Small Single-copy Region Research Articles

De novo assembly and characterization of the complete chloroplast genome of Elymus magellanicus (É.Desv.) Á.Löve, 1984 (Poaceae, Pooideae)

Elymus magellanicus (É.Desv.) Á.Löve is a foliage accent plant that originated in South America. In this study, the complete chloroplast genome of E. magellanicus is reported. It was found to have a total size of 133,249 bp. The chloroplast genome was found to consist of two inverted repeats (IRA and IRB) of 21,421 bp each, a small single-copy region of 12,709 bp, and a large single-copy region (77,698 bp). The annotation results show the GC content of the chloroplast genome to be 38.47%, including 40 tRNA genes, 82 protein-coding genes, and 8 rRNA genes. Phylogenetic analysis of 29 species revealed that E. magellanicus is closely related to E. arenarius.

The complete chloroplast genome of the endangered species garra de león [Bomarea ovallei (Phil.) Ravenna] from Chile

Bomarea ovallei (Phil.) Ravenna (2n=2x=18) is an endangered endemic species that inhabits only a small part of the coast of the Atacama region. We describe the structure, gene composition and phylogeny of the complete chloroplast sequence of this elusive species. The chloroplast genome consists of 155,018 bp, with typical quadripartite structures: a large single copy region (LSC) of 84,132 bp, a small single copy region (SSC) of 17,794 bp, and two inverted repeat regions (IRs) contain 26,546 bp. One hundred and thirty-four genes were identified out of which 84 coding genes, 8 rRNA, 38 tRNA and 4 pseudogenes. B. ovallei chloroplast resembles chloroplasts from seven species of the order Liliales in length and structure and is most similar to Bomarea edulis (BP=100). The average nucleotide variability (Pi) of 0.00254 between these two Bomarea species is moderate. Nine loci with increased variability were identified: rps16-trnQ, atpF, trnL, ndhC-trnV, rbcL, psbJ, rpl32-trnL, ndhD and ycf1. These loci could be used as DNA markers for classification and evaluation studies in Bomarea populations.

The complete chloroplast genome of Campsis grandiflora (Bignoniaceae)

Campsis grandiflora (Thunb.) K. Schum is an ornamental species with various useful biological effects. The chloroplast genome of C. grandiflora isolated in Korea is 154,293 bp long (GC ratio: 38.1%) and has four subregions: 84,121 bp of large single-copy (36.2%) and 18,521 bp of small single-copy (30.0%) regions are separated by 24,332 bp of inverted repeat (42.9%) regions including 132 genes (87 protein-coding genes, eight rRNAs, and 37 tRNAs). One single-nucleotide polymorphism and five insertion and deletion (INDEL) regions (40-bp in total) were identified, indicating a low level of intraspecific variation in the chloroplast genome. All five INDEL regions were linked to the repetitive sequences. Seventy-two normal simple sequence repeats (SSRs) and 47 extended SSRs were identified to develop molecular markers. The phylogenetic trees of 29 representative Bignoniaceae chloroplast genomes indicate that the tribe-level phylogenic relationship is congruent with the findings of previous studies.

Full-length chloroplast genome of Dongxiang wild rice reveals small single-copy region switching.

BackgroundPlant chloroplast DNA (cpDNA) typically has a circular structure, including a large single-copy region (LSC), a small single-copy region (SSC) and two inverted repeats (IR1 and IR2). The organization of these four elementary regions LSC-IR1-SSC-IR2 is highly conserved across all plant cpDNAs. Very few structural variations (SVs) occurring at the elementary-region level have been reported.ResultsIn the present study, we assembled the full-length cpDNA of Dongxiang wild rice line 159 (DXWR159). Using the long PacBio subreads, we discovered a large inversion of SSC and a large duplication of IR in DXWR159 cpDNAs. Significantly, we reported for the first time forward and reverse SSCs of cpDNAs in similar proportions and named the frequent inversion of a whole SSC as SSC switching.ConclusionsOur study helps researchers to correctly assemble the chloroplast genomes. Our recombination model explained the formation of large SVs in cpDNAs and provided insights into a novel scientific question that if there are common mechanisms in the formation or translocation of all kinds of transposon-like elements (TLEs). We propose that: (1) large inversion is the most accepted mutation type of SVs in cpDNAs; (2) SSC switching ubiquitous occurs in plant cpDNAs; and (3) further investigation of molecular mechanism underlying SSC switching may reveal new driving forces for large SVs.

