The size diversity of the Pteridaceae family chloroplast genome is caused by overlong intergenic spacers.

BACKGROUND: While the size of chloroplast genomes (cpDNAs) is often influenced by the expansion and contraction of inverted repeat regions and the enrichment of repeats, it is the intergenic spacers (IGSs) that appear to play a pivotal role in determining the size of Pteridaceae cpDNAs. This provides an opportunity to delve into the evolution of chloroplast genomic structures of the Pteridaceae family. This study added five Pteridaceae species, comparing them with 36 published counterparts. RESULTS: Poor alignment in the non-coding regions of the Pteridaceae family was observed, and this was attributed to the widespread presence of overlong IGSs in Pteridaceae cpDNAs. These overlong IGSs were identified as a major factor influencing variations in cpDNA size. In comparison to non-expanded IGSs, overlong IGSs exhibited significantly higher GC content and were rich in repetitive sequences. Species divergence time estimations suggest that these overlong IGSs may have already existed during the early radiation of the Pteridaceae family. CONCLUSIONS: This study reveals new insights into the genetic variation, evolutionary history, and dynamic changes in the cpDNA structure of the Pteridaceae family, providing a fundamental resource for further exploring its evolutionary research.

The complete Chloroplast genome of Stachys geobombycis and comparative analysis with related Stachys species.

Herb genomics, at the forefront of traditional Chinese medicine research, combines genomics with traditional practices, facilitating the scientific validation of ancient remedies. This integration enhances public understanding of traditional Chinese medicine's efficacy and broadens its scope in modern healthcare. Stachys species encompass annual or perennial herbs or small shrubs, exhibiting simple petiolate or sessile leaves. Despite their wide-ranging applications across various fields, molecular data have been lacking, hindering the precise identification and taxonomic elucidation of Stachys species. To address this gap, we assembled the complete chloroplast (CP) genome of Stachys geobombycis and conducted reannotation and comparative analysis of seven additional species within the Stachys genus. The findings demonstrate that the CP genomes of these species exhibit quadripartite structures, with lengths ranging from 14,523 to 150,599 bp. Overall, the genome structure remains relatively conserved, hosting 131 annotated genes, including 87 protein coding genes, 36 tRNA genes, and 8 rRNA genes. Additionally, 78 to 98 SSRs and long repeat sequences were detected , and notably, 6 highly variable regions were identified as potential molecular markers in the CP genome through sequence alignment. Phylogenetic analysis based on Bayesian inference and maximum likelihood methods strongly supported the phylogenetic position of the genus Stachys as a member of Stachydeae tribe. Overall, this comprehensive bioinformatics study of Stachys CP genomes lays the groundwork for phylogenetic classification, plant identification, genetic engineering, evolutionary studies, and breeding research concerning medicinal plants within the Stachys genus.

Comparative analysis of chloroplast genomes of Pulsatilla species reveals evolutionary and taxonomic status of newly discovered endangered species Pulsatilla saxatilis.

