Phylogenomic analysis and dynamic evolution of chloroplast genomes of Clematis nannophylla.

Clematis nannophylla is a perennial shrub of Clematis with ecological, ornamental, and medicinal value, distributed in the arid and semi-arid areas of northwest China. This study successfully determined the chloroplast (cp) genome of C. nannophylla, reconstructing a phylogenetic tree of Clematis. This cp genome is 159,801 bp in length and has a typical tetrad structure, including a large single-copy, a small single-copy, and a pair of reverse repeats (IRa and IRb). It contains 133 unique genes, including 89 protein-coding, 36 tRNA, and 8 rRNA genes. Additionally, 66 simple repeat sequences, 50 dispersed repeats, and 24 tandem repeats were found; many of the dispersed and tandem repeats were between 20-30 bp and 10-20 bp, respectively, and the abundant repeats were located in the large single copy region. The cp genome was relatively conserved, especially in the IR region, where no inversion or rearrangement was observed, further revealing that the coding regions were more conserved than the noncoding regions. Phylogenetic analysis showed that C. nannophylla is more closely related to C. fruticosa and C. songorica. Our analysis provides reference data for molecular marker development, phylogenetic analysis, population studies, and cp genome processes to better utilise C. nannophylla.

The complete chloroplast genome of Marupa (Simarouba amara Aubl., Simaroubaceae).

Marupa (Simarouba amara Aublet 1775) is a tropical tree of the family Simaroubaceae. It is commonly used for its wood in the Amazonian forest, and it is an important species for restoring degraded environments. Yet, very little genetic resources are available to study this plant. In this paper, we sequenced for the first time the complete chloroplast genome of Marupa, using Oxford Nanopore long-read technology. The genome is 159,838 bp, includes 131 genes in total and presents a classic quadripartite structure. Its length and structure are similar to those of sister species of the Simaroubaceae family. A maximum likelihood phylogeny of the order Sapindale reveals that Simarouba amara is well positioned in its family. This complete plastome is a first step towards a better analysis of Marupa future evolution.

The complete chloroplast genome sequences of nine melon varieties (Cucumis melo L.): lights into comparative analysis and phylogenetic relationships.

Melon (Cucumis melo L.) is one of the most extensively grown horticulture crops of the world. Based on the morphological characters, melon was formerly divided into two subspecies, Cucumis melo ssp. melo and C. melo ssp. agrestis. However, the present methods are still inadequate to distinguish between them. The phylogenetic analysis based on chloroplast genome sequences could provide essential evidence for the classification of melon varieties. We sequenced the chloroplast genomes of nine different melon varieties by the Illumina Hiseq and performed bioinformatic analyses including repeat element analysis, genome comparison and phylogenetic analysis. The results showed that the melon chloroplast genome has a typical quadripartite structure that was conserved across the analyzed sequences. Its length ranges between 155, 558 and 156, 569 bp, with a total GC content varying from 36.7% to 37%. We found 127-132 genes in melon chloroplast genomes, including 85-87 protein-coding regions, 34-37 tRNA and 6-8 rRNA genes. The molecular structure, gene order, content, codon usage, long repeats, and simple sequence repeats (SSRs) were mostly conserved among the nine sequenced genomes. Phylogenetic analysis showed that the chloroplast genome could clearly distinguish between C. melo ssp. melo and C. melo ssp. agrestis. This study not only provides valuable knowledge on melon chloroplasts, but also offers a theoretical basis and technical support for the genetic breeding of melons.

The chloroplast genome of a subtropical tree Sassafras randaiense (Hayata) Rehder, 1920 (Lauraceae).

The complete chloroplast genome sequence of Sassafras randaiense (Hayata) Rehder, 1920, a subtropical tree in the family Lauraceae, was determined. For a better understanding of the differences between S. randaiense and S. tzumu, the complete chloroplast genome of S. randaiense was sequenced and analyzed. The complete chloroplast genome is 151,781 bp in length, consisting of a pair of inverted repeat (IR) regions of 20,114 bp, one large single-copy (LSC) region of 92,740 bp, and one small single-copy (SSC) region of 18,813 bp. The overall GC content of the complete chloroplast genome is 39.2%. Further, maximum-likelihood phylogenetic analysis was conducted using 31 complete plastome sequences, which support that S. randaiense and S. tzumu are nested among the members of Cinnamomum, suggesting that Sassafras belongs to Cinnamomum.