Does IR-loss promote plastome structural variation and sequence evolution?

Plastids are one of the main distinguishing characteristics of the plant cell. The plastid genome (plastome) of most autotrophic seed plants possesses a highly conserved quadripartite structure containing a large single-copy (LSC) and a small single-copy (SSC) region separated by two copies of the inverted repeat (termed as IRA and IRB). The IRs have been inferred to stabilize the plastid genome via homologous recombination-induced repair mechanisms. IR loss has been documented in seven autotrophic flowering plant lineages and two autotrophic gymnosperm lineages, and the plastomes of these species (with a few exceptions) are rearranged to a great extent. However, some plastomes containing normal IRs also show high structural variation. Therefore, the role of IRs in maintaining plastome stability is still controversial. In this study, we first integrated and compared genome structure and sequence evolution of representative plastomes of all nine reported IR-lacking lineages and those of their closest relative(s) with canonical inverted repeats (CRCIRs for short) to explore the role of the IR in maintaining plastome structural stability and sequence evolution. We found the plastomes of most IR-lacking lineages have experienced significant structural rearrangement, gene loss and duplication, accumulation of novel small repeats, and acceleration of synonymous substitution compared with those of their CRCIRs. However, the IR-lacking plastomes show similar structural variation and sequence evolution rate, and even less rearrangement distance, dispersed repeat number, tandem repeat number, indels frequency and GC3 content than those of IR-present plastomes with variation in Geraniaceae. We argue that IR loss is not a driver of these changes but is instead itself a consequence of other processes that more broadly shape both structural and sequence-level plastome evolution.

Evolutionary Comparison of the Complete Chloroplast Genomes in Convallaria Species and Phylogenetic Study of Asparagaceae.

The genus Convallaria (Asparagaceae) comprises three herbaceous perennial species that are widely distributed in the understory of temperate deciduous forests in the Northern Hemisphere. Although Convallaria species have high medicinal and horticultural values, studies related to the phylogenetic analysis of this genus are few. In the present study, we assembled and reported five complete chloroplast (cp) sequences of three Convallaria species (two of C. keiskei Miq., two of C. majalis L., and one of C. montana Raf.) using Illumina paired-end sequencing data. The cp genomes were highly similar in overall size (161,365–162,972 bp), and all consisted of a pair of inverted repeats (IR) regions (29,140–29,486 bp) separated by a large single-copy (LSC) (85,183–85,521 bp) and a small single-copy (SSC) region (17,877–18,502 bp). Each cp genome contained the same 113 unique genes, including 78 protein-coding genes, 30 transfer RNA genes, and 4 ribosomal RNA genes. Gene content, gene order, AT content and IR/SC boundary structure were nearly identical among all of the Convallaria cp genomes. However, their lengths varied due to contraction/expansion at the IR/LSC borders. Simple sequence repeat (SSR) analyses indicated that the richest SSRs are A/T mononucleotides. Three highly variable regions (petA-psbJ, psbI-trnS and ccsA-ndhD) were identified as valuable molecular markers. Phylogenetic analysis of the family Asparagaceae using 48 cp genome sequences supported the monophyly of Convallaria, which formed a sister clade to the genus Rohdea. Our study provides a robust phylogeny of the Asparagaceae family. The complete cp genome sequences will contribute to further studies in the molecular identification, genetic diversity, and phylogeny of Convallaria.

