CPGAVAS2, an integrated plastome sequence annotator and analyzer

Characterizing the chloroplast genome of Mammillaria elongata DC. 1828 in the Cactaceae family and unveiling its phylogenetic affinities within the genus Mammillaria

With its nearly 200 species, the Mammillaria genus is the most species-rich within the Cactaceae family, yet surprisingly, few of its chloroplast genomes have been studied. We focused on the species Mammillaria elongata DC. 1828, a petite cactus native to Mexico and favored by horticulturists, yet whose phylogenetic relationships remain uncertain due to a lack of genomic data. We extracted the DNA from a sample obtained in China, sequenced it using the NovaSeq 6000 platform, and assembled the chloroplast genome using GetOrganelle software. Our assembly resulted in a chloroplast genome of 110,981 base pairs with an overall GC content of 36.28%, which included 100 genes (95 unique). Notably, several protein-coding genes were absent. Phylogenetic analysis using 59 shared genes across nine Mammillaria species and one Obregonia species revealed that M. elongata and M. gracilis are closely related, suggesting a recent common ancestor and possible shared evolutionary pressures or ecological niches. This study provides crucial genomic data for M. elongata and hints at intriguing phylogenetic relationships within the Mammillaria genus.

Complete chloroplast genome assembly and phylogenetic analysis of blackcurrant (Ribes nigrum), red and white currant (Ribes rubrum), and gooseberry (Ribes uva-crispa) provide new insights into the phylogeny of Grossulariaceae

Background

Blackcurrant (Ribes nigrum), red currant (R. rubrum), white currant (R. rubrum), and gooseberry (R. uva-crispa) belong to Grossulariaceae and are popular small-berry crops worldwide. The lack of genomic data has severely limited their systematic classification and molecular breeding.

Methods

The complete chloroplast (cp) genomes of these four taxa were assembled for the first time using MGI-DNBSEQ reads, and their genome structures, repeat elements and protein-coding genes were annotated. By genomic comparison of the present four and previous released five Ribes cp genomes, the genomic variations were identified. By phylogenetic analysis based on maximum-likelihood and Bayesian methods, the phylogeny of Grossulariaceae and the infrageneric relationships of the Ribes were revealed.

Results

The four cp genomes have lengths ranging from 157,450 to 157,802 bp and 131 shared genes. A total of 3,322 SNPs and 485 Indels were identified from the nine released Ribes cp genomes. Red currant and white currant have 100% identical cp genomes partially supporting the hypothesis that white currant (R. rubrum) is a fruit color variant of red currant (R. rubrum). The most polymorphic genic and intergenic region is ycf1 and trnT-psbD, respectively. The phylogenetic analysis demonstrated the monophyly of Grossulariaceae in Saxifragales and the paraphyletic relationship between Saxifragaceae and Grossulariaceae. Notably, the Grossularia subgenus is well nested within the Ribes subgenus and shows a paraphyletic relationship with the co-ancestor of Calobotrya and Coreosma sections, which challenges the dichotomous subclassification of the Ribes genus based on morphology (subgenus Ribes and subgenus Grossularia). These data, results, and insights lay a foundation for the phylogenetic research and breeding of Ribes species.

Structural divergence and phylogenetic relationships of Ajania (Asteraceae) from plastomes and ETS

BACKGROUND

Ajania Poljakov, an Asteraceae family member, grows mostly in Asia's arid and semi-desert areas and is a significant commercial and decorative plant. Nevertheless, the genus' classification has been disputed, and the evolutionary connections within the genus have not been thoroughly defined. Hence, we sequenced and analyzed Ajania's plastid genomes and combined them with ETS data to assess their phylogenetic relationships.

RESULTS

We obtained a total of six new Ajania plastid genomes and nine ETS sequences. The whole plastome lengths of the six species sampled ranged from 151,002 bp to 151,115 bp, showing conserved structures. Combined with publicly available data from GenBank, we constructed six datasets to reconstruct the phylogenetic relationships, detecting nucleoplasmic clashes. Our results reveal the affinities of Artemisia, Chrysanthemum and Stilpnolepis to Ajania and validate the early taxonomy reclassification. Some of the plastid genes with low phylogenetic information and gene trees with topological differences may have contributed to the ambiguous phylogenetic results of Ajania. There is extensive evolutionary rate heterogeneity in plastid genes. The psbH and ycf2 genes, which are involved in photosynthesis and ATP transport, are under selective pressure. Plastomes from Ajania species diverged, and structural aspects of plastomes may indicate some of the real evolutionary connections. We suggest the ycf1 gene as a viable plastid DNA barcode because it has significant nucleotide diversity and better reflects evolutionary connections.

CONCLUSION

Our findings validate the early Ajania taxonomy reclassification and show evolutionary rate heterogeneity, genetic variety, and phylogenetic heterogeneity of plastid genes. This research might provide new insights into the taxonomy and evolution of Ajania, as well as provide useful information for germplasm innovation and genetic enhancement in horticultural species.

The complete chloroplast genome of Allium wallichii Kunth (Amaryllidaceae)

Allium wallichii Kunth is a herb species with potentially extensive applications because of its edible, ornamental, and pharmaceutical values. The structural characteristics and phylogenetic relationships of its chloroplast genome were determined here for the first time. The complete cp genome was found to be 152,496 bp long, with a GC content of 37.04%. It consists of four distinct regions: a large single copy (LSC) region of 82,510 bp, a small single copy (SSC) region of 17,460 bp, and two inverted repeat (IR) regions of 26,263 bp each. The genome encodes 129 genes, including 86 protein-coding genes, 37 tRNA genes, and six rRNA genes. Our phylogenetic analysis revealed that A. wallichii was closely related to Allium wallichii var. platyphyllum, which are included in the section Bromatorrhiza, subgenus Amerallium Traub of the genus Allium. Our report provides valuable information on the genetic diversity of Allium species.

The complete chloroplast genome of Scutellaria barbata D. Don 1825 revealed the phylogenetic relationships of the Scutellaria genus

Scutellaria barbata D. Don 1825 is an important medicinal plant distributed in wetlands about 2000 m above sea level and used to treat various diseases. The complete chloroplast genome of S. barbata is 152,050 bp with four subregions consisting of a large single-copy region (84,053 bp), a small single-copy region (17,517 bp), and a pair of inverted repeats (25,240 bp). In the chloroplast genome of S. barbata, 131 genes were detected, comprising 87 protein-encoding genes, eight ribosomal RNA (rRNA) genes, and 36 transfer RNA (tRNA) genes. Phylogenetic analysis based on the complete chloroplast genome and protein-coding DNA sequences of 27 related taxa of the genus (out group included Holmskioldia sanguinea and Tinnea aethiopica) indicates that S. barbata was made a clade with S. orthocalyx, and S. meehanioides was a sister to them. The first chloroplast genome of S. barbata was reported in this work, serving as a potential reference for important medicinal plants within the Scutellaria genus.