BACKGROUND: Pulsatilla saxatilis, a new species of the genus Pulsatilla has been discovered. The morphological information of this species has been well described, but its chloroplast genome characteristics and comparison with species of the same genus remain to be reported. RESULTS: Our results showed that the total length of chloroplast (cp.) genome of P. saxatilis is 162,659 bp, with a GC content of 37.5%. The cp. genome contains 134 genes, including 90 known protein-coding genes, 36 tRNA genes, and 8 rRNA genes. P. saxatilis demonstrated similar characteristics to other species of genus Pulsatilla. Herein, we compared cp. genomes of 10 species, including P. saxatilis, and found that the cp. genomes of the genus Pulsatilla are extremely similar, with a length of 162,322-163,851 bp. Furthermore, The SSRs of Pulsatilla ranged from 10 to 22 bp in length. Among the four structural regions of the cp. genome, most long repeats and SSRs were detected in the LSC region, followed by that in the SSC region, and least in IRA/ IRB regions. The most common types of long repeats were forward and palindromic repeats, followed by reverse repeats, and only a few complementary repeats were found in 10 cp. genomes. We also analyzed nucleotide diversity and identified ccsA_ndhD, rps16_trnK-UUU, ccsA, and rbcL, which could be used as potential molecular markers for identification of Pulsatilla species. The results of the phylogenetic tree constructed by connecting the sequences of high variation regions were consistent with those of the cp. gene phylogenetic tree, and the species more closely related to P. saxatilis was identified as the P. campanella. CONCLUSION: It was determined that the closest species to P. saxatilis is P. campanella, which is the same as the conclusion based on pollen grain characteristics, but different from the P. chinensis determined based on morphological characteristics. By revealing information on the chloroplast characteristics, development, and evolution of the cp. genome and the potential molecular markers, this study provides effective molecular data regarding the evolution, genetic diversity, and species identification of the genus Pulsatilla.

Extraction and analysis of high-quality chloroplast DNA with reduced nuclear DNA for medicinal plants.

BACKGROUND: Obtaining high-quality chloroplast genome sequences requires chloroplast DNA (cpDNA) samples that meet the sequencing requirements. The quality of extracted cpDNA directly impacts the efficiency and accuracy of sequencing analysis. Currently, there are no reported methods for extracting cpDNA from Erigeron breviscapus. Therefore, we developed a suitable method for extracting cpDNA from E. breviscapus and further verified its applicability to other medicinal plants. RESULTS: We conducted a comparative analysis of chloroplast isolation and cpDNA extraction using modified high-salt low-pH method, the high-salt method, and the NaOH low-salt method, respectively. Subsequently, the number of cpDNA copies relative to the nuclear DNA (nDNA ) was quantified via qPCR. As anticipated, chloroplasts isolated from E. breviscapus using the modified high-salt low-pH method exhibited intact structures with minimal cell debris. Moreover, the concentration, purity, and quality of E. breviscapus cpDNA extracted through this method surpassed those obtained from the other two methods. Furthermore, qPCR analysis confirmed that the modified high-salt low-pH method effectively minimized nDNA contamination in the extracted cpDNA. We then applied the developed modified high-salt low-pH method to other medicinal plant species, including Mentha haplocalyx, Taraxacum mongolicum, and Portulaca oleracea. The resultant effect on chloroplast isolation and cpDNA extraction further validated the generalizability and efficacy of this method across different plant species. CONCLUSIONS: The modified high-salt low-pH method represents a reliable approach for obtaining high-quality cpDNA from E. breviscapus. Its universal applicability establishes a solid foundation for chloroplast genome sequencing and analysis of this species. Moreover, it serves as a benchmark for developing similar methods to extract chloroplast genomes from other medicinal plants.

Sequence characteristics, genetic diversity and phylogenetic analysis of the Cucurbita ficifolia (Cucurbitaceae) chloroplasts genome.

BACKGROUND: Curcubita ficifolia Bouché (Cucurbitaceae) has high value as a food crop and medicinal plant, and also has horticultural value as rootstock for other melon species. China is home to many different cultivars, but the genetic diversity of these resources and the evolutionary relationships among them, as well as the differences between C. ficifolia and other Cucurbita species, remain unclear. RESULTS: We investigated the chloroplast (cp) genomes of 160 C. ficifolia individuals from 31 populations in Yunnan, a major C. ficifolia production area in China. We found that the cp genome of C. ficifolia is ~151 kb and contains 128 genes, of which 86 are protein coding genes, 34 encode tRNA, and eight encode rRNAs. We also identified 64 SSRs, mainly AT repeats. The cp genome was found to contain a total of 204 SNP and 57 indels, and a total of 21 haplotypes were found in the 160 study individuals. The reverse repeat (IR) region of C. ficifolia contained a few differences compared with this region in the six other Cucurbita species. Sequence difference analysis demonstrated that most of the variable regions were concentrated in the single copy (SC) region. Moreover, the sequences of the coding regions were found to be more similar among species than those of the non-coding regions. The phylogenies reconstructed from the cp genomes of 61 representative species of Cucurbitaceae reflected the currently accepted classification, in which C. ficifolia is sister to the other Cucurbita species, however, different interspecific relationships were found between Cucurbita species. CONCLUSIONS: These results will be valuable in the classification of C. ficifolia genetic resources and will contribute to our understanding of evolutionary relationships within the genus Cucurbita.

