Complete Chloroplast Genome Sequence of Corroborates Structural Heterogeneity of Inverted Repeats in Wild Progenitors of Cultivated Bananas and Plantains

Comparative analysis of whole chloroplast genomes of three common species of Nekemias from vine tea

Nekemias grossedentata (N. grossedentata) is a medicinal and edible plant. The young leaves and tender stems are specifically utilized to manufacture vine tea, which is traditionally employed in the treatment of conditions such as the common cold fever, sore throat, jaundice hepatitis, and other ailments. The morphologically of N. grossedentata similar to Nekemias cantoniensis (N. cantoniensis) and Nekemias megalophylla (N. megalophylla), which lead to a chaotic market supply. Numerious studies have confirmed that chloroplast genomes and chromatography play important role in plant classification. Here, the whole chloroplast (cp) genomes of the three Nekemias species were sequenced in Illumina sequencing platform. Meanwhile, their chromatographic fingerprints have constructed using high-performance liquid chromatography (HPLC). The annotation results demonstrated that the three chloroplast genomes were typical quadripartite structures, with lengths of 162,147 bp (N. grossedentata), 161,981 bp (N. megalophylla), and 162,500 bp (N. cantoniensis), respectively. A total of 89 (N. grossedentata) /86 (N. megalophylla and N. cantoniensis) protein-coding genes, 37 tRNA gene and 8 rRNA genes were annotated. The IR/SC boundary regions were relatively conserved across the three species, although three regions (rps19-rpl2, rpl32-trnL-UAG, ccsA-ndhD) exhibited nucleotide diversity values (Pi) of variable sites higher than 1%. Phylogenetic analysis indicated that N. grossedentata had a closer genetic relationship with N. megalophylla than that of N. cantoniensis. Moreover, the chromatographic fingerprints revealed that the main functional components and genetic relatedness of three species were highly similar with their morphological results. In conclusion, N. grossedentata and N. megalophylla can be consider as the origin plants of vine tea. This study provides appropriate information for species identification, phylogeny, quality assessment of three medicinal plants of the genus Nekemias and will contribute to the standardization of vine tea raw materials.

Comparative and phylogenetic analyses of nine complete chloroplast genomes of Orchidaceae

The orchid family has 200,000 species and 700 genera, and it is found worldwide in the tropics and subtropics. In China, there are 1247 species and subspecies of orchids belonging to the Orchidaceae family. Orchidaceae is one of the most diverse plant families in the world, known for their lush look, remarkable ecological tolerance, and capability for reproduction. It has significant decorative and therapeutic value. In terms of evolution, the orchid family is one of the more complicated groups, but up until now, little has been known about its affinities. This study examined the properties of 19 chloroplast (cp) genomes, of which 11 had previously been published and nine had only recently been revealed. Following that, topics such as analysis of selection pressure, codon usage, amino acid frequencies, repeated sequences, and reverse repeat contraction and expansion are covered. The Orchidaceae share similar cp chromosomal characteristics, and we have conducted a preliminary analysis of their evolutionary connections. The cp genome of this family has a typical tepartite structure and a high degree of consistency across species. Platanthera urceolata with more tandem repeats of the cp genome. Similar cp chromosomal traits can be seen in the orchidaceae. Galearis roborowskyi, Neottianthe cucullata, Neottianthe monophylla, Platanthera urceolata and Ponerorchis compacta are the closest cousins, according to phylogenetic study.

The First Complete Chloroplast Genome of Cordia monoica: Structure and Comparative Analysis

Cordia monoica is a member of the Boraginaceae family. This plant is widely distributed in tropical regions and has a great deal of medical value as well as economic importance. In the current study, the complete chloroplast (cp) genome of C. monoica was sequenced, assembled, annotated, and reported. This circular chloroplast genome had a size of 148,711 bp, with a quadripartite structure alternating between a pair of repeated inverted regions (26,897-26,901 bp) and a single copy region (77,893 bp). Among the 134 genes encoded by the cp genome, there were 89 protein-coding genes, 37 transfer RNA (tRNA) genes, and 8 ribosomal RNA (rRNA) genes. A total of 1387 tandem repeats were detected, with the hexanucleotides class making up 28 percent of the repeats. Cordia monoica has 26,303 codons in its protein-coding regions, and leucine amino acid was the most frequently encoded amino acid in contrast to cysteine. In addition, 12 of the 89 protein-coding genes were found to be under positive selection. The phyloplastomic taxonomical clustering of the Boraginaceae species provides further evidence that chloroplast genome data are reliable not only at family level but also in deciphering the phylogeny at genus level (e.g., Cordia).

