The chloroplast genomes of four Bupleurum (Apiaceae) species endemic to Southwestern China, a diversity center of the genus, as well as their evolutionary implications and phylogenetic inferences

The complete plastid genome of Polygonatum gracile P. Y. Li (Asparagaceae): characterization and phylogeny

Polygonatum gracile P. Y. Li is a perennial rhizomatous medicinal herb endemic to China with recognized medicinal value. Here, the first complete plastid genome of P. gracile is reported and characterized, and the phylogenetic relationships of P. gracile with other Polygonatum species are clarified by phylogenetic inferences based on complete plastid genome sequences. The complete plastid genome of P. gracile is 155,734 bp in length and exhibits the typical quadripartite circular structure consisting of a large single-copy (LSC, 84,385 bp) region, a small single-copy (SSC, 18,519 bp) region, and a pair of inverted repeat regions (IRa/b, 26,415 bp). A total of 112 unique genes, including 78 protein-coding genes, 30 tRNA genes, and four rRNA genes were identified. Seven protein-coding genes, eight tRNA genes, and four rRNA genes were duplicated in the IR regions. Phylogenetic reconstructions indicated that P. gracile belongs to sect. Verticillata and is most closely related to P. zanlanscianense Pamp. This study provides a basis for further phylogenetic reconstructions, conservation and utilization of Polygonatum species.

Speciation and diversification of the Bupleurum (Apiaceae) in East Asia

Bupleurum, belonging to the Apiaceae, is widely distributed across the Eurasian continent. The origin and species diversification of Bupleurum in East Asia, remain incompletely resolved due to the limited samples in previous studies. To address these issues, we have reconstructed a robust phylogenetic framework for Bupleurum in East Asia based on the ITS and three plastid genes. Our phylogenetic analysis confirms the monophyly of Bupleurum with strong support. Both ITS and chloroplast dataset divided the Bupleurum in East Asia into East Asia Group I and East Asia Group II in this study. The divergence time and ancestral area reconstruction of ITS dataset indicated that the Bupleurum originated in the Mediterranean basin and its adjacent areas around 50.33 Ma. subg. Penninervia and subg. Bupleurum diverged at about 44.35 Ma, which may be related to the collision of India with the Eurasian continent. Both East Asia Group I and East Asia Group II originated from a common ancestor in the Mediterranean, East Asia Group I divergence around 12.95 Ma; East Asia Group II divergence around 13.32 Ma. The character reconstruction showed that the morphological characters and altitude distribution analyzed in this study exhibit a scattered distribution in East Asian Group I and East Asian Group II. Additionally, diversification rate analysis shows that the East Asian Group I and East Asian Group II exhibited no significant shifts in diversification rates in the evolutionary history according to ITS and combined dataset. Both molecular and morphological data supports that East Asian Bupleurum is a museum taxon, meaning that the species diversity of East Asian Bupleurum has gradually accumulated over time.

The complete chloroplast genome of Dryas octopetala var. asiatica (Dryadoideae, Rosaceae) and phylogenetic analysis

Dryas octopetala L. var. asiatica (Nakai) Nakai 1918 is a dwarf shrub that mainly grow in alpine and arctic zones of the Northern Hemisphere, representing an endemic variety in Asia. In the present study, the complete chloroplast (cp) genome of D. octopetala var. asiatica was first characterized and used for its phylogenetic analysis. The cp genome span 158,271 bp with an overall GC content of 36.5%. A total of 129 genes were identified, including 84 protein-coding genes (PCGs), 37 tRNA genes, and 8 rRNA genes. In addition, repetitive sequences and microsatellites were detected within this species. Phylogenetic analysis involving 39 cp genomes from Rosaceae family indicated that D. octopetala var. asiatica was sister to the clade of Amygdaloideae. This study contributes fundamental insights into the cp genome of Dryas octopetala var. asiatica, which will have expanded its use in photosynthesis and evolutionary study.

