Complete chloroplast genomes provide insights into evolution and phylogeny of Zingiber (Zingiberaceae)

Subfamily evolution analysis using nuclear and chloroplast data from the same reads

The chloroplast (cp) genome is a widely used tool for exploring plant evolutionary relationships, yet its effectiveness in fully resolving these relationships remains uncertain. Integrating cp genome data with nuclear DNA information offers a more comprehensive view but often requires separate datasets. In response, we employed the same raw read sequencing data to construct cp genome-based trees and nuclear DNA phylogenetic trees using Read2Tree, a cost-efficient method for extracting conserved nuclear gene sequences from raw read data, focusing on the Aurantioideae subfamily, which includes Citrus and its relatives. The resulting nuclear DNA trees were consistent with existing nuclear evolutionary relationships derived from high-throughput sequencing, but diverged from cp genome-based trees. To elucidate the underlying complex evolutionary processes causing these discordances, we implemented an integrative workflow that utilized multiple alignments of each gene generated by Read2Tree, in conjunction with other phylogenomic methods. Our analysis revealed that incomplete lineage sorting predominantly drives these discordances, while introgression and ancient introgression also contribute to topological discrepancies within certain clades. This study underscores the cost-effectiveness of using the same raw sequencing data for both cp and nuclear DNA analyses in understanding plant evolutionary relationships.

Comparative genomics and phylogenetic analysis of six Malvaceae species based on chloroplast genomes

The Malvaceae family, comprising 9 subfamilies and 4,225 species, includes economically significant taxa, such as Ceiba pentandra, Gossypium ekmanianum, Gossypium stephensii, Kokia drynarioides, Talipariti hamabo, and Durio zibethinus. Chloroplast (cp) genome research is crucial for elucidating the evolutionary divergence and species identification within this family. In this study, we assembled and annotated cp genomes of six Malvaceae species, conducting comprehensive comparative genomic and phylogenomic analyses. The assembled genomes range from 160,495 to 163,970 bp in size, with 125-129 genes annotated. Notable differences were observed in the IR (inverted repeat) regions, and SSR analysis revealed that Durio zibethinus has the highest number of specific variation sites. Among the six species, Talipariti hamabo uniquely exhibits more palindromic repeats than forward repeats. Seven highly mutated regions were identified, offering potential markers for species identification. Phylogenetic reconstruction using the maximum likelihood method revealed two primary clades within Malvaceae: Byttneriina and Malvadendrina. Within Malvadendrina, the subfamily Helicteroideae represents the earliest divergence, followed by Sterculioideae. This study provides a robust phylogenetic framework and valuable insights into the classification and evolutionary history of Malvaceae species.

Complete chloroplast genome data reveal the existence of the Solidago canadensis L. complex and its potential introduction pathways into China

Solidago canadensis, native to North America, is an invasive species in many areas of the world, where it causes serious damage to natural ecosystems and economic losses. However, a dearth of genetic resources and molecular markers has hampered our understanding of its invasion history. Here, we de novo assembled 40 complete chloroplast genomes of Solidago species, including 21 S. canadensis individuals, 15 S. altissima individuals, and four S. decurrens individuals, the sizes of which ranged from 152,412 bp to 153,170 bp. The phylogenetic trees based on the complete chloroplast genome sequences and nuclear genome-wide SNP data showed that S. canadensis and S. altissima cluster together and form a monophyletic pair, as sister to S. decurrens, indicating the existence of the S. canadensis L. complex in China. Three potential introduction pathways were identified. The chloroplast-genome structure and gene contents are conservative in the genomes of the S. canadensis L. complex and S. decurrens. The analysis of sequence divergence indicated five variable regions, and 10 chloroplast protein-coding genes that underwent positive selection were identified. Our findings shed new light on the invasion history of S. canadensis and the data sets generated in this study will facilitate future research on its chloroplast genome evolution.

Comparative Chloroplast Genome Study of Zingiber in China Sheds Light on Plastome Characterization and Phylogenetic Relationships

BACKGROUND

Zingiber Mill., a morphologically diverse herbaceous perennial genus of Zingiberaceae, is distributed mainly in tropical to warm-temperate Asia. In China, species of Zingiber have crucial medicinal, edible, and horticultural values; however, their phylogenetic relationships remain unclear.

