Chloroplast Genome Structure Research Articles

Chloroplast genome characterization of Uncaria guianensis and Uncaria tomentosa and evolutive dynamics of the Cinchonoideae subfamily

Uncaria species are used in traditional medicine and are considered of high therapeutic value and economic importance. This work describes the assembly and annotation of the chloroplast genomes of U. guianensis and U. tomentosa, as well as a comparative analysis. The genomes were sequenced on MiSeq Illumina, assembled with NovoPlasty, and annotated using CHLOROBOX GeSeq. Addictionaly, comparative analysis were performed with six species from NCBI databases and primers were designed in Primer3 for hypervariable regions based on the consensus sequence of 16 species of the Rubiaceae family and validated on an in-silico PCR in OpenPrimeR. The genome size of U. guianensis and U. tomentosa was 155,505 bp and 156,390 bp, respectively. Both Species have 131 genes and GC content of 37.50%. The regions rpl32-ccsA, ycf1, and ndhF-ccsA showed the three highest values of nucleotide diversity within the species of the Rubiaceae family and within the Uncaria genus, these regions were trnH-psbA, psbM-trnY, and rps16-psbK. Our results indicates that the primer of the region ndhA had an amplification success for all species tested and can be promising for usage in the Rubiaceae family. The phylogenetic analysis recovered a congruent topology to APG IV. The gene content and the chloroplast genome structure of the analyzed species are conserved and most of the genes are under negative selection. We provide the cpDNA of Neotropical Uncaria species, an important genomic resource for evolutionary studies of the group.

Characterization and comparative analysis of the complete plastid genomes of four Astragalus species.

Astragalus is the largest flowering plant genus. We assembled the plastid genomes of four Astragalus species (Astragalus iranicus, A. macropelmatus, A. mesoleios, A. odoratus) using next-generation sequencing and analyzed their plastomes including genome organization, codon usage, nucleotide diversity, prediction of RNA editing and etc. The total length of the newly sequenced Astragalus plastomes ranged from 121,050 bp to 123,622 bp, with 110 genes comprising 76 protein-coding genes, 30 transfer RNA (tRNA) genes and four ribosome RNA (rRNA) genes. Comparative analysis of the chloroplast genomes of Astragalus revealed several hypervariable regions comprising three non-coding sites (trnQ(UUG)-accD, rps7 -trnV(GAC) and trnR(ACG)-trnN(GUU)) and four protein-coding genes (ycf1, ycf2, accD and clpP), which have potential as molecular markers. Positive selection signatures were found in five genes in Astragalus species including rps11, rps15, accD, clpP and ycf1. The newly sequenced species, A. macropelmatus, has an approximately 13-kb inversion in IR region. Phylogenetic analysis based on 75 protein-coding gene sequences confirmed that Astragalus form a monophyletic clade within the tribe Galegeae and Oxytropis is sister group to the Coluteoid clade. The results of this study may helpful in elucidating the chloroplast genome structure, understanding the evolutionary dynamics at genus Astragalus and IRLC levels and investigating the phylogenetic relationships. Moreover, the newly plastid genomes sequenced have been increased the plastome data resources on Astragalus that can be useful in further phylogenomic studies.

The complete chloroplast genome sequence of Eugenia klotzschiana O. Berg unveils the evolutionary dynamics in plastomes of Myrteae DC. Tribe (Myrtaceae)

Myrteae is the most diversified tribe in the Myrtaceae family and has great ecological and economic importance. Here, we performed the assembly and annotation of the chloroplast genome of Eugenia klotzschiana O. Berg and used this in a comparative analysis with other 13 species from the Myrteae tribe. The E. klotzschiana plastome exhibited a length of 158,977 bp and a very conserved structure and gene composition when compared with other Myrteae genomes. We identified 34 large repetitive sequences and 94 SSR repeats in E. klotzschiana plastome. The trnT-trnL, rpl32-trnL, ndhF-rpl32, psbE-petL, and ycf1 regions were identified as mutational hotspots. A negative selection signal was detected in 74 protein-coding genes while neutral evolution was detected in two genes (rps12 and psaI). Furthermore, 222 RNA editing sites were identified in the E. klotzschiana plastome. We also obtained a plastome-based Myrtales phylogenetic tree, including E. klotzschiana for the first time in a molecular phylogeny, recovering its sister relationship for all other Eugenia species. Our results illuminate how evolution shaped the chloroplast genome structure and composition in the Myrteae tribe, especially in the E. klotzschiana plastome.