Complete chloroplast genomes of eight Delphinium taxa (Ranunculaceae) endemic to Xinjiang, China: insights into genome structure, comparative analysis, and phylogenetic relationships

BACKGROUND

Delphinium L. represents a taxonomically intricate genus of significant phylogenetic and economic importance in Ranunculaceae. Despite the existence of few chloroplast genome datasets, a comprehensive understanding of genome structures and selective pressures within the genus remains unknown. Furthermore, several taxa in this genus are exclusively found in Xinjiang, China, a region renowned for its distribution and diversity of Chinese and Central Asian Delphinium species. Therefore, investigating the features of chloroplast genomes in this area will provide valuable insights into the evolutionary processes and phylogenetic relationships of the genus.

RESULTS

In this study, the eight newly completed chloroplast genomes are examined, ranging in length from 153,979 bp to 154,284 bp. Alongside these, analysing six previously reported taxa re-annotated in Delphinium, 111 unique genes are identified across all samples. Genome structure, distributions of simple sequence repeats and short dispersed repeats, as well as gene content are similar among these Delphinium taxa. Nine hypervariable intergenic spacers and protein coding regions, including ndhF-trnL(TAG), rpl16-intron, rpl33, rps15, rps18, trnK(TTT)-trnQ(TTG), trnP(TGG)-psaJ, trnT(GGT)-psbD and ycf1, are identified among 13 perennial Delphinium. Selective pressure and codon usage bias of all the plastid genes are performed within 14 Delphinium taxa. Phylogenetic analysis based on 14 Delphinium plastomes, alongside two Aconitum (Ranunculaceae) species serving as outgroup taxa, reveals the monophyletic nature of Delphinium. Our findings further discern Delphinium into two distinct clades: perennial species (clade I) and annual species (clade II). In addition, compared with the nrDNA ITS topology, cytological data and morphological characters, D. mollifolium and D. maackianum showed potential involvement in hybridization or polyploidization processes. Excluding these two species, the perennial Delphinium (clade I) exhibits a stronger consistency with the morphology-based system that utilized seed morphology.

CONCLUSION

This study represents the first comprehensive analysis of plastomic variations among Delphinium taxa, based on the examination of 14 complete plastomes. The chloroplast genome structure of Delphinium is similar to other angiosperms and possesses the typical quadripartite structure with the conserved genome arrangement and gene features. In addition, the variation of non-coding regions is larger than coding regions of the chloroplast genome. Through DNA sequence divergence across Delphinium plastomes and subsequent phylogenomic analyses ndhF-trnL(TAG) and ycf1 are identified as promising molecular markers. These highly variable loci held significant potential for future phylogenetic and phylogeographic studies on Delphinium. Our phylogenomic analyses based on the whole plastomes, concatenation of 132 unique intergenic spacer regions, concatenation of 77 unique protein-coding genes and nrDNA ITS, all support the monophyly of Delphinium and perennial taxa clusters together into one clade within this genus. These findings provide crucial data for systematic, phylogenomic and evolutionary research in the genus for future studies.

Comparative and phylogenetic analysis of the complete chloroplast genomes of 10 Artemisia selengensis resources based on high-throughput sequencing

BACKGROUND

Artemisia selengensis, classified within the genus Artemisia of the Asteraceae family, is a perennial herb recognized for its dual utility in culinary and medicinal domains. There are few studies on the chloroplast genome of A. selengensis, and the phylogeographic classification is vague, which makes phylogenetic analysis and evolutionary studies very difficult.

RESULTS

The chloroplast genomes of 10 A. selengensis in this study were highly conserved in terms of gene content, gene order, and gene intron number. The genome lengths ranged from 151,148 to 151,257 bp and were typical of a quadripartite structure with a total GC content of approximately 37.5%. The chloroplast genomes of all species encode 133 genes, including 88 protein-coding genes, 37 tRNA genes, and 8 rRNA genes. Due to the contraction and expansion of the inverted repeats (IR), the overlap of ycf1 and ndhF genes occurred at the inverted repeats B (IRB) and short single copy sequence (SSC) boundaries. According to a codon use study, the frequent base in the chloroplast genome of A. selengensis' third codon position was A/T. The number of SSR repeats was 42-44, most of which were single nucleotide A/T repeats. Sequence alignment analysis of the chloroplast genome showed that variable regions were mainly distributed in single copy regions, nucleotide diversity values of 0 to 0.009 were calculated by sliding window analysis, 8 mutation hotspot regions were detected, and coding regions were more conserved than non-coding regions. Analysis of non-synonymous substitution (Ka) and synonymous substitution (Ks) revealed that accD, rps12, petB, and atpF genes were affected by positive selection and no genes were affected by neutral selection. Based on the findings of the phylogenetic analysis, Artemisia selengensis was sister to the genus Artemisia Chrysanthemum and formed a monophyletic group with other Artemisia genera.

