Complete chloroplast genome sequences of Dipterygium glaucum and Cleome chrysantha and other Cleomaceae Species,comparative analysis and phylogenetic relationships

This current study presents, for the first time, the complete chloroplast genome of two Cleomaceae species: Dipterygium glaucum and Cleome chrysantha in order to evaluate the evolutionary relationship. The cp genome is 158,576 bp in length with 35.74% GC content in D. glaucum and 158,111 bp with 35.96% GC in C. chrysantha. Inverted repeats IR 26,209 bp, 26,251 bp each, LSC of 87,738 bp, 87,184 bp and SSC of 18,420 bp, 18,425 bp respectively. There are 136 genes in the genome, which includes 80 protein coding genes, 31 tRNA genes and four rRNA genes were observed in both chloroplast genomes. 117 genes are unique while the remaining 19 genes are duplicated in IR regions. The analysis of repeats shows that the cp genome includes all types of repeats with more frequent occurrences of palindromic; Also, this analysis indicates that the total number of simple sequence repeats (SSR) were 323 in D. glaucum, and 313 in C. chrysantha, of which the majority of the SSRs in these plastid genomes were mononucleotide repeats A/T which are located in the intergenic spacer. Moreover, the comparative analysis of the four cp sequences revealed four hotspot genes (atpF, rpoC2, rps19, and ycf1), these variable regions could be used as molecular makers for the species authentication as well as resources for inferring phylogenetic relationships of the species. All the relationships in the phylogenetic tree are with high support, this indicate that the complete chloroplast genome is a useful data for inferring phylogenetic relationship within the Cleomaceae and other families. The simple sequence repeats identified will be useful for identification, genetic diversity, and other evolutionary studies of the species. This study reported the first cp genome of the genus Dipterygium and Cleome. The finding of this study will be beneficial for biological disciplines such as evolutionary and genetic diversity studies of the species within the core Cleomaceae.     

The Complete Chloroplast Genome Sequence of the Medicinal Plant Salvia miltiorrhiza

Salvia miltiorrhiza is an important medicinal plant with great economic and medicinal value. The complete chloroplast (cp) genome sequence of Salvia miltiorrhiza, the first sequenced member of the Lamiaceae family, is reported here. The genome is 151,328 bp in length and exhibits a typical quadripartite structure of the large (LSC, 82,695 bp) and small (SSC, 17,555 bp) single-copy regions, separated by a pair of inverted repeats (IRs, 25,539 bp). It contains 114 unique genes, including 80 protein-coding genes, 30 tRNAs and four rRNAs. The genome structure, gene order, GC content and codon usage are similar to the typical angiosperm cp genomes. Four forward, three inverted and seven tandem repeats were detected in the Salvia miltiorrhiza cp genome. Simple sequence repeat (SSR) analysis among the 30 asterid cp genomes revealed that most SSRs are AT-rich, which contribute to the overall AT richness of these cp genomes. Additionally, fewer SSRs are distributed in the protein-coding sequences compared to the non-coding regions, indicating an uneven distribution of SSRs within the cp genomes. Entire cp genome comparison of Salvia miltiorrhiza and three other Lamiales cp genomes showed a high degree of sequence similarity and a relatively high divergence of intergenic spacers. Sequence divergence analysis discovered the ten most divergent and ten most conserved genes as well as their length variation, which will be helpful for phylogenetic studies in asterids. Our analysis also supports that both regional and functional constraints affect gene sequence evolution. Further, phylogenetic analysis demonstrated a sister relationship between Salvia miltiorrhiza and Sesamum indicum. The complete cp genome sequence of Salvia miltiorrhiza reported in this paper will facilitate population, phylogenetic and cp genetic engineering studies of this medicinal plant.     