Characterization of the plastome of Physaliscordata and comparative analysis of eight species of Physalis sensu stricto

In this study, we sequenced, assembled, and annotated the plastome of Physaliscordata Mill. and compared it with seven species of the genus Physalis sensu stricto. Sequencing, annotating, and comparing plastomes allow us to understand the evolutionary mechanisms associated with physiological functions, select possible molecular markers, and identify the types of selection that have acted in different regions of the genome. The plastome of P.cordata is 157,000 bp long and presents the typical quadripartite structure with a large single-copy (LSC) region of 87,267 bp and a small single-copy (SSC) region of 18,501 bp, which are separated by two inverted repeat (IRs) regions of 25,616 bp each. These values are similar to those found in the other species, except for P.angulata L. and P.pruinosa L., which presented an expansion of the LSC region and a contraction of the IR regions. The plastome in all Physalis species studied shows variation in the boundary of the regions with three distinct types, the percentage of the sequence identity between coding and non-coding regions, and the number of repetitive regions and microsatellites. Four genes and 10 intergenic regions show promise as molecular markers and eight genes were under positive selection. The maximum likelihood analysis showed that the plastome is a good source of information for phylogenetic inference in the genus, given the high support values and absence of polytomies. In the Physalis plastomes analyzed here, the differences found, the positive selection of genes, and the phylogenetic relationships do not show trends that correspond to the biological or ecological characteristics of the species studied.

The banana genome hub: a community database for genomics in the Musaceae

The Banana Genome Hub provides centralized access for genome assemblies, annotations, and the extensive related omics resources available for bananas and banana relatives. A series of tools and unique interfaces are implemented to harness the potential of genomics in bananas, leveraging the power of comparative analysis, while recognizing the differences between datasets. Besides effective genomic tools like BLAST and the JBrowse genome browser, additional interfaces enable advanced gene search and gene family analyses including multiple alignments and phylogenies. A synteny viewer enables the comparison of genome structures between chromosome-scale assemblies. Interfaces for differential expression analyses, metabolic pathways and GO enrichment were also added. A catalogue of variants spanning the banana diversity is made available for exploration, filtering, and export to a wide variety of software. Furthermore, we implemented new ways to graphically explore gene presence-absence in pangenomes as well as genome ancestry mosaics for cultivated bananas. Besides, to guide the community in future sequencing efforts, we provide recommendations for nomenclature of locus tags and a curated list of public genomic resources (assemblies, resequencing, high density genotyping) and upcoming resources-planned, ongoing or not yet public. The Banana Genome Hub aims at supporting the banana scientific community for basic, translational, and applied research and can be accessed at https://banana-genome-hub.southgreen.fr.

Comparative plastome analysis of Musaceae and new insights into phylogenetic relationships

Background

Musaceae is an economically important family consisting of 70-80 species. Elucidation of the interspecific relationships of this family is essential for a more efficient conservation and utilization of genetic resources for banana improvement. However, the scarcity of herbarium specimens and quality molecular markers have limited our understanding of the phylogenetic relationships in wild species of Musaceae. Aiming at improving the phylogenetic resolution of Musaceae, we analyzed a comprehensive set of 49 plastomes for 48 species/subspecies representing all three genera of this family.

Results

Musaceae plastomes have a relatively well-conserved genomic size and gene content, with a full length ranging from 166,782 bp to 172,514 bp. Variations in the IR borders were found to show phylogenetic signals to a certain extent in Musa. Codon usage bias analysis showed different preferences for the same codon between species and three genera and a common preference for A/T-ending codons. Among the two genes detected under positive selection (dN/dS > 1), ycf2 was indicated under an intensive positive selection. The divergent hotspot analysis allowed the identification of four regions (ndhF-trnL, ndhF, matK-rps16, and accD) as specific DNA barcodes for Musaceae species.