CONCLUSIONS

In this research, the present study systematically compared the chloroplast genomic features of A. selengensis and provided important information for the study of the chloroplast genome of A. selengensis and the evolutionary relationships among Asteraceae species.

Characterization of Firmiana danxiaensis plastomes and comparative analysis of Firmiana: insight into its phylogeny and evolution

BACKGROUND

Firmiana danxiaensis is a critically endangered and ecologically important tree currently only found in four locations in Danxia or Karst habitats in northern Guangdong Province, China. The specialized habitat preference makes it an ideal model species for study of adaptive evolution. Meanwhile, the phylogenetic relationships of F. danxiaensis in four locations under two landforms are unclear. Therefore, we sequenced its complete chloroplast (cp.) genomes and conducted comprehensive interspecific and intrageneric plastome studies.

RESULTS

The F. danxiaensis plastomes in four locations showed a typical quadripartite and circular structure that ranged from 160,832 to 161,206 bp in size, with 112 unique genes encoded. Comparative genomics showed that the plastomes of F. danxiaensis were relatively conserved with high similarity of genome organization, gene number, GC content and SSRs. While the genomes revealed higher biased codon preferences in Karst habitat than those in Danxia habitats. Eighteen and 11 divergent hotpots were identified at interspecific and intrageneric levels for species identification and further phylogenetic studies. Seven genes (clpP, accD, ccsA, ndhH, rpl20, rpoC2, and rps4) were under positive selection and may be related to adaptation. Phylogenetic analysis revealed that F. danxiaensis is sister to F. major and F. simplex. However, the interspecific relationships are not consistent with the habitat types.

CONCLUSIONS

The characteristics and interspecific relationship of F. danxiaensis plastomes provide new insights into further integration of geographical factors, environmental factors, and genetic variations on the genomic study of F. danxiaensis. Together, our study will contribute to the study of species identification, population genetics, and conservation biology of F. danxiaensis.

Comparative and phylogenetic analysis of the complete chloroplast genomes of Uncaria (Rubiaceae) species

The genus Uncaria is famous for its high medicinal value. However, the high morphological similarities and unclear interspecific genetic relationships have posed challenges to the classification and identification of Uncaria species. Here, we newly sequenced six chloroplast genomes of Uncaria species: U. hirsuta, U. rhynchophylla, U. rhynchophylloides, U. homomalla, U. sinensis, and U. lancifolia. Comparisons among the chloroplast genomes of Uncaria species showed their conservation in structure, gene content, and order. Ten highly variable loci could be potentially used as specific molecular markers in the identification of Uncaria species. The third position of codons tended to use A/U base, and natural selection contributed more to the formation of codon usage bias in comparison to mutation pressure. Four genes (rbcL, ndhF, rps8, and ycf2) were detected to be subjected to positive selection. Phylogenetic analysis showed that the genus Uncaria was a monophyletic group, belonging to the tribe Naucleeae. Moreover, U. sinensis was not a variant of U. rhynchophylla. U. rhynchophylloides and U. rhynchophylla were not the same species. The results of the comparative and phylogenetic analysis provide valuable references for further research studies of classification, identification, breeding improvement, and phylogenetic relationships in Uncaria species.

