LSC Regions Research Articles

Comparative Analysis and Phylogenetic Implications of Plastomes of Five Genera in Subfamily Amyridoideae (Rutaceae)

In the most recent classification of Rutaceae, Amyridoideae is the largest and most diverse subfamily. In Amyridoideae, the genera Phellodendron, Tetradium, Toddalia and Zanthoxylum were proposed as “proto-Rutaceae”due to substantial phytochemical similarities. In this study, we investigated the plastome varia-tions in eight species representing these four genera and Melicope. All plastomes exhibited a typical quadripartite structure with four regions (LSC, SSC, IRa and IRb). The whole chloroplast genome size ranged from 158,383 bp to 159,014 bp and the gene number ranged from 115 to 116. By comparative analyses, we found that there were structural variations at the LSC/IR and SSC/IR borders of the plastomes in the five genera, especially in Melicope. Three most divergent regions (trnH-psbA, trnE-trnT and psaB) were found from the LSC region, which had great potential for developing effective genetic markers. In addition, we conducted a phylogenomic analyses of the “proto-Rutaceae”and related taxa with plastomes data from 36 species. Our results showed that (1) Phellodendron, Tetradium, Toddalia and Zanthoxylum were confirmed as close relatives and grouped together as the ‘proto-Rutaceae’, (2) Phellodendron was sister to Tetradium, and Toddalia was deeply nested within Zanthoxylum, and (3) Toddalia asiatica was closely related to the Southwest Pacific and East Asian species of Zanthoxylum, and Melicope pteleifolia was more closely related to Acronychia than it is to Tetradium. This study provided new insights into the plastome structural varia-tions in subfamily Amyridoideae, and demonstrated that the plastomes data were sufficiently robust to explore implications of the phylogeny for the previous phylogenetic hypotheses.

Comparative Analyses of Euonymus Chloroplast Genomes: Genetic Structure, Screening for Loci With Suitable Polymorphism, Positive Selection Genes, and Phylogenetic Relationships Within Celastrineae.

In this study, we assembled and annotated the chloroplast (cp) genome of the Euonymus species Euonymus fortunei, Euonymus phellomanus, and Euonymus maackii, and performed a series of analyses to investigate gene structure, GC content, sequence alignment, and nucleic acid diversity, with the objectives of identifying positive selection genes and understanding evolutionary relationships. The results indicated that the Euonymus cp genome was 156,860–157,611bp in length and exhibited a typical circular tetrad structure. Similar to the majority of angiosperm chloroplast genomes, the results yielded a large single-copy region (LSC) (85,826–86,299bp) and a small single-copy region (SSC) (18,319–18,536bp), separated by a pair of sequences (IRA and IRB; 26,341–26,700bp) with the same encoding but in opposite directions. The chloroplast genome was annotated to 130–131 genes, including 85–86 protein coding genes, 37 tRNA genes, and eight rRNA genes, with GC contents of 37.26–37.31%. The GC content was variable among regions and was highest in the inverted repeat (IR) region. The IR boundary of Euonymus happened expanding resulting that the rps19 entered into IR region and doubled completely. Such fluctuations at the border positions might be helpful in determining evolutionary relationships among Euonymus. The simple-sequence repeats (SSRs) of Euonymus species were composed primarily of single nucleotides (A)n and (T)n, and were mostly 10–12bp in length, with an obvious A/T bias. We identified several loci with suitable polymorphism with the potential use as molecular markers for inferring the phylogeny within the genus Euonymus. Signatures of positive selection were seen in rpoB protein encoding genes. Based on data from the whole chloroplast genome, common single copy genes, and the LSC, SSC, and IR regions, we constructed an evolutionary tree of Euonymus and related species, the results of which were consistent with traditional taxonomic classifications. It showed that E. fortunei sister to the Euonymus japonicus, whereby E. maackii appeared as sister to Euonymus hamiltonianus. Our study provides important genetic information to support further investigations into the phylogenetic development and adaptive evolution of Euonymus species.

