most important crops worldwide and has been a target of nuclear-based transformation biotechnology to improve it and satisfy the food demand of the ever-growing global population. However, the maize plastid transformation has not been accomplished due to the recalcitrant condition of the crop. RESULTS: In this study, we constructed two different vectors with homologous recombination sequences from maize (Zea mays var. LPC13) and grass (Bouteloua gracilis var. ex Steud) (pZmcpGFP and pBgcpGFP, respectively). Both vectors were designed to integrate into rrn23S/rrn16S from an inverted repeat region in the chloroplast genome. Moreover, the vector had the mgfp5 gene driven by Prrn, a leader sequence of the atpB gene and a terminator sequence from the rbcL gene. Also, constructs have an hph gene as a selection marker gene driven by Prrn, a leader sequence from rbcL gene and a terminator sequence from the rbcL gene. Explants of maize, tobacco and Escherichia coli cells were transformed with both vectors to evaluate the transitory expression­an exhibition of green and red fluorescent light under epifluorescence microscopy. These results showed that both vectors were expressed; the reporter gene in all three organisms confirmed the capacity of the vectors to express genes in the cell compartments. CONCLUSIONS: This paper is the first report of transient expression of GFP in maize embryos and offers new information for genetically improving recalcitrant crops; it also opens new possibilities for the improvement in maize chloroplast transformation with these vectors.

Comparison of complete chloroplast genome sequences of Amygdalus pedunculata Pall / 生物工程学报

Amygdalus pedunculata Pall. is one of the 12 important woody oil crops in China. In this study, we determined the complete chloroplast genome sequence of A. pedunculata Pall. (MG602257) from Mu Us desert in Yulin city, Shaanxi province, China. The plastome was 157 851 bp with 36.8% GC content. Comparisons among the plastomes of MG602257 and other two MG869261 and KY101153 from Genebank of NCBI showed that the total length of these chloroplast genomes was MG602257< MG869261

Analysis of the chloroplast genome characteristics of Rhus chinensis by de novo sequencing / 生物工程学报

Rhus chinensis is an important economic species, which could provide raw materials for pharmaceutical and industrial dyes. Rhus chinensis is famous for its resistance to drought, cold, and salt. It grows in temperate, warm temperate, and subtropical regions. We report here Rhus chinensis chloroplast genomes by de novo sequencing. The results show that the length of Rhus chinensis was 159 082 bp, exhibiting a typical four-part structure with two single-copy regions (long single copy [LSC] and short single copy [SSC] sections) separated by a pair of inverted repeats (IRs). The length of LSC and SSC was 85 394 bp and 18 663 bp, respectively. The genomes contained 126 genes, including 88 protein encoding genes, 8 rRNA and 30 tRNA genes. In the chloroplast genome, 61.97% of the sequence were gene coding region. In the sequence of gene encoding region, the vast majority of sequences were protein encoding region, accounting for 86.65%, followed by rRNA (10 620 bp, 10.77%) and tRNA (2 540 bp, 2.58%). In Rhus chinensis chloroplast genome, only 8 genes contain introns, all containing 1 intron except ycf3 gene (2 introns). The Rhus chinensis chloroplast genome contains 755 SSR locies. SSR mainly consists of dinucleotide and mononucleotide, accounting for 60% (453) and 28.74% (217) respectively. The clustering results show that Anacardiaceae were closest to Rhus chinensis, followed by Aceraceae and Sapindaceae. This study provides a molecular basis for the classification of Rhus chinensis.

Development of nuclear SSR and chloroplast genome markers in diverse Liriodendron chinense germplasm based on low-coverage whole genome sequencing

BACKGROUND: Liriodendron chinense ranges widely in subtropical China and northern Vietnam; however, it inhabits several small, isolated populations and is now an endangered species due to its limited seed production. The objective of this study was to develop a set of nuclear SSR (simple sequence repeats) and multiple chloroplast genome markers for genetic studies in L. chinense and their characterization in diverse germplasm. RESULTS: We performed low-coverage whole genome sequencing of the L. chinense from four genotypes, assembled the chloroplast genome and identified nuclear SSR loci by searching in contigs for SSR motifs. Comparative analysis of the four chloroplast genomes of L. chinense revealed 45 SNPs, 17 indels, 49 polymorphic SSR loci, and five small inversions. Most chloroplast intraspecific polymorphisms were located in the interspaces of single-copy regions. In total, 6147 SSR markers were isolated from low-coverage whole genome sequences. The most common SSR motifs were dinucleotide (70.09%), followed by trinucleotide motifs (23.10%). The motif AG/TC (33.51%) was the most abundant, followed by TC/AG (25.53%). A set of 13 SSR primer combinations were tested for amplification and their ability to detect polymorphisms in a set of 109 L. chinense individuals, representing distinct varieties or germplasm. The number of alleles per locus ranged from 8 to 28 with an average of 21 alleles. The expected heterozygosity (He) varied from 0.19 to 0.93 and the observed heterozygosity (Ho) ranged from 0.11 to 0.79. CONCLUSIONS: The genetic resources characterized and tested in this study provide a valuable tool to detect polymorphisms in L. chinense for future genetic studies and breeding programs.

High-throughput pyrosequencing of the complete chloroplast genome of Magnolia officinalis and its application in species identification / 药学学报

Chloroplast genome sequences have comprehensive application prospects in DNA barcoding and chloroplast engineering in traditional Chinese medicine. The complete chloroplast genome of Magnolia officinalis sequenced by high-throughput pyrosequencing and a sequencing procedure was established. Fourteen contigs were obtained after de nove assembly. The sequencing percent of coverage was 99.99%. The chloroplast genome is 160 183 bp in size, and has a typical quadripartite structure with the large (LSC, 88 210 bp) and small copy (SSC, 18 843 bp) regions separated by two copies of an inverted repeat (IRs, 26 565 bp each). chloroplast genes were successfully annotated, of which 17 genes located in each IR region. The chloroplast genome features in Magnolia officinalis are nearly identical to those from other Magnoliid chloroplast genomes. Phylogenetic analyses were performed based on 81 shared coding-genes for a total of 9 Magnolia samples of 5 closely related species. Results showed that distinguishing among species was generally straightforward at the species and population level. This study confirmed the effectiveness of our chloroplast genome sequencing procedure. The chloroplast genome can provide distinguishing differences to help identify Magnolia officinalis and its closely related plants.