Bayesian and maximum likelihood phylogenetic analyses using full plastome resulted in nearly identical tree topologies with highly supported relationships between species. The monospecies genus Musella is sister to Ensete, and the genus Musa was divided into two large clades, which corresponded well to the basic number of n = x = 11 and n = x =10/9/7, respectively. Four subclades were divided within the genus Musa. A dating analysis covering the whole Zingiberales indicated that the divergence of Musaceae family originated in the Palaeocene (59.19 Ma), and the genus Musa diverged into two clades in the Eocene (50.70 Ma) and then started to diversify from the late Oligocene (29.92 Ma) to the late Miocene. Two lineages (Rhodochlamys and Australimusa) radiated recently in the Pliocene /Pleistocene periods.

Conclusions

The plastome sequences performed well in resolving the phylogenetic relationships of Musaceae and generated new insights into its evolution. Plastome sequences provided valuable resources for population genetics and phylogenetics at lower taxon.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08454-3.

Comparative Analysis the Complete Chloroplast Genomes of Nine Musa Species: Genomic Features, Comparative Analysis, and Phylogenetic Implications

Musa (family Musaceae) is monocotyledonous plants in order Zingiberales, which grows in tropical and subtropical regions. It is one of the most important tropical fruit trees in the world. Herein, we used next-generation sequencing technology to assemble and perform in-depth analysis of the chloroplast genome of nine new Musa plants for the first time, including genome structure, GC content, repeat structure, codon usage, nucleotide diversity and etc. The entire length of the Musa chloroplast genome ranged from 167,975 to 172,653 bp, including 113 distinct genes comprising 79 protein-coding genes, 30 transfer RNA (tRNA) genes and four ribosomal RNA (rRNA) genes. In comparative analysis, we found that the contraction and expansion of the inverted repeat (IR) regions resulted in the doubling of the rps19 gene. The several non-coding sites (psbI-atpA, atpH-atpI, rpoB-petN, psbM-psbD, ndhf-rpl32, and ndhG-ndhI) and three genes (ycf1, ycf2, and accD) showed significant variation, indicating that they have the potential of molecular markers. Phylogenetic analysis based on the complete chloroplast genome and coding sequences of 77 protein-coding genes confirmed that Musa can be mainly divided into two groups. These genomic sequences provide molecular foundation for the development and utilization of Musa plants resources. This result may contribute to the understanding of the evolution pattern, phylogenetic relationships as well as classification of Musa plants.

Comparative Analysis of the Complete Chloroplast Genomes of Nine Paphiopedilum Species

Paphiopedilum is known as “lady’s or Venus” slipper orchids due to its prominent shoe-shaped labellum, with high ornamental value. Phylogenetic relationships among some species in Paphiopedilum genus cannot be effectively determined by morphological features alone or through the analysis of nuclear or chloroplast DNA fragments. In order to provide aid in understanding the evolutionary and phylogenetic relationship in Paphiopedilum at chloroplast (cp) genome-scale level, the complete cp genomes of six Paphiopedilum species were newly sequenced in this study, and three other published cp genome sequences of Paphiopedilum were included in the comparative analyses. The cp genomes of the six Paphiopedilum species ranged from 154,908 bp (P. hirsutissimum) to 161,300 bp (P. victoria-mariae) in size, all constituting four-part annular structures. Analyses of the nucleotide substitutions, insertions/deletions, and simple sequence repeats in the cp genomes were conducted. Ten highly variable regions that could serve as potential DNA barcodes or phylogenetic markers for this diverse genus were identified. Sequence variations in the non-coding regions were greater than that in the conserved protein-coding regions, as well as in the large single copy (LSC) and small single copy (SSC) regions than in the inverted repeat (IR) regions. Phylogenetic analysis revealed that all Paphiopedilum species clustered in one monophyletic clade in the Cypripedioideae subfamily and then subdivided into seven smaller branches corresponding to different subgenus or sections of the genus, with high bootstrap supports, indicate that cp genome sequencing can be an effective means in resolving the complex relationship in Paphiopedilum.

Comprehensive analysis of chloroplast genome of Albizia julibrissin Durazz. (Leguminosae sp.)