The complete chloroplast genome sequence of Populus szechuanica, a medicinal plant for child anesthesia application

Populus szechuanica C.K. Schneid. is used for wind and sand fixation, farmland protection, soil and water conservation. And some varieties bud fat and inflorescence are available for medicinal use; poplar bark contains tannin and can be used as tanning material. It is also widely used in afforestation and greening in cities across China. In addition, the P. szechuanica also showed vital important application values on the child anesthesia, which could significantly reduce the occurrence of hypotension after anesthesia. The complete chloroplast genome sequence of P. szechuanica was characterized from Illumina pair-end sequencing. The chloroplast genome of P. szechuanica was 156,717 bp in length, containing a large single-copy region (LSC) of 84,900 bp, a small single-copy region (SSC) of 16,527 bp, and two inverted repeat (IR) regions of 27,645 bp. The overall GC content is 36.70%, while the corresponding values of the LSC, SSC, and IR regions are 34.5%, 30.7%, and 41.9%, respectively. The genome contains 131 complete genes, including 86 protein-coding genes (68 protein-coding gene species), 37 tRNA genes (29 tRNA species) and 8 rRNA genes (4 rRNA species). The Maximum Likelihood phylogenetic analysis showed that P. szechuanica and P. koreana clustered together as sisters to other Populus species.

The complete chloroplast genome sequence of medicinal plant: Dianthus chinensis (Caryophyllaceae)

Dianthus chinensis is a medicinal plant. Its complete chloroplast genome sequence is 149,570 bp in length, containing 126 complete genes, including 84 protein-coding genes (84 PCGs), 8 ribosomal RNA genes (8 rRNAs), and 34 tRNA genes (34 tRNAs). The overall GC content of cp DNA is 34.1%, the corresponding values of the LSC, SSC, and IR regions are 34.0%, 29.8%, and 42.5%, respectively. Phylogenetic tree shows that D. chinensis is a sister to D. longicalyx.

The complete chloroplast genome sequence of Gentiana atropurpurea and phylogenetic analysis

Gentiana atropurpurea is an annual herb belonging to section Microsperma T.N. Ho series Suborbisepalae Marquand. This species is endemic to China with its distribution limited to the southeast of the QTP. In this study, the complete chloroplast genome sequence of G. atropurpurea was characterized from Illumina pair-end sequencing. The chloroplast genome of G. atropurpurea was 145,757 bp in length, containing a large single-copy region (LSC) of 78,287 bp, a small single-copy region (SSC) of 16,750 bp, and two inverted repeat (IR) regions of 25,360 bp. The overall GC content is 37.90%, while the corresponding values of the LSC, SSC, and IR regions are 35.8, 31.7, and 43.4%, respectively. The genome contains 132 complete genes, including 86 protein-coding genes (62 protein-coding gene species), 37 tRNA genes (29 tRNA species), and eight rRNA genes (four rRNA species). Phylogenetic analysis based on complete chloroplast genomes showed that G. atropurpurea and G. tongolensis clustered together as sisters to other related species.

The complete chloroplast genome of Crateva unilocularis (Capparaceae)

Crateva unilocularis is naturally distributed in Southern China, which is an elite natural tree with high edible and medicinal value. In this study, whole chloroplast (cp) genome of Crateva unilocularis was assembled and characterized on the basis of Illumina pair-end sequencing data. The complete cp genome was 156,417 bp in length, containing a large single-copy region (LSC) of 85,607 bp and a small single-copy region (SSC) of 18,164 bp, which were separated by a pair of 26,323 bp inverted repeat regions (IRs). The genome contained 128 genes, including 85 protein-coding genes, 35 tRNA genes, and 8 rRNA genes. The overall GC content is 36.32%, while the corresponding values of the LSC, SSC, and IR regions were 33.98, 29.45, and 42.48%, respectively. The maximum-likelihood phylogenetic analysis showed a strong sister relationship with Crateva tapia. These findings provide a foundation for further investigation of cp genome evolution in Crateva unilocularis and other higher plants.