Whole chloroplast genome sequences contribute to phylogenetic relatedness and cultivar identification in cacao (Theobroma cacao L.)

Cacao (Theobroma cacao L.) is considered as economic importance crop playing a major role as source of chocolate industries for production of both chocolate candy and cocoa butter. Despite the advantages of cacao in industrial sector, understanding the global structure of cacao chloroplast genome plays a crucial role in explaining phylogenetic relationships and cultivar identification. This study aimed to perform phylogenetic analysis of cacao genotypes and develop DNA barcode markers using cacao chloroplast sequences. Chloroplast genome sequencing of two cacao genotypes (DR-1 and Sca-12) was conducted by the Illumina Miseq platform. Phylogenetic analysis of 12 cacao genotypes including two genotypes sequenced in this study (DR-1 and Sca-12) and ten genotypes previously sequenced (HQ336404, EET-64, ICS-01, ICS-06, ICS-39, Pentagonum, Sca-6, Stahel, Amelonado, and Criollo-22) showed a clear separation between bulk and fine types. This result demonstrated the usefulness of chloroplast sequences in revealing phylogenetic relatedness. Based on comparative chloroplast genome analysis of two cacao genotypes, DR-1 and Sca-12, three insertion/deletion (InDel) markers named as Theca_indel01, Theca_indel02, and Theca_indel03 which designed from the regions of trnA-UGC-rrn23, trnK-UUU-rps16, and rps16 intron, respectively were successfully developed to reveal barcode system for cacao genetic discrimination. Overall, these findings would provide valuable insight into the chloroplast genome structure of cacao plant, as well as information about the benefits of chloroplast sequences for constructing phylogenetic relationships and developing DNA barcode markers.

Chloroplast genomes of four Carex species: Long repetitive sequences trigger dramatic changes in chloroplast genome structure.

The chloroplast genomes of angiosperms usually have a stable circular quadripartite structure that exhibits high consistency in genome size and gene order. As one of the most diverse genera of angiosperms, Carex is of great value for the study of evolutionary relationships and speciation within its genus, but the study of the structure of its chloroplast genome is limited due to its highly expanded and restructured genome with a large number of repeats. In this study, we provided a more detailed account of the chloroplast genomes of Carex using a hybrid assembly of second- and third-generation sequencing and examined structural variation within this genus. The study revealed that chloroplast genomes of four Carex species are significantly longer than that of most angiosperms and are characterized by high sequence rearrangement rates, low GC content and gene density, and increased repetitive sequences. The location of chloroplast genome structural variation in the species of Carex studied is closely related to the positions of long repeat sequences; this genus provides a typical example of chloroplast structural variation and expansion caused by long repeats. Phylogenetic relationships constructed based on the chloroplast protein-coding genes support the latest taxonomic system of Carex, while revealing that structural variation in the chloroplast genome of Carex may have some phylogenetic significance. Moreover, this study demonstrated a hybrid assembly approach based on long and short reads to analyze complex chloroplast genome assembly and also provided an important reference for the analysis of structural rearrangements of chloroplast genomes in other taxa.

CPGView: A package for visualizing detailed chloroplast genome structures.