Comparative chloroplast genome analysis of four Polygonatum species insights into DNA barcoding, evolution, and phylogeny

The Polygonatum genus represents a perennial herb with the Liliaceae family, boasting substantial economic and medicinal significance. The majority of Polygonatum plants exhibit notable similarity while lacking distinctive identifying characteristics, thus resulting in the proliferation of adulterated medicinal materials within the market. Within this study, we conducted an in-depth analysis of the complete chloroplast (cp) genomes of four Polygonatum plants and compared them with four closely akin species. The primary objectives were to unveil structural variations, species divergence, and the phylogenetic interrelations among taxa. The cp genomes of the four Polygonatum species were typified by a conventional quadripartite structure, incorporating a large single copy region (LSC), a small single copy region (SSC), and a pair of inverted repeat regions. In total, we annotated a range of 131 to 133 genes, encompassing 84 to 86 protein-coding genes, 38 transfer RNA (tRNA) genes, 8 ribosomal RNA (rRNA) genes, and 0 to 2 pseudogenes (ycf1, infA). Our comparative analyses unequivocally revealed a remarkable consistency in gene order and GC content within the Polygonatum genus. Furthermore, we predicted a potential 59 to 64 RNA editing sites distributed across 22 protein-coding genes, with the ndhB gene exhibiting the most prominent propensity for RNA editing sites, boasting a tally of 15 sites. Notably, six regions of substantial potential variability were ascertained, characterized by elevated Pi values. Noteworthy, molecular markers for species identification, population genetic scrutiny, and phylogenetic investigations within the genus were identified in the form of the psaJ-rpl33 and trnS + trnT-psaD barcodes. The resultant phylogenetic tree unequivocally depicted the formation of a monophyletic clade comprising species within the evolutionary framework of Liliaceae, demonstrating closer evolutionary affinities with Maianthemum, Dracaeneae, and Asparageae. This comprehensive compendium of findings collectively contributes to the advancement of molecular species identification, elucidation of phylogenetic interrelationships, and the establishment of DNA barcodes tailored to the Polygonatum species.

Comprehensive Comparative Analyses of Aspidistra Chloroplast Genomes: Insights into Interspecific Plastid Diversity and Phylogeny

Limestone karsts are renowned for extremely high species richness and endemism. Aspidistra (Asparagaceae) is among the highly diversified genera distributed in karst areas, making it an ideal group for studying the evolutionary mechanisms of karst plants. The taxonomy and identification of Aspidistra species are mainly based on their specialized and diverse floral structures. Aspidistra plants have inconspicuous flowers, and the similarity in vegetative morphology often leads to difficulties in species discrimination. Chloroplast genomes possess variable genetic information and offer the potential for interspecies identification. However, as yet there is little information about the interspecific diversity and evolution of the plastid genomes of Aspidistra. In this study, we reported chloroplast (cp) genomes of seven Aspidistra species (A. crassifila, A. dolichanthera, A. erecta, A. longgangensis, A. minutiflora, A. nankunshanensis, and A. retusa). These seven highly-conserved plastid genomes all have a typical quartile structure and include a total of 113 unique genes, comprising 79 protein-coding genes, 4 rRNA genes and 30 tRNA genes. Additionally, we conducted a comprehensive comparative analysis of Aspidistra cp genomes. We identified eight divergent hotspot regions (trnC-GCA-petN, trnE-UUC-psbD, accD-psaI, petA-psbJ, rpl20-rps12, rpl36-rps8, ccsA-ndhD and rps15-ycf1) that serve as potential molecular markers. Our newly generated Aspidistra plastomes enrich the resources of plastid genomes of karst plants, and an investigation into the plastome diversity offers novel perspectives on the taxonomy, phylogeny and evolution of Aspidistra species.

A Comprehensive Analysis of Chloroplast Genome Provides New Insights into the Evolution of the Genus Chrysosplenium

Chrysosplenium, a perennial herb in the family Saxifragaceae, prefers to grow in low light and moist environments and is divided into two sections of Alternifolia and Oppositifolia based on phyllotaxy. Although there has been some progress in the phylogeny of Chrysosplenium over the years, the phylogenetic position of some species is still controversial. In this study, we assembled chloroplast genomes (cp genomes) of 34 Chrysosplenium species and performed comparative genomic and phylogenetic analyses in combination with other cp genomes of previously known Chrysosplenium species, for a total of 44 Chrysosplenium species. The comparative analyses revealed that cp genomes of Chrysosplenium species were more conserved in terms of genome structure, gene content and arrangement, SSRs, and codon preference, but differ in genome size and SC/IR boundaries. Phylogenetic analysis showed that cp genomes effectively improved the phylogenetic support and resolution of Chrysosplenium species and strongly supported Chrysosplenium species as a monophyletic taxon and divided into three branches. The results also showed that the sections of Alternifolia and Oppositifolia were not monophyletic with each other, and that C. microspermum was not clustered with other Chrysosplenium species with alternate leaves, but with C. sedakowii into separate branches. In addition, we identified 10 mutational hotspot regions that could serve as potential DNA barcodes for Chrysosplenium species identification. In contrast to Peltoboykinia, the clpP and ycf2 genes of Chrysosplenium were subjected to positive selection and had multiple significant positive selection sites. We further detected a significant positive selection site on the petG gene between the two sections of Chrysosplenium. These evolutionary characteristics may be related to the growth environment of Chrysosplenium species. This study enriches the cp genomes of Chrysosplenium species and provides a reference for future studies on its evolution and origin.

Comparative analyses of Linderniaceae plastomes, with implications for its phylogeny and evolution

Introduction

The recently established Linderniaceae, separated from the traditionally defined Scrophulariaceae, is a taxonomically complicated family. Although previous phylogenetic studies based on a few short DNA markers have made great contributions to the taxonomy of Linderniaceae, limited sampling and low resolution of the phylogenetic tree have failed to resolve controversies between some generic circumscriptions. The plastid genome exhibits a powerful ability to solve phylogenetic relationships ranging from shallow to deep taxonomic levels. To date, no plastid phylogenomic studies have been carried out in Linderniaceae.

Methods

In this study, we newly sequenced 26 plastid genomes of Linderniaceae, including eight genera and 25 species, to explore the phylogenetic relationships and genome evolution of the family through plastid phylogenomic and comparative genomic analyses.

Results

The plastid genome size of Linderniaceae ranged from 152,386 bp to 154,402 bp, exhibiting a typical quartile structure. All plastomes encoded 114 unique genes, comprising 80 protein-coding genes, 30 tRNA genes, and four rRNA genes. The inverted repeat regions were more conserved compared with the single-copy regions. A total of 1803 microsatellites and 1909 long sequence repeats were identified, and five hypervariable regions (petN-psbM, rps16-trnQ, rpl32-trnL, rpl32, and ycf1) were screened out. Most protein-coding genes were relatively conserved, with only the ycf2 gene found under positive selection in a few species. Phylogenomic analyses confirmed that Linderniaceae was a distinctive lineage and revealed that the presently circumscribed Vandellia and Torenia were non-monophyletic.

Discussion

Comparative analyses showed the Linderniaceae plastomes were highly conservative in terms of structure, gene order, and gene content. Combining morphological and molecular evidence, we supported the newly established Yamazakia separating from Vandellia and the monotypic Picria as a separate genus. These findings provide further evidence to recognize the phylogenetic relationships among Linderniaceae and new insights into the evolution of the plastid genomes.

Characteristics and phylogenetic analysis of the complete chloroplast genome of Primulina hedyotidea

Primulina hedyotidea (Woon Young Chun) Yin Zheng Wang 2011 is an important medicinal plant that has a long history of medicinal use in China. In this experiment, the whole chloroplast genome of P. hedyotidea was determined by next-generation sequencing technology. The total base length of P. hedyotidea was 153,297 bp, the GC content was 37.62%, the inverted repeat (IR) region length was 25,494 bp, the large single copy (LSC) region was 84,158 bp and the small single copy (SSC) region was 18,151 bp. In addition, the genome consisted of 80 protein-coding genes, 4 rRNA genes, and 28 tRNA genes, for a total of 112 genes. A phylogenetic tree was constructed to explore the evolutionary relationship between P. hedyotidea and other species. The findings of phylogenetic tree analysis show that Primulina huaijiensis and P. hedyotidea have a close relationship, and this study can help with species identification and phylogenetic analysis within Primulina and Gesneriaceae species.