The complete chloroplast genome of Mussaenda pubescens and phylogenetic analysis.

The chloroplast (cp) genome sequence of Mussaenda pubescens, a promising resource that is used as a traditional medicine and drink, is important for understanding the phylogenetic relationships among the Mussaenda family and genetic improvement and reservation. This research represented the first comprehensive description of the morphological characteristics of M. pubescens, as well as an analysis of the complete cp genome and phylogenetic relationship. The results indicated a close relationship between M. pubescens and M. hirsutula based on the morphological characteristics of the flower and leaves. The cp was sequenced using the Illumina NovaSeq 6000 platform. The results indicated the cp genome of M. pubescens spanned a total length of 155,122 bp, including a pair of inverted repeats (IRA and IRB) with a length of 25,871 bp for each region, as well as a large single-copy (LSC) region and a small single-copy (SSC) region with lengths of 85,370 bp and 18,010 bp, respectively. The results of phylogenetic analyses demonstrated that species within the same genus displayed a tendency to group closely together. It was suggested that Antirhea, Cinchona, Mitragyna, Neolamarckia, and Uncaria might have experienced an early divergence. Furthermore, M. hirsutula showed a close genetic connection to M. pubescens, with the two species having partially overlapping distributions in China. This study presents crucial findings regarding the identification, evolution, and phylogenetic research on Mussaenda plants, specifically targeting M. pubescens.

Twelve newly assembled jasmine chloroplast genomes: unveiling genomic diversity, phylogenetic relationships and evolutionary patterns among Oleaceae and Jasminum species.

BACKGROUND: Jasmine (Jasminum), renowned for its ornamental value and captivating fragrance, has given rise to numerous species and accessions. However, limited knowledge exists regarding the evolutionary relationships among various Jasminum species. RESULTS: In the present study, we sequenced seven distinct Jasminum species, resulting in the assembly of twelve high-quality complete chloroplast (cp) genomes. Our findings revealed that the size of the 12 cp genomes ranged from 159 to 165 kb and encoded 134-135 genes, including 86-88 protein-coding genes, 38-40 tRNA genes, and 8 rRNA genes. J. nudiflorum exhibited a larger genome size compared to other species, mainly attributed to the elevated number of forward repeats (FRs). Despite the typically conservative nature of chloroplasts, variations in the presence or absence of accD have been observed within J. sambac. The calculation of nucleotide diversity (Pi) values for 19 cp genomes indicated that potential mutation hotspots were more likely to be located in LSC regions than in other regions, particularly in genes ycf2, rbcL, atpE, ndhK, and ndhC (Pi > 0.2). Ka/Ks values revealed strong selection pressure on the genes rps2, atpA, rpoA, rpoC1, and rpl33 when comparing J. sambac with the three most closely related species (J. auriculatum, J. multiflorum, and J. dichotomum). Additionally, SNP identification, along with the results of Structure, PCA, and phylogenetic tree analyses, divided the Jasminum cp genomes into six groups. Notably, J. polyanthum showed gene flow signals from both the G5 group (J. nudiflorum) and the G3 group (J. tortuosum and J. fluminense). Phylogenetic tree analysis reflected that most species from the same genus clustered together with robust support in Oleaceae, strongly supporting the monophyletic nature of cp genomes within the genus Jasminum. CONCLUSION: Overall, this study provides comprehensive insights into the genomic composition, variation, and phylogenetic relationships among various Jasminum species. These findings enhance our understanding of the genetic diversity and evolutionary history of Jasminum.