METHODS

To address this issue, the complete plastomes of the 29 Zingiber accessions were assembled and characterized. Comparative plastome analysis and phylogenetic analysis were conducted to develop genomic resources and elucidate the intraspecific phylogeny of Zingiber.

RESULTS

The newly reported plastomes ranged from 161,495 to 163,880 bp in length with highly conserved structure. Results of comparative analysis suggested that IR expansions/contractions and changes of repeats were the main reasons that influenced the genome size of the Zingiber plastome. A large number of SSRs and six highly variable regions (rpl20, clpP, ycf1, petA-psbJ, rbcL-accD, and rpl32-trnL) have been identified, which could serve as potential DNA markers for future population genetics or phylogeographic studies on this genus. The well-resolved plastome phylogeny suggested that Zingiber could be divided into three clades, corresponding to sect. Pleuranthesis (sect. Zingiber + sect. Dymczewiczia) and sect. Cryptanthium.

CONCLUSIONS

Overall, this study provided a robust phylogeny of Zingiber plants in China, and the newly reported plastome data and plastome-derived markers will be of great significance for the accurate identification, protection, and agricultural management of Zingiber resources in the future.

Kazakhstan tulips: comparative analysis of complete chloroplast genomes of four local and endangered species of the genus Tulipa L

Species of Tulipa are important ornamental plants used for horticultural purposes in various countries, across Asia, Europe, and North Africa. The present study is the first report on typical features of the complete chloroplast genome sequence of four local and endangered species including T. alberti, T. kaufmanniana, T. greigii, and T. dubia from Kazakhstan using Illumina sequencing technology. The comparative analyses revealed that the complete genomes of four species were highly conserved in terms of total genome size (152. 006 bp - 152. 382 bp), including a pair of inverted repeat regions (26. 330 bp - 26. 371 bp), separated by a large single copy region (82.169 bp - 82,378 bp) and a small copy region (17.172 bp -17.260 bp). Total GC content (36.58-36.62 %), gene number (131), and intron length (540 bp - 2620 bp) of 28 genes. The complete genomes of four species showed nucleotide diversity (π =0,003257). The total number of SSR loci was 159 in T. alberti, 158 in T. kaufmanniana, 174 in T. greigii, and 163 in T. dubia. The result indicated that ten CDS genes, namely rpoC2, cemA, rbcL, rpl36, psbH, rps3, rpl22, ndhF, ycf1, and matK, with effective polymorphic simple sequence repeats (SSRs), high sequence variability (SV) ranging from 2.581 to 6.102, and high nucleotide diversity (Pi) of these loci ranging from 0,004 to 0,010. For all intergenic regions longer than 150 bp, twenty one most variable regions were found with high sequence variability (SV) ranging from 4,848 to 11,862 and high nucleotide diversity (Pi) ranging from 0,01599 to 0,01839. Relative synonymous codon usage (RSCU) analysis was used to identify overrepresented and underrepresented codons for each amino acid. Based on the phylogenic analysis, the sequences clustered into four major groups, reflecting distinct evolutionary lineages corresponding to the subgenera Eriostemons, Tulipa, and Orithyia. Notably, T. greigii was distinctively grouped with species from Orithyia and Eriostemons rather than with other Tulipa species, suggesting a unique evolutionary history potentially shaped by geographical isolation or specific ecological pressures. The complete chloroplast genome of the four Tulipa species provides fundamental information for future research studies, even for designing the high number of available molecular markers.