The complete plastid genome sequence of Lysidice brevicalyx (Fabaceae: Detarioideae), an arbor species endemic to China

The plastid genome of Lysidice brevicalyx was successfully assembled using Illumina sequencing reads for the first time. The complete plastid genome of L. brevicalyx is a circular structure of 159,084 bp with a GC content of 36.4%. It comprises a large single-copy (LSC) region of 87,783 bp, a small single-copy (SSC) region of 19,557 bp, and two inverted repeat regions (IRA and IRB) of 25,872 bp, each. The plastome of L. brevicalyx contains a total of 128 genes, including 83 protein-coding genes, 37 tRNAs, and 8 rRNAs. The phylogenetic analysis strongly supports the monophyly of Lysidice. This study provides the first complete plastid genome sequence of L. brevicalyx and contributes to our understanding of the molecular characteristics and evolutionary relationships of this plant species.

Complete chloroplast genome of Adonis pseudoamurensis W.T.Wang (Ranunculaceae)

Adonis pseudoamurensis W.T. Wang 1980 is an important traditional medicinal plant used for the treatment of cardiac diseases. The complete chloroplast (cp) genome of Adonis pseudoamurensis is reported for the first time in this study. The circular cp genome is 156,917 bp in length, consisting of a large single-copy region (86,262 bp), a small single-copy region (18,067 bp), and two inverted repeat regions (26,294 bp). The genome encodes 129 genes, comprising 84 protein-coding genes, 37 transfer RNA (tRNA) genes, and 8 ribosomal RNA (rRNA) genes. Phylogenetic analysis showed that A. pseudoamurensis is closely related to A. amurensis.

The complete chloroplast genome of Vaccinium oxycoccos (Ericaceae)

Vaccinium species have great significance as fruit crops due to their economic and food values. Here we report the chloroplast genome of V. oxycoccos. The chloroplast genome of V. oxycoccos was 177,088 bp in length with a GC content of 36.74%. LSC, SSC, and IR regions were 104,139 bp, 3031 bp, and 34,959 bp in length, respectively. The chloroplast genome contained 105 different genes, including 73 protein-coding genes, 4 rRNA genes, and 28 tRNA genes. The phylogenetic analysis indicated that V. oxycoccos was closely related to V. microcarpum in the family Ericaceae. This chloroplast genome not only enriches the genome information of Vaccinium, but also will be useful in the evolution study of the family Ericaceae.

Complete chloroplast genome and phylogenetic analysis of Smallanthus sonchifolius (Asteraceae)

Smallanthus sonchifolius (Asteraceae), is an important food plant in the world. There is no systematic report on the chloroplast genome of S. sonchifolius. Here we reported its complete chloroplast genome and analyzed the basic characteristics. The chloroplast genome was 152,301 bp in length, had a GC content of 37.55%, and encoded 113 unique genes, including 79 protein-coding genes, 4 ribosomal RNA genes, and 30 transfer RNA genes. Phylogenetic analysis showed that the tribe Millerieae and the tribe Madieae are closely related in the Asteraceae family. In the tribe Millerieae, Smallanthus was more closely related to Guizotia and Sigesbeckia. This chloroplast genome not only enriches the genome information of Smallanthus, but also lays the foundation for understanding the phylogeny within the genus Smallanthus.

The complete chloroplast genome and phylogenomic analysis of Camellia sinensis var. sinensis cultivar 'Liupao', a landrace from Guangxi, China

Liupao tea is one of the well-known Chinese tea brands and a famous local specialty in Wuzhou, Guangxi, China. However, the genetic background and phylogenetic relationship of the native resource plants of Liupao tea need study, especially at the genomic level. In this study, we reported the complete chloroplast (cp) genome sequence of Camellia sinensis var. sinensis cultivar 'Liupao' (LP, Liupao tea population) and inferred its phylogenetic relationship to other tea plant variants or cultivars. The cp genome had a total length of 157,097 bp and the overall GC content was 37.3%. The cp genome contained one LSC region (86,641 bp) and one SSC region (18,276 bp), which were separated by two IR regions (26,090 bp, respectively). Moreover, the cp genomes were composed of 130 genes, including 86 protein-coding genes, 36 tRNA genes, and eight rRNA genes. The phylogenetic analysis showed that LP was closely related to C. sinensis var. pabilimba cv. 'Lingyunbaihao'. This study will provide useful information for further investigating the genetic background, evolution, and breeding of LP as well as other tea cultivars and varieties.

The complete chloroplast genome of Salix lindleyana (salicaceae), a plateau plant species

Salix lindleyana Wallich ex Andersson 1851 is a species of genus Salix which mainly grows on mountains above 3000 m at sea level in Qinghai-Tibetan Plateau (including the Himalayas and Hengduan Mountains). To determine its phylogenetic position within Salix, we reconstructed S. lindleyana complete chloroplast (cp) genome sequence by de novo assembly using whole-genome sequencing data. The completed chloroplast genome was 155,304 bp, with a total GC content of 36.7%. It had a very typical tetrad structure, including a large single-copy (LSC) region of 84,539 bp, a small single-copy (SSC) region of 16,161 bp, and two inverted repeats (IR) regions of 27,302 bp. A total of 132 functional genes were distributed in the chloroplast genome, including 87 protein-coding genes, 37 tRNA genes, and 8 rRNA genes. Phylogenetic analysis showed that S. lindleyana was clustered with Salix dasyclados Wimmer 1849 and Salix variegata Franchet 1887. The complete chloroplast genome of S. lindleyana provides potential genetic resources for further phylogenetic studies.

Complete mitochondrial genome of Agrostis stolonifera: insights into structure, Codon usage, repeats, and RNA editing

BACKGROUND

Plants possess mitochondrial genomes that are large and complex compared to animals. Despite their size, plant mitochondrial genomes do not contain significantly more genes than their animal counterparts. Studies into the sequence and structure of plant mitochondrial genomes heavily imply that the main mechanism driving replication of plant mtDNA, and offer valuable insights into plant evolution, energy production, and environmental adaptation.

RESULTS

This study presents the first comprehensive analysis of Agrostis stolonifera's mitochondrial genome, characterized by a branched structure comprising three contiguous chromosomes, totaling 560,800 bp with a GC content of 44.07%. Annotations reveal 33 unique protein-coding genes (PCGs), 19 tRNA genes, and 3 rRNA genes. The predominant codons for alanine and glutamine are GCU and CAA, respectively, while cysteine and phenylalanine exhibit weaker codon usage biases. The mitogenome contains 73, 34, and 23 simple sequence repeats (SSRs) on chromosomes 1, 2, and 3, respectively. Chromosome 1 exhibits the most frequent A-repeat monomeric SSR, whereas chromosome 2 displays the most common U-repeat monomeric SSR. DNA transformation analysis identifies 48 homologous fragments between the mitogenome and chloroplast genome, representing 3.41% of the mitogenome's total length. The PREP suite detects 460 C-U RNA editing events across 33 mitochondrial PCGs, with the highest count in the ccmFn gene and the lowest in the rps7 gene. Phylogenetic analysis confirms A. stolonifera's placement within the Pooideae subfamily, showing a close relationship to Lolium perenne, consistent with the APG IV classification system. Numerous homologous co-linear blocks are observed in A. stolonifera's mitogenomes and those of related species, while certain regions lack homology.