The Albizia julibrissin chloroplasts have a classical chloroplast genome structure, containing 93 coding genes and 34 non-coding genes. Our research provides basic data for plant phylogenetic evolutionary studies. There is limited genomic information available for the important Chinese herb Albizia julibrissin Durazz. In this study, we constructed the chloroplast (Cp) genome of A. julibrissin. The length of the assembled Cp genome was 175,922 bp consisting of four conserved regions: a 5145 bp small single-copy (SSC) region, a 91,323 bp large single-copy (LSC) region, and two identical length-inverted repeat (IR) regions (39,725 bp). This Cp genome included 34 non-coding RNAs and 93 unique genes, the former contains 30 transfer and 4 ribosomal RNA genes. Gene annotation indicated some of the coding genes (82) in the A. julibrissin Cp genome classified in the Leguminosae family, with some to other related families (11). The results show that low GC content (36.9%) and codon bias towards A- or T-terminal codons may affect the frequency of gene codon usage. The sequence analysis identified 30 forward, 18 palindrome, and 1 reverse repeat > 30 bp length, and 149 simple sequence repeats (SSR). Fifty-five RNA editing sites in the Cp of A. julibrissin were predicted, most of which are C-to-U conversions. Analysis of the reverse repeat expansion or contraction and divergence area between several species, including A. julibrissin, was performed. The phylogenetic tree revealed that A. julibrissin was most closely related to Albizia odoratissima and Albizia bracteata, followed by Samanea saman, forming an evolutionary branch with Mimosa pudica and Leucaena trichandra. The research results are helpful for breeding and genetic improvement of A. julibrissin, and also provide valuable information for understanding the evolution of this plant.

Complete Chloroplast Genome Sequence and Comparative and Phylogenetic Analyses of the Cultivated Cyperus esculentus

Cyperus esculentus produces large amounts of oil as one of the main oil storage reserves in underground tubers, making this crop species not only a promising resource for edible oil and biofuel in food and chemical industry, but also a model system for studying oil accumulation in non-seed tissues. In this study, we determined the chloroplast genome sequence of the cultivated C. esculentus (var. sativus Boeckeler). The results showed that the complete chloroplast genome of C. esculentus was 186,255 bp in size, and possessed a typical quadripartite structure containing one large single copy (100,940 bp) region, one small single copy (10,439 bp) region, and a pair of inverted repeat regions of 37,438 bp in size. Sequence analyses indicated that the chloroplast genome encodes 141 genes, including 93 protein-coding genes, 40 transfer RNA genes, and 8 ribosomal RNA genes. We also identified 396 simple-sequence repeats and 49 long repeats, including 15 forward repeats and 34 palindromes within the chloroplast genome of C. esculentus. Most of these repeats were distributed in the noncoding regions. Whole chloroplast genome comparison with those of the other four Cyperus species indicated that both the large single copy and inverted repeat regions were more divergent than the small single copy region, with the highest variation found in the inverted repeat regions. In the phylogenetic trees based on the complete chloroplast genomes of 13 species, all five Cyperus species within the Cyperaceae formed a clade, and C. esculentus was evolutionarily more related to C. rotundus than to the other three Cyperus species. In summary, the chloroplast genome sequence of the cultivated C. esculentus provides a valuable genomic resource for species identification, evolution, and comparative genomic research on this crop species and other Cyperus species in the Cyperaceae family.

Chloroplast genome features of Moricandia arvensis (Brassicaceae), a C3-C4 intermediate photosynthetic species