Chloroplast genome sequencing and divergence analysis of 18 Pyrus species: insights into intron length polymorphisms and evolutionary processes

Pears constitute an essential temperate crop and are primarily produced through interspecific hybridization owing to self-incompatibility that complicates their breeding history. To address this, we sequenced the complete chloroplast (cp) genomes of 18 Pyrus and one Malus species using the Illumina HiSeq4000 platform. The cp genomes ranged from 159,885 bp to 160,153 bp and exhibited a conserved circular DNA structure with an average GC content of 36.5%. Each cp genome contained 127 genes, including 83 protein-coding, 36 tRNA, and 8 rRNA genes. Divergence analysis with mVISTA showed high conservation in the coding regions and notable variations in the non-coding regions. All species shared 17 intron-containing genes, with ycf3 and clpP each having two introns. Five intron-containing genes (ndhB, rpl2, rps12, trnA-UGC, and trnE-UUC) were located in the inverted repeat regions, while trnL-UAA was located in the large single-copy region, with conserved intron lengths across Pomoideae. We identified polymorphic intron sequences in the rpl22, petB, clpP, ndhA, and rps16 genes and designed primers for these regions. Notably, the two Pyrus ussuriensis accessions Doonggeullebae and Cheongdangrori showed intron-length polymorphisms despite being classified as the same species. Phylogenetic analysis of the cp genome sequences revealed two major clusters, indicating distinct maternal lineages and evolutionary origins. This study underscores the importance of cp gene polymorphisms in P. fauriei, P. calleryana, P. ussuriensis, and P. pyrifolia, providing valuable insights into Pyrus evolution as well as aiding in the conservation and breeding of pear germplasm.

Comparative analysis of the complete chloroplast genomes of thirteen Bougainvillea cultivars from South China with implications for their genome structures and phylogenetic relationships

Bougainvillea spp., belonging to the Nyctaginaceae family, have high economic and horticultural value in South China. Despite the high similarity in terms of leaf appearance and hybridization among Bougainvillea species, especially Bougainvillea × buttiana, their phylogenetic relationships are very complicated and controversial. In this study, we sequenced, assembled and analyzed thirteen complete chloroplast genomes of Bougainvillea cultivars from South China, including ten B. × buttiana cultivars and three other Bougainvillea cultivars, and identified their phylogenetic relationships within the Bougainvillea genus and other species of the Nyctaginaceae family for the first time. These 13 chloroplast genomes had typical quadripartite structures, comprising a large single-copy (LSC) region (85,169-85,695 bp), a small single-copy (SSC) region (18,050-21,789 bp), and a pair of inverted-repeat (IR) regions (25,377-25,426 bp). These genomes each contained 112 different genes, including 79 protein-coding genes, 29 tRNAs and 4 rRNAs. The gene content, codon usage, simple sequence repeats (SSRs), and long repeats were essentially conserved among these 13 genomes. Single-nucleotide polymorphisms (SNPs) and insertions/deletions (indels) were detected among these 13 genomes. Four divergent regions, namely, trnH-GUG_psbA, trnS-GCU_trnG-UCC-exon1, trnS-GGA_rps4, and ccsA_ndhD, were identified from the comparative analysis of 16 Bougainvillea cultivar genomes. Among the 46 chloroplast genomes of the Nyctaginaceae family, nine genes, namely, rps12, rbcL, ndhF, rpoB, rpoC2, ndhI, psbT, ycf2, and ycf3, were found to be under positive selection at the amino acid site level. Phylogenetic relationships within the Bougainvillea genus and other species of the Nyctaginaceae family based on complete chloroplast genomes and protein-coding genes revealed that the Bougainvillea genus was a sister to the Belemia genus with strong support and that 35 Bougainvillea individuals were divided into 4 strongly supported clades, namely, Clades Ⅰ, Ⅱ, Ⅲ and Ⅳ. Clade Ⅰ included 6 individuals, which contained 2 cultivars, namely, B. × buttiana 'Gautama's Red' and B. spectabilis 'Flame'. Clades Ⅱ only contained Bougainvillea spinosa. Clade Ⅲ comprised 7 individuals of wild species. Clade Ⅳ included 21 individuals and contained 11 cultivars, namely, B. × buttiana 'Mahara', B. × buttiana 'California Gold', B. × buttiana 'Double Salmon', B. × buttiana 'Double Yellow', B. × buttiana 'Los Banos Beauty', B. × buttiana 'Big Chitra', B. × buttiana 'San Diego Red', B. × buttiana 'Barbara Karst', B. glabra 'White Stripe', B. spectabilis 'Splendens' and B. × buttiana 'Miss Manila' sp. 1. In conclusion, this study not only provided valuable genome resources but also helped to identify Bougainvillea cultivars and understand the chloroplast genome evolution of the Nyctaginaceae family.