A Comprehensive Analysis of Chloroplast Genome Provides New Insights into the Evolution of the Genus Chrysosplenium

Chrysosplenium, a perennial herb in the family Saxifragaceae, prefers to grow in low light and moist environments and is divided into two sections of Alternifolia and Oppositifolia based on phyllotaxy. Although there has been some progress in the phylogeny of Chrysosplenium over the years, the phylogenetic position of some species is still controversial. In this study, we assembled chloroplast genomes (cp genomes) of 34 Chrysosplenium species and performed comparative genomic and phylogenetic analyses in combination with other cp genomes of previously known Chrysosplenium species, for a total of 44 Chrysosplenium species. The comparative analyses revealed that cp genomes of Chrysosplenium species were more conserved in terms of genome structure, gene content and arrangement, SSRs, and codon preference, but differ in genome size and SC/IR boundaries. Phylogenetic analysis showed that cp genomes effectively improved the phylogenetic support and resolution of Chrysosplenium species and strongly supported Chrysosplenium species as a monophyletic taxon and divided into three branches. The results also showed that the sections of Alternifolia and Oppositifolia were not monophyletic with each other, and that C. microspermum was not clustered with other Chrysosplenium species with alternate leaves, but with C. sedakowii into separate branches. In addition, we identified 10 mutational hotspot regions that could serve as potential DNA barcodes for Chrysosplenium species identification. In contrast to Peltoboykinia, the clpP and ycf2 genes of Chrysosplenium were subjected to positive selection and had multiple significant positive selection sites. We further detected a significant positive selection site on the petG gene between the two sections of Chrysosplenium. These evolutionary characteristics may be related to the growth environment of Chrysosplenium species. This study enriches the cp genomes of Chrysosplenium species and provides a reference for future studies on its evolution and origin.

Complete chloroplast of four Sanicula taxa (Apiaceae) endemic to China: lights into genome structure, comparative analysis, and phylogenetic relationships

BACKGROUND

The genus Sanicula comprises ca. 45 taxa, widely distributed from East Asia to North America, which is a taxonomically difficult genus with high medicinal value in Apiaceae. The systematic classification of the genus has been controversial for a long time due to varied characters in key morphological traits. China is one of the most important distributed centers, with ca. 18 species and two varieties. At present, chloroplast genomes are generally considered to be conservative and play an important role in evolutionary relationship study. To investigate the plastome evolution and phylogenetic relationships of Chinese Sanicula, we comprehensively analyzed the structural characteristics of 13 Chinese Sanicula chloroplasts and reconstructed their phylogenetic relationships.

RESULTS

In present study, four newly complete chloroplast genome of Sanicula taxa by using Illumina sequencing were reported, with the typical quadripartite structure and 155,396-155,757 bp in size. They encoded 126 genes, including 86 protein-coding genes, 32 tRNA genes and 8 rRNA genes. Genome structure, distributions of SDRs and SSRs, gene content, among Sanicula taxa, were similar. The nineteen intergenic spacers regions, including atpH-atpI, ndhC-trnM, petB-petD, petD-rpoA, petN-psbM, psaJ-rpl33, rbcL-accD, rpoB-trnC, rps16-trnQ, trnE-psbD, trnF-ndhJ, trnH-psbA, trnN-ndhF, trnS-psbZ, trnS-trnR, trnT-trnF, trnV-rps12, ycf3-trnS and ycf4-cemA, and one coding region (ycf1 gene) were the most variable. Results of maximum likelihood analysis based on 79 unique coding genes of 13 Chinese Sanicula samples and two Eryngium (Apiaceae-Saniculoideae) species as outgroup taxa revealed that they divided into four subclades belonged to two clades, and one subclade was consistent with previously traditional Sanicula section of its system. The current classification based on morphology at sect. Sanicla and Sect. Tuberculatae in Chinese Sanicula was not supported by analysis of cp genome phylogeny.

CONCLUSIONS

The chloroplast genome structure of Sanicula was similar to other angiosperms and possessed the typical quadripartite structure with the conserved genome arrangement and gene features. However, their size varied owing to expansion/contraction of IR/SC boundaries. The variation of non-coding regions was larger than coding regions of the chloroplast genome. Phylogenetic analysis within these Chinese Sanicula were determined using the 79 unique coding genes. These results could provide important data for systematic, phylogenomic and evolutionary research in the genus for the future studies.