Assembly and comparative analysis of the initial complete mitochondrial genome of Primulina hunanensis (Gesneriaceae): a cave-dwelling endangered plant.

BACKGROUND: Primulina hunanensis, a troglobitic plant within the Primulina genus of Gesneriaceae family, exhibits robust resilience to arid conditions and holds great horticultural potential as an ornamental plant. The work of chloroplast genome (cpDNA) has been recently accomplished, however, the mitochondrial genome (mtDNA) that is crucial for plant evolution has not been reported. RESULTS: In this study, we sequenced and assembled the P. hunanensis complete mtDNA, and elucidated its evolutionary and phylogenetic relationships. The assembled mtDNA spans 575,242 bp with 43.54% GC content, encompassing 60 genes, including 37 protein-coding genes (PCGs), 20 tRNA genes, and 3 rRNA genes. Notably, high number of repetitive sequences in the mtDNA and substantial sequence translocation from chloroplasts to mitochondria were observed. To determine the evolutionary and taxonomic positioning of P. hunanensis, a phylogenetic tree was constructed using mitochondrial PCGs from P. hunanensis and 32 other taxa. Furthermore, an exploration of PCGs relative synonymous codon usage, identification of RNA editing events, and an investigation of collinearity with closely related species were conducted. CONCLUSIONS: This study reports the initial assembly and annotation of P. hunanensis mtDNA, contributing to the limited mtDNA repository for Gesneriaceae plants and advancing our understanding of their evolution for improved utilization and conservation.

Solanum aculeatissimum and Solanum torvum chloroplast genome sequences: a comparative analysis with other Solanum chloroplast genomes.

BACKGROUND: Solanum aculeatissimum and Solanum torvum belong to the Solanum species, and they are essential plants known for their high resistance to diseases and adverse conditions. They are frequently used as rootstocks for grafting and are often crossbred with other Solanum species to leverage their resistance traits. However, the phylogenetic relationship between S. aculeatissimum and S. torvum within the Solanum genus remains unclear. Therefore, this paper aims to sequence the complete chloroplast genomes of S. aculeatissimum and S. torvum and analyze them in comparison with 29 other previously published chloroplast genomes of Solanum species. RESULTS: We observed that the chloroplast genomes of S. aculeatissimum and S. torvum possess typical tetrameric structures, consisting of one Large Single Copy (LSC) region, two reverse-symmetric Inverted Repeats (IRs), and one Small Single Copy (SSC) region. The total length of these chloroplast genomes ranged from 154,942 to 156,004 bp, with minimal variation. The highest GC content was found in the IR region, while the lowest was in the SSC region. Regarding gene content, the total number of chloroplast genes and CDS genes remained relatively consistent, ranging from 128 to 134 and 83 to 91, respectively. Nevertheless, there was notable variability in the number of tRNA genes and rRNAs. Relative synonymous codon usage (RSCU) analysis revealed that both S. aculeatissimum and S. torvum preferred codons that utilized A and U bases. Analysis of the IR boundary regions indicated that contraction and expansion primarily occurred at the junction between SSC and IR regions. Nucleotide polymorphism analysis and structural variation analysis demonstrated that chloroplast variation in Solanum species mainly occurred in the LSC and SSC regions. Repeat sequence analysis revealed that A/T was the most frequent base pair in simple repeat sequences (SSR), while Palindromic and Forward repeats were more common in long sequence repeats (LSR), with Reverse and Complement repeats being less frequent. Phylogenetic analysis indicated that S. aculeatissimum and S. torvum belonged to the same meristem and were more closely related to Cultivated Eggplant. CONCLUSION: These findings enhance our comprehension of chloroplast genomes within the Solanum genus, offering valuable insights for plant classification, evolutionary studies, and potential molecular markers for species identification.