Analysis of chloroplast genome structure and phylogeny of the traditional medicinal of Ardisia crispa (Myrsinaceae)

Ardisia crispa(Myrsinaceae) is an ethnomedicine with horticultural and important medicinal values. Its morphology is complex, and its identification is difficult. We analyse the chloroplast genome characteristics and phylogenetic position of A. crispa to provide basic research data for the identification of A. crispa species and resource conservation. This study assemble and annotate the chloroplast genome of A. crispa and to compare it with the chloroplast genome within Ardisia. The A. crispa chloroplast genome is 156,785 bp in length, with a typical quadripartite structure containing 131 genes, including 86 protein-coding genes, 37 tRNA genes, and 8 rRNA genes; a total of 59 SSRs sites were identified, and the codon preference of this chloroplast genome is greater in A/U than in G/C, and leucine is the amino acid with the highest frequency of use. The chloroplast genomes of the nine Ardisia species are conserved in gene content and number, with more stable boundaries and less variation. In the phylogenetic tree, A. crispa is clustered on a branch with A. crispa var dielsii, and is closely related to A. mamillata and A. pedalis. In this study, we constructed and analyzed the chloroplast genome structure of A. crispa, and conducted phylogenetic analysis using the whole chloroplast genome sequence data of Ardisia plants, which is of great significance in understanding the genetic basis of A. crispa and adaptive evolution in Ardisia plants, and this will lay the foundation for the future research on A. crispa resource conservation and species identification.

Phylogenomic analysis and dynamic evolution of chloroplast genomes of Clematis nannophylla

Clematis nannophylla is a perennial shrub of Clematis with ecological, ornamental, and medicinal value, distributed in the arid and semi-arid areas of northwest China. This study successfully determined the chloroplast (cp) genome of C. nannophylla, reconstructing a phylogenetic tree of Clematis. This cp genome is 159,801 bp in length and has a typical tetrad structure, including a large single-copy, a small single-copy, and a pair of reverse repeats (IRa and IRb). It contains 133 unique genes, including 89 protein-coding, 36 tRNA, and 8 rRNA genes. Additionally, 66 simple repeat sequences, 50 dispersed repeats, and 24 tandem repeats were found; many of the dispersed and tandem repeats were between 20-30 bp and 10-20 bp, respectively, and the abundant repeats were located in the large single copy region. The cp genome was relatively conserved, especially in the IR region, where no inversion or rearrangement was observed, further revealing that the coding regions were more conserved than the noncoding regions. Phylogenetic analysis showed that C. nannophylla is more closely related to C. fruticosa and C. songorica. Our analysis provides reference data for molecular marker development, phylogenetic analysis, population studies, and cp genome processes to better utilise C. nannophylla.

The pan-plastome of Prunus mume: insights into Prunus diversity, phylogeny, and domestication history

Backgrounds

Prunus mume in the Rosaceae and commonly referred to as mei or Chinese plum is widely used as a traditional ornamental flowering plant and fruit tree in China. Although some population and genetic analyses have been conducted for this species, no extensive comparisons of genetic variation from plastomes have yet been investigated.

Methods

We de novo assembled a total of 322 complete P. mume plastomes in this study and did a series of comparative analyses to better resolve pan-plastomic patterns of P. mume. To determine the phylogeny and domestication history of this species, we reconstructed the phylogenetic tree of Prunus genus, and resolved the population structure of P. mume. We also examined the nucleotide variation of P. mume to find potential DNA barcodes.

Results

The assembled plastomes exhibited a typical quadripartite structure and ranged from 157,871 bp to 158,213 bp in total size with a GC content ranging from 36.73 to 36.75%. A total of 112 unique genes were identified. Single nucleotide variants (SNVs) were the most common variants found among the plastomes, followed by nucleotide insertions/deletions (InDels), and block substitutions with the intergenic spacer (IGS) regions containing the greatest number of variants. From the pan-plastome data six well-supported genetic clusters were resolved using multiple different population structure analyses. The different cultivars were unevenly distributed among multiple clades. We also reconstructed a phylogeny for multiple species of Prunus to better understand genus level diversity and history from which a complex introgressive relationship between mei and other apricots/plums was resolved.