Characterization of the complete chloroplast genome of Rhodiola sachalinensis and comparative analysis with its congeneric plants.

Rhodiola, belonging to the Crassulaceae family, is a perennial herbaceous plant genus. There are about 90 Rhodiola species worldwide, some of which have been reported to have medicinal properties. Rhodiola sachalinensis is a perennial medicinal herb within this genus and, in the present study, its chloroplast genome was sequenced, assembled, annotated and compared with 24 other Rhodiola species. The results obtained show that the chloroplast genome of R. sachalinensis is 151 595 bp long and has a CG content of 37.7%. The inverted repeats (IR) region of the Rhodiola chloroplast genome is the most conserved region, with the main differences being observed in the ycf1 and ndhF genes at the IRb-small single copy boundary, and rps19 and trnH genes at the IRa-large single copy boundary. Phylogenetic analysis showed that Rhodiola species form two major clades, and species with recorded medicinal properties, clustered together in one branch except for R. dumulosa. Within the genus, R. sachalinensis is most closely related to Rhodiola rosea, although comparative analyses showed that only R. sachalinensis and Rhodiola subopposita contained the psbZ gene, which encodes a highly conserved protein subunit of the Photosystem II core complex. Overall, the present study contributes to the understanding of the chloroplast genome of Rhodiola species, and provides a theoretical basis for the study of their genetic diversity and possible use as medicinal plants.

Characterization, comparison, and phylogenetic analyses of chloroplast genomes of Euphorbia species.

The genus Euphorbia (Euphorbiaceae) has near-cosmopolitan distribution and serves as a significant resource for both ornamental and medicinal purposes. Despite its economic importance, Euphorbia's taxonomy has long been challenged by the intricate nature of morphological traits exhibiting high levels of convergence. While molecular markers are essential for phylogenetic studies, their availability for Euphorbia has been limited. To address this gap, we conducted comparative analyses focusing on the chloroplast (CP) genomes of nine Euphorbia species, incorporating three newly sequenced and annotated accessions. In addition, phylogenetic informativeness and nucleotide diversity were computed to identify candidate markers for phylogenetic analyses among closely related taxa in the genus. Our investigation revealed relatively conserved sizes and structures of CP genomes across the studied species, with notable interspecific variations observed primarily in non-coding regions and IR/SC borders. By leveraging phylogenetic informativeness and nucleotide diversity, we identified rpoB gene as the optimal candidate for species delimitation and shallow-level phylogenetic inference within the genus. Through this comprehensive analysis of CP genomes across multiple taxa, our study sheds light on the evolutionary dynamics and taxonomic intricacies of Euphorbia, offering valuable insights into its CP genome evolution and taxonomy.

Complete chloroplast genome and phylogenetic analysis of Amorphophallus paeoniifolius (Araceae).

Amorphophallus paeoniifolius (Dennst.) Nicolson, 1885, often known as elephant foot yam, is a tropical tuber crop that originates from south-east Asia and belongs to the Araceae family. It is known for its high production potential and popularity as a medicinal plant. However, the phylogeny and genes for this species are still unavailable. In this study, the first complete chloroplast genome of A. paeoniifolius was reported and phylogenetic analysis was conducted with Araceae species. The chloroplast genome was 176,258 bp in length with 34.80% overall GC content and includes a large single-copy (LSC) region (93,951 bp), a small single-copy (SSC) region (15,013 bp), and a pair of inverted repeat (IRs) regions (33,647 bp). The chloroplast genome has 130 genes, which include 85 protein-coding genes, 37 tRNA genes, and eight rRNA genes. A maximum-likelihood (ML) phylogenetic analysis indicated that all Amorphophallus species formed a single monophyletic clade with a high bootstrap value and A. paeoniifolius was closely related to A. konjac, A. albus, A. krausei, and A. titanum. The chloroplast genome reported in this study will be useful for further taxonomic and evolutionary studies of Amorphophallus.