Chloroplast genome analysis and evolutionary insights in the versatile medicinal plant Calendula officinalis L.

Calendula officinalis L.is a versatile medicinal plant with numerous applications in various fields. However, its chloroplast genome structure, features, phylogeny, and patterns of evolution and mutation remain largely unexplored. This study examines the chloroplast genome, phylogeny, codon usage bias, and divergence time of C. officinalis, enhancing our understanding of its evolution and adaptation. The chloroplast genome of C. officinalis is a 150,465 bp circular molecule with a G + C content of 37.75% and comprises 131 genes. Phylogenetic analysis revealed a close relationship between C. officinalis, C. arvensis, and Osteospermum ecklonis. A key finding is the similarity in codon usage bias among these species, which, coupled with the divergence time analysis, supports their close phylogenetic proximity. This similarity in codon preference and divergence times underscores a parallel evolutionary adaptation journey for these species, highlighting the intricate interplay between genetic evolution and environmental adaptation in the Asteraceae family. Moreover unique evolutionary features in C. officinalis, possibly associated with certain genes were identified, laying a foundation for future research into the genetic diversity and medicinal value of C. officinalis.

Comparative Analysis of Chloroplast Genomes for the Genus Manglietia Blume (Magnoliaceae): Molecular Structure and Phylogenetic Evolution.

Manglietia Blume, belonging to the Magnoliaceae family and mainly distributed in tropical and subtropical regions of Asia, has great scientific and economic value. In this study, we employed next-generation sequencing followed by de novo assembly to investigate the adaptive evolution of Manglietia using plastid genetic information. We newly sequenced the complete or nearly complete plastomes of four Manglietia species (Manglietia aromatica, Manglietia calcarea, Manglietia kwangtungensis, and Manglietia glauca) and conducted comparative analysis with seventeen published plastomes to examine the evolutionary pattern within this genus. The plastomes of these five newly sequenced Manglietia species range from 157,093 bp (M. calcarea2) to 160,493 bp (M. kwangtungensis), all exhibiting circular structures when mapped. Nucleotide diversity was observed across the plastomes, leading us to identify 13 mutational hotspot regions, comprising eight intergenic spacer regions and five gene regions. Our phylogenetic analyses based on 77 protein-coding genes generated phylogenetic relationships with high support and resolution for Manglietia. This genus can be divided into three clades, and the previously proposed infrageneric classifications are not supported by our studies. Furthermore, the close affinity between M. aromatica and M. calcarea is supported by the present work, and further studies are necessary to conclude the taxonomic treatment for the latter. These results provide resources for the comparative plastome, breeding, and plastid genetic engineering of Magnoliaceae and flowering plants.

Wasabi Gone Wild? Origin and Characterization of the Complete Plastomes of Ulleung Island Wasabi (Eutrema japonicum; Brassicaceae) and Other Cultivars in Korea.

Korean wasabi occurs naturally on the young oceanic, volcanic Ulleung Island off the east coast of the Korean Peninsula. Although the Ulleung Island wasabi is reported as Eutrema japonicum and has been suggested to be morphologically identical to cultivars in Korea, very little is known about its taxonomic identity and relationship with other cultivars. In this study, we sequenced the complete chloroplast DNA sequences of three naturally occurring Ulleung Island wasabi plants and six cultivars ('Daewang', 'Daruma', 'Micado', 'Orochi', 'Green Thumb', and 'Shogun') from continental Korea and determined the taxonomic identity of Korean wasabi on Ulleung Island. The size and organization of the complete chloroplast genomes of the nine accessions were nearly identical to those of previously reported wasabi cultivars. In addition, phylogenetic analysis based on the complete plastomes suggested that Ulleung Island wasabi most likely comprises various wasabi cultivars with three chlorotypes ('Shogun', 'Green Thumb', and a unique Chusan type). Based on the complete plastomes, we identified eight chlorotypes for the major wasabi cultivars and the Ulleung Island wasabi. Two major groups (1-'Mazuma' and 'Daruma', and 2-'Fujidaruma'/'Shimane No. 3'/Ulleung Island wasabi/five cultivars in Korea) were also identified based on mother line genealogical history. Furthermore, different types of variations (mutations, insertions/deletions (indels), mononucleotide repeats, and inversions) in plastomes were identified to distinguish different cultivar lines and five highly divergent hotspots. The nine newly obtained complete plastomes are valuable organelle genomic resources for species identification and infraspecific phylogeographic studies on wild and cultivated wasabi.