Conclusion

This study constructed the pan-plastome of P. mume, which indicated the domestication of P. mume involved multiple genetic origins and possible matrilineal introgression from other species. The phylogenetic analysis in Prunus and the population structure of P. mume provide an important maternal history for Prunus and the groundwork for future studies on intergenomic sequence transfers, cytonuclear incompatibility, and conservation genetics.

Characterization and phylogenetic analysis of the complete chloroplast genome of Curcuma comosa and C. latifolia

Members of the Curcuma genus, a crop in the Zingiberaceae, are widely utilized rhizomatous herbs globally. There are two distinct species, C. comosa Roxb. and C. latifolia Roscoe, referred to the same vernacular name "Wan Chak Motluk" in Thai. C. comosa holds economic importance and is extensively used as a Thai traditional medicine due to its phytoestrogenic properties. However, its morphology closely resembles that of C. latifolia, which contains zederone, a compound known for its hepatotoxic effects. They are often confused, which may affect the quality, efficacy and safety of the derived herbal materials. Thus, DNA markers were developed for discriminating C. comosa from C. latifolia. This study focused on analyzing core DNA barcode regions, including rbcL, matK, psbA-trnH spacer and ITS2, of the authentic C. comosa and C. latifolia species. As a result, no variable nucleotides in core DNA barcode regions were observed. The complete chloroplast (cp) genome was introduced to differentiate between the two species. The comparison revealed that the cp genomes of C. comosa and C. latifolia were 162,272 and 162,289 bp, respectively, with a total of 133 identified genes. The phylogenetic analysis revealed that C. comosa and C. latifolia exhibited a very close relationship with other Curcuma species. The cp genome of C. comosa and C. latifolia were identified for the first time, providing valuable insights for species identification and evolutionary research within the Zingiberaceae family.

Comparative chloroplast genomics, phylogenetic relationships and molecular markers development of Aglaonema commutatum and seven green cultivars of Aglaonema

Aglaonema commutatum is a famous species in the Aglaonema genus, which has important ornamental and economic value. However, its chloroplast genome information and phylogenetic relationships among popular green cultivars of Aglaonema in southern China have not been reported. Herein, chloroplast genomes of one variety of A. commutatum and seven green cultivars of Aglaonema, namely, A. commutatum 'San Remo', 'Kai Sa', 'Pattaya Beauty', 'Sapphire', 'Silver Queen', 'Snow White', 'White Gem', and 'White Horse Prince', were sequenced and assembled for comparative analysis and phylogeny. These eight genomes possessed a typical quadripartite structure that consisted of a LSC region (90,799-91,486 bp), an SSC region (20,508-21,137 bp) and a pair of IR regions (26,661-26,750 bp). Each genome contained 112 different genes, comprising 79 protein-coding genes, 29 tRNA genes and 4 rRNA genes. The gene orders, GC contents, codon usage frequency, and IR/SC boundaries were highly conserved among these eight genomes. Long repeats, SSRs, SNPs and indels were analyzed among these eight genomes. Comparative analysis of 15 Aglaonema chloroplast genomes identified 7 highly variable regions, including trnH-GUG-exon1-psbA, trnS-GCU-trnG-UCC-exon1, trnY-GUA-trnE-UUC, psbC-trnS-UGA, trnF-GAA-ndhJ, ccsA-ndhD, and rps15-ycf1-D2. Reconstruction of the phylogenetic trees based on chloroplast genomes, strongly supported that Aglaonema was a sister to Anchomanes, and that the Aglaonema genus was classified into two sister clades including clade I and clade II, which corresponded to two sections, Aglaonema and Chamaecaulon, respectively. One variety and five cultivars, including A. commutatum 'San Remo', 'Kai Sa', 'Pattaya Beauty', 'Silver Queen', 'Snow White', and 'White Horse Prince', were classified into clade I; and the rest of the two cultivars, including 'Sapphire' and 'White Gem', were classified into clade II. Positive selection was observed in 34 protein-coding genes at the level of the amino acid sites among 77 chloroplast genomes of the Araceae family. Based on the highly variable regions and SSRs, 4 DNA markers were developed to differentiate the clade I and clade II in Aglaonema. In conclusion, this study provided chloroplast genomic resources for Aglaonema, which were useful for its classification and phylogeny.