Moricandia arvensis, a plant species originating from the Mediterranean, has been classified as a rare C3-C4 intermediate species, and it is a possible bridge during the evolutionary process from C3 to C4 plant photosynthesis in the family Brassicaceae. Understanding the genomic structure, gene order, and gene content of chloroplasts (cp) of such species can provide a glimpse into the evolution of photosynthesis. In the present study, we obtained a well-annotated cp genome of M. arvensis using long PacBio and short Illumina reads with a de novo assembly strategy. The M. arvensis cp genome was a quadripartite circular molecule with the length of 153,312 bp, including two inverted repeats (IR) regions of 26,196 bp, divided by a small single copy (SSC) region of 17,786 bp and a large single copy (LSC) region of 83,134 bp. We detected 112 unigenes in this genome, comprising 79 protein-coding genes, 29 tRNAs, and four rRNAs. Forty-nine long repeat sequences and 51 simple sequence repeat (SSR) loci of 15 repeat types were identified. The analysis of Ks (synonymous) and Ka (non-synonymous) substitution rates indicated that the genes associated with “subunits of ATP synthase” (atpB), “subunits of NADH-dehydrogenase” (ndhG and ndhE), and “self-replication” (rps12 and rpl16) showed relatively higher Ka/Ks values than those of the other genes. The gene content, gene order, and LSC/IR/SSC boundaries and adjacent genes of the M. arvensis cp genome were highly conserved compared to those in related C3 species. Our phylogenetic analysis demonstrated that M. arvensis was clustered into a subclade with cultivated Brassica species and Raphanus sativus, indicating that M. arvensis was not involved in an independent evolutionary origin event. These results will open the way for further studies on the evolutionary process from C3 to C4 photosynthesis and hopefully provide guidance for utilizing M. arvensis as a resource for improvinng photosynthesis efficiency in cultivated Brassica species.

Complete chloroplast genome features and phylogenetic analysis of Eruca sativa (Brassicaceae)

Eruca sativa Mill. (Brassicaceae) is an important edible vegetable and a potential medicinal plant due to the antibacterial activity of its seed oil. Here, the complete chloroplast (cp) genome of E. sativa was de novo assembled with a combination of long PacBio reads and short Illumina reads. The E. sativa cp genome had a quadripartite structure that was 153,522 bp in size, consisting of one large single-copy region of 83,320 bp and one small single-copy region of 17,786 bp which were separated by two inverted repeat (IRa and IRb) regions of 26,208 bp. This complete cp genome harbored 113 unique genes: 79 protein-coding genes, 30 tRNA genes, and four rRNA genes. Forty-nine long repetitive sequences and 69 simple sequence repeats were identified in the E. sativa cp genome. A codon usage analysis of the E. sativa cp genome showed a bias toward codons ending in A/T. The E. sativa cp genome was similar in size, gene composition, and linearity of the structural region when compared with other Brassicaceae cp genomes. Moreover, the analysis of the synonymous (Ks) and non-synonymous (Ka) substitution rates demonstrated that protein-coding genes generally underwent purifying selection pressure, expect ycf1, ycf2, and rps12. A phylogenetic analysis determined that E. sativa is evolutionarily close to important Brassica species, indicating that it may be possible to transfer favorable E. sativa alleles into other Brassica species. Our results will be helpful to advance genetic improvement and breeding of E. sativa, and will provide valuable information for utilizing E. sativa as an important resource to improve other Brassica species.

Complete chloroplast genome of a rare and endangered plant species Osteomeles subrotunda: genomic features and phylogenetic relationships with other Rosaceae plants

Osteomeles subrotunda is a rare and endangered plant species with extremely small populations. In our study, we sequenced the complete chloroplast (CP) genome of O. subrotunda and described its structural organization, and performed comparative genomic analyses with other Rosaceae CP genomes. The plastome of O. subrotunda was 159,902 bp in length with 36.6% GC content and contained a pair of inverted repeats of 26,367 bp which separated a large single-copy region of 87,933 bp and a small single-copy region of 19,235 bp. The CP genome included 130 genes, of which 85 were protein-coding genes, 37 were transfer RNAs, and eight were ribosomal RNAs. Two genes, rps19 and ycf1, which are located at the borders of IRB/SSC and IRB/LSC, were presumed to be pseudogenes. A total of 61 SSRs were detected, of which, 59 loci were mono-nucleotide repeats, and two were di-nucleotide repeats. The phylogenic analysis indicated that the 14 Rosaceae species were divided into three groups, among which O. subrotunda grouped with P. rupicola, E. japonica, P. pashia, C. japonica, S. torminalis, and M. florentina, and it was found to be a sister clade to C. japonica. Our newly sequenced CP genome of O. subrotunda will provide essential data for further studies on population genetics and biodiversity.