The chloroplast genome sequence from <Emphasis Type="Italic">Eugenia uniflora</Emphasis>, a Myrtaceae from Neotropics

Eugenia uniflora is a plant native to tropical America that holds great ecological and economic importance. The complete chloroplast (cp) genome sequence of Eugenia uniflora, a member of the Neotropical Myrtaceae family, is reported here. The genome is 158,445 bp in length and exhibits a typical quadripartite structure of the large (LSC, 87,459 bp) and small (SSC, 18,318 bp) single-copy regions, separated by a pair of inverted repeats (IRs, 26,334 bp). It contains 111 unique genes, including 77 protein-coding genes, 30 tRNAs and 4 rRNAs. The genome structure, gene order, GC content and codon usage are similar to the typical angiosperm cp genomes. Comparison of the entire cp genomes of E. uniflora L. and three other Myrtaceae revealed an expansion of 43 bp in the intergenic spacer located between the IRA/large single-copy (LSC) border and the first gene of LSC region. Simple sequence repeat (SSR) analysis revealed that most SSRs are AT rich, which contribute to the overall AT richness of the cp genome. Additionally, fewer SSRs are distributed in the protein-coding sequences compared to the noncoding regions. Phylogenetic analysis among 58 species based on 57 cp genes demonstrated a closer relationship between E. uniflora L. and Syzygium cumini (L). Skeels compared to the Eucalyptus clade in the Myrtaceae family. The complete cp genome sequence of E. uniflora reported here has importance for population genetics, as well as phylogenetic and evolutionary studies in this species and other Myrtaceae species from Neotropical regions.     

Complete Chloroplast Genome Sequence of Poisonous and Medicinal Plant Datura stramonium: Organizations and Implications for Genetic Engineering

Datura stramonium is a widely used poisonous plant with great medicinal and economic value. Its chloroplast (cp) genome is 155,871 bp in length with a typical quadripartite structure of the large (LSC, 86,302 bp) and small (SSC, 18,367 bp) single-copy regions, separated by a pair of inverted repeats (IRs, 25,601 bp). The genome contains 113 unique genes, including 80 protein-coding genes, 29 tRNAs and four rRNAs. A total of 11 forward, 9 palindromic and 13 tandem repeats were detected in the D. stramonium cp genome. Most simple sequence repeats (SSR) are AT-rich and are less abundant in coding regions than in non-coding regions. Both SSRs and GC content were unevenly distributed in the entire cp genome. All preferred synonymous codons were found to use A/T ending codons. The difference in GC contents of entire genomes and of the three-codon positions suggests that the D. stramonium cp genome might possess different genomic organization, in part due to different mutational pressures. The five most divergent coding regions and four non-coding regions (trnH-psbA, rps4-trnS, ndhD-ccsA, and ndhI-ndhG) were identified using whole plastome alignment, which can be used to develop molecular markers for phylogenetics and barcoding studies within the Solanaceae. Phylogenetic analysis based on 68 protein-coding genes supported Datura as a sister to Solanum. This study provides valuable information for phylogenetic and cp genetic engineering studies of this poisonous and medicinal plant.     

The Chloroplast Genome Sequence of Mungbean (Vigna radiata) Determined by High-throughput Pyrosequencing: Structural Organization and Phylogenetic Relationships

Mungbean is an economically important crop which is grown principally for its protein-rich dry seeds. However, genomic research of mungbean has lagged behind other species in the Fabaceae family. Here, we reported the complete chloroplast (cp) genome sequence of mungbean obtained by the 454 pyrosequencing technology. The mungbean cp genome is 151 271 bp in length which includes a pair of inverted repeats (IRs) of 26 474 bp separated by a small single-copy region of 17 427 bp and a large single-copy region of 80 896 bp. The genome contains 108 unique genes and 19 of these genes are duplicated in the IR. Of these, 75 are predicted protein-coding genes, 4 ribosomal RNA genes and 29 tRNA genes. Relative to other plant cp genomes, we observed two distinct rearrangements: a 50-kb inversion between accD/rps16 and rbcL/trnK-UUU, and a 78-kb rearrangement between trnH/rpl14 and rps19/rps8. We detected sequence length polymorphism in the cp homopolymeric regions at the intra- and inter-specific levels in the Vigna species. Phylogenetic analysis demonstrated a close relationship between Vigna and Phaseolus in the phaseolinae subtribe and provided a strong support for a monophyletic group of the eurosid I.     