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 Analysis of Complete Chloroplast Genomes of Rubus in China: Hypervariable Regions and Phylogenetic Relationships.

With more than 200 species of native Rubus, China is considered a center of diversity for this genus. Due to a paucity of molecular markers, the phylogenetic relationships for this genus are poorly understood. In this study, we sequenced and assembled the plastomes of 22 out of 204 Chinese Rubus species (including varieties) from three of the eight sections reported in China, i.e., the sections Chamaebatus, Idaeobatus, and Malachobatus. Plastomes were annotated and comparatively analyzed with the inclusion of two published plastomes. The plastomes of all 24 Rubus species were composed of a large single-copy region (LSC), a small single-copy region (SSC), and a pair of inverted repeat regions (IRs), and ranged in length from 155,464 to 156,506 bp. We identified 112 unique genes, including 79 protein-coding genes, 29 transfer RNAs, and four ribosomal RNAs. With highly consistent gene order, these Rubus plastomes showed strong collinearity, and no significant changes in IR boundaries were noted. Nine divergent hotspots were identified based on nucleotide polymorphism analysis: trnH-psbA, trnK-rps16, rps16-trnQ-psbK, petN-psbM, trnT-trnL, petA-psbJ, rpl16 intron, ndhF-trnL, and ycf1. Based on whole plastome sequences, we obtained a clearer phylogenetic understanding of these Rubus species. All sampled Rubus species formed a monophyletic group; however, sections Idaeobatus and Malachobatus were polyphyletic. These data and analyses demonstrate the phylogenetic utility of plastomes for systematic research within Rubus.

Phylogeny, Genetic Diversity and Population Structure of Fritillaria cirrhosa and Its Relatives Based on Chloroplast Genome Data.

Fritillaria cirrhosa and its relatives have been utilized in traditional Chinese medicine for many years and are under priority protection in China. Despite their medicinal and protective value, research on their phylogeny, genetic diversity, and divergence remains limited. Here, we investigate the chloroplast genome variation architecture of 46 samples of F. cirrhosa and its relatives collected from various regions, encompassing the majority of wild populations across diverse geographical areas. The results indicate abundant variations in 46 accessions including 1659 single-nucleotide polymorphisms and 440 indels. Six variable markers (psbJ, ndhD, ycf1, ndhG, trnT-trnL, and rpl32-trnL) were identified. Phylogenetic and network analysis, population structure analysis, and principal component analysis showed that the 46 accessions formed five clades with significant divergence, which were related to their geographical distribution. The regions spanning from the southern Hengduan Mountains to the Qinghai-Tibet Plateau exhibited the highest levels of genetic diversity. F. cirrhosa and its relatives may have suffered a genetic bottleneck and have a relatively low genetic diversity level. Moreover, geographical barriers and discrete patches may have accelerated population divergence. The study offers novel perspectives on the phylogeny, genetic diversity, and population structure of F. cirrhosa and its relatives, information that can inform conservation and utilization strategies in the future.

Complete Organelle Genome of the Desiccation-Tolerant (DT) Moss Tortula atrovirens and Comparative Analysis of the Pottiaceae Family.

Tortula atrovirens (Sm.) Lindb. is an important component of biological soil crusts and possesses an extraordinary tolerance against desiccation in dryland habitats. However, knowledge of the organelle genome of this desiccation-tolerant (DT) moss is still lacking. Here, we assembled the first reported Tortula organelle genome and conducted a comprehensive analysis within the Pottiaceae family. T. atrovirens exhibited the second largest chloroplast genome (129,646 bp) within the Pottiaceae, whereas its mitogenome (105,877 bp) and those of other mosses were smaller in size compared to other land plants. The chloroplast and mitochondrial genomes of T. atrovirens were characterized by the expansion of IR boundaries and the absence of homologous recombination-mediated by large repeats. A total of 57 RNA editing sites were detected through mapping RNA-seq data. Moreover, the gene content and order were highly conserved among the Pottiaceae organelle genomes. Phylogenetic analysis showed that bryophytes are paraphyletic, with their three lineages (hornworts, mosses, and liverworts) and vascular plants forming successive sister clades. Timmiella anomala is clearly separated from the monophyletic Pottiaceae, and T. atrovirens is closely related to Syntrichia filaris within the Pottioideae. In addition, we detected four hypervariable regions for candidate-molecular markers. Our findings provide valuable insights into the organelle genomes of T. atrovirens and the evolutionary relationships within the Pottiaceae family, facilitating future discovery of DT genetic resources from bryophytes.