Complete chloroplast genome of Engelhardtia fenzlii (Juglandaceae)

In this study, we successfully assembled and analyzed the chloroplast genome of Engelhardtia fenzlii. The chloroplast genome of E. fenzlii was very similar to those of other Juglandaceae species. The E. fenzlii chloroplast genome is 161,713 bp in length and displays the typical quadripartite structure, which consists of a pair of IR regions (26,016 bp) separated by an LSC region (90,478 bp) and an SSC region (19,203 bp). The chloroplast genome of E. fenzlii contained a total of 112 unique genes, including 78 protein-coding genes, 30 tRNAs, and 4 rRNAs. Phylogenetic analysis based on the complete chloroplast genomes showed that Engelhardtia formed a monophyletic clade and E. fenzlii was sister to E. roxburghiana.

The complete plastid genome of Phoenix canariensis Chabaud (Arecaceae) and phylogenetic analysis

Phoenix canariensis Chabaud is a vital ornamental and widely planted in the urban landscape of China. In this study, we reported the complete chloroplast genome (cpDNA) of P. canariensis, which is 158,477 bp in length, including a large single copy region (LSC) of 86,189 bp, a small single copy region (SSC) of 17,704 bp, and a pair of inverted repeats (IR) regions of 27,292 bp inserted between LSC and SSC. 132 genes are encoded, including 86 protein-encoding genes, 8 ribosomal RNA genes, and 38 transfer RNA genes. The overall GC content of the chloroplast genome is 37.22%, wherein the corresponding values in the LSC, SSC, and IR regions are 35.3%, 30.79%, and 42.35%, respectively. Phylogenetic analysis showed that P. canariensis is sister to P. dactylifera with strong bootstrap support.

Characterization of the complete chloroplast genome sequence of medicinal plant: Potentilla bifurca (Rosaceae)

Potentilla bifurca is a medicinal plant, the root extracts have been applied for the treatment of certain viral infections as folk medicinal herbs. The complete chloroplast genome sequence of is 155,841 bp in length, contains 128 complete genes, including 84 protein-coding genes (84 PCGs), 8 ribosomal RNA genes (4 rRNAs), and 37 tRNA genes (37 tRNAs). The overall GC content of cp DNA is 37.1%, the corresponding values of the LSC, SSC, and IR regions are 35.0%, 31.0%, and 42.8%. Phylogenetic tree shows that P. bifurca was identified as the basal clade of Potentilla.

The complete chloroplast genome of Scutellaria scordifolia (Labiatae)

Scutellaria scordifolia Fisch. ex Schrank Li is a traditional Chinese medicinal plant of genus Scutellaria from the Labiatae family. The complete chloroplast genome of was 152,336 bp in length, which contained 133 complete genes including 87 protein-coding genes (87 PCGs), 8 ribosomal RNA genes (8 rRNAs), and 37 transfer RNA genes (37 tRNAs). The GC content of chloroplast DNA was 38.3%. The corresponding values of the LSC, SSC, and IR regions were 36.3%, 32.5%, and 43.6%, respectively. Phylogenetic tree showed that the species from genus Scutellaria were divided into two monophyletic clades, and the divergence time of S. scordifolia was earlier than that of the other species.

The characterization and phylogenetic analysis of complete chloroplast genome in Morella cerifera (Myricaceae)

The first complete chloroplast genome of Morella cerifera was obtained by illumina platform sequencing technology in this study. The size of genome is 158,943 base pairs, consist of a pair of IRs 26,043 bp in length, the LSC region of 88,167 bp and SSC region of 18,690 bp. The genome has 112 unique genes, among which 79 protein-coding genes, 29 tRNAs, and 4 rRNAs. Phylogenetic analysis revealed that M. cerifera clustered with M. rubra within Myricaceae.

Comparison of complete chloroplast genome sequences of Amygdalus pedunculata Pall.