Complete Chloroplast Genome of Gladiolus gandavensis (Gladiolus) and Genetic Evolutionary Analysis.

Gladiolus is an important ornamental plant that is one of the world’s four most-grown cut flowers. Gladiolus gandavensis has only been found in the Cangnan County (Zhejiang Province) of China, which is recorded in the “Botanical”. To explore the origin of G. gandavensis, chloroplast genome sequencing was conducted. The results indicated that a total of 151,654 bp of circular DNA was obtained. The chloroplast genome of G. gandavensis has a quadripartite structure (contains a large single-copy (LSC) region (81,547 bp), a small single-copy region (SSC) (17,895 bp), and two inverted repeats (IRs) (IRa and IRb, 52,212 bp)), similar to that of other species. In addition, a total of 84 protein-coding genes, 8 rRNA-encoding genes, and 38 tRNA-encoding genes were present in the chloroplast genome. To further study the structural characteristics of the chloroplast genome in G. gandavensis, a comparative analysis of eight species of the Iridaceae family was conducted, and the results revealed higher similarity in the IR regions than in the LSC and SSC regions. In addition, 265 simple sequence repeats (SSRs) were detected in this study. The results of the phylogenetic analysis indicated that the chloroplast genome of G. gandavensis has high homology with the Crocus cartwrightianus and Crocus sativus chloroplast genomes. Genetic analysis based on the rbcl sequence among 49 Gladiolus species showed that samples 42, 49, 50, and 54 had high homology with the three samples from China (64, 65, and 66), which might be caused by chance similarity in genotypes. These results suggest that G. gandavensis may have originated from South Africa.

Characteristics and phylogenetic analysis of the complete chloroplast genome of Rosa glomerata (Rosaceae)

Rosa glomerata is a diffuse shrub belonging to Rosa sect. Synstylae. It is endemic to Southwest China and of high ornamental and economic value. However, its systematic position remains unclear. Here, the complete chloroplast genome of R. glomerata was assembled using high-throughput sequencing data. The cp genome is 157,064 bp in length with a large single-copy region (LSC) of 86,216 bp, a small single-copy region (SSC) of 18,752 bp, and a pair of inverted repeats (IRs) of 26,048 bp. The overall GC content is 37.2%. A total of 137 genes were annotated, including 90 protein-coding genes, 37 tRNA genes, and eight rRNA genes. Phylogenetic analysis revealed that R. glomerata is closely related to R. praelucens of R. sect. Microphyllae rather than species of R. sect. Synstylae.

Characterization and phylogenetic relationship of the complete chloroplast genome of a Chinese traditional medicinal plant Potentilla anserina L

Potentilla anserina L. is an important traditional Chinese medicinal herb and edible plant with a long usage history. As an indispensable sustainable resource, it has various pharmacological functions and active ingredients. Here, we report its complete chloroplast (cp) genome for the first time. The complete chloroplast genome of Potentilla anserina L. (OL678458) was 155,659 bp in length and contained a pair of inverted repeat regions (IRa and IRb, 25,947 bp), a large single-copy region (LSC, 85,052 bp), and a small single-copy region (SSC, 18,713 bp). A total of 118 functional genes were observed in this cp genome, including 80 protein-coding genes, 30 transfer RNA genes, and eight ribosomal RNA genes. Phylogenetic analysis indicated that P. anserina has the closest relationship with Potentilla lineata.

Characterization of the complete chloroplast genome sequence of Isodon japonicus (N. Burman) H. Hara (Lamiaceae)

Isodon japonicus (N. Burman) H. Hara (family: Lamiaceae), is a traditional herbal plant from Henan Province, China. In this study, we sequenced the complete chloroplast genome of I. japonicus sampled from the Funiu Mountains, Henan Province, China. The total length of the chloroplast genome is 152,298 bp, and has a typical quadripartite structure, including a large single-copy region (LSC) of 83,184 bp, a small single-copy region (SSC) of 17,806 bp and a pair of inverted repeats of 25,654 bp. The chloroplast genome of I. japonicus consists of 133 genes, including 88 protein-coding genes, eight rRNA genes, and 37 tRNA genes. There are 34 tandem repeats and 50 simple sequence repeats (SSRs) in the chloroplast genome. The total guanine-cytosine (GC) content of the whole chloroplast genome is 37.6%. Phylogenetic analysis indicated that I. japonicus forms a clade with six other Isodon species and is closely associated with I. rubescens.