Phylogenomics and plastome evolution of Indigofera (Fabaceae)

Introduction

Indigofera L. is the third largest genus in Fabaceae and includes economically important species that are used for indigo dye-producing, medicinal, ornamental, and soil and water conservation. The genus is taxonomically difficult due to the high level of overlap in morphological characters of interspecies, fewer reliability states for classification, and extensive adaptive evolution. Previous characteristic-based taxonomy and nuclear ITS-based phylogenies have contributed to our understanding of Indigofera taxonomy and evolution. However, the lack of chloroplast genomic resources limits our comprehensive understanding of the phylogenetic relationships and evolutionary processes of Indigofera.

Methods

Here, we newly assembled 18 chloroplast genomes of Indigofera. We performed a series of analyses of genome structure, nucleotide diversity, phylogenetic analysis, species pairwise Ka/Ks ratios, and positive selection analysis by combining with allied species in Papilionoideae.

Results and discussion

The chloroplast genomes of Indigofera exhibited highly conserved structures and ranged in size from 157,918 to 160,040 bp, containing 83 protein-coding genes, 37 tRNA genes, and eight rRNA genes. Thirteen highly variable regions were identified, of which trnK-rbcL, ndhF-trnL, and ycf1 were considered as candidate DNA barcodes for species identification of Indigofera. Phylogenetic analysis using maximum likelihood (ML) and Bayesian inference (BI) methods based on complete chloroplast genome and protein-coding genes (PCGs) generated a well-resolved phylogeny of Indigofera and allied species. Indigofera monophyly was strongly supported, and four monophyletic lineages (i.e., the Pantropical, East Asian, Tethyan, and Palaeotropical clades) were resolved within the genus. The species pairwise Ka/Ks ratios showed values lower than 1, and 13 genes with significant posterior probabilities for codon sites were identified in the positive selection analysis using the branch-site model, eight of which were associated with photosynthesis. Positive selection of accD suggested that Indigofera species have experienced adaptive evolution to selection pressures imposed by their herbivores and pathogens. Our study provided insight into the structural variation of chloroplast genomes, phylogenetic relationships, and adaptive evolution in Indigofera. These results will facilitate future studies on species identification, interspecific and intraspecific delimitation, adaptive evolution, and the phylogenetic relationships of the genus Indigofera.

Analysis of the Chloroplast Genome of Ficus simplicissima Lour Collected in Vietnam and Proposed Barcodes for Identifying Ficus Plants

Ficus simplicissima Lour. is an Asian species of fig tree in the family Moraceae. The chloroplast (cp) genome of F. simplicissima m3 was sequenced using the Pacbio sequel platform. The F. simplicissima cpDNA has a size of 160,321 bp in length, of which GC content accounts for 36.13%. The cp genome of F. simplicissima consists of a single large copy (LSC) with a size of 91,346 bp, a single small copy (SSC) with a size of 20,131 bp, and a pair of inverted repeats with a size of 24,421 to 24,423 bp. The cp genome of F. simplicissima has 127 genes, including 85 protein-coding genes, eight rRNA genes, and 34 tRNA genes; 92 simple sequence repeats and 39 long repeats were detected in the cpDNA of F. simplicissim. A comparative cp genome analysis among six species in the Ficus genus indicated that the genome structure and gene content were highly conserved. The non-coding regions show more differentiation than the coding regions, and the LSC and SSC regions show more differences than the inverted repeat regions. Phylogenetic analysis supported that F. simplicissima m3 had a close relationship with F. hirta. The complete cp genome of F. simplicissima was proposed as a chloroplast DNA barcoding for genus-level in the Moraceae family and the psbA-trnH gene region for species-level identification.

Phylogenetic relationship and comparative analysis of the main Bupleuri Radix species in China

Background

Bupleuri Radix (Chaihu) is a famous traditional Chinese medicine derived from Bupleurum, Apiaceae. The origin of cultivated Chaihu germplasm in China is unclear, which has led to unstable Chaihu quality. In this study, we reconstructed the phylogeny of the main Chaihu germplasm species in China and identified potential molecular markers to authenticate its origin.

Methods

Three Bupleurum species (eight individuals), B. bicaule, B. chinense, and B. scorzonerifolium, were selected for genome skimming. Published genomes from B. falcatum and B. marginatum var. stenophyllum were used for comparative analysis.