The complete chloroplast genome sequence of the Canna edulis Ker Gawl. (Cannaceae)

Canna edulis Ker Gawl. is an essential traditional tuber crop used for fresh consumption and to isolate starch in some tropical and semitropical regions. The complete chloroplast genome sequence of C. edulis has been determined in this study. The total genome size is 164,650 bp in length and contains a pair of inverted repeats (IRs) of 27,278 bp, which were separated by large single-copy (LSC) and small single-copy (SSC) of 91,421 bp and 18,673 bp, respectively. A total of 131 genes were predicted including 86 protein-coding genes, 8 rRNA genes and 37 tRNA genes. Further, maximum-likelihood phylogenetic analysis revealed that C. edulis belongs to Cannaceae in Zingiberales. The chloroplast genome of C. edulis is first complete genome sequence in Cannaceae and would play a significant role in the development of molecular markers in plant phylogenetic and population genetic studies.

Comparative analysis of plastid genomes within the Campanulaceae and phylogenetic implications

The conflicts exist between the phylogeny of Campanulaceae based on nuclear ITS sequence and plastid markers, particularly in the subdivision of Cyanantheae (Campanulaceae). Besides, various and complicated plastid genome structures can be found in species of the Campanulaceae. However, limited availability of genomic information largely hinders the studies of molecular evolution and phylogeny of Campanulaceae. We reported the complete plastid genomes of three Cyanantheae species, compared them to eight published Campanulaceae plastomes, and shed light on a deeper understanding of the applicability of plastomes. We found that there were obvious differences among gene order, GC content, gene compositions and IR junctions of LSC/IRa. Almost all protein-coding genes and amino acid sequences showed obvious codon preferences. We identified 14 genes with highly positively selected sites and branch-site model displayed 96 sites under potentially positive selection on the three lineages of phylogenetic tree. Phylogenetic analyses showed that Cyananthus was more closely related to Codonopsis compared with Cyclocodon and also clearly illustrated the relationship among the Cyanantheae species. We also found six coding regions having high nucleotide divergence value. Hotpot regions were considered to be useful molecular markers for resolving phylogenetic relationships and species authentication of Campanulaceae.

Complete chloroplast genome of Castanopsis sclerophylla (Lindl.) Schott: Genome structure and comparative and phylogenetic analysis

Castanopsis sclerophylla (Lindl.) Schott is an important species of evergreen broad-leaved tree in subtropical areas and has high ecological and economic value. However, there are few studies on its chloroplast genome. In this study, the complete chloroplast genome sequence of C. sclerophylla was determined using the Illumina HiSeq 2500 platform. The complete chloroplast genome of C. sclerophylla is 160,497 bp long, including a pair of inverted repeat (IR) regions (25,675 bp) separated by a large single-copy (LSC) region of 90,255 bp and a small single-copy (SSC) region of 18,892 bp. The overall GC content of the chloroplast genome is 36.82%. A total of 131 genes were found; of these, 111 genes are unique and annotated, including 79 protein-coding genes, 27 transfer RNA genes (tRNAs), and four ribosomal RNA genes (rRNAs). Twenty-one genes were found to be duplicated in the IR regions. Comparative analysis indicated that IR contraction might be the reason for the smaller chloroplast genome of C. sclerophylla compared to three congeneric species. Sequence analysis indicated that the LSC and SSC regions are more divergent than IR regions within Castanopsis; furthermore, greater divergence was found in noncoding regions than in coding regions. The maximum likelihood phylogenetic analysis showed that four species of the genus Castanopsis form a monophyletic clade and that C. sclerophylla is closely related to Castanopsis hainanensis with strong bootstrap values. These results not only provide a basic understanding of Castanopsis chloroplast genomes, but also illuminate Castanopsis species evolution within the Fagaceae family. Furthermore, these findings will be valuable for future studies of genetic diversity and enhance our understanding of the phylogenetic evolution of Castanopsis.