Chloroplast genomes have been widely used in studying plant phylogeny and evolution. Several chloroplast genome visualization tools have been developed to display the distribution of genes on the genome. However, these tools do not draw features, such as exons, introns, repetitive elements, and variable sites, disallowing in-depth examination of the genome structures. Here, we developed and validated a software package called Chloroplast Genome Viewers (CPGView). CPGView can draw three maps showing (i) the distributions of genes, variable sites, and repetitive sequences, including microsatellites, tandem and dispersed repeats; (ii) the structure of the cis-splicing genes after adjusting the exon-intron boundary positions using a coordinate scaling algorithm, and (iii) the structure of the trans-splicing gene rps12. To test the accuracy of CPGView, we sequenced, assembled, and annotated 31 chloroplast genomes from 31 genera of 22 families. CPGView drew maps correctly for all the 31 chloroplast genomes. Lastly, we used CPGView to examine 5998 publicly released chloroplast genomes from 2513 genera of 553 families. CPGView succeeded in plotting maps for 5882 but failed to plot maps for 116 chloroplast genomes. Further examination showed that the annotations of these 116 genomes had various errors needing manual correction. The test on newly generated data and publicly available data demonstrated the ability of CPGView to identify errors in the annotations of chloroplast genomes. CPGView will become a widely used tool to study the detailed structure of chloroplast genomes. The web version of CPGView can be accessed from http://www.1kmpg.cn/cpgview.

Are the Organellar Genomes Useful for Fine Scale Population Structure Analysis of Endangered Plants?-A Case Study of Pulsatilla patens (L.) Mill.

Pulsatilla patens is a rare and endangered species in Europe and its population resources have significantly decreased over the past decades. Previous genetic studies of this species made it possible to estimate the genetic diversity of the European population and to describe the structure of chloroplast and mitochondrial genomes. The main aim of these studies was to characterize the variability of chloroplast and mitochondrial genomes in more detail at the intra-population and inter-population levels. Our study presents new organelle genome reference sequences that allow the design of novel markers that can be the starting point for testing hypotheses, past and modern biogeography of rare and endangered species P. patens, and adaptive responses of this species to changing environments. The study included sixteen individuals from five populations located in Northeastern Poland. Comparative analysis of 16 P. patens plastomes from 5 populations enabled us to identify 160 point mutations, including 64 substitutions and 96 InDels. The most numerous detected SNPs and Indels (75%) were accumulated in three intergenic spacers: ndhD-ccsA, rps4-rps16, and trnL(UAG)-ndhF. The mitogenome dataset, which was more than twice as large as the plastome (331 kbp vs. 151 kbp), revealed eight times fewer SNPs (8 vs. 64) and six times fewer InDels (16 vs. 96). Both chloroplast and mitochondrial genome identified the same number of haplotypes-11 out of 16 individuals, but both organellar genomes slightly differ in haplotype clustering. Despite the much lower variation, mitogenomic data provide additional resolution in the haplotype detection of P. patens, enabling molecular identification of individuals, which were unrecognizable based on the plastome dataset.

Characterization of the complete chloroplast genome of Begonia handelii

Begonia is the fifth largest genus of angiosperms in the world, and Begonia handelii is a member of the Begonia(Begoniaceae), and is one of the few species with floral fragrance in this genus. However, the chloroplast genome structure and phylogenetic relationship of this species is still unclear. In this study, the chloroplast genome of B. handelii was sequenced by Illumina HiSeq X platform, and the phylogenetic relationship of this species in Begonia was analyzed with related species. The whole chloroplast genome of B. handelii is 169,406 bp in size, which consist one large single-copy region (LSC) with 95,403 bp, one small single-copy region (SSC) with 20,089 bp, and two inverted repeat regions (IR) with 26,957 bp. The GC content of this chloroplast genome is 35.6%. Moreover, 140 genes were found in the chloroplast of B. handelii, including 90 protein-coding genes, 8 rRNA genes, 42 tRNA genes. Phylogenetic analysis showed that B. handelii is closed to B. coptidifolia and B. pulchrifolia. This study lays the foundation for further research on the chloroplast genome evolution of B. handelii chloroplasts.