A High-Quality Assembly and Comparative Analysis of the Mitogenome of Actinidia macrosperma.

The mitochondrial genome (mitogenome) of Actinidia macrosperma, a traditional medicinal plant within the Actinidia genus, remains relatively understudied. This study aimed to sequence the mitogenome of A. macrosperma, determining its assembly, informational content, and developmental expression. The results revealed that the mitogenome of A. macrosperma is circular, spanning 752,501 bp with a GC content of 46.16%. It comprises 63 unique genes, including 39 protein-coding genes (PCGs), 23 tRNA genes, and three rRNA genes. Moreover, the mitogenome was found to contain 63 SSRs, predominantly mono-nucleotides, as well as 25 tandem repeats and 650 pairs of dispersed repeats, each with lengths equal to or greater than 60, mainly comprising forward repeats and palindromic repeats. Moreover, 53 homologous fragments were identified between the mitogenome and chloroplast genome (cp-genome), with the longest segment measuring 4296 bp. This study represents the initial report on the mitogenome of the A. macrosperma, providing crucial genetic materials for phylogenetic research within the Actinidia genus and promoting the exploitation of species genetic resources.

Chloroplast genomes of Caragana tibetica and Caragana turkestanica: structures and comparative analysis.

BACKGROUND: The genus Caragana encompasses multiple plant species that possess medicinal and ecological value. However, some species of Caragana are quite similar in morphology, so identifying species in this genus based on their morphological characteristics is considerably complex. In our research, illumina paired-end sequencing was employed to investigate the genetic organization and structure of Caragana tibetica and Caragana turkestanica, including the previously published chloroplast genome sequence of 7 Caragana plants. RESULTS: The lengths of C. tibetica and C. turkestanica chloroplast genomes were 128,433 bp and 129,453 bp, respectively. The absence of inverted repeat sequences in these two species categorizes them under the inverted repeat loss clade (IRLC). They encode 110 and 111 genes (4 /4 rRNA genes, 30 /31tRNA genes, and 76 /76 protein-coding genes), respectively. Comparison of the chloroplast genomes of C. tibetica and C. turkestanica with 7 other Caragana species revealed a high overall sequence similarity. However, some divergence was observed between certain intergenic regions (matK-rbcL, psbD-psbM, atpA-psbI, and etc.). Nucleotide diversity (π) analysis revealed the detection of five highly likely variable regions, namely rps2-atpI, accD-psaI-ycf4, cemA-petA, psbN-psbH and rpoA-rps11. Phylogenetic analysis revealed that C. tibetica's sister species is Caragana jubata, whereas C. turkestanica's closest relative is Caragana arborescens. CONCLUSIONS: The present study provides worthwhile information about the chloroplast genomes of C. tibetica and C. turkestanica, which aids in the identification and classification of Caragana species.

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.

Comparative chloroplast genomes of Dactylicapnos species: insights into phylogenetic relationships.