Complete chloroplast genome sequence of Magnolia grandiflora and comparative analysis with related species

Magnolia grandiflora is an important medicinal,ornamental and horticultural plant species.The chloroplast(cp) genome of M.grandiflora was sequenced using a 454 sequencing platform and the genome structure was compared with other related species.The complete cp genome of M.grandiflora was 159623 bp in length and contained a pair of inverted repeats(IR) of 26563 bp separated by large and small single copy(LSC,SSC) regions of 87757 and 18740 bp,respectively.A total of 129 genes were successfully annotated,18 of which included introns.The identity,number and GC content of M.grandiflora cp genes were similar to those of other Magnoliaceae species genomes.Analysis revealed 218 simple sequence repeat(SSR) loci,most composed of A or T,contributing to a bias in base composition.The types and abundances of repeat units in Magnoliaceae species were relatively conserved and these loci will be useful for developing M.grandiflora cp genome vectors.In addition,results indicated that the cp genome size in Magnoliaceae species and the position of the IR border were closely related to the length of the ycf1 gene.Phylogenetic analyses based on 66 shared genes from 30 species using maximum parsimony(MP) and maximum likelihood(ML) methods provided strong support for the phylogenetic position of Magnolia.The availability of the complete cp genome sequence of M.grandiflora provides valuable information for breeding of desirable varieties,cp genetic engineering,developing useful molecular markers and phylogenetic analyses in Magnoliaceae.     

Complete chloroplast genomes of Liliaceae (s.l.) species: comparative genomic and phylogenetic analyses

We first report the complete chloroplast (cp) genome of Fritillaria taipaiensis and determine its characteristics, sequence divergence and phylogenetic relationships by comparing it with complete cp genomes of Liliaceae s.l. (including e.g. Nartheciaceae, Amaryllidaceae and Asparagaceae) species obtained from NCBI Genbank. We show that the ycf1, ycf15 and infA genes have become pseudogenes or are lost in some of the seventeen Liliaceae species, and that dispersed repeats are prevailing among the four types of repeats (dispersed, palindromic, complement and tandem repeats). The number of simple sequence repeats ranged from 53 to 84 in the seventeen species, with mononucleotide repeats being the most abundant, followed by dinucleotides. A total of nine genes with positive selection sites were identified (atpB, atpE, ndhF, ndhH, petB, rpl2, rpl20, rpl22 and ycf2). Furthermore, we examined 19 mutational hotspot regions, including three coding regions (rps16, infA and rpl22) and sixteen non-coding regions. A phylogenetic analysis of the complete cp genomes and protein-coding sequences showed that Fritillaria is most closely related to Lilium. Moreover, Asparagus and Polygonatum, Hosta and Yucca are closely related to the Liliaceae. These results will contribute to further study of evolutionary patterns and phylogenetic relationships in Liliaceae s.l.     

Comparative Chloroplast Genomes of Camellia Species

Background

Camellia , comprising more than 200 species, is a valuable economic commodity due to its enormously popular commercial products: tea leaves, flowers, and high-quality edible oils. It is the largest and most important genus in the family Theaceae. However, phylogenetic resolution of the species has proven to be difficult. Consequently, the interspecies relationships of the genus Camellia are still hotly debated. Phylogenomics is an attractive avenue that can be used to reconstruct the tree of life, especially at low taxonomic levels.

Methodology/Principal Findings

Seven complete chloroplast (cp) genomes were sequenced from six species representing different subdivisions of the genus Camellia using Illumina sequencing technology. Four junctions between the single-copy segments and the inverted repeats were confirmed and genome assemblies were validated by PCR-based product sequencing using 123 pairs of primers covering preliminary cp genome assemblies. The length of the Camellia cp genome was found to be about 157kb, which contained 123 unique genes and 23 were duplicated in the IR regions. We determined that the complete Camellia cp genome was relatively well conserved, but contained enough genetic differences to provide useful phylogenetic information. Phylogenetic relationships were analyzed using seven complete cp genomes of six Camellia species. We also identified rapidly evolving regions of the cp genome that have the potential to be used for further species identification and phylogenetic resolution.