CONCLUSIONS

The unique features and complexities of the A. stolonifera mitochondrial genome, along with its similarities and differences to related species, provide valuable insights into plant evolution, energy production, and environmental adaptation. The findings from this study significantly contribute to the growing body of knowledge on plant mitochondrial genomes and their role in plant biology.

Classification of Isatis indigotica Fortune and Isatis tinctoria Linnaeus via comparative analysis of chloroplast genomes

BACKGROUND

Isatis tinctoria Linnaeus and Isatis indigotica Fortune are very inconsistent in their morphological characteristics, but the Flora of China treats them as the same species. In this work, a new technology that differs from conventional barcodes is developed to prove that they are different species and to clarify their classification.

RESULTS AND METHODS

I. indigotica was indistinguishable from I. tinctoria when using ITS2. CPGAVAS2 was used to construct the chloroplast genomes. MAFFT and DnaSP were used to calculate nucleotide polymorphism, the chloroplast genomes of the two have high diversity in the rpl32 ~ trnL-UAG short region. When using this region as a mini barcode, it was found that there are obvious differences in the base numbers of I. tinctoria and different ploidy I. indigotica were found, but diploid and tetraploid I. indigotica had the same number of bases. Moreover, the reconstruction of the maximum likelihood (ML) tree, utilizing the mini-barcode, demonstrated that I. tinctoria and both diploid and tetraploid I. indigotica are located on distinct branches. The genome size of tetraploid I. indigotica was approximately 643.773 MB, the heterozygosity rate was approximately 0.98%, and the repeat sequence content was approximately 90.43%. This species has a highly heterozygous, extremely repetitive genome.

CONCLUSION

A new method was established to differentiate between I. indigotica and I. tinctoria. Furthermore, this approach provides a reference and basis for the directional breeding of Isatis.

New insights into the plastome evolution of Lauraceae using herbariomics

BACKGROUND

The family Lauraceae possesses ca. 50 genera and 2,500-3,000 species that are distributed in the pantropics. Only half of the genera of the family were represented in previously published plastome phylogenies because of the difficulty of obtaining research materials. Plastomes of Hypodaphnideae and the Mezilaurus group, two lineages with unusual phylogenetic positions, have not been previously reported and thus limit our full understanding on the plastome evolution of the family. Herbariomics, promoted by next generation sequencing technology, can make full use of herbarium specimens, and provides opportunities to fill the sampling gap.

RESULTS

In this study, we sequenced five new plastomes (including four genera which are reported for the first time, viz. Chlorocardium, Hypodaphnis, Licaria and Sextonia) from herbarium specimens using genome skimming to conduct a comprehensive analysis of plastome evolution of Lauraceae as a means of sampling representatives of all major clades of the family. We identified and recognized six types of plastomes and revealed that at least two independent loss events at the IR-LSC boundary and an independent expansion of SSC occurred in the plastome evolution of the family. Hypodaphnis possesses the ancestral type of Lauraceae with trnI-CAU, rpl23 and rpl2 duplicated in the IR regions (Type-I). The Mezilaurus group shares the same plastome structure with the core Lauraceae group in the loss of trnI-CAU, rpl23 and rpl2 in the IRa region (Type-III). Two new types were identified in the Ocotea group: (1) the insertion of trnI-CAU between trnL-UAG and ccsA in the SSC region of Licaria capitata and Ocotea bracteosa (Type-IV), and (2) trnI-CAU and pseudogenizated rpl23 inserted in the same region of Nectandra angustifolia (Type-V). Our phylogeny suggests that Lauraceae are divided into nine major clades largely in accordance with the plastome types. The Hypodaphnideae are the earliest diverged lineage supported by both robust phylogeny and the ancestral plastome type. The monophyletic Mezilaurus group is sister to the core Lauraceae.

CONCLUSIONS

By using herbariomics, we built a more complete picture of plastome evolution and phylogeny of the family, thus providing a convincing case for further use of herbariomics in phylogenetic studies of the Lauraceae.

Analysis of the complete plastomes of Albizia kalkora (Roxb.) Prain 1897 (Fabaceae)

Albizia kalkora (Roxb.) Prain 1897, belonging to the family Fabaceae, is not only a landscape tree but also a medicinal plant. At present, few plastomes have been reported from Albizia, which delays the in-depth phylogenomic studies and the development of high-resolution discriminating markers for this genus. Herein, we sequenced the first plastome of A. kalkora by NGS technology. The genome is a circular structure (176,158 bp), containing a large single-copy (LSC) region (91,521 bp), a small copy (SSC) region (5237 bp), and two inverted repeat (IR) regions (39,700 bp each). It has 35.45% GC content and encodes 109 unique genes, which are 76 protein-coding, 4 rRNA, and 29 tRNA genes. The genetic distance analysis of the intergenic spacer regions for A. kalkora, A. odoratissima and A. bracteate shows four intergenic regions with very high K2p values, namely, ccsA-ndhD (15.04), matK-rps16 (10.77), rps11-rpl36 (17.63) and rps3-rps19 (20.08), which can discriminate the three Albizia species. In addition, we identified ten pairs of regions that could be utilized to design primers to discriminate the three Albizia species. The phylogenetic analysis showed Albizia was closely related to Samanea. The results in this study will provide valuable information to elucidate the classification, identification and evolutionary history of Albizia.

Integrative analysis of chloroplast genome, chemicals, and illustrations in Bencao literature provides insights into the medicinal value of Peucedanum huangshanense

The genus Peucedanum L. (Apiaceae) is a large group comprising more than 120 species distributed worldwide. Many plants of the genus Peucedanum have been studied and used in traditional Chinese medicine. In 2020, a new species, Peucedanum huangshanense Lu Q. Huang, H. S. Peng & S. S. Chu, was found in the Huangshan Mountains of Anhui Province, China. However, little is known about its medicinal properties. Thus, the objective of this study is to explore the potential medicinal value of P. huangshanense and its relationship with other Peucedanum species. Through textual research on illustrations of Qianhu in Bencao literature, it can be inferred that at least five species of genus Peucedanum have been used in Chinese medicine. Therefore, we chose these five species of Peucedanum and P. huangshanense together for subsequent research. We conducted morphological, chloroplast genome, and chemical analyses of six Peucedanum species, including the newly discovered P. huangshanense. The chloroplast genomes of Peucedanum showed a typical tetrad structure, and the gene structure and content were similar and conservative. There were significant differences in genome size and the expansion of the inverted repeat boundary. Through nucleotide polymorphism analysis, we screened 14 hotspot mutation regions that have the potential to be used as specific molecular markers for the taxonomy of Peucedanum. Our results showed an inversion of the trnD-trnY-trnE gene in the P. huangshanense chloroplast genome, which can be developed as a specific molecular marker for species identification. Phylogenetic analysis showed that the phylogenetic trees had high support and resolution, which strongly supports the view that Peucedanum is not a monophyletic group. P. huangshanense had the closest genetic relationship to P. ampliatum K. T. Fu, followed by P. harry-smithii Fedde ex Wolff. Furthermore, the main coumarins of P. huangshanense were most similar to those of P. japonicum Thunb. and P. harry-smithii. In summary, our research lays a foundation for the systematic classification of Peucedanum and sheds light on the medicinal value of P. huangshanense.