Complete chloroplast genome sequences of Acanthocalyx alba and Acanthocalyx nepalensis subsp. delavayi (Caprifoliaceae)

In this study, the chloroplast genomes of Acanthocalyx alba (Hand.-Mazz., 1925) and Acanthocalyx nepalensis subsp. delavayi (Franchet, 1885) were sequenced, and their total lengths were 148,720 bp and 149,253 bp, respectively. The A. alba genome contained two inverted repeat regions (IRs) of 21,849 bp, a large single-copy region (LSC) of 89,084 bp, and a small single-copy region (SSC) of 15,938 bp, whereas A. nepalensis subsp. delavayi contained two IRs of 21,736 bp, one LSC of 89,034 bp, and one SSC of 16,747 bp. The chloroplast genomes of both A. alba and A. nepalensis subsp. delavayi contained 109 genes, including 72 mRNA, 33 tRNA, and four rRNA genes. Phylogenetic analysis suggested that A. alba is in a clade with A. nepalensis subsp. delavayi. This study provides useful data for further phylogenetic studies of A. alba and A. nepalensis subsp. delavayi.

The complete chloroplast genome of Rubus pacificus (Rosaceae)

The complete chloroplast genome of Rubus pacificus, a representative species of R. sect. Malachobatus subsect. Stipulosi, has been characterized by reference-based assembly using Illumina paired-end data. The complete chloroplast genome is 156,255 bp in length, containing a large single-copy region (LSC) of 85,864 bp and a small single-copy region (SSC) of 18,849 bp, which are separated by a pair of inverted repeat regions (IR) of 25,771 bp. A total of 129 genes were predicted from the chloroplast genome, including 85 protein-coding genes, 36 tRNA genes, and eight rRNA genes. According to the present sampling, phylogenetic analysis reveals that R. pacificus and R. laciniatostipulatus form a strongly supported clade and R. sect. Malachobatus subsect. Stipulosi is not monophyletic.

The complete chloroplast genome of Zanthoxylum stenophyllum Hemsl. (Rutaceae), a traditional Chinese medicinal plant

Zanthoxylum stenophyllum Hemsl., a type species for the genus Zanthoxylum (Rutaceae), is a traditional medicinal plant. We studied the complete chloroplast genome of this species using BGISEQ-500 platform. The chloroplast genome was 158,314 bp in size with a GC content of 38.45%. The genome contained two short inverted repeat (IRa and IRb) regions of 27,052 bp, a large single-copy region (LSC, 86,029 bp) and a small single-copy region (SSC, 18,181 bp). The annotated complete chloroplast genome contains 133 distinct genes, including 88 protein-coding genes, 37 transfer RNAs (tRNAs), and 8 ribosomal RNAs (rRNAs). Phylogenetic analysis indicated that Z. stenophyllum is clustered with Z. schiniflium and Z. pinnatum in the same branch with 100% bootstrap support. This complete chloroplast genome provides valuable genomic information for the molecular phylogeny and sustainable utilization of Zanthoxylum.

Characterization of the complete chloroplast genome of Homalocladium platycladum (Polygonaceae) and its phylogenetic analysis

Homalocladium platycladum is a fascinating ornamental plant that has long been used in Chinese medicine. Here, we characterize the complete chloroplast genome sequence of this plant (GenBank: NC_062330). This circular genome has a total length of 163,202 bp containing a large single-copy region (87,820bp), a small single-copy region (13,538bp), and a pair of inverted repeat regions (30,922bp). A total of 130 predicted genes were identified, including 85 protein-coding genes, 37 transfer RNA genes, and 8 ribosomal RNA genes. Phylogenetic analysis demonstrated that H. platycladum belongs to the Polygonaceae family and is highly analogous with Homalocladium and Muehlenbeckia families.