Results

Sequences of the complete plastid genomes were conserved with 113 identical genes ranging from 155,540 to 155,866 bp in length. Phylogenetic reconstruction based on complete plastid genomes resolved intrageneric relationships of the five Bupleurum species with high support. Conflicts between the plastid and nuclear phylogenies were observed, which were mainly ascribed to introgressive hybridization. Comparative analysis showed that noncoding regions of the plastomes had most of the variable sequences. Eight regions (atpF-atpH, petN-psbM, rps16-psbK, petA-psbJ, ndhC-trnV/UAC and ycf1) had high divergence values in Bupleurum species and could be promising DNA barcodes for Chaihu authentication. A total of seven polymorphic cpSSRs and 438 polymorphic nSSRs were detected across the five Chaihu germplasms. Three photosynthesis-related genes were under positive selection, of which accD reflected the adaptation fingerprint of B. chinense to different ecological habitats. Our study provides valuable genetic information for phylogenetic investigation, germplasm authentication, and molecular breeding of Chaihu species.

Niche divergence at the intraspecific level in an endemic rare peony (Paeonia rockii): A phylogenetic, climatic and environmental survey

Ecological factors have received increasing attention as drivers of speciation but also in the maintenance of postspeciation divergence. However, the relative significance of the responses of species to climate oscillations for driving niche divergence or conservatism in the evolution of many species that pass through diverse environments and limited geographical boundaries remains poorly understood. Paeonia rockii (one of the ancient species of Paeonia) comprising two subspecies called Paeonia rockii subsp. rockii and Paeonia rockii subsp. taibaishanica is an endemic, rare, and endangered medicinal plant in China. In this study, we integrated whole chloroplast genomes, and ecological factors to obtain insights into ecological speciation and species divergence in this endemic rare peony. RAxML analysis indicated that the topological trees recovered from three different data sets were identical, where P. rockii subsp. rockii and P. rockii subsp. taibaishanica clustered together, and molecular dating analyses suggested that the two subspecies diverged 0.83 million years ago. In addition, ecological niche modeling showed that the predicted suitable distribution areas for P. rockii subsp. rockii and P. rockii subsp. taibaishanica differed considerably, although the predicted core distribution areas were similar, where the population contracted in the last interglacial and expanded in the last glacial maximum. Under the emissions scenarios for the 2050s and 2070s, the suitable distribution areas were predicted to contract significantly, where the migration routes of the two subspecies tended to migrate toward high latitudes and elevations, thereby suggesting strong responses of the distributions of the two subspecies to climate change. These findings combined with the phylogeographic relationships provide comprehensive insights into niche variation and differentiation in this endemic rare peony, and they highlight the importance of geological and climatic changes for species divergence and changes in the population geographic patterns of rare and endangered medicinal plants in East Asia.

Comparative chloroplast genome analysis of Ficus (Moraceae): Insight into adaptive evolution and mutational hotspot regions

As the largest genus in Moraceae, Ficus is widely distributed across tropical and subtropical regions and exhibits a high degree of adaptability to different environments. At present, however, the phylogenetic relationships of this genus are not well resolved, and chloroplast evolution in Ficus remains poorly understood. Here, we sequenced, assembled, and annotated the chloroplast genomes of 10 species of Ficus, downloaded and assembled 13 additional species based on next-generation sequencing data, and compared them to 46 previously published chloroplast genomes. We found a highly conserved genomic structure across the genus, with plastid genome sizes ranging from 159,929 bp (Ficus langkokensis) to 160,657 bp (Ficus religiosa). Most chloroplasts encoded 113 unique genes, including a set of 78 protein-coding genes, 30 transfer RNA (tRNA) genes, four ribosomal RNA (rRNA) genes, and one pseudogene (infA). The number of simple sequence repeats (SSRs) ranged from 67 (Ficus sagittata) to 89 (Ficus microdictya) and generally increased linearly with plastid size. Among the plastomes, comparative analysis revealed eight intergenic spacers that were hotspot regions for divergence. Additionally, the clpP, rbcL, and ccsA genes showed evidence of positive selection. Phylogenetic analysis indicated that none of the six traditionally recognized subgenera of Ficus were monophyletic. Divergence time analysis based on the complete chloroplast genome sequences showed that Ficus species diverged rapidly during the early to middle Miocene. This research provides basic resources for further evolutionary studies of Ficus.