The complete chloroplast genome of Aster altaicus Willd. (Asteraceae: Aster) and phylogenetic analysis

Aster altaicus Willd. is an important medicinal plant and can also be used as a forage grass. To better understand the diversity and phylogeny between A. altaicus and other Aster species, we sequenced and annotated the complete chloroplast genome of A. altaicus by using the Illumina Hiseq 2500 platform. This complete chloroplast genome is 152,473 bp long and the GC content is 37.3% presented a negative AT-skew (-0.002) and a positive GC-skew (0.003). The genome contains a large single-copy region (LSC) of 84,235 bp, a small single-copy region (SSC) of 18,212 bp, which separated by a pair of inverted repeat regions (IRA and IRB) of 25,013 bp. Moreover, 129 genes were found in the chloroplast of A. altaicus, including 85 protein-coding genes (PCGs), 36 transfer RNA genes (tRNAs), 8 ribosomal RNA unit genes (rRNAs). Phylogenetic analysis showed that A. altaicus was more closely related to A. altaicus and A. altaicus var. uchiyamae. This study lays the foundation for further studies on the evolution and phylogeny of Aster.

Assembly and analysis of the mitochondrial genome of Prunella vulgaris

Prunella vulgaris (Lamiaceae) is widely distributed in Eurasia. Former studies have demonstrated that P. vulgaris has a wide range of pharmacological effects. Nevertheless, no complete P. vulgaris mitochondrial genome has been reported, which limits further understanding of the biology of P. vulgaris. Here, we assembled the first complete mitochondrial genome of P. vulgaris using a hybrid assembly strategy based on sequencing data from both Nanopore and Illumina platforms. Then, the mitochondrial genome of P. vulgaris was analyzed comprehensively in terms of gene content, codon preference, intercellular gene transfer, phylogeny, and RNA editing. The mitochondrial genome of P. vulgaris has two circular structures. It has a total length of 297, 777 bp, a GC content of 43.92%, and 29 unique protein-coding genes (PCGs). There are 76 simple sequence repeats (SSRs) in the mitochondrial genome, of which tetrameric accounts for a large percentage (43.4%). A comparative analysis between the mitochondrial and chloroplast genomes revealed that 36 homologous fragments exist in them, with a total length of 28, 895 bp. The phylogenetic analysis showed that P. vulgaris belongs to the Lamiales family Lamiaceae and P. vulgaris is closely related to Salvia miltiorrhiza. In addition, the mitochondrial genome sequences of seven species of Lamiaceae are unconservative in their alignments and undergo frequent genome reorganization. This work reports for the first time the complete mitochondrial genome of P. vulgaris, which provides useful genetic information for further Prunella studies.

Plastome evolution in the genus Sium (Apiaceae, Oenantheae) inferred from phylogenomic and comparative analyses

BACKGROUND

Sium L. (Apiaceae) is a small genus distributed primarily in Eurasia, with one species also occurring in North America. Recently, its circumscription has been revised to include 10 species, however, the phylogenetic relationships within its two inclusive clades were poorly supported or collapsed in previous studies based on nuclear ribosomal DNA ITS or cpDNA sequences. To identify molecular markers suitable for future intraspecific phylogeographic and population genetic studies, and to evaluate the efficacy of plastome in resolving the phylogenetic relationships of the genus, the complete chloroplast (cp) genomes of six Sium species were sequenced.

RESULTS

The Sium plastomes exhibited typical quadripartite structures of Apiaceae and most other higher plant plastid DNAs, and were relatively conserved in their size (153,029-155,006 bp), gene arrangement and content (with 114 unique genes). A total of 61-67 SSRs, along with 12 highly divergent regions (trnQ, trnG-atpA, trnE-trnT, rps4-trnT, accD-psbI, rpl16, ycf1-ndhF, ndhF-rpl32, rpl32-trnL, ndhE-ndhG, ycf1a and ycf1b) were discovered in the plastomes. No significant IR length variation was detected showing that plastome evolution was conserved within this genus. Phylogenomic analysis based on whole chloroplast genome sequences produced a highly resolved phylogenetic tree, in which the monophyly of Sium, as well as the sister relationship of its two inclusive clades were strongly supported.

CONCLUSIONS

The plastome sequences could greatly improve phylogenetic resolution, and will provide genomic resources and potential markers useful for future studies of the genus.

Complete assembly of the chloroplast genome of Amorphophallus coaetaneus S. Y. Liu & S. J. Wei 1986 (Araceae) from southwestern China

Amorphophallus coaetaneus S. Y. Liu & S. J. Wei 1986 is a perennial herb belonging to the Araceae family in southwestern China (Guangxi and Yunnan provinces). Although this species have not been list in the red list of International Union for Conservation of Nature (IUCN), the populations are declining due to human over exploitation. To help to genetic diversity studies, we sequenced and assembled the complete chloroplast (cp) genome of A. coaetaneus (GenBank accession number of national center for biotechnology information (NCBI): OQ404947). The assembled genome revealed 175,465 bp in length with a GC content of 34.90%, including a large single-copy (LSC) region (98,561 bp), a small single-copy (SSC) region (16,504 bp) and two inverted repeat regions (IRs) (30,200 bp each). A total of 133 genes were annotated, of which 85 are protein-coding genes, 40 are tRNA genes and 8 are rRNA genes. As an output of this study, a maximum likelihood (ML) phylogenetic inference of 16 Araceae species clustered all four Amorphophallus species in one clade, and showed a relatively close relationship between the tribes Pythonieae and Colocasieae. The cp genome will serve as a basis in a more extensive molecular works covering all possible extant population of Amorphophallus, as well as conservation, breeding, and other ethnobotanical utilization of this species.

The complete chloroplast genome and phylogenetic analysis of Jacobaea maritima (Asteraceae)

Jacobaea maritima is an important horticulture plant in the genus Jacobaea. Here, we assembled the complete chloroplast genome of J. maritima. The chloroplast genome was 153,857 bp in length, with a pair of inverted repeat regions (IRs) (27,936 bp) separated by a large single-copy region (LSC) (82,771 bp) and a small single-copy region (SSC) (15,214 bp). The complete chloroplast genome contained 112 unique genes, including 79 protein-coding genes, 29 tRNA genes, and 4 rRNA genes. The phylogenetic analysis showed Jacobaea was more closely related to Senecio, Crassocephalum and Gynura. The chloroplast genome of J. maritima can provide data to support future phylogenetic studies of Jacobaea.

Complete chloroplast genome of two nutmeg species, Myristica argentea Warb. 1891 and Myristica fatua Houtt. 1774 (Myristicaceae)

Myristica argentea Warb. 1891 and M. fatua Houtt. 1774 are two South-East Asian food tree species. They are harvested from the wild or cultivated for local uses as a condiment (nutmeg and mace), medicine, and source of wood. In this study, we reconstructed the complete chloroplast (cp) genomes of these two species from whole genome sequencing data using the Illumina NovaSeq platform. The genome sizes of M. argentea and M. fatua were respectively 155,871 base pairs (bp) and 155,898 bp, including 126 genes and an overall GC content of 39.20% in both species. Our study provides useful resources for future evolutionary research and diversity analysis of Myristica species.

Sequencing the chloroplast genome of a jujube genotype (Ziziphus jujuba Mill. 'Fengmiguan') uncovered a 101 bp insertion in the large-single copy region

Ziziphus jujuba Mill., commonly referred to as jujube, is a species of fruiting buckthorn (family Rhamnaceae) that is frequently found across the Shaanxi, Shanxi, and Hebei provinces of China. The 'Fengmiguan' variety of jujube, also known as 'Honey jar,' is distinguished by its high yield and sugar content, as well as its strong ability to adapt to different environments. In this study, we sequenced and assembled the chloroplast genome (i.e. the plastome) of 'Fengmiguan' jujube using a paired-end short-read sequencing technique. The plastome exhibits a quadripartite structure with a total length of 161,818 bp that consists of a large single-copy region (89,427 bp), a small single-copy region (19,361 bp), and two inverted repeats (26,515 bp). The GC content of the plastome is 36.75%. Annotation of the 'Fengmiguan' jujube plastome revealed 123 genes, including 79 protein-coding genes, 36 transfer RNA genes, and eight ribosomal RNA genes. Phylogenetic analysis revealed that the 'Fengmiguan' variety is closely related to the 'Bokjo' variety. Furthermore, we found four variations between these two varieties of jujube, one of which was a 101 bp insertion. Our findings enhance the current understanding of the phylogenetic relationship between different varieties of Z. jujuba Mill., which could possibly aid in the improvement of genetic breeding and population selection in jujubes.