The complete chloroplast genome of Verbascum thapsus L. (Scrophulariaceae) and its phylogenetic affinities

Verbascum thapsus L. has extensive pharmacological effects, including antioxidative and antineoplastic action, memory improvement and neuroprotection. However, its phylogenetic position is not established in Scrophulariaceae. In this study, we reported the complete chloroplast genome sequence of V. thapsus L. for the first time and investigate its phylogenetic relationship in Scrophulariaceae. The assembled chloroplast genome is a circular 153,338 bp sequence, including a large single copy (LSC) region of 84,627 bp, a small single copy (SSC) region of 17,829 bp and a pair of inverted repeats (IRs) of 25,441 bp. The genome contains 135 genes, including 86 protein coding genes, 37 tRNA genes, and eight rRNA genes. The phylogenetic tree showed that V. thapsus is closely associated with V. chinense and V. phoeniceum.

Characterization of the complete chloroplast genome of Zanthoxylum esquirolii Levl. (Rutaceae)

Zanthoxylum esquirolii Léveillé 1914 is mainly distributed in southwest China, and its wild germplasm resources are scarce and in urgent need of conservation. In this study, we report the first complete chloroplast genome sequence of Z. esquirolii using next-generation sequencing. The circular genome is 158,390 bp in length, containing two inverted repeat (IR) regions of 27,622 bp separated by a large single copy (LSC) region of 85,580 bp and a small single copy (SSC) region of 17,566 bp. The chloroplast genome contains a total of 132 genes, including 87 protein-coding genes, 37 tRNA genes, and eight rRNA genes. The overall GC content of the chloroplast genome was 38.46%, with corresponding values in the LSC, SSC, and IR regions of 36.84%, 33.55%, and 42.51%, respectively. The phylogenetic tree revealed that Z. esquirolii Levl. formed a clade with Z. piperitum DC., Z. bungeanum Maxim., Z. simulans Hance and Z. sp. NH-2018, and had a strongly supported sister relationship with Z. bungeanum.

Comparative chloroplast genomes and phylogenetic relationships of Aglaonema modestum and five variegated cultivars of Aglaonema.

Aglaonema, commonly called Chinese evergreens, are widely used for ornamental purposes. However, attempts to identify Aglaonema species and cultivars based on leaf morphology have been challenging. In the present study, chloroplast sequences were used to elucidate the phylogenetic relationships of cultivated Aglaonema in South China. The chloroplast genomes of one green species and five variegated cultivars of Aglaonema, Aglaonema modestum, 'Red Valentine', 'Lady Valentine', 'Hong Yan', 'Hong Jian', and 'Red Vein', were sequenced for comparative and phylogenetic analyses. The six chloroplast genomes of Aglaonema had typical quadripartite structures, comprising a large single copy (LSC) region (91,092-91,769 bp), a small single copy (SSC) region (20,816-26,501 bp), and a pair of inverted repeat (IR) regions (21,703-26,732 bp). The genomes contained 112 different genes, including 79-80 protein coding genes, 28-29 tRNAs and 4 rRNAs. The molecular structure, gene order, content, codon usage, long repeats, and simple sequence repeats (SSRs) were generally conserved among the six sequenced genomes, but the IR-SSC boundary regions were significantly different, and 'Red Vein' had a distinct long repeat number and type frequency. For comparative and phylogenetic analyses, Aglaonema costatum was included; it was obtained from the GenBank database. Single-nucleotide polymorphisms (SNPs) and insertions/deletions (indels) were determined among the seven Aglaonema genomes studied. Nine divergent hotspots were identified: trnH-GUG-CDS1_psbA, trnS-GCU_trnS-CGA-CDS1, rps4-trnT-UGU, trnF-GAA-ndhJ, petD-CDS2-rpoA, ycf1-ndhF, rps15-ycf1-D2, ccsA-ndhD, and trnY-GUA-trnE-UUC. Additionally, positive selection was found for rpl2, rps2, rps3, ycf1 and ycf2 based on the analyses of Ka/Ks ratios among 16 Araceae chloroplast genomes. The phylogenetic tree based on whole chloroplast genomes strongly supported monophyletic Aglaonema and clear relationships among Aroideae, Lasioideae, Lemnoideae, Monsteroideae, Orontioideae, Pothoideae and Zamioculcadoideae in the family Araceae. By contrast, protein coding gene phylogenies were poorly to strongly supported and incongruent with the whole chloroplast genome phylogenetic tree. This study provided valuable genome resources and helped identify Aglaonema species and cultivars.