Amygdalus pedunculata Pall. is one of the 12 important woody oil crops in China. In this study, we determined the complete chloroplast genome sequence of A. pedunculata Pall. (MG602257) from Mu Us desert in Yulin city, Shaanxi province, China. The plastome was 157 851 bp with 36.8% GC content. Comparisons among the plastomes of MG602257 and other two MG869261 and KY101153 from Genebank of NCBI showed that the total length of these chloroplast genomes was MG602257< MG869261<KY101153, the GC contents of these genomes were same, and 149 mutation events including 93 substitutions and 56 indels were accurately located. The codon numbers and RSCU values among the three were similar. They shared the same genes at the four boundaries of the LSC, SSC, IRa, and IRb regions. The lengths of ndhF at the LSC/IRa boundary in MG602257 and MG869261 were same while adjusting 9 bp in KY101153. The length of ycf1 gene at the SSC/IRb boundary in MG602257, MG869261 and KY101153 was 5 657, 5 588 and 5 684 bp, respectively, which was the one of the reasons for the size difference among the three plastomes. Phylogenetic analyses based on 13 complete plastomes of Rosaceae species confirmed close relationships between A. trilob and A. pedunculata.

Plastid Phylogenomics of Dendroseris (Cichorieae; Asteraceae): Insights Into Structural Organization and Molecular Evolution of an Endemic Lineage From the Juan Fernández Islands

Dendroseris D. Don comprises 11 species endemic to the Juan Fernández islands in Chile. They demonstrate spectacular and unusual growth forms of rosette trees with extremely variable morphology and occupy wide ecological ranges on the islands. These unique plants are now highly threatened with extinction with very small population sizes, typically consisting of 10 or fewer individuals in wild. Despite morphological and ecological divergence among species of Dendroseris, their monophyly has been supported in previous studies, but with little resolution among subgeneric groups. We assembled seven complete plastome sequences from seven species of Dendroseris, including representatives from three subgenera, and carried out comparative phylogenomic analyses. The plastomes are highly conserved in gene content and order, with size ranging from 152,199 to 152,619 bp and containing 130 genes (87 coding genes, 6 rRNA genes, and 37 tRNA genes). Plastid phylogenomic analyses based on both the complete plastome sequences and 81 concatenated coding genes only show Dendroseris nested within Sonchus sensu lato, and also that inter-subgeneric relationships are fully resolved. Subg. Phoenicoseris is resolved as sister to the remaining species of the genus and a sister relationship between the two subgenera Dendroseris and Rea. Ten mutation hotspots from LSC and SSC regions and variable SSRs are identified as potential chloroplast markers for future phylogenetic and phylogeographic studies of Sonchus and related groups.

The complete chloroplast genome of Turpinia arguta (Staphyleaceae)

The complete chloroplast genome of Turpinia arguta was sequenced and assembled for the first time. The chloroplast genome was 160,139 bp in length, containing a large single-copy region (LSC) of 89,625 bp and a small single-copy region (SSC) of 18,262 bp, separated by a pair of inverted repeats (IRs) of 26,126 bp. The genome contained 113 unique genes, including 79 protein-coding genes, 30 tRNA genes, and four rRNA genes. Among them, 15 genes had one intron each and 3 genes containing two introns. The overall GC content was 37.4%, while the corresponding values of LSC, SSC, and IR regions were 35.4%, 31.8%, and 42.8%, respectively. Phylogenetic analysis showed that T. arguta is more closely related to Staphylea trifolia and provided new insight into the evolution of Staphyleaceae.

Methods of analysis of chloroplast genomes of C3, Kranz type C4 and Single Cell C4 photosynthetic members of Chenopodiaceae