Conclusions/Significance

In this study, we wanted to determine if analyzing completely sequenced cp genomes could help settle these controversies of interspecies relationships in Camellia . The results demonstrate that cp genome data are beneficial in resolving species definition because they indicate that organelle-based “barcodes”, can be established for a species and then used to unmask interspecies phylogenetic relationships. It reveals that phylogenomics based on cp genomes is an effective approach for achieving phylogenetic resolution between Camellia species.     

The complete chloroplast genome sequence of the endangered species Syringa pinnatifolia (Oleaceae)

Syringa pinnatifolia is an endangered endemic species in China with important ornamental and medicinal value, and it needs urgent protection. Here, we report the complete chloroplast (cp) genome structure of S. pinnatifolia and its evolution is inferred through comparative studies with related species. The S. pinnatifolia cp genome was 155 326 bp and contained a large single copy region (LSC) of 86 167 bp and a small single copy region (SSC) of 17 775 bp, as well as a pair of inverted repeat regions (IRs) of 25 692 bp. A total of 113 unique genes were annotated, including 79 protein‐coding genes, 30 tRNA genes and four rRNA genes. The GC content of the S. pinnatifolia cp genome was 37.9%, and the corresponding values in the LSC, SSC and IR regions were 36.0, 32.1, 43.2% respectively. Repetitive sequences analysis revealed that the S. pinnatifolia cp genome contained 38 repeats. Microsatellite marker detection analysis identified 253 simple sequence repeats (SSRs), which provides opportunities for future studies of the population genetics and phylogenetic relationships of Syringa. Phylogenetic analysis of 29 selected cp genomes revealed that S. pinnatifolia is closely related to Syringa vulgaris and all 27 Lamiales species formed a clade separate from the two outgroup species. This newly characterized S. pinnatifolia chloroplast genome will provide a useful genomic resource of phylogenetic inference and the development of more genetic markers for species discrimination and population studies in the genus Syringa.     

Insights from the Complete Chloroplast Genome into the Evolution of Sesamum indicum L

Sesame (Sesamum indicum L.) is one of the oldest oilseed crops. In order to investigate the evolutionary characters according to the Sesame Genome Project, apart from sequencing its nuclear genome, we sequenced the complete chloroplast genome of S. indicum cv. Yuzhi 11 (white seeded) using Illumina and 454 sequencing. Comparisons of chloroplast genomes between S. indicum and the 18 other higher plants were then analyzed. The chloroplast genome of cv. Yuzhi 11 contains 153,338 bp and a total of 114 unique genes ({"type":"entrez-nucleotide","attrs":{"text":"KC569603","term_id":"496538580","term_text":"KC569603"}}KC569603). The number of chloroplast genes in sesame is the same as that in Nicotiana tabacum, Vitis vinifera and Platanus occidentalis. The variation in the length of the large single-copy (LSC) regions and inverted repeats (IR) in sesame compared to 18 other higher plant species was the main contributor to size variation in the cp genome in these species. The 77 functional chloroplast genes, except for ycf1 and ycf2, were highly conserved. The deletion of the cp ycf1 gene sequence in cp genomes may be due either to its transfer to the nuclear genome, as has occurred in sesame, or direct deletion, as has occurred in Panax ginseng and Cucumis sativus. The sesame ycf2 gene is only 5,721 bp in length and has lost about 1,179 bp. Nucleotides 1–585 of ycf2 when queried in BLAST had hits in the sesame draft genome. Five repeats (R10, R12, R13, R14 and R17) were unique to the sesame chloroplast genome. We also found that IR contraction/expansion in the cp genome alters its rate of evolution. Chloroplast genes and repeats display the signature of convergent evolution in sesame and other species. These findings provide a foundation for further investigation of cp genome evolution in Sesamum and other higher plants.     