Complete chloroplast genome and phylogenetic analysis of Bupleurum kaoi Liu, Chao, and Chuang, 1977: an endemic species in Taiwan

Bupleurum kaoi Liu, Chao, and Chuang is an endemic and endangered herb in Taiwan. In this study, the complete circular chloroplast genome of B. kaoi was reconstructed and annotated using Illumina sequencing. The genome size of B. kaoi is 155,938 bp, including a pair of inverted repeat regions (IRs: 26308 bp), separated by a large single-copy (LSC) region of 85,784 bp and a small single-copy (SSC) region of 17,538 bp. The GC content of the chloroplast genome is 37.6%. There are 113 different genes in the chloroplast genome of B. kaoi, including 79 protein-coding genes, 30 tRNA genes, and four rRNA genes. A maximum-likelihood phylogenetic analysis showed that Bupleurum species is the monophyletic group, and B. kaoi belongs to subgenus Bupleurum and is closely related to B. scorzonerifolium.

Application of chloroplast genome in the identification of Traditional Chinese Medicine Viola philippica

BACKGROUND

Viola philippica Cav. is the only source plant of "Zi Hua Di Ding", which is a Traditional Chinese Medicine (TCM) that is utilized as an antifebrile and detoxicant agent for the treatment of acute pyogenic infections. Historically, many Viola species with violet flowers have been misused in "Zi Hua Di Ding". Viola have been recognized as a taxonomically difficult genera due to their highly similar morphological characteristics. Here, all common V. philippica adulterants were sampled. A total of 24 complete chloroplast (cp) genomes were analyzed, among these 5 cp genome sequences were downloaded from GenBank and 19 cp genomes, including 2 "Zi Hua Di Ding" purchased from a local TCM pharmacy, were newly sequenced.

RESULTS

The Viola cp genomes ranged from 156,483 bp to 158,940 bp in length. A total of 110 unique genes were annotated, including 76 protein-coding genes, 30 tRNAs, and four rRNAs. Sequence divergence analysis screening identified 16 highly diverged sequences; these could be used as markers for the identification of Viola species. The morphological, maximum likelihood and Bayesian inference trees of whole cp genome sequences and highly diverged sequences were divided into five monophyletic clades. The species in each of the five clades were identical in their positions within the morphological and cp genome tree. The shared morphological characters belonging to each clade was summarized. Interestingly, unique variable sites were found in ndhF, rpl22, and ycf1 of V. philippica, and these sites can be selected to distinguish V. philippica from samples all other Viola species, including its most closely related species. In addition, important morphological characteristics were proposed to assist the identification of V. philippica. We applied these methods to examine 2 "Zi Hua Di Ding" randomly purchased from the local TCM pharmacy, and this analysis revealed that the morphological and molecular characteristics were valid for the identification of V. philippica.

CONCLUSIONS

This study provides invaluable data for the improvement of species identification and germplasm of V. philippica that may facilitate the application of a super-barcode in TCM identification and enable future studies on phylogenetic evolution and safe medical applications.

Comparative Analysis of the Complete Chloroplast Genomes in Allium Section Bromatorrhiza Species (Amaryllidaceae): Phylogenetic Relationship and Adaptive Evolution