Characterization and Comparative Analysis of Complete Chloroplast Genomes of Four Bromus (Poaceae, Bromeae) Species.

Bromus (Poaceae Bromeae) is a forage grass with high adaptability and ecological and economic value. Here, we sequenced Bromus ciliatus, Bromus benekenii, Bromus riparius, and Bromus rubens chloroplast genomes and compared them with four previously described species. The genome sizes of Bromus species ranged from 136,934 bp (Bromus vulgaris) to 137,189 bp (Bromus ciliates, Bromus biebersteinii), with a typical quadripartite structure. The studied species had 129 genes, consisting of 83 protein-coding, 38 tRNA-coding, and 8 rRNA-coding genes. The highest GC content was found in the inverted repeat (IR) region (43.85-44.15%), followed by the large single-copy (LSC) region (36.25-36.65%) and the small single-copy (SSC) region (32.21-32.46%). There were 33 high-frequency codons, with those ending in A/U accounting for 90.91%. A total of 350 simple sequence repeats (SSRs) were identified, with single-nucleotide repeats being the most common (61.43%). A total of 228 forward and 141 palindromic repeats were identified. No reverse or complementary repeats were detected. The sequence identities of all sequences were very similar, especially with respect to the protein-coding and inverted repeat regions. Seven highly variable regions were detected, which could be used for molecular marker development. The constructed phylogenetic tree indicates that Bromus is a monophyletic taxon closely related to Triticum. This comparative analysis of the chloroplast genome of Bromus provides a scientific basis for species identification and phylogenetic studies.

Comparative analysis the chloroplast genomes of Celastrus (Celastraceae) species: Provide insights into molecular evolution, species identification and phylogenetic relationships.

BACKGROUND: The genus Celastrus is an important medicinal plant resource. The similarity of morphology and the lack of complete chloroplast genome analysis have significantly impeded the exploration of species identification, molecular evolution and phylogeny of Celastrus. PURPOSE: In order to resolve the phylogenic controversy of Celastrus species, the chloroplast genome comparative analysis was performed to provide genetic evidence. METHODS: In this study, we collected and sequenced ten chloroplast genomes of Celastrus species from China and downloaded three chloroplast genomes from the databases. The chloroplast genomes were compared and analyzed to explore their characteristics and evolution. Furthermore, the phylogenetic relationships of Celastrus species were inferred based on the whole chloroplast genomes and protein-coding genes. RESULTS: All the 13 Celastrus species chloroplast genomes showed a typical quadripartite structure with genome sizes ranging from 155,113 to 157,366 bp. The intron loss of the rps16 gene occurred in all the 13 Celastrus species. The GC content, gene sequence, repeat types and codon bias pattern were highly conserved. Ten highly variation regions were identified, which can be used as potential DNA markers in molecular identification of Celastrus species. Eight genes, including accD, atp4, ndhB, rpoC1, rbcL, rpl2, rpl20 and ycf1, were detected to experience positive selection. Phylogenetic analysis showed that Celastrus was a monophyletic group and Tripterygium was the closest sister-group. Noteworthy, C. gemmatus Loes. and C. orbiculatus Thunb. can be discriminated using the chloroplast genome as a super barcode. The comparative and phylogenetic analysis results proposed that C. tonkinensis Pitard. was the synonym of C. hindsii Benth. CONCLUSION: The comparative analysis of the Celastrus chloroplast genomes can provide comprehensive genetic evidence for molecular evolution, species identification and phylogenetic relationships.

The complete chloroplast genomes of Polygonatum hunanense, P. verticillatum, and P. caulialatum and their phylogenetic positions.