Characterization of the chloroplast genome sequence of oil palm (Elaeis guineensis Jacq.)

Oil palm (Elaeis guineensis Jacq.) is an economically important crop, which is grown for oil production. To better understand the molecular basis of oil palm chloroplasts, we characterized the complete chloroplast (cp) genome sequence obtained from 454 pyrosequencing. The oil palm cp genome is 156,973 bp in length consisting of a large single-copy region of?85,192 bp flanked on each side by inverted repeats of 27,071 bp with a small single-copy region of 17,639 bp joining the?repeats. The genome contains 112 unique genes: 79 protein-coding genes, 4 ribosomal RNA genes and 29 tRNA genes. By aligning the cp?genome sequence with oil palm cDNA sequences, we observed 18 non-silent and 10 silent RNA editing events among 19 cp protein-coding genes. Creation of an initiation codon by RNA editing in rpl2 has been reported in several monocots and was also found in the oil palm cp genome. Fifty common chloroplast protein-coding genes from 33 plant taxa were used to construct ML and MP?phylogenetic trees. Their topologies are similar and strongly support for the position of E. guineensis as the sister of closely related species Phoenix dactylifera in Arecaceae (palm families) of monocot subtrees.     

Complete chloroplast genome of cultivated flowering cherry, <Emphasis Type="Italic">Prunus</Emphasis> ×<Emphasis Type="Italic">yedoensis</Emphasis> ‘Somei-yoshino’ in comparison with wild <Emphasis Type="Italic">Prunus yedoensis</Emphasis> Matsum. (Rosaceae)

Prunus ×yedoensis Matsum. ‘Somei-yoshino’ is the most common and widespread cultivar of the ornamental flowering cherries. We hereby report its complete chloroplast (cp) genome sequences generated by whole-genome next-generation sequencing approach. The cp genome size was 157,792 bp in length consisting of four regions; large single-copy region (85,914 bp), small single-copy region (19,120 bp), and a pair of inverted repeat regions (26,379 bp). The genome contained a total of 131 genes, including 86 coding genes, 8 rRNA genes, and 37 tRNA genes. A total of 92 simple sequence repeats (SSRs) were detected within the cp genome. Its molecular features were compared with the complete cp genome of wild P. yedoensis, which occurs rarely in natural habitats of Mt. Halla in Jeju Island, Korea, displaying nearly indistinguishable morphology as P. ×yedoensis ‘Somei-yoshino’. Although both cp genomes were structured highly alike, the sequence variations between them were revealed in several single-nucleotide polymorphisms (SNPs). Using additional individuals of wild and cultivated flowering cherries, PCR amplification confirmed that those SNPs were phylogenetically informative, providing distinction between wild and cultivated flowering cherries. In future study, the SNPs and SSRs reported in this study could be used to identify wild individuals from morphologically identical cultivars of flowering cherries and also to conserve the genetic diversity of wild flowering cherries in Jeju Island.     

The complete chloroplast genome of the spring ephemeral plant Alyssum desertorum and its implications for the phylogenetic position of the tribe Alysseae within the Brassicaceae

Alyssum desertorum (Alysseae, Brassicaceae) is an annual spring ephemeral plant whose life cycle is only 2–3 months. It typically has high photosynthetic capacity and a high growth rate. However, little was known about the chloroplast (cp) genome structure of this species. Furthermore, the phylogenetic position of the tribe Alysseae relative to other tribes in the Brassicaceae has not been established and there appear to be inconsistences between different DNA markers. This study is the first report on a cp genome of the genus Alyssum and discusses the phylogenetic relationships of the tribe Alysseae relative to other tribes in the family. The complete cp genome of A. desertorum was 151 677 bp in size and is thus the smallest cp genome of Brassicaceae sequenced to date. The genome includes a large single‐copy region of 81 551 bp, a small single‐copy region of 17 804 bp, and two inverted repeats of 26 161 bp each. The genome contains 132 genes, including 86 protein‐coding genes (PCGs), 38 tRNA genes and 8 rRNA genes. A total of 16 genes contained introns, including 10 PCGs and 6 tRNA genes; the ycf3 and clpP genes contained two introns, and the remaining genes each contained one. Compared to the cp genomes of 21 other Brassicaceae species, the cp genome of Alyssum desertorum was the smallest, as due to variation in gene content and gene length, such as a lack of the rps16 gene and the deletion of some coding genes. Additionally, deletions of introns and intergenic spacers were observed, but their total length was not significantly shorter than those of other taxa. Phylogenetic analysis at the tribal level based on a cp genome dataset revealed that the tribe Alysseae is an early‐diverging lineage that is sister to other species within subclade B of clade II.     