Plastomes of Sonchus (Asteraceae) endemic to the Atlantic Madeira archipelago: Genome structure, comparative analysis, and phylogenetic relationships

The woody Sonchus alliance, a spectacular example of adaptive radiation with six genera and approximately 31 species, is found exclusively on three Macaronesian Islands (Madeira, Canaries, and Cape Verdes) in the Atlantic Ocean. Four of the Sonchus taxa are restricted to Madeira, including shrubs and small trees at higher elevations (S. fruticosus and S. pinnatus), and caudex perennials in the lower coastal areas (S. ustulatus subsp. maderensis and S. ustulatus subsp. ustulatus). The Madeiran Sonchus stemmed from a single colonization event that originated from the Canaries < 3 million years ago. However, the plastome evolution and species relationships remains insufficiently explored. We therefore assembled and characterized the plastomes of four Sonchus taxa from Madeira and conducted a phylogenomic analysis. We found highly conserved plastome sequences among the taxa, further supporting a single and recent origin. We also found highly conserved plastomes among the cosmopolitan weedy Sonchus, Macaronesian Sonchus in the Atlantic, and Juan Fernández Islands Dendroseris in the Pacific. Furthermore, we identified four mutation hotspot regions (trnK-rps16, petN-psbM, ndhF-Ψycf1, and ycf1) and simple sequence repeat motifs. This study strongly supports the monophyly of Madeiran Sonchus. However, its relationship with the remaining woody Sonchus alliance from the Canary Islands requires further investigation.

Comparative analysis of 17 complete chloroplast genomes reveals intraspecific variation and relationships among Pseudostellaria heterophylla (Miq.) Pax populations

Pseudostellaria heterophylla (Miq.) Pax is a well-known medicinal and ecologically important plant. Effectively distinguishing its different genetic resources is essential for its breeding. Plant chloroplast genomes can provide much more information than traditional molecular markers and provide higher-resolution genetic analyses to distinguish closely related planting materials. Here, seventeen P. heterophylla samples from Anhui, Fujian, Guizhou, Hebei, Hunan, Jiangsu, and Shandong provinces were collected, and a genome skimming strategy was employed to obtain their chloroplast genomes. The P. heterophylla chloroplast genomes ranged from 149,356 bp to 149,592 bp in length, and a total of 111 unique genes were annotated, including 77 protein-coding genes, 30 tRNA genes, and four rRNA genes. Codon usage analysis showed that leucine had the highest frequency, while UUU (encoding phenylalanine) and UGC (encoding cysteine) were identified as the most and least frequently used codons, respectively. A total of 75-84 SSRs, 16-21 short tandem repeats, and 27-32 long repeat structures were identified in these chloroplast genomes. Then, four primer pairs were revealed for identifying SSR polymorphisms. Palindromes are the dominant type, accounting for an average of 47.86% of all long repeat sequences. Gene orders were highly collinear, and IR regions were highly conserved. Genome alignment indicated that there were four intergenic regions (psaI-ycf4, ycf3-trnS, ndhC-trnV, and ndhI-ndhG) and three coding genes (ndhJ, ycf1, and rpl20) that were highly variable among different P. heterophylla samples. Moreover, 10 SNP/MNP sites with high polymorphism were selected for further study. Phylogenetic analysis showed that populations of Chinese were clustered into a monophyletic group, in which the non-flowering variety formed a separate subclade with high statistical support. In this study, the comparative analysis of complete chloroplast genomes revealed intraspecific variations in P. heterophylla and further supported the idea that chloroplast genomes could elucidate relatedness among closely related cultivation materials.

Assembly and analysis of the first complete mitochondrial genome of Punica granatum and the gene transfer from chloroplast genome

Pomegranate (Punica granatum L.) is one of the oldest fruits with edible, medicinal and ornamental values. However, there is no report on the mitochondrial genome of pomegranate. In this study, the mitochondrial genome of P. granatum was sequenced, assembled and analyzed in detail, while the chloroplast genome was assembled using the same set of data. The results showed that the P. granatum mitogenome had a multi branched structure, using BGI + Nanopore mixed assembly strategy. The total genome length was 404,807 bp, with the GC content of 46.09%, and there were 37 protein coding genes, 20 tRNA genes and three rRNA genes. In the whole genome, 146 SSRs were identified. Besides, 400 pairs of dispersed repeats were detected, including 179 palindromic, 220 forward and one reverse. In the P. granatum mitochondrial genome, 14 homologous fragments of chloroplast genome were found, accounting for 0.54% of the total length. Phylogenetic analysis showed that among the published mitochondrial genomes of related genera, P. granatum had the closest genetic relationship with Lagerstroemia indica of Lythraceae. The 580 and 432 RNA editing sites were predicted on 37 protein coding genes of mitochondrial genome using BEDTools software and online website PREPACT respectively, but all were from C to U, of which ccmB and nad4 gene were most frequently edited, with 47 sites. This study provides a theoretical basis for understanding the evolution of higher plants, species classification and identification, and will also be useful for further utilization of pomegranate germplasm resources.

The characteristic of the complete chloroplast genome of Lithocarpus konishii (Fagaceae), a rare and endemic species in South China

Lithocarpus konishii, a rare species endemic to islands in South China, was evaluated as a vulnerable species (VU) by the 'China Species Red List.' Here, we first presented the complete chloroplast genome sequence of L. konishii. The chloroplast genome was 161,059 bp in length with 36.76% GC content, containing a small single-copy region (SSC, 18,967 bp), a large single-copy region (LSC, 90,250 bp), and a pair of inverted repeats (IRs, 25,921 bp each). A total of 139 genes were predicted, including 87 protein-coding genes (CDS), 8 rRNAs, and 44 tRNAs. Based on the concatenated shared unique CDS sequence dataset, maximum-likelihood and Bayesian inference methods were used to build the phylogenetic trees of 18 species from the Fagaceae family. Results indicated that L. konishii is closely related to L. longnux and L. pachyphyllus var. fruticosus, and forms a monophyly of the subfamily Castaneoideae with Castanopsis and Castanea. This study provides a theoretical basis for the conservation genomics of this endangered plant.

The genome of Acorus deciphers insights into early monocot evolution

Acorales is the sister lineage to all the other extant monocot plants. Genomic resource enhancement of this genus can help to reveal early monocot genomic architecture and evolution. Here, we assemble the genome of Acorus gramineus and reveal that it has ~45% fewer genes than the majority of monocots, although they have similar genome size. Phylogenetic analyses based on both chloroplast and nuclear genes consistently support that A. gramineus is the sister to the remaining monocots. In addition, we assemble a 2.2 Mb mitochondrial genome and observe many genes exhibit higher mutation rates than that of most angiosperms, which could be the reason leading to the controversies of nuclear genes- and mitochondrial genes-based phylogenetic trees existing in the literature. Further, Acorales did not experience tau (τ) whole-genome duplication, unlike majority of monocot clades, and no large-scale gene expansion is observed. Moreover, we identify gene contractions and expansions likely linking to plant architecture, stress resistance, light harvesting, and essential oil metabolism. These findings shed light on the evolution of early monocots and genomic footprints of wetland plant adaptations.