Complete Chloroplast Genome Sequence and Phylogenetic Analysis of Quercus acutissima

Quercus acutissima, an important endemic and ecological plant of the Quercus genus, is widely distributed throughout China. However, there have been few studies on its chloroplast genome. In this study, the complete chloroplast (cp) genome of Q. acutissima was sequenced, analyzed, and compared to four species in the Fagaceae family. The size of the Q. acutissima chloroplast genome is 161,124 bp, including one large single copy (LSC) region of 90,423 bp and one small single copy (SSC) region of 19,068 bp, separated by two inverted repeat (IR) regions of 51,632 bp. The GC content of the whole genome is 36.08%, while those of LSC, SSC, and IR are 34.62%, 30.84%, and 42.78%, respectively. The Q. acutissima chloroplast genome encodes 136 genes, including 88 protein-coding genes, four ribosomal RNA genes, and 40 transfer RNA genes. In the repeat structure analysis, 31 forward and 22 inverted long repeats and 65 simple-sequence repeat loci were detected in the Q. acutissima cp genome. The existence of abundant simple-sequence repeat loci in the genome suggests the potential for future population genetic work. The genome comparison revealed that the LSC region is more divergent than the SSC and IR regions, and there is higher divergence in noncoding regions than in coding regions. The phylogenetic relationships of 25 species inferred that members of the Quercus genus do not form a clade and that Q. acutissima is closely related to Q. variabilis. This study identified the unique characteristics of the Q. acutissima cp genome, which will provide a theoretical basis for species identification and biological research.

Complete Chloroplast Genome Sequence and Phylogenetic Analysis of Paeonia ostii

Paeonia ostii, a common oil-tree peony, is important ornamentally and medicinally. However, there are few studies on the chloroplast genome of Paeonia ostii. We sequenced and analyzed the complete chloroplast genome of P. ostii. The size of the P. ostii chloroplast genome is 152,153 bp, including a large single-copy region (85,373 bp), a small single-copy region (17,054 bp), and a pair of inverted repeats regions (24,863 bp). The P. ostii chloroplast genome encodes 111 genes, including 77 protein-coding genes, four ribosomal RNA genes, and 30 transfer RNA genes. The genome contains forward repeats (22), palindromic repeats (28), and tandem repeats (24). The presence of rich simple-sequence repeat loci in the genome provides opportunities for future population genetics work for breeding new varieties. A phylogenetic analysis showed that P. ostii is more closely related to Paeonia delavayi and Paeonialudlowii than to Paeoniaobovata and Paeoniaveitchii. The results of this study provide an assembly of the whole chloroplast genome of P. ostii, which may be useful for future breeding and further biological discoveries. It will provide a theoretical basis for the improvement of peony yield and the determination of phylogenetic status.

The Complete Chloroplast Genomes of Three Cardiocrinum (Liliaceae) Species: Comparative Genomic and Phylogenetic Analyses

The genus Cardiocrinum (Endlicher) Lindley (Liliaceae) comprises three herbaceous perennial species that are distributed in East Asian temperate-deciduous forests. Although all three Cardiocrinum species have horticultural and medical uses, studies related to species identification and molecular phylogenetic analysis of this genus have not been reported. Here, we report the complete chloroplast (cp) sequences of each Cardiocrinum species using Illumina paired-end sequencing technology. The cp genomes of C. giganteum, C. cathayanum, and C. cordatum were found to be 152,653, 152,415, and 152,410 bp in length, respectively, including a pair of inverted repeat (IR) regions (26,364-26,500 bp) separated by a large single-copy (LSC) region (82,186-82,368 bp) and a small single-copy (SSC) region (17,309-17,344 bp). Each cp genome contained the same 112 unique genes consisting of 30 transfer RNA genes, 4 ribosomal RNA genes, and 78 protein-coding genes. Gene content, gene order, AT content, and IR/SC boundary structures were almost the same among the three Cardiocrinum cp genomes, yet their lengths varied due to contraction/expansion of the IR/SC borders. Simple sequence repeat (SSR) analysis further indicated the richest SSRs in these cp genomes to be A/T mononucleotides. A total of 45, 57, and 45 repeats were identified in C. giganteum, C. cathayanum, and C. cordatum, respectively. Six cpDNA markers (rps19, rpoC2-rpoC1, trnS-psbZ, trnM-atpE, psaC-ndhE, ycf15-ycf1) with the percentage of variable sites higher than 0.95% were identified. Phylogenomic analyses of the complete cp genomes and 74 protein-coding genes strongly supported the monophyly of Cardiocrinum and a sister relationship between C. cathayanum and C. cordatum. The availability of these cp genomes provides valuable genetic information for further population genetics and phylogeography studies on Cardiocrinum.