Characterization of the complete chloroplast genome of the Helleborus atrorubens Waldst. & Kit. (Ranunculaceae)

Helleborus atrorubens is an economically important perennial garden plant with medicinal value. Here, we sequenced the complete chloroplast genome of H. atrorubens. The results revealed the chloroplast genome to be 166,695 bp in length. It possesses a typical quadripartite structure containing one large single copy (LSC) region (84994 bp), one small single copy (SSC) region (17,825 bp), and a pair of inverted repeat (IR) regions (31938 bp). This chloroplast genome encoded 130 genes, out of which 85 code for proteins, 37 for transfer RNAs, and 8 for ribosomal RNAs. Simple sequence repeat (SSR) markers and the top variable coding regions were identified. Our study lays a foundation for further research, such as species differentiation and phylogenetic reconstruction of the Helleborus genus.

The complete chloroplast genome of Miliusa glochidioides (Annonaceae) and phylogenetic analysis

The chloroplast (cp) genome of Miliusa glochidioides has been fully sequenced. The cp genome of this species has a typical quadripartite structure comprised of four parts: a large single copy (LSC; 88,782 bp) region, a small single copy (SSC; 18,949 bp) region, and two inverted repeat (IR; 26,029 bp each) regions. The full length of the cp genome is 159,789 bp; its GC content is 36.7%, and it encodes a total of 129 genes including 84 protein-coding genes, 37 tRNA genes, and 8 rRNA genes. Among the protein-coding genes, nine (rps16, rpl2, rpl16, atpF, rpoC1, petB, petD, ndhA, and ndhB) contain one intron, and three (rps12, clpP, and ycf3) have two introns. A maximum-likelihood (ML) phylogenetic tree shows that M. glochidioides is a sister to Chieniodendron hainanense.

The complete chloroplast genome sequence of Litsea coreana var. lanuginosa (Lauraceae): genome structure and phylogenetic analysis

Litsea coreana var. lanuginose is a perennial, indeciduous, and broad-leaved tree used as an essential medicinal and edible plant. In addition, this species is well-known for its leaves are rich in aromatic oil. In this study, we firstly assembled and characterized the complete chloroplast genome of L. coreana var. lanuginose using Illumina pair-end sequencing and performed a phylogenetic analysis with other 13 species in Lauraceae. The results revealed that its chloroplast genome was 152,859 bp in total length with 39% of GC content, containing a pair of inverted repeats of 20,084 bp (IRA and IRB), separated by a large single-copy (LSC) region of 93,795 bp and a small single-copy (SSC) region of 18,896 bp. The plastid genome of L. coreana var. lanuginose encoded 125 genes, including 81 protein-coding genes, 36 transfer RNA (tRNA), and eight ribosomal RNA (rRNA) genes. The phylogenetic analysis suggested that L. coreana var. lanuginose was closely related to the clade of Litsea monopetala, Litsea garrettii, and Litsea elongate in Lauraceae family.