The Chloroplast Genome of the Lichen Photobiont Trebouxiophyceae sp. DW1 and Its Phylogenetic Implications.

Lichens are symbiotic associations of algae and fungi. The genetic mechanism of the symbiosis of lichens and the influence of symbiosis on the size and composition of the genomes of symbiotic algae have always been intriguing scientific questions explored by lichenologists. However, there were limited data on lichen genomes. Therefore, we isolated and purified a lichen symbiotic alga to obtain a single strain (Trebouxiophyceae sp. DW1), and then obtained its chloroplast genome information by next-generation sequencing (NGS). The chloroplast genome is 129,447 bp in length, and the GC content is 35.2%. Repetitive sequences with the length of 30–35 bp account for 1.27% of the total chloroplast genome. The simple sequence repeats are all mononucleotide repeats. Codon usage analysis showed that the genome tended to use codon ending in A/U. By comparing the length of different regions of Trebouxiophyceae genomes, we found that the changes in the length of exons, introns, and intergenic sequences affect the size of genomes. Trebouxiophyceae had an unstable chloroplast genome structure, with IRs repeatedly losing during evolution. Phylogenetic analysis showed that Trebouxiophyceae is paraphyletic, and Trebouxiophyceae sp. DW1 is sister to the clade of Koliella longiseta and Pabia signiensis.

Chloroplast genome structure and phylogeny of Geoffroea decorticans, a native tree from Atacama Desert

BackgroundGeoffroea decorticans is a vulnerable native species inhabiting the Atacama Desert. Here, we describe the structure, gene composition and phylogeny of the complete chloroplast genome of this legume species. ResultsThe chloroplast genome consisted of 158,399 bp, with typical quadripartite structures: a large single copy (88,081 bp), a small single copy (18,976 bp), and two inverted repeats (25,671 bp). Geoffroea decorticans chloroplast genome was similar in size and gene number to that of G. spinosa, but it was slightly different in structure. Complete chloroplast analysis of G. decorticans revealed 129 genes, including 83 protein-coding genes, 37 tRNA genes, 8 rRNA genes and 1 pseudogene (rpl22). In G. decorticans, the rps16 gene showed a deletion, which led to a premature stop codon, probably causing loss of functionality. Phylogenetic analysis of 20 complete chloroplast genomes confirmed the placement to G. decorticans within the Pterocarpus clade. ConclusionsIn this study, we report the complete chloroplast genome of Geoffroea decorticans for the first time, which can be used for phylogenetic studies and reconstruction of the biogeography history of the genus Geoffroea in South America.How to cite: Contreras-Díaz R, Carevic FS, Huanca-Mamani W, et al. Chloroplast genome structure and phylogeny of Geoffroea decorticans, a native tree from Atacama Desert. Electron J Biotechnol 2022;60. https://doi.org/10.1016/j.ejbt.2022.09.005.

Complete chloroplast genome structure of four Ulmus species and Hemiptelea davidii and comparative analysis within Ulmaceae species