BackgroundChloroplast genome information is critical to understanding forms of photosynthesis in the plant kingdom. During the evolutionary process, plants have developed different photosynthetic strategies that are accompanied by complementary biochemical and anatomical features. Members of family Chenopodiaceae have species with C3 photosynthesis, and variations of C4 photosynthesis in which photorespiration is reduced by concentrating CO2 around Rubisco through dual coordinated functioning of dimorphic chloroplasts. Among dicots, the family has the largest number of C4 species, and greatest structural and biochemical diversity in forms of C4 including the canonical dual-cell Kranz anatomy, and the recently identified single cell C4 with the presence of dimorphic chloroplasts separated by a vacuole. This is the first comparative analysis of chloroplast genomes in species representative of photosynthetic types in the family.ResultsMethodology with high throughput sequencing complemented with Sanger sequencing of selected loci provided high quality and complete chloroplast genomes of seven species in the family and one species in the closely related Amaranthaceae family, representing C3, Kranz type C4 and single cell C4 (SSC4) photosynthesis six of the eight chloroplast genomes are new, while two are improved versions of previously published genomes. The depth of coverage obtained using high-throughput sequencing complemented with targeted resequencing of certain loci enabled superior resolution of the border junctions, directionality and repeat region sequences. Comparison of the chloroplast genomes with previously sequenced plastid genomes revealed similar genome organization, gene order and content with a few revisions. High-quality complete chloroplast genome sequences resulted in correcting the orientation the LSC region of the published Bienertia sinuspersici chloroplast genome, identification of stop codons in the rpl23 gene in B. sinuspersici and B. cycloptera, and identifying an instance of IR expansion in the Haloxylon ammodendron inverted repeat sequence. The rare observation of a mitochondria-to-chloroplast inter-organellar gene transfer event was identified in family Chenopodiaceae.ConclusionsThis study reports complete chloroplast genomes from seven Chenopodiaceae and one Amaranthaceae species. The depth of coverage obtained using high-throughput sequencing complemented with targeted resequencing of certain loci enabled superior resolution of the border junctions, directionality, and repeat region sequences. Therefore, the use of high throughput and Sanger sequencing, in a hybrid method, reaffirms to be rapid, efficient, and reliable for chloroplast genome sequencing.

Higher Genomic Variation in Wild Than Cultivated Rubber Trees, Hevea brasiliensis, Revealed by Comparative Analyses of Chloroplast Genomes

Rubber tree is the only commercialized natural resource to produce high-quality natural rubber with unique physical and chemical properties. They currently foster in Southeast Asia with marked morphological and productive differences with wild germplasms native to the Amazonian basin of South America. Here, we report complete chloroplast (cp) genomes of six cultivated and six wild accessions of H. brasiliensis using Illumina paired-end sequencing platform. The twelve H. brasiliensis cp genomes ranged from 161,168 to 161,254 bp. All twelve cp genomes displayed a typical quadripartite structure, which consisted of a pair of IR regions (26,787-26,804 bp) separated by a LSC region (89,216-89,284 bp) and a SSC region (18,370-18,377 bp). Phylogenomic analysis revealed that cultivated and wild rubber trees failed formed separate clades. However, we observed that wild rubber trees possessed more variable sites and ~2.8-fold higher level of nucleotide variation than cultivated rubber trees despite a short domestication history. We drew a comprehensive map of genomic variation across rubber tree plastomes, exhibiting that the density of genomic variants in wild rubber trees was slightly higher than that detected in cultivated ones. The obtainability of genomic variation across cp genomes will provide useful information for better conserving and utilizing rubber tree germplasms.

Plastome comparative genomics in maples resolves the infrageneric backbone relationships.