Highly variable chloroplast genome from two endangered Papaveraceae lithophytes Corydalis tomentella and Corydalis saxicola

The increasingly wide application of chloroplast (cp) genome super‐barcode in taxonomy and the recent breakthrough in cp genetic engineering make the development of new cp gene resources urgent and significant. Corydalis is recognized as the most genotypes complicated and taxonomically challenging plant taxa in Papaveraceae. However, there currently are few reports about cp genomes of the genus Corydalis. In this study, we sequenced four complete cp genomes of two endangered lithophytes Corydalis saxicola and Corydalis tomentella in Corydalis, conducted a comparison of these cp genomes among each other as well as with others of Papaveraceae. The cp genomes have a large genome size of 189,029–190,247 bp, possessing a quadripartite structure and with two highly expanded inverted repeat (IR) regions (length: 41,955–42,350 bp). Comparison between the cp genomes of C. tomentella, C. saxicola, and Papaveraceae species, five NADH dehydrogenase‐like genes (ndhF, ndhD, ndhL, ndhG, and ndhE) with psaC, rpl32, ccsA, and trnL‐UAG normally located in the SSC region have migrated to IRs, resulting in IR expansion and gene duplication. An up to 9 kb inversion involving five genes (rpl23, ycf2, ycf15, trnI‐CAU, and trnL‐CAA) was found within IR regions. The accD gene was found to be absent and the ycf1 gene has shifted from the IR/SSC border to the SSC region as a single copy. Phylogenetic analysis based on the sequences of common CDS showed that the genus Corydalis is quite distantly related to the other genera of Papaveraceae, it provided a new clue for recent advocacy to establish a separate Fumariaceae family. Our results revealed one special cp genome structure in Papaveraceae, provided a useful resources for classification of the genus Corydalis, and will be valuable for understanding Papaveraceae evolutionary relationships.     

First reported chloroplast genome sequence of <Emphasis Type="Italic">Punica granatum</Emphasis> (cultivar Helow) from Jabal Al-Akhdar,Oman: phylogenetic comparative assortment with <Emphasis Type="Italic">Lagerstroemia</Emphasis>

Pomegranate (Punica granatum L.) is one of the oldest known edible fruits. It has grown in popularity and is a profitable fruit crop due to its attractive features including a bright red appearance and its biological activities. Scientific exploration of the genetics and evolution of these beneficial traits has been hampered by limited genomic information. In this study, we sequenced the complete chloroplast (cp) genome of the native P. granatum (cultivar Helow) cultivated in the mountains of Jabal Al-Akhdar, Oman. The results revealed a P. granatum cp genome length of 158,630 bp, characterized by a relatively conserved structure containing 2 inverted repeat regions of 25,466 bp, an 18,686 bp small single copy regions, and an 89,015 bp large single copy region. The 86 protein-coding genes included 37 transfer RNA genes and 8 ribosomal RNA genes. Comparison of the P. granatum whole cp genome with seven Lagerstroemia species revealed an overall high degree of sequence similarity with divergence among intergenic spacers. The location, distribution, and divergence of repeat sequences and shared genes of the Punica and Lagerstroemia species were highly similar. Analyses of nucleotide substitution, insertion/deletions, and highly variable regions in these cp genomes identified potential plastid markers for taxonomic and phylogenetic studies in Myrtales. A phylogenetic study of the cp genomes and 76 shared coding regions generated similar cladograms. The complete cp genome of P. granatum will aid in taxonomical studies of the family Lythraceae.     