In this study, the chloroplast (cp) genomes of Hemiptelea davidii, Ulmus parvifolia, Ulmus lamellosa, Ulmus castaneifolia, and Ulmus pumila ‘zhonghuajinye’ were spliced, assembled and annotated using the Illumina HiSeq PE150 sequencing platform, and then compared to the cp genomes of other Ulmus and Ulmaceae species. The results indicated that the cp genomes of the five sequenced species showed a typical tetrad structure with full lengths ranging from 159,113 to 160,388 bp. The large single copy (LSC), inverted repeat (IR), and small single copy (SSC) lengths were in the range of 87,736–88,466 bp, 26,317–26,622 bp and 18,485–19,024 bp, respectively. A total of 130–131 genes were annotated, including 85–86 protein-coding genes, 37 tRNA genes and eight rRNA genes. The GC contents of the five species were similar, ranging from 35.30 to 35.62%. Besides, the GC content was different in different region and the GC content in IR region was the highest. A total of 64-133 single sequence repeat (SSR) loci were identified among all 21 Ulmaceae species. The (A)n and (T)n types of mononucleotide were highest in number, and the lengths were primarily distributed in 10–12 bp, with a clear AT preference. A branch-site model and a Bayes Empirical Bayes analysis indicated that the rps15 and rbcL had the positive selection sites. Besides, the analysis of mVISTA and sliding windows got a lot of hotspots such as trnH/psbA, rps16/trnQ, trnS/trnG, trnG/trnR and rpl32/trnL, which could be utilized as potential markers for the species identification and phylogeny reconstruction within Ulmus in the further studies. Moreover, the evolutionary tree of Ulmaceae species based on common protein genes, whole cp genome sequences and common genes in IR region of the 23 Ulmaceae species were constructed using the ML method. The results showed that these Ulmaceae species were divided into two branches, one that included Ulmus, Zelkova and Hemiptelea, among which Hemiptelea was the first to differentiate and one that included Celtis, Trema, Pteroceltis, Gironniera and Aphananthe. Besides, these variations found in this study could be used for the classification, identification and phylogenetic study of Ulmus species. Our study provided important genetic information to support further investigations into the phylogenetic development and adaptive evolution of Ulmus and Ulmaceae species.

Newly reported chloroplast genome of Sinosenecio albonervius Y. Liu & Q. E. Yang and comparative analyses with other Sinosenecio species

BackgroundSinosenecio B. Nordenstam (Asteraceae) currently comprises 44 species. To investigate the interspecific relationship, several chloroplast markers, including ndhC-trnV, rpl32-trnL, matK, and rbcL, are used to analyze the phylogeny of Sinosenecio. However, the chloroplast genomes of this genus have not been thoroughly investigated. We sequenced and assembled the Sinosenecio albonervius chloroplast genome for the first time. A detailed comparative analysis was performed in this study using the previously reported chloroplast genomes of three Sinosenecio species.ResultsThe results showed that the chloroplast genomes of four Sinosenecio species exhibit a typical quadripartite structure. There are equal numbers of total genes, protein-coding genes and RNA genes among the annotated genomes. Per genome, 49–56 simple sequence repeats and 99 repeat sequences were identified. Thirty codons were identified as RSCU values greater than 1 in the chloroplast genome of S. albonervius based on 54 protein-coding genes, indicating that they showed biased usage. Among 18 protein-coding genes, 46 potential RNA editing sites were discovered. By comparing these chloroplast genomes' structures, inverted repeat regions and coding regions were more conserved than single-copy and non-coding regions. The junctions among inverted repeat and single-copy regions showed slight difference. Several hot spots of genomic divergence were detected, which can be used as new DNA barcodes for species identification. Phylogenetic analysis of the whole chloroplast genome showed that the four Sinosenecio species have close interspecific relationships.ConclusionsThe complete chloroplast genome of Sinosenecio albonervius was revealed in this study, which included a comparison of Sinosenecio chloroplast genome structure, variation, and phylogenetic analysis for related species. These will help future research on Sinosenecio taxonomy, identification, origin, and evolution to some extent.

Comparative Genomic and Phylogenetic Analysis of Forty Gentiana Chloroplast Genomes.