With the development of molecular sequencing approaches, many taxonomic and phylogenetic problems of the genus Allium L. have been solved; however, the phylogenetic relationships of some subgenera or sections, such as section Bromatorrhiza, remain unresolved, which has greatly impeded our full understanding of the species relationships among the major clades of Allium. In this study, the complete chloroplast (cp) genomes of nine species in the Allium sect. Bromatorrhiza were determined using the Illumina paired-end sequencing, the NOVOPlasty de novo assembly strategy, and the PGA annotation method. The results showed that the cp genome exhibited high conservation and revealed a typical circular tetrad structure. Among the sect. Bromatorrhiza species, the gene content, SSRs, codon usage, and RNA editing site were similar. The genome structure and IR regions’ fluctuation were investigated while genes, CDSs, and non-coding regions were extracted for phylogeny reconstruction. Evolutionary rates (Ka/Ks values) were calculated, and positive selection analysis was further performed using the branch-site model. Five hypervariable regions were identified as candidate molecular markers for species authentication. A clear relationship among the sect. Bromatorrhiza species were detected based on concatenated genes and CDSs, respectively, which suggested that sect. Bromatorrhiza is monophyly. In addition, there were three genes with higher Ka/Ks values (rps2, ycf1, and ycf2), and four genes (rpoC2, atpF, atpI, and rpl14) were further revealed to own positive selected sites. These results provide new insights into the plastome component, phylogeny, and evolution of Allium species.

Complete Chloroplast Genome of Cnidium monnieri (Apiaceae) and Comparisons with Other Tribe Selineae Species

Cnidium monnieri is an economically important traditional Chinese medicinal plant. In this study, the complete chloroplast (cp) genome of C. monnieri was determined using the Illumina paired-end sequencing, the GetOrganelle de novo assembly strategy, as well as the GeSeq annotation method. Our results showed that the cp genome was 147,371 bp in length with 37.4% GC content and included a large single-copy region (94,361 bp) and a small single-copy region (17,552 bp) separated by a pair of inverted repeat regions (17,729 bp). A total of 129 genes were contained in the cp genome, including 85 protein-coding genes, 36 tRNA genes, and eight rRNA genes. We also investigated codon usage, RNA editing, repeat sequences, simple sequence repeats (SSRs), IR boundaries, and pairwise Ka/Ks ratios. Four hypervariable regions (trnD-trnY-trnE-trnT, ycf2, ndhF-rpl32-trnL, and ycf1) were identified as candidate molecular markers for species authentication. The phylogenetic analyses supported non-monophyly of Cnidium and C. monnieri located in tribe Selineae based on the cp genome sequences and internal transcribed spacer (ITS) sequences. The incongruence of the phylogenetic position of C. monnieri between ITS and cpDNA phylogenies suggested that C. monnieri might have experienced complex evolutions with hybrid and incomplete lineage sorting. All in all, the results presented herein will provide plentiful chloroplast genomic resources for studies of the taxonomy, phylogeny, and species authentication of C. monnieri. Our study is also conducive to elucidating the phylogenetic relationships and taxonomic position of Cnidium.

Metabolomics Analysis Reveals the Differences Between Bupleurum chinense DC. and Bupleurum scorzonerifolium Willd

Bupleurum chinense DC. and Bupleurum scorzonerifolium Willd. are two varieties of Bupleuri Radix in Chinese Pharmacopoeia 2020. The clinical efficacy of the two bupleurum species is different. The difference in clinical efficacy is closely related to the composition of plant metabolites. In order to analyze the difference in metabolites, we used liquid chromatography coupled with mass spectrometry (LC-MS) for untargeted metabolome and gas chromatography coupled with mass spectrometry (GC-MS) for widely targeted metabolome to detect the roots (R), stems (S), leaves (L), and flowers (F) of two varieties, and detected 1,818 metabolites in 25 classes. We performed a statistical analysis of metabolites. Differential metabolites were screened by fold-change and variable importance in the projection values of the OPLS-DA model, and significant differences were found among different groups. The content of active components (triterpenoid saponins) was found to be high in the BcR group than in the BsR group. Other pharmacological metabolites were significantly different. By Kyoto Encyclopedia of Genes and Genomes annotation and enrichment analysis, we found that differential metabolites of the aboveground parts mainly concentrated in monoterpenoid biosynthesis, while the differential metabolites of the root mainly concentrated in sesquiterpenoid and triterpenoid biosynthesis. Differences in metabolic networks may indirectly affect the metabolic profile of Bc and Bs, leading to differences in clinical efficacy. Our study provides a scientific basis for subsequent biosynthesis pathway and related bioactivity research, and provides a reference for developing non-medicinal parts and guiding the clinical application of Bupleuri Radix.