The cp genome characterization of Adenium obesum: Gene content,repeat organization and phylogeny

Adenium obesum (Forssk.) Roem. & Schult. belonging to the family Apocynaceae, is remarkable for its horticultural and ornamental values, poisonous nature, and medicinal uses. In order to have understanding of cp genome characterization of highly valued medicinal plant, and the evolutionary and systematic relationships, the complete plastome / chloroplast (cp) genome of A. obesum was sequenced. The assembled cp genome of A. obesum was found to be 154,437 bp, with an overall GC content of 38.1%. A total of 127 unique coding genes were annotated including 96 protein-coding genes, 28 tRNA genes, and 3 rRNA genes. The repeat structures were found to comprise of only mononucleotide repeats. The SSR loci are compososed of only A/T bases. The phylogenetic analysis of cp genomes revealed its proximity with Nerium oleander.     

Complete chloroplast genome sequences of Praxelis (Eupatorium catarium Veldkamp), an important invasive species

Praxelis (Eupatorium catarium Veldkamp) is a new hazardous invasive plant species that has caused serious economic losses and environmental damage in the Northern hemisphere tropical and subtropical regions. Although previous studies focused on detecting the biological characteristics of this plant to prevent its expansion, little effort has been made to understand the impact of Praxelis on the ecosystem in an evolutionary process. The genetic information of Praxelis is required for further phylogenetic identification and evolutionary studies. Here, we report the complete Praxelis chloroplast (cp) genome sequence. The Praxelis chloroplast genome is 151,410 bp in length including a small single-copy region (18,547 bp) and a large single-copy region (85,311 bp) separated by a pair of inverted repeats (IRs; 23,776 bp). The genome contains 85 unique and 18 duplicated genes in the IR region. The gene content and organization are similar to other Asteraceae tribe cp genomes. We also analyzed the whole cp genome sequence, repeat structure, codon usage, contraction of the IR and gene structure/organization features between native and invasive Asteraceae plants, in order to understand the evolution of organelle genomes between native and invasive Asteraceae. Comparative analysis identified the 14 markers containing greater than 2% parsimony-informative characters, indicating that they are potential informative markers for barcoding and phylogenetic analysis. Moreover, a sister relationship between Praxelis and seven other species in Asteraceae was found based on phylogenetic analysis of 28 protein-coding sequences. Complete cp genome information is useful for plant phylogenetic and evolutionary studies within this invasive species and also within the Asteraceae family.     

Comparative and phylogenetic analyses of Swertia L. (Gentianaceae) medicinal plants (from Qinghai,China) based on complete chloroplast genomes

Swertia L. is a large genus in Swertiinae (Gentianaceae). In China, many Swertia species are used as traditional Tibetan medicines, known as “Zangyinchen” or “Dida”. However, the phylogenetic relationships among Swertia medicinal plants and their wild relatives have remained unclear. In this study, we sequenced and assembled 16 complete chloroplast (cp) genomes of 10 Swertia species, mainly distributed in Qinghai Province, China. The results showed that these species have typical structures and characteristics of plant cp genomes. The sizes of Swertia cp genomes are ranging from 149,488 bp to 154,097 bp. Most Swertia cp genomes presented 134 genes, including 85 protein coding genes, eight rRNA genes, 37 tRNA genes, and four pseudogenes. Furthermore, the GC contents and boundaries of cp genomes are similar among Swertia species. The phylogenetic analyses indicated that Swertia is a complex polyphyletic group. In addition, positive selection was found in psaI and petL genes, indicating the possible adaptation of Qinghai Swertia species to the light environment of the Qinghai-Tibet plateau. These new cp genome data could be further investigated to develop DNA barcodes for Swertia medicinal plants and for additional systematic studies of Swertia and Swertiinae species.     