Gentiana plants, which have great medicinal and ornamental value, are widely distributed in diverse habitats and have complex taxonomy. Here 40 Gentiana chloroplast genomes were used for comparative genomic analysis and divergence time estimation. The complete chloroplast genome of G. rhodantha was sequenced, assembled, and annotated. Comparative genomic and phylogenetic analysis were provided for variation analysis of Gentiana. Gentiana species satisfy the characteristics of intra-Sect conservation and inter-Sect variation in chloroplast genome structure and IR boundaries. All Gentiana Sects can be clustered into a single one and separated from each other; however, Ser. Apteroideae and Ser. Confertifoliae in Sect. Monopodiae are more closely related to Sect. Frigida and Sect. Cruciata, respectively. Gentiana has experienced two large gene loss events; the first, the collective loss of the rps16 gene at genus formation and the second, the collective loss of the ndh gene when Ser. Ornatae and Ser. Verticillatae completed their differentiation. Comparative genomic analysis support that Sect. Stenogyne and Sect. Otophora became the independent genera Metagentiana and Kuepferia. Seven divergence hotspot regions were screened based on Pi values, and could serve as DNA-specific barcodes for Gentiana. This study provides a further theoretical basis for taxonomic analysis, genetic diversity, evolutionary mechanism and molecular identification in Gentiana.

Comparative Genomic and Phylogenetic Analysis of Chloroplast Genomes of Hawthorn (Crataegus spp.) in Southwest China.

The hawthorns (Crataegus spp.) are widely distributed and famous for their edible and medicinal values. There are ∼18 species and seven varieties of hawthorn in China distributed throughout the country. We now report the chloroplast genome sequences from C. scabrifolia, C. chungtienensis and C. oresbia, from the southwest of China and compare them with the previously released six species in Crataegus and four species in Rosaceae. The chloroplast genome structure of Crataegus is typical and can be divided into four parts. The genome sizes are between 159,654 and 159,898bp. The three newly sequenced chloroplast genomes encode 132 genes, including 85 protein-coding genes, 37 tRNA genes, and eight rRNA genes. Comparative analysis of the chloroplast genomes revealed six divergent hotspot regions, including ndhA, rps16-trnQ-UUG, ndhF-rpl32, rps16-psbK, trnR-UCU-atpA and rpl32-trnL-UAG. According to the correlation and co-occurrence analysis of repeats with indels and SNPs, the relationship between them cannot be ignored. The phylogenetic tree constructed based on the complete chloroplast genome and intergenic region sequences indicated that C. scabrifolia has a different origin from C. chungtienensis and C. oresbia. We support the placement of C. hupehensis, C. cuneata, C. scabrifolia in C. subg. Crataegus and C. kansuensis, C. oresbia, C. kansuensis in C. subg. Sanguineae. In addition, based on the morphology, geographic distribution and phylogenetic relationships of C. chungtienensis and C. oresbia, we speculate that these two species may be the same species. In conclusion, this study has enriched the chloroplast genome resources of Crataegus and provided valuable information for the phylogeny and species identification of this genus.

Chloroplast genome structure and phylogenetic analysis of Glycosmis parviflora (Sims) Little 1948, a folk medicinal plant featured in Lingnan Region, China

Glycosmis parviflora is the most widely spread and the most morphologically varied species of Chinese Glycosmis, and its roots and leaves serve as folk medicines. We sequenced the complete chloroplast (cp) genome of G. parviflora. The cp genome obtained was a circular DNA molecule of 159,825 bp in length, containing one large and one small single copy region (LSC and SSC) of 87,517 and 18,352 bp separated by a pair of 26,978 bp inverted repeat regions (IRs). The overall GC content of the cp genome was 38.40%. The phylogenetic analysis revealed that Glycosmis was strongly supported as a monophyletic group belonging to Clauseneae, and G. parviflora was closely related to G. pentaphylla. The results will provide the basis for the further study of molecular markers and phylogeny of G. parviflora.

Comprehensive analysis of complete chloroplast genome and phylogenetic aspects of ten Ficus species