BACKGROUND: Dactylicapnos is a climbing herbaceous vine, distributed from the Himalayas to southwestern China, and some of the species have important medicinal values. However, the chloroplast genomes of Dactylicapnos have never been investigated. In this study, chloroplast genomes of seven Dactylicapnos species covering all three sections and one informal group of Dactylicapnos were sequenced and assembled, and the detailed comparative analyses of the chloroplast genome structure were provided for the first time. RESULTS: The results showed that the chloroplast genomes of Dactylicapnos have a typical quadripartite structure with lengths from 172,344 bp to 176,370 bp, encoding a total of 133-140 genes, containing 88-94 protein-coding genes, 8 rRNAs and 37-39 tRNAs. 31 codons were identified as relative synonymous codon usage values greater than one in the chloroplast genome of Dactylicapnos genus based on 80 protein-coding genes. The results of the phylogenetic analysis showed that seven Dactylicapnos species can be divided into three main categories. Phylogenetic analysis revealed that seven species form three major clades which should be treated as three sections. CONCLUSIONS: This study provides the initial report of the chloroplast genomes of Dactylicapnos, their structural variation, comparative genomic and phylogenetic analysis for the first time. The results provide important genetic information for development of medical resources, species identification, infrageneric classification and diversification of Dactylicapnos.

Codon usage bias and phylogenetic analysis of chloroplast genome in 36 gracilariaceae species.

Gracilariaceae is a group of marine large red algae and main source of agar with important economic and ecological value. The codon usage patterns of chloroplast genomes in 36 species from Graciliaceae show that GC range from 0.284 to 0.335, the average GC3 range from 0.135 to 0.243 and the value of ENC range from 35.098 to 42.327, which indicates these genomes are rich in AT and prefer to use codons ending with AT in these species. Nc plot, PR2 plot, neutrality plot analyses and correlation analysis indicate that these biases may be caused by multiple factors, such as natural selection and mutation pressure, but prolonged natural selection is the main driving force influencing codon usage preference. The cluster analysis and phylogenetic analysis show that the differentiation relationship of them is different and indicate that codons with weak or unbiased preferences may also play an irreplaceable role in these species' evolution. In addition, we identified 26 common high-frequency codons and 8-18 optimal codons all ending in A/U in these 36 species. Our results will not only contribute to carrying out transgenic work in Gracilariaceae species to maximize the protein yield in the future, but also lay a theoretical foundation for further exploring systematic classification of them.

Chloroplast genome of Calamus tetradactylus revealed rattan phylogeny.

BACKGROUND: Calamus tetradactylus, a species primarily distributed in Vietnam, Laos, and southern China, is highly valued for its utilization as a small-diameter rattan material. While its physical and mechanical properties have been extensively studied, the genomic characteristics of C. tetradactylus remain largely unexplored. RESULTS: To gain a better understanding of its chloroplast genomic features and evolutionary relationships, we conducted sequencing and assembly of the chloroplast genome of C. tetradactylus. The complete chloroplast genome exhibited the typical highly conserved quartile structure, with specific variable regions identified in the single-copy region (like psbF-psbE, π = 0.10327, ndhF-rpl32, π = 0.10195), as well as genes such as trnT-GGU (π = 0.05764) and ycf1 (π = 0.03345) and others. We propose that these regions and genes hold potential as markers for species identification. Furthermore, phylogenetic analysis revealed that C. tetradactylus formed a distinct clade within the phylogenetic tree, alongside other Calamus species, and C. tetradactylus was most closely related to C. walkeri, providing support for the monophyly of the genus. CONCLUSION: The analysis of the chloroplast genome conducted in this study provides valuable insights that can contribute to the improvement of rattan breeding programs and facilitate sustainable development in the future.

Comparative Analysis of the Chloroplast Genomes of Eight Species of the Genus Lirianthe Spach with Its Generic Delimitation Implications.