Sequencing and Analysis of Complete Chloroplast Genomes Provide Insight into the Evolution and Phylogeny of Chinese Kale (Brassica oleracea var. alboglabra)

Chinese kale is a widely cultivated plant in the genus Brassica in the family Brassicaceae. The origin of Brassica has been studied extensively, but the origin of Chinese kale remains unclear. In contrast to Brassica oleracea, which originated in the Mediterranean region, Chinese kale originated in southern China. The chloroplast genome is often used for phylogenetic analysis because of its high conservatism. Fifteen pairs of universal primers were used to amplify the chloroplast genomes of white-flower Chinese kale (Brassica oleracea var. alboglabra cv. Sijicutiao (SJCT)) and yellow-flower Chinese kale (Brassica oleracea var. alboglabra cv. Fuzhouhuanghua (FZHH)) via PCR. The lengths of the chloroplast genomes were 153,365 bp (SJCT) and 153,420 bp (FZHH) and both contained 87 protein-coding genes and eight rRNA genes. There were 36 tRNA genes in SJCT and 35 tRNA genes in FZHH. The chloroplast genomes of both Chinese kale varieties, along with eight other Brassicaceae, were analyzed. Simple sequence repeats, long repeats, and variable regions of DNA barcodes were identified. An analysis of inverted repeat boundaries, relative synonymous codon usage, and synteny revealed high similarity among the ten species, albeit the slight differences that were observed. The Ka/Ks ratios and phylogenetic analysis suggest that Chinese kale is a variant of B. oleracea. The phylogenetic tree shows that both Chinese kale varieties and B. oleracea var. oleracea were clustered in a single group. The results of this study suggest that white and yellow flower Chinese kale comprise a monophyletic group and that their differences in flower color arose late in the process of artificial cultivation. Our results also provide data that will aid future research on genetics, evolution, and germplasm resources of Brassicaceae.

Comparative chloroplast genome analysis of Sambucus L. (Viburnaceae): inference for phylogenetic relationships among the closely related Sambucus adnata Wall. ex DC Sambucus javanica Blume

Sambucus L. is found in the family Viburnaceae (syn. Adoxaceae) and encompasses approximately 29 accepted species. The complex morphology of these species has caused continued confusion concerning their nomenclature, classification, and identification. Despite previous attempts to resolve taxonomic complexities in the Sambucus genus, there are still unclear phylogenetic relationships among several species. In this study, the newly obtained plastome of Sambucus williamsii Hance. as well as the populations of Sambucus canadensis L., Sambucus javanica Blume, and Sambucus adnata Wall. ex DC were sequenced, and their sizes, structural similarity, gene order, gene number, and guanine-cytosine (GC) contents were analyzed. The phylogenetic analyses were conducted using the whole chloroplast genomes and protein-coding genes (PCGs). The findings revealed that the chloroplast genomes of Sambucus species exhibited typical quadripartite double-stranded DNA molecules. Their lengths ranged from 158,012 base pairs (bp) (S. javanica) to 158,716 bp (S. canadensis L). Each genome comprised a pair of inverted repeats (IRs), which separated the large single-copy (LSC) and small single-copy (SSC) regions. In addition, the plastomes contained 132 genes, encompassing 87 protein-coding, 37 tRNA, and four rRNA genes. In the simple sequence repeat (SSR) analysis, A/T mononucleotides had the highest proportion, with the most repetitive sequences observed in S. williamsii. The comparative genome analyses showed high similarities in structure, order, and gene contents. The hypervariable regions in the studied chloroplast genomes were trnT-GGU, trnF-GAA, psaJ, trnL-UAG, ndhF, and ndhE, which may be used as candidate barcodes for species discrimination in Sambucus genus. Phylogenetic analyses supported the monophyly of Sambucus and revealed the separation of S. javanica and S. adnata populations. Sambucus chinensis Lindl. was nested within S. javanica in the same clade, collaborating their conspecific treatment. These outcomes indicate that the chloroplast genome of Sambucus plants is a valuable genetic resource for resolving taxonomic discrepancies at the lower taxonomic levels and can be applied in molecular evolutionary studies.

Comparative chloroplast genome analysis of Sambucus L. (Viburnaceae): inference for phylogenetic relationships among the closely related Sambucus adnata Wall. ex DC Sambucus javanica Blume

Sambucus L. is found in the family Viburnaceae (syn. Adoxaceae) and encompasses approximately 29 accepted species. The complex morphology of these species has caused continued confusion concerning their nomenclature, classification, and identification. Despite previous attempts to resolve taxonomic complexities in the Sambucus genus, there are still unclear phylogenetic relationships among several species. In this study, the newly obtained plastome of Sambucus williamsii Hance. as well as the populations of Sambucus canadensis L., Sambucus javanica Blume, and Sambucus adnata Wall. ex DC were sequenced, and their sizes, structural similarity, gene order, gene number, and guanine–cytosine (GC) contents were analyzed. The phylogenetic analyses were conducted using the whole chloroplast genomes and protein-coding genes (PCGs). The findings revealed that the chloroplast genomes of Sambucus species exhibited typical quadripartite double-stranded DNA molecules. Their lengths ranged from 158,012 base pairs (bp) (S. javanica) to 158,716 bp (S. canadensis L). Each genome comprised a pair of inverted repeats (IRs), which separated the large single-copy (LSC) and small single-copy (SSC) regions. In addition, the plastomes contained 132 genes, encompassing 87 protein-coding, 37 tRNA, and four rRNA genes. In the simple sequence repeat (SSR) analysis, A/T mononucleotides had the highest proportion, with the most repetitive sequences observed in S. williamsii. The comparative genome analyses showed high similarities in structure, order, and gene contents. The hypervariable regions in the studied chloroplast genomes were trnT-GGU, trnF-GAA, psaJ, trnL-UAG, ndhF, and ndhE, which may be used as candidate barcodes for species discrimination in Sambucus genus. Phylogenetic analyses supported the monophyly of Sambucus and revealed the separation of S. javanica and S. adnata populations. Sambucus chinensis Lindl. was nested within S. javanica in the same clade, collaborating their conspecific treatment. These outcomes indicate that the chloroplast genome of Sambucus plants is a valuable genetic resource for resolving taxonomic discrepancies at the lower taxonomic levels and can be applied in molecular evolutionary studies.

Host shift promotes divergent evolution between closely related holoparasitic species

Distinct hosts have been hypothesized to possess the potential for affecting species differentiation and genome evolution of parasitic organisms. However, what host shift history is experienced by the closely related parasites and whether disparate evolution of their genomes occur remain largely unknown. Here, we screened horizontal gene transfer (HGT) events in a pair of sister species of holoparasitic Boschniakia (Orobanchaceae) having obligate hosts from distinct families to recall the former host-parasite associations and performed a comparative analysis to investigate the difference of their organelle genomes. Except those from the current hosts (Ericaceae and Betulaceae), we identified a number of HGTs from Rosaceae supporting the occurrence of unexpected ancient host shifts. Different hosts transfer functional genes which changed nuclear genomes of this sister species. Likewise, different donors transferred sequences to their mitogenomes, which vary in size due to foreign and repetitive elements rather than other factors found in other parasites. The plastomes are both severely reduced, and the degree of difference in reduction syndrome reaches the intergeneric level. Our findings provide new insights into the genome evolution of parasites adapting to different hosts and extend the mechanism of host shift promoting species differentiation to parasitic plant lineages.