Maples (Acer) are among the most diverse and ecologically important tree genera of the north-temperate forests. They include species highly valued as ornamentals and as a source of timber and sugar products. Previous phylogenetic studies employing plastid markers have not provided sufficient resolution, particularly at deeper nodes, leaving the backbone of the maple plastid tree essentially unresolved. We provide the plastid genome sequences of 16 species of maples spanning the sectional diversity of the genus and explore the utility of these sequences as a source of information for genetic and phylogenetic studies in this group. We analyzed the distribution of different types of repeated sequences and the pattern of codon usage, and identified variable regions across the plastome. Maximum likelihood and Bayesian analyses using two partitioning strategies were performed with these and previously published sequences. The plastomes ranged in size from 155,212 to 157,023 bp and had structure and gene content except for Acer palmatum (sect. Palmata), which had longer inverted repeats and an additional copy of the rps19 gene. Two genes, rps2 and rpl22, were found to be truncated at different positions and might be non-functional in several species. Most dispersed repeats, SSRs, and overall variation were detected in the non-coding sequences of the LSC and SSC regions. Fifteen loci, most of which have not been used before in the genus, were identified as the most variable and potentially useful as molecular markers for barcoding and genetic studies. Both ML and Bayesian analyses produced similar results irrespective of the partitioning strategy used. The plastome-based tree largely supported the topology inferred in previous studies using cp markers while providing resolution to the backbone relationships but was highly incongruous with a recently published nuclear tree presenting an opportunity for further research to investigate the causes of discordance, and particularly the role of hybridization in the diversification of the genus. Plastome sequences are valuable tools to resolve deep-level relationships within Acer. The variable loci and SSRs identified in this study will facilitate the development of markers for ecological and evolutionary studies in the genus. This study underscores the potential of plastid genome sequences to improve our understanding of the evolution of maples.

The complete chloroplast genome sequence of Leucanthemella linearis (Matsum. ex Matsum.) Tzvelev (Asteraceae), endangered plant of Korea

The complete chloroplast (cp) genome sequence of LHeucanthemella linearis was newly analyzed in this study. It was 151,395 bp in length and was a typical circular structure composed of a large single-copy region (LSC) (83,080 bp) and a small single-copy (SSC) region (18,391 bp) which were separated by two inverted repeat regions (24,962 bp). It was totally 6 bp shorter than the Chinese L. linearis cp genome and was composed of 132 genes. There were four regional specific Indels between them in the LSC region as well as 20 bp insertion in the intergenic spacer region excluding poly-A/T sequence variation. And it was clear that both of Luecanthemella linearis were sister to Chrysanthemum – Artemisia groups and their phylogenetic relationship from this study.

The complete chloroplast genome of Lindera pulcherrima var. hemsleyana (Lauraceae)

Lindera pulcherrima var. hemsleyana is an evergreen tree of the genus Lindera with important medicinal value. The complete chloroplast genome of L. pulcherrima var. hemsleyana is 152,710 bp in length, containing a LSC region of 93,751 bp, a SSC region of 18,813 bp, and a pair of inverted repeats (IRA and IRB) of 20,073 bp each. The genome encoded 128 genes, including 83 protein-coding genes, 8 ribosomal RNA genes, 36 transfer RNA genes, and one pseudogene (ycf1). Most of these genes occurred in a single copy, whereas 15 genes occurred in double copies, including all rRNA, 6 tRNA, and 5 protein-coding genes. The GC content of the whole genome, LSC, SSC, and IR regions is 39.2%, 38.0%, 33.9%, and 44.4%, respectively. A total of 90 SSRs were discovered, the numbers of mono-, di-, tri-, tetra-, penta-, and hexa-nucleotides SSRs were 66, 10, 4, 8, 1, and 1, respectively. Phylogenetic analysis of cp genomes from 24 species of Lauraceae revealed that cp genomes of L. pulcherrima var. hemsleyana, L. pulcherrima var. attenuata, and L. pulcherrima formed a monophyletic clade with 100% bootstrap value.

The complete chloroplast genome sequence of Meconopsis punicea

Meconopsis Vig. is a genus possessing important medicinal and ornamental values in the Papaveraceae. Many species in this genus are commonly used in traditional Tibetan medicines over thousands of years. In this study, we reported the complete chloroplast genome sequence of Meconopsis punicea. Total lengths of the chloroplast genomes were 152,933 bp. The genome had typical quadripartite structure, LSC region (83,031 bp) and SSC region (17,920 bp) were separated by a pair of IRs (25,991 bp), respectively. Moreover, they were composed of 131 genes, including 86 protein coding genes, 37 tRNA genes, 8 rRNA genes and one pseudogene. Phylogenetic analysis based on complete chloroplast genomes showed that M. integrifolia had closer relationship with M. punicea; meanwhile, Meconopsis was closely related to Papaver in Papaveraceae.