The complete chloroplast genome sequence of Mahonia bealei (Berberidaceae) reveals a significant expansion of the inverted repeat and phylogenetic relationship with other angiosperms

Mahonia bealei (Berberidaceae) is a frequently-used traditional Chinese medicinal plant with efficient anti-inflammatory ability. This plant is one of the sources of berberine, a new cholesterol-lowering drug with anti-diabetic activity. We have sequenced the complete nucleotide sequence of the chloroplast (cp) genome of M. bealei. The complete cp genome of M. bealei is 164,792 bp in length, and has a typical structure with large (LSC 73,052 bp) and small (SSC 18,591 bp) single-copy regions separated by a pair of inverted repeats (IRs 36,501 bp) of large size. The Mahonia cp genome contains 111 unique genes and 39 genes are duplicated in the IR regions. The gene order and content of M. bealei are almost unarranged which is consistent with the hypothesis that large IRs stabilize cp genome and reduce gene loss-and-gain probabilities during evolutionary process. A large IR expansion of over 12 kb has occurred in M. bealei, 15 genes (rps19, rpl22, rps3, rpl16, rpl14, rps8, infA, rpl36, rps11, petD, petB, psbH, psbN, psbT and psbB) have expanded to have an additional copy in the IRs. The IR expansion rearrangement occurred via a double-strand DNA break and subsequence repair, which is different from the ordinary gene conversion mechanism. Repeat analysis identified 39 direct/inverted repeats 30 bp or longer with a sequence identity ≥ 90%. Analysis also revealed 75 simple sequence repeat (SSR) loci and almost all are composed of A or T, contributing to a distinct bias in base composition. Comparison of protein-coding sequences with ESTs reveals 9 putative RNA edits and 5 of them resulted in non-synonymous modifications in rpoC1, rps2, rps19 and ycf1. Phylogenetic analysis using maximum parsimony (MP) and maximum likelihood (ML) was performed on a dataset composed of 65 protein-coding genes from 25 taxa, which yields an identical tree topology as previous plastid-based trees, and provides strong support for the sister relationship between Ranunculaceae and Berberidaceae. Molecular dating analyses suggest that Ranunculaceae and Berberidaceae diverged between 90 and 84 mya, which is congruent with the fossil records and with recent estimates of the divergence time of these two taxa.     

The complete chloroplast genome sequence of the Chinese endemic species Sorbus setschwanensis (Rosaceae) and its phylogenetic analysis

Sorbus setschwanensis Koehne is a pinnate-leaved Sorbus s.str. species endemic to China with narrow distribution and intriguing phylogeny that needs wider attention. In this paper, the complete chloroplast (cp) genome of S. setschwanensis is reported, and its phylogenetic position is analyzed. The complete cp genome of S. setschwanensis is 160 064 bp in size with 36.50% GC content. It has a typical quadripartite structure including a pair of inverted repeat regions (IRs) of 26 378 bp that separates a large single copy (LSC) region of 86 013 bp and a small single copy (SSC) region of 19 295 bp. The cp genome encodes 108 genes, comprising 76 protein-coding genes, 28 tRNA genes and 4 rRNA genes. Additionally, 52 simple sequence repeats (SSRs) and 43 dispersed repeats were identified. Comparison of the whole cp genome with those of other Sorbus species showed an overall high degree of sequence similarity, but there are six highly variable regions (trnR-atpA, petN-psbM, ndhC-trnV, trnE-trnT, trnT-trnL and rpl32-trnL) located in intergenic spacers that may be useful as molecular markers in future population genetic and phylogenetic studies in the genus. Phylogenetic analyses based on 108 coding genes from 25 species in Rosaceae revealed that S. setschwanensis is nested within Sorbus sect. Sorbus together with other pinnately leaved species, but does not form a sister lineage to S. rufopilosa belonging to the same series Multijugae. Thus, the systematic position of S. setschwanensis and relationships with other species in the genus needs to be further studied.