BackgroundThe large genus Ficus comprises approximately 800 species, most of which possess high ornamental and ecological values. However, its evolutionary history remains largely unknown. Plastome (chloroplast genome) analysis had become an essential tool for species identification and for unveiling evolutionary relationships between species, genus and other rank groups. In this work we present the plastomes of ten Ficus species.ResultsThe complete chloroplast (CP) genomes of eleven Ficus specimens belonging to ten species were determined and analysed. The full length of the Ficus plastome was nearly 160 kbp with a similar overall GC content, ranging from 35.88 to 36.02%. A total of 114 unique genes, distributed in 80 protein-coding genes, 30 tRNAs, and 4 rRNAs, were annotated in each of the Ficus CP genome. In addition, these CP genomes showed variation in their inverted repeat regions (IR). Tandem repeats and mononucleotide simple sequence repeat (SSR) are widely distributed across the Ficus CP genome. Comparative genome analysis showed low sequence variability. In addition, eight variable regions to be used as potential molecular markers were proposed for future Ficus species identification. According to the phylogenetic analysis, these ten Ficus species were clustered together and further divided into three clades based on different subgenera. Simultaneously, it also showed the relatedness between Ficus and Morus.ConclusionThe chloroplast genome structure of 10 Ficus species was similar to that of other angiosperms, with a typical four-part structure. Chloroplast genome sizes vary slightly due to expansion and contraction of the IR region. And the variation of noncoding regions of the chloroplast genome is larger than that of coding regions. Phylogenetic analysis showed that these eleven sampled CP genomes were divided into three clades, clustered with species from subgenus Urostigma, Sycomorus, and Ficus, respectively. These results support the Berg classification system, in which the subgenus Ficus was further decomposed into the subgenus Sycomorus. In general, the sequencing and analysis of Ficus plastomes, especially the ones of species with no or limited sequences available yet, contribute to the study of genetic diversity and species evolution of Ficus, while providing useful information for taxonomic and phylogenetic studies of Ficus.

A large-scale population based organelle pan-genomes construction and phylogeny analysis reveal the genetic diversity and the evolutionary origins of chloroplast and mitochondrion in Brassica napus L.

BackgroundAllotetraploid oilseed rape (Brassica napus L.) is an important worldwide oil-producing crop. The origin of rapeseed is still undetermined due to the lack of wild resources. Despite certain genetic architecture and phylogenetic studies have been done focus on large group of Brassica nuclear genomes, the organelle genomes information under global pattern is largely unknown, which provide unique material for phylogenetic studies of B. napus. Here, based on de novo assemblies of 1,579 B. napus accessions collected globally, we constructed the chloroplast and mitochondrial pan-genomes of B. napus, and investigated the genetic diversity, phylogenetic relationships of B. napus, B. rapa and B. oleracea.ResultsBased on mitotype-specific markers and mitotype-variant ORFs, four main cytoplasmic haplotypes were identified in our groups corresponding the nap, pol, ole, and cam mitotypes, among which the structure of chloroplast genomes was more conserved without any rearrangement than mitochondrial genomes. A total of 2,092 variants were detected in chloroplast genomes, whereas only 326 in mitochondrial genomes, indicating that chloroplast genomes exhibited a higher level of single-base polymorphism than mitochondrial genomes. Based on whole-genome variants diversity analysis, eleven genetic difference regions among different cytoplasmic haplotypes were identified on chloroplast genomes. The phylogenetic tree incorporating accessions of the B. rapa, B. oleracea, natural and synthetic populations of B. napus revealed multiple origins of B. napus cytoplasm. The cam-type and pol-type were both derived from B. rapa, while the ole-type was originated from B. oleracea. Notably, the nap-type cytoplasm was identified in both the B. rapa population and the synthetic B. napus, suggesting that B. rapa might be the maternal ancestor of nap-type B. napus.ConclusionsThe phylogenetic results provide novel insights into the organelle genomic evolution of Brassica species. The natural rapeseeds contained at least four cytoplastic haplotypes, of which the predominant nap-type might be originated from B. rapa. Besides, the organelle pan-genomes and the overall variation data offered useful resources for analysis of cytoplasmic inheritance related agronomical important traits of rapeseed, which can substantially facilitate the cultivation and improvement of rapeseed varieties.