Polygonatum hunanense H.H. Liu & B.Z. Wang (2021) and P. verticillatum (L.) All. (1875) have been widely used as foods and as folk medicines in China and India, and P. caulialatum S. R. Yi (2021) has recently been described as a new medical plant in China. There is at present a lack of genome information regarding the species. Hence, this study reports the complete chloroplast genomes of the three species. The genomes of P. hunanense, P. verticillatum, and P. caulialatum were 155,583 bp, 155,650 bp, and 155,352 bp in length, respectively. They contained large single-copy (LSC) regions of 84,412 bp, 84,404 bp, and 84,285 bp, small single-copy (SSC) regions of 18,427 bp, 18,416 bp, and 18,463 bp, and a pair of inverted repeats of 26,372 bp, 26,415 bp, and 26,302 bp, respectively. The chloroplast genomes of P. hunanense, P. verticillatum, and P. caulialatum had 133 (103 unique) genes, consisting of 87 protein-coding genes, 38 ribosomal ribonucleic acid (RNA) genes, and eight transfer RNA genes, respectively. A maximum-likelihood phylogenetic tree showed that P. kingianum Coll. et Hemsl. var. grandifolium D.M. Liu & W.Z. Zeng (1991) was closer to P. cyrtonema Hua (1892) rather than to P. kingianum Coll. et Hemsl. (1890), further supporting its status as a unique species of the genus. Moreover, P. verticillatum was separated from the easily confused herb P. cirrhifolium (Wall.) Royle (1839), while P. caulialatum was closest to P. humile Fisch. ex Maxim. (1859). This research provides a foundation for further study of these herbs.

Complete chloroplast genome structural characterization of two Aerides (Orchidaceae) species with a focus on phylogenetic position of Aerides flabellata.

BACKGROUND: The disputed phylogenetic position of Aerides flabellata Rolfe ex Downie, due to morphological overlaps with related species, was investigated based on evidence of complete chloroplast (cp) genomes. The structural characterization of complete cp genomes of A. flabellata and A. rosea Lodd. ex Lindl. & Paxton were analyzed and compared with those of six related species in "Vanda-Aerides alliance" to provide genomic information on taxonomy and phylogeny. RESULTS: The cp genomes of A. flabellata and A. rosea exhibited conserved quadripartite structures, 148,145 bp and 147,925 bp in length, with similar GC content (36.7 ~ 36.8%). Gene annotations revealed 110 single-copy genes, 18 duplicated in inverted regions, and ten with introns. Comparative analysis across related species confirmed stable sequence identity and higher variation in single-copy regions. However, there are notable differences in the IR regions between two Aerides Lour. species and the other six related species. The phylogenetic analysis based on CDS from complete cp genomes indicated that Aerides species except A. flabellata formed a monophyletic clade nested in the subtribe Aeridinae, being a sister group to Renanthera Lour., consistent with previous studies. Meanwhile, a separate clade consisted of A. flabellata and six Vanda R. Br. species was formed, as a sister taxon to Holcoglossum Schltr. CONCLUSIONS: This research was the first report on the complete cp genomes of A. flabellata. The results provided insights into understanding of plastome evolution and phylogenetic relationships of Aerides. The phylogenetic analysis based on complete cp genomes showed that A. flabellata should be placed in Vanda rather than in Aerides.

A comparative plastome approach enhances the assessment of genetic variation in the Melilotus genus.

BACKGROUND: Melilotus, a member of the Fabaceae family, is a pivotal forage crop that is extensively cultivated in livestock regions globally due to its notable productivity and ability to withstand abiotic stress. However, the genetic attributes of the chloroplast genome and the evolutionary connections among different Melilotus species remain unresolved. RESULTS: In this study, we compiled the chloroplast genomes of 18 Melilotus species and performed a comprehensive comparative analysis. Through the examination of protein-coding genes, we successfully established a robust phylogenetic tree for these species. This conclusion is further supported by the phylogeny derived from single-nucleotide polymorphisms (SNPs) across the entire chloroplast genome. Notably, our findings revealed that M. infestus, M. siculus, M. sulcatus, and M. speciosus formed a distinct subgroup within the phylogenetic tree. Additionally, the chloroplast genomes of these four species exhibit two shared inversions. Moreover, inverted repeats were observed to have reemerged in six species within the IRLC. The distribution patterns of single-nucleotide polymorphisms (SNPs) and insertions/deletions (InDels) within protein-coding genes indicated that ycf1 and ycf2 accumulated nonconservative alterations during evolutionary development. Furthermore, an examination of the evolutionary rate of protein-coding genes revealed that rps18, rps7, and rpl16 underwent positive selection specifically in Melilotus. CONCLUSIONS: We present a comparative analysis of the complete chloroplast genomes of Melilotus species. This study represents the most thorough and detailed exploration of the evolution and variability within the genus Melilotus to date. Our study provides valuable chloroplast genomic information for improving phylogenetic reconstructions and making biogeographic inferences about Melilotus and other Papilionoideae species.