The Phylogeography of Deciduous Tree Ulmus macrocarpa (Ulmaceae) in Northern China

Disentangling how climate oscillations and geographical events significantly influence plants' genetic architecture and demographic history is a central topic in phytogeography. The deciduous ancient tree species Ulmus macrocarpa is primarily distributed throughout Northern China and has timber and horticultural value. In the current study, we studied the phylogenic architecture and demographical history of U. macrocarpa using chloroplast DNA with ecological niche modeling. The results indicated that the populations' genetic differentiation coefficient (NST) value was significantly greater than the haplotype frequency (GST) (p < 0.05), suggesting that U. macrocarpa had a clear phylogeographical structure. Phylogenetic inference showed that the putative chloroplast haplotypes could be divided into three groups, in which the group Ⅰ was considered to be ancestral. Despite significant genetic differentiation among these groups, gene flow was detected. The common ancestor of all haplotypes was inferred to originate in the middle-late Miocene, followed by the haplotype overwhelming diversification that occurred in the Quaternary. Combined with demography pattern and ecological niche modeling, we speculated that the surrounding areas of Shanxi and Inner Mongolia were potential refugia for U. macrocarpa during the glacial period in Northern China. Our results illuminated the demography pattern of U. macrocarpa and provided clues and references for further population genetics investigations of precious tree species distributed in Northern China.

Phylogenetic relationships, selective pressure and molecular markers development of six species in subfamily Polygonoideae based on complete chloroplast genomes

The subfamily Polygonoideae encompasses a diverse array of medicinal and horticultural plants that hold significant economic value. However, due to the lack of a robust taxonomy based on phylogenetic relationships, the classification within this family is perplexing, and there is also a scarcity of reports on the chloroplast genomes of many plants falling under this classification. In this study, we conducted a comprehensive analysis by sequencing and characterizing the complete chloroplast genomes of six Polygonoideae plants, namely Pteroxygonum denticulatum, Pleuropterus multiflorus, Pleuropterus ciliinervis, Fallopia aubertii, Fallopia dentatoalata, and Fallopia convolvulus. Our findings revealed that these six plants possess chloroplast genomes with a typical quadripartite structure, averaging 162,931 bp in length. Comparative chloroplast analysis, codon usage analysis, and repetitive sequence analysis demonstrated a high level of conservation within the chloroplast genomes of these plants. Furthermore, phylogenetic analysis unveiled a distinct clade occupied by P. denticulatum, while P. ciliinrvis displayed a closer relationship to the three plants belonging to the Fallopia genus. Selective pressure analysis based on maximum likelihood trees showed that a total of 14 protein-coding genes exhibited positive selection, with psbB and ycf1 having the highest number of positive amino acid sites. Additionally, we identified four molecular markers, namely petN-psbM, psal-ycf4, ycf3-trnS-GGA, and trnL-UAG-ccsA, which exhibit high variability and can be utilized for the identification of these six plants.

Thirteen complete chloroplast genomes of the costaceae family: insights into genome structure, selective pressure and phylogenetic relationships

BACKGROUND

Costaceae, commonly known as the spiral ginger family, consists of approximately 120 species distributed in the tropical regions of South America, Africa, and Southeast Asia, of which some species have important ornamental, medicinal and ecological values. Previous studies on the phylogenetic and taxonomic of Costaceae by using nuclear internal transcribed spacer (ITS) and chloroplast genome fragments data had low resolutions. Additionally, the structures, variations and molecular evolution of complete chloroplast genomes in Costaceae still remain unclear. Herein, a total of 13 complete chloroplast genomes of Costaceae including 8 newly sequenced and 5 from the NCBI GenBank database, representing all three distribution regions of this family, were comprehensively analyzed for comparative genomics and phylogenetic relationships.