The complete chloroplast genome and phylogenetic analysis of Lemmaphyllum carnosum var. drymoglossoides (baker) X. P. Wei, 2013

Lemmaphyllum carnosum var. drymoglossoides (Baker) X. P. Wei, 2013 is a valuable medicinal fern in China. Its complete chloroplast genome was determined using Illumina paired-end sequencing. The genome was 157,571 bp in length with 130 genes, including 87 protein-coding genes, eight ribosomal RNA genes, and 35 tRNA genes. It displayed a quadripartite structure consisting of a small single-copy (SSC) of 21,691 bp, a large single-copy (LSC) of 81,106 bp, and two inverted repeats (IRs) of 27,387 bp, respectively. The phylogenetic results indicated that L. carnosum var. drymoglossoides exhibited the closest relationship with L. intermedium, and this study provided new information for the phylogenetic relationship of the Polypodiaceae family.

The complete chloroplast genome sequence of Aconitum tschangbaischanense (Ranunculaceae)

The perennial herbal medicine species Aconitum tschangbaischanense, is endemic to Changhai Mountain, Jilin province. In this study, we attempted to uncover the complete chloroplast (cp) genome of A. tschangbaischanense based on sequencing data using the Illumina sequencing technology. As per the results: (1) the length of its complete cp genome is 155,881 bp with a typical tetrad structure; (2) the structure of its cp genome contains large single-copy and small single-copy (LSC and SSC) regions of 86,351 and 16,9444 bp, respectively, isolated by two inverted repeat regions (IRs) of 26,293 bp; (3) we annotated a total 131 genes, consisting of 86 protein-coding genes, eight rRNA genes, and 37 tRNA genes. According to the maximum-likelihood phylogenetic tree based on complete cp genomes, A. tschangbaischanense, showed close association with A. carmichaelii, which belongs to clade I. Finally, this study provides the characteristics of the cp genome of A. tschangbaischanense, and its phylogenetic position.

The complete chloroplast genome of Corethrodendron multijugum (Fabaceae: Corethrodendron) and phylogenetic analysis

Corethrodendron multijugum (Maxim.) (Fabaceae: Corethrodendron), also known as Hedysarum multijugum, is an important medicinal plant and is widely used in traditional Chinese medicine. To better understand the diversity and phylogeny of C. multijugum and other Fabaceae species, we sequenced and annotated the complete chloroplast genome of C. multijugum using the Illumina HiSeq 2500 platform. This complete genome was 122,994 bp long, and encodes a total of 110 genes, including 76 protein-coding genes (PCGs), 30 transfer RNA genes (tRNAs), and four ribosomal RNA unit genes (rRNAs). The C. multijugum plastid with a G + C content of 34.5% presents a negative AT -skew (-0.002) and a positive GC -skew (0.032). Phylogenetic analysis revealed that C. multijugum is more closely related to Hedysarum petrovii. This study provides genetic resource information for the further study of Corethrodendron.

Comparative study on chloroplast genomes of three Hansenia forbesii varieties (Apiaceae)

To find the gene hypervariable regions of three varieties of Hansenia forbesii H. Boissieu and determine their phylogenetic relationship, the chloroplast (cp) genome of these three varieties were firstly sequencing by the Illumina hiseq platform. In this study, we assembled the complete cp genome sequences of Hansenia forbesii LQ (156,954 bp), H. forbesii QX (157,181 bp), H. forbesii WQ (156,975 bp). They all contained 84 protein-coding genes, 37 tRNAs, and 8 rRNAs. The hypervariable regions between three cp genomes were atpF-atpH, petD, and rps15-ycf1. Phylogenetic analysis showed that H. forbesii LQ and H. forbesii WQ were closely related, followed by H. forbesii QX. This study showed that the three varieties of H. forbesii could be identified by the complete cp genome and specific DNA barcode (trnC-GCA-petN) and provided a new idea for germplasm identification of similar cultivated varieties.

Uncovering the first complete chloroplast genomics, comparative analysis, and phylogenetic relationships of the medicinal plants Rhamnus cathartica and Frangula alnus (Rhamnaceae)

Rhamnus cathartica and Frangula alnus are economically valuable medicinal plants from the Rhamnaceae family. However, their chloroplast genome structure, phylogenetic position, relationships, and evolution remain poorly understood. Herein, the complete chloroplast genome resources of R. cathartica and F. alnus have been added. The first comparative analysis of the Rhamnus and Frangula species based on complete chloroplast genomes was provided. The chloroplast genomes of R. cathartica and F. alnus exhibited a quadripartite structure, with total lengths of 161,149 bp and 161,255 bp, respectively. The lack of the infA and psbL genes does not negatively impact the normal functioning of Rhamnus and Frangula species. The rpl20 and rpl33 genes are undergoing rapid evolution. Rhamnus and Frangula species prefer amino acids with A/U-terminal codons. There were between 100 and 126 simple sequence repeats and between 38 and 100 long repeats. Several highly divergent intergenic regions (trnK-UUU-trnQ-UUG, atpH-atpI, trnY-GUA-trnE-UUC, trnG-GCC-trnfM-CAU, trnT-UGU-trnF-GAA, rpl20-rps12, and rpl22-rps19) and highly divergent genes (ycf3, ndhA, rpl32, and ycf1) were identified, which could serve as potential phylogenetic markers due to their variability. We reconstructed the phylogenetic relationships among Rhamnus species and F. alnus using complete chloroplast genomes. There is no significant correlation between the medicinal value of the species analyzed and their phylogenetic relationships. These results provide valuable insights for understanding the phylogenetic relationship and evolution of Rhamnus and Frangula species. These findings could serve as a foundation for future studies on the Rhamnaceae.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12298-023-01331-7.

A complete chloroplast genome of a traditional Chinese medicine herb, Rubia podantha, and phylogenomics of Rubiaceae

Rubia podantha Diels is endemic to southwestern China and belongs to the family Rubiaceae. It is used in traditional Chinese medicines. To enrich the genetic data and resolve Rubiaceae's phylogeny, we assembled a complete chloroplast (cp) genome of R. podantha using Illumina HiSeq reads. The whole length of the cp genome was 154,866 bp. Annotation using PGA software found 113 genes, including 79 protein coding genes, 30 tRNA genes, and four rRNA genes. The large single-copy region was 84,717 bp, the inverted repeat B (IRa) region was 26,516 bp, the small single copy was 17,117 bp, and the inverted repeats B (IRb) region was 26,516 bp. Moreover, 64 SSRs were identified. Phylogenomic analysis using cp genomes of 109 Rubiaceae species found that R. podantha is closely related to R. cordifola. Rubiaceae was separated into three subfamilies: Ixoroideae, Cinchonoideae, and Rubiodeae. The genus Saprosma was not imbedded within the Spermacoceae alliance as reported in previous studies. Instead, it was imbedded within the Psychotrieae alliance. Divergence time estimation indicated that R. podantha split from its relative R. cordifolia around 1.25 million years ago. The assembled chloroplast genome in this study provided useful molecular information about the evolution of R. podantha and was a basis for phylogenetic analyses of Rubiaceae.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12298-023-01302-y.

The complete plastid genome and characteristics analysis of Achillea millefolium

Achillea is a crop with Chinese herbal characteristics and horticultural values. Its leaves and flowers contain aromatic oil, and the ripe herb can also be used as medicine to induce sweat and relieve rheumatic pains. It is seen cultivated in gardens all over China. Currently, the most comprehensive chloroplast genome sample involved in the study refers to New World clades of Achillea, which are used for marker selection and phylogenetic research. We completely sequenced