The complete chloroplast genome of Arachis lutescens Krapov. & Rigoni (Fabaceae).

Arachis lutescens Krapov. & Rigoni 1958 is an important species due to their potentially extensive applications for cultivated peanut breeding. The whole chloroplast genome of A. lutescens was successfully assembled and annotated for the first time. The complete chloroplast genome of A. lutescens is a typically circular structure of 156,398 bp with a GC content of 36.3%. It comprises a large single-copy (LSC) region of 85,950 bp, a small single-copy (SSC) region of 18,800 bp, and two inverted repeat regions (IRs) of 25,824 bp, each. The plastome of A. lutescens contains a total of 125 genes, including 81 protein-coding genes, 36 tRNAs, and eight rRNAs. The phylogenetic analysis strongly supports the close relationship between A. lutescens and cultivated peanut clades. This study contributes to our understanding of the molecular characteristics and evolutionary relationships of this plant species.

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 the complete chloroplast genome sequence of Bassia scoparia (L.) A. J. Scott 1978 (Amaranthaceae) and its phylogenetic analysis.

Bassia scoparia, an annual potherb belonging to the family Amaranthaceae, has been widely used in traditional Chinese and Japanese medicine for over 2000 years. Herein, we presented its complete chloroplast. The chloroplast genome sequence was 151,278 bp in length with a 36.6% content of GC. The genome showed the typical quadripartite structure, comprising a pair of inverted repeat (IR) regions (24,353 bp) separated by a large single-copy (LSC) region (84,067 bp) and a small single-copy (SSC) region (18,505 bp). This chloroplast genome harbored 133 predicted genes, including 88 protein-coding genes, 37 transfer RNA (tRNA) genes, and eight ribosomal RNA (rRNA) genes. The phylogenetic analysis indicated that B. scoparia was closely related to B. littorea. This newly sequenced chloroplast genome not only enhances our understanding of the genome of Bassia but also provides valuable insights for the evolutionary study of the family Amaranthaceae.

The complete chloroplast genome of Meconopsis torquata (Papaveraceae), a traditional Tibetan medicine.

Meconopsis torquata Prain 1906, a national second-class rare and endangered plant, is reported here for the first time for its complete chloroplast genome. The genome is 153,290 bp in length, comprising a large single-copy region (LSC, 83,918 bp), a small single-copy region (SSC, 17,740 bp), and two inverted repeat sequences (IRa and IRb, each 25,816 bp). The overall GC content is 38.7%, with the IR region having the highest content (43.1%). The genome is annotated with 112 unique genes, including 4 rRNA genes, 29 tRNA genes, and 79 protein-coding genes. Analysis of codon usage bias reveals that codons ending in A/T account for 96.7% of those with a Relative Synonymous Codon Usage (RSCU) value above 1. This predominance of A/T-ending codons might be indicative of M. torquata adaptation to high-altitude environments. Phylogenetic analysis reveals a close kinship between M. torquata and M. pinnatifolia and M. paniculata, indicating that the ancestral groups of these species might have a complex evolutionary history. This study uncovers the genetic characteristics and adaptive evolution of M. torquata, offering a new perspective in understanding the phylogenetic relationships within the genus. The findings not only provide a solid theoretical foundation for the conservation and sustainable use of this rare and endangered species but also offer significant scientific support for the conservation of biodiversity.