RESULT

The 13 complete chloroplast genomes of Costaceae possessed typical quadripartite structures with lengths from 166,360 to 168,966 bp, comprising a large single copy (LSC, 90,802 - 92,189 bp), a small single copy (SSC, 18,363 - 20,124 bp) and a pair of inverted repeats (IRs, 27,982 - 29,203 bp). These genomes coded 111 - 113 different genes, including 79 protein-coding genes, 4 rRNA genes and 28 - 30 tRNAs genes. The gene orders, gene contents, amino acid frequencies and codon usage within Costaceae were highly conservative, but several variations in intron loss, long repeats, simple sequence repeats (SSRs) and gene expansion on the IR/SC boundaries were also found among these 13 genomes. Comparative genomics within Costaceae identified five highly divergent regions including ndhF, ycf1-D2, ccsA-ndhD, rps15-ycf1-D2 and rpl16-exon2-rpl16-exon1. Five combined DNA regions (ycf1-D2 + ndhF, ccsA-ndhD + rps15-ycf1-D2, rps15-ycf1-D2 + rpl16-exon2-rpl16-exon1, ccsA-ndhD + rpl16-exon2-rpl16-exon1, and ccsA-ndhD + rps15-ycf1-D2 + rpl16-exon2-rpl16-exon1) could be used as potential markers for future phylogenetic analyses and species identification in Costaceae. Positive selection was found in eight protein-coding genes, including cemA, clpP, ndhA, ndhF, petB, psbD, rps12 and ycf1. Maximum likelihood and Bayesian phylogenetic trees using chloroplast genome sequences consistently revealed identical tree topologies with high supports between species of Costaceae. Three clades were divided within Costaceae, including the Asian clade, Costus clade and South American clade. Tapeinochilos was a sister of Hellenia, and Parahellenia was a sister to the cluster of Tapeinochilos + Hellenia with strong support in the Asian clade. The results of molecular dating showed that the crown age of Costaceae was about 30.5 Mya (95% HPD: 14.9 - 49.3 Mya), and then started to diverge into the Costus clade and Asian clade around 23.8 Mya (95% HPD: 10.1 - 41.5 Mya). The Asian clade diverged into Hellenia and Parahellenia at approximately 10.7 Mya (95% HPD: 3.5 - 25.1 Mya).

CONCLUSION

The complete chloroplast genomes can resolve the phylogenetic relationships of Costaceae and provide new insights into genome structures, variations and evolution. The identified DNA divergent regions would be useful for species identification and phylogenetic inference in Costaceae.

Chloroplast Genome Comparison and Phylogenetic Analysis of the Commercial Variety Actinidia chinensis 'Hongyang'

Actinidia chinensis 'Hongyang', also known as red yangtao (red heart kiwifruit), is a vine fruit tree native to China possessing significant nutritional and economic value. However, information on its genetic diversity and phylogeny is still very limited. The first chloroplast (cp) genome of A. chinensis 'Hongyang' cultivated in China was sequenced using de novo technology in this study. A. chinensis 'Hongyang' possesses a cp genome that spans 156,267 base pairs (bp), exhibiting an overall GC content of 37.20%. There were 132 genes that were annotated, with 85 of them being protein-coding genes, 39 transfer RNA (tRNA) genes, and 8 ribosomal RNA (rRNA) genes. A total of 49 microsatellite sequences (SSRs) were detected, mainly single nucleotide repeats, mostly consisting of A or T base repeats. Compared with 14 other species, the cp genomes of A. chinensis 'Hongyang' were biased towards the use of codons containing A/U, and the non-protein coding regions in the A. chinensis 'Hongyang' cpDNA showed greater variation than the coding regions. The nucleotide polymorphism analysis (Pi) yielded nine highly variable region hotspots, most in the large single copy (LSC) region. The cp genome boundary analysis revealed a conservative order of gene arrangement in the inverted repeats (IRs) region of the cp genomes of 15 Actinidia plants, with small expansions and contractions of the boundaries. Furthermore, phylogenetic tree indicated that A. chinensis 'Hongyang' was the closest relative to A. indochinensis. This research provides a useful basis for future genetic and evolutionary studies of A. chinensis 'Hongyang', and enriches the biological information of Actinidia species.