Complete chloroplast genome sequence and annotation of Actinodaphne lecomtei C.K.Allen, 1938 (Lauraceae)

Actinodaphne lecomtei C.K.Allen, 1938 is an evergreen tree of the Lauraceae family and grows at the mountainous areas of southwestern China. In this study, we presented the first complete chloroplast genome sequence of A. lecomtei. We analyzed the chloroplast genome structure of A. lecomtei and performed a phylogenetic analysis. The complete chloroplast genome of A. lecomtei was 152,863 bp in length which contains a large single-copy (LSC) region of 93,763 bp, a small single-copy (SSC) region of 18,814 bp, and two inverted repeat (IR) regions of 20,143 bp. The analysis identified 128 genes, comprised of 84 protein-coding genes, 36 tRNAs, and eight rRNAs. The GC content of A. lecomtei complete chloroplast genome was 39.1%. The phylogenetic analysis result demonstrated that A. lecomtei was closely related to A. obovate.

Comparative and Phylogenetic Analysis Based on the Chloroplast Genome of Coleanthus subtilis (Tratt.) Seidel, a Protected Rare Species of Monotypic Genus.

Coleanthus subtilis (Tratt.) Seidel (Poaceae) is an ephemeral grass from the monotypic genus Coleanthus Seidl, which grows on wet muddy areas such as fishponds or reservoirs. As a rare species with strict habitat requirements, it is protected at international and national levels. In this study, we sequenced its whole chloroplast genome for the first time using the next-generation sequencing (NGS) technology on the Illumina platform, and performed a comparative and phylogenetic analysis with the related species in Poaceae. The complete chloroplast genome of C. subtilis is 135,915 bp in length, with a quadripartite structure having two 21,529 bp inverted repeat regions (IRs) dividing the entire circular genome into a large single copy region (LSC) of 80,100 bp and a small single copy region (SSC) of 12,757 bp. The overall GC content is 38.3%, while the GC contents in LSC, SSC, and IR regions are 36.3%, 32.4%, and 43.9%, respectively. A total of 129 genes were annotated in the chloroplast genome, including 83 protein-coding genes, 38 tRNA genes, and 8 rRNA genes. The accD gene and the introns of both clpP and rpoC1 genes were missing. In addition, the ycf1, ycf2, ycf15, and ycf68 were pseudogenes. Although the chloroplast genome structure of C. subtilis was found to be conserved and stable in general, 26 SSRs and 13 highly variable loci were detected, these regions have the potential to be developed as important molecular markers for the subfamily Pooideae. Phylogenetic analysis with species in Poaceae indicated that Coleanthus and Phippsia were sister groups, and provided new insights into the relationship between Coleanthus, Zingeria, and Colpodium. This study presents the initial chloroplast genome report of C. subtilis, which provides an essential data reference for further research on its origin.

The chloroplast genome comparative characteristic of artificial breeding tree, a case about Broussonetia kazinoki �Broussonetia papyrifera

Broussonetia kazinoki × Broussonetia papyrifera (ZJGS) is a hybrid species in Moraceae family, which has a very complicated hybrid origin. The excellent characteristics of fast growth, strong soil and water conservation ability, high leaf protein content and stem fiber content in ZJGS make it both ecological benefits in the mining area and economically valuable. This study aims to further understand ZJGS and other Moraceae taxa through the ZJGS chloroplast (cp) genome structure and the comparison with 12 closely related Moraceae species. Among the 13 Moraceae species, the cp genome length of seven Broussonetia species (ranges from 160,239 bp to 162,594 bp) is larger than that of six Morus species (ranges from 158,459 bp to 159,265 bp). Among the 77 shared protein-coding genes (PCGs) in Moraceae species, the obvious positive selection of Ka/Ks ratios acted on petD and rpl16 genes of B. kazinoki and B. papyrifera, respectively. Phylogenetic analysis based on shared PCGs from 28 species shows that ZJGS is closely related to maternal B. kazinoki. These findings provide data support for the origin of ZJGS hybridization and provide genomic resources for future ZJGS resource development and molecular breeding.