Based on Sima and Lu's system of the family Magnoliaceae, the genus Lirianthe Spach s. l. includes approximately 25 species, each with exceptional landscaping and horticultural or medical worth. Many of these plants are considered rare and are protected due to their endangered status. The limited knowledge of species within this genus and the absence of research on its chloroplast genome have greatly impeded studies on the relationship between its evolution and systematics. In this study, the chloroplast genomes of eight species from the genus Lirianthe were sequenced and analyzed, and their phylogenetic relationships with other genera of the family Magnoliaceae were also elucidated. The results showed that the chloroplast genome sizes of the eight Lirianthe species ranged from 159,548 to 159,833 bp. The genomes consisted of a large single-copy region, a small single-copy region, and a pair of inverted repeat sequences. The GC content was very similar across species. Gene annotation revealed that the chloroplast genomes contained 85 protein-coding genes, 37 tRNA genes, and 8 rRNA genes, totaling 130 genes. Codon usage analysis indicated that codon usage was highly conserved among the eight Lirianthe species. Repeat sequence analysis identified 42-49 microsatellite sequences, 16-18 tandem repeats, and 50 dispersed repeats, with microsatellite sequences being predominantly single-nucleotide repeats. DNA polymorphism analysis revealed 10 highly variable regions located in the large single-copy and small single-copy regions, among which rpl32-trnL, petA-psbJ, and trnH-psbA were the recommended candidate DNA barcodes for the genus Lirianthe species. The inverted repeat boundary regions show little variation between species and are generally conserved. The result of phylogenetic analysis confirmed that the genus Lirianthe s. l. is a monophyletic taxon and the most affinal to the genera, Talauma and Dugandiodendron, in Sima and Lu's system and revealed that the genus Lirianthe s. s. is paraphyletic and the genus Talauma s. l. polyphyletic in Xia's system, while Magnolia subsection Gwillimia is paraphyletic and subsection Blumiana polyphyletic in Figlar and Nooteboom's system. Morphological studies found noticeable differences between Lirianthe species in aspects including leaf indumentum, stipule scars, floral orientation, tepal number, tepal texture, and fruit dehiscence. In summary, this study elucidated the chloroplast genome evolution within Lirianthe and laid a foundation for further systematic and taxonomic research on this genus.

The newly assembled chloroplast genome of Aeluropus littoralis: molecular feature characterization and phylogenetic analysis with related species.

Aeluropus littoralis, a halophyte grass, is widely distributed from the Mediterranean to the Indian subcontinent through the Mongolian Gobi. This model halophyte has garnered increasing attention owing to its use as forage and its high tolerance to environmental stressors. The chloroplast genomes of many plants have been extensively examined for molecular, phylogenetic and transplastomic applications. However, no published research on the A. littoralis chloroplast (cp) genome was discovered. Here, the entire chloroplast genome of A. littoralis was assembled implementing accurate long-read sequences. The entire chloroplast genome, with an estimated length of 135,532 bp (GC content: 38.2%), has a quadripartite architecture and includes a pair of inverted repeat (IR) regions, IRa and IRb (21,012 bp each), separated by a large and a small single-copy regions (80,823 and 12,685 bp, respectively). The features of A. littoralis consist of 133 genes that synthesize 87 peptides, 38 transfer RNAs, and 8 ribosomal RNAs. Of these genes, 86 were unique, whereas 19 were duplicated in IR regions. Additionally, a total of forty-six simple sequence repeats, categorized into 32-mono, four-di, two-tri, and eight-tetranucleotides, were discovered. Furthermore, ten sets of repeats greater than 20 bp were located primarily in the LSC region. Evolutionary analysis based on chloroplast sequence data revealed that A. littoralis with A. lagopoides and A. sinensis belong to the Aeluropodinae subtribe, which is a sister to the Eleusininae in the tribe Cynodonteae and the subfamily Chloridoideae. This subfamily belongs to the PACMAD clade, which contains the majority of the C4 photosynthetic plants in the Poaceae. The newly constructed A. littoralis cp genome offers valuable knowledge for DNA barcoding, phylogenetic, transplastomic research, and other biological studies.