Complete chloroplast genome of Lens lamottei reveals intraspecies variation among with Lens culinaris

Lens lamottei is a member of the Fabaceae family and the second gene pool of the genus Lens. The environmental factors that drove the divergence among wild and cultivated species have been studied extensively. Recent research has focused on genomic signatures associated with various phenotypes with the acceleration of next-generation techniques in molecular profiling. Therefore, in this study, we provide the complete sequence of the chloroplast genome sequence in the wild Lens species L. lamottei with a deep coverage of 713 × next-generation sequencing (NGS) data for the first time. Compared to the cultivated species, Lens culinaris, we identified synonymous, and nonsynonymous changes in the protein-coding regions of the genes ndhB, ndhF, ndhH, petA, rpoA, rpoC2, rps3, and ycf2 in L. lamottei. Phylogenetic analysis of chloroplast genomes of various plants under Leguminosae revealed that L. lamottei and L. culinaris are closest to one another than to other species. The complete chloroplast genome of L. lamottei also allowed us to reanalyze previously published transcriptomic data, which showed high levels of gene expression for ATP-synthase, rubisco, and photosystem genes. Overall, this study provides a deeper insight into the diversity of Lens species and the agricultural importance of these plants through their chloroplast genomes.

The complete chloroplast genome sequence of Zingiber teres S. Q. Tong & Y. M. Xia (Zingiberaceae)

Here, the complete chloroplast genome sequence of Zingiber teres is described using MGI paired-end sequencing. The genome is 163,428 bp in length and contains a small single-copy region (SSC) of 15,782 bp, a large single-copy region (LSC) of 88,142 bp, and two inverted repeat (IR) regions of 29,752 bp. The overall GC content is 36.1%, and the GC content of the IR regions is 41.1%, which is higher than that of both the LSC region (33.8%) and SSC region (29.5%). The genome of Z. teres contains 133 complete genes, including 88 protein-coding genes (79 protein-coding gene species), 38 tRNA genes (28 tRNA species), and 8 rRNA genes (four rRNA species). Maximum likelihood phylogenetic analysis yielded a well-resolved tree of the genus Zingiber, and Z. teres and Zingiber mioga were sister species in this tree. The development of DNA barcodes could aid the identification of Zingiber species.

Chloroplast Pan-Genomes and Comparative Transcriptomics Reveal Genetic Variation and Temperature Adaptation in the Cucumber

Although whole genome sequencing, genetic variation mapping, and pan-genome studies have been done on a large group of cucumber nuclear genomes, organelle genome information is largely unclear. As an important component of the organelle genome, the chloroplast genome is highly conserved, which makes it a useful tool for studying plant phylogeny, crop domestication, and species adaptation. Here, we have constructed the first cucumber chloroplast pan-genome based on 121 cucumber germplasms, and investigated the genetic variations of the cucumber chloroplast genome through comparative genomic, phylogenetic, haplotype, and population genetic structure analysis. Meanwhile, we explored the changes in expression of cucumber chloroplast genes under high- and low-temperature stimulation via transcriptome analysis. As a result, a total of 50 complete chloroplast genomes were successfully assembled from 121 cucumber resequencing data, ranging in size from 156,616-157,641 bp. The 50 cucumber chloroplast genomes have typical quadripartite structures, consisting of a large single copy (LSC, 86,339-86,883 bp), a small single copy (SSC, 18,069-18,363 bp), and two inverted repeats (IRs, 25,166-25,797 bp). Comparative genomic, haplotype, and population genetic structure results showed that there is more genetic variation in Indian ecotype cucumbers compared to other cucumber cultivars, which means that many genetic resources remain to be explored in Indian ecotype cucumbers. Phylogenetic analysis showed that the 50 cucumber germplasms could be classified into 3 types: East Asian, Eurasian + Indian, and Xishuangbanna + Indian. The transcriptomic analysis showed that matK were significantly up-regulated under high- and low-temperature stresses, further demonstrating that cucumber chloroplasts respond to temperature adversity by regulating lipid metabolism and ribosome metabolism. Further, accD has higher editing efficiency under high-temperature stress, which may contribute to the heat tolerance. These studies provide useful insight into genetic variation in the chloroplast genome, and established the foundation for exploring the mechanisms of temperature-stimulated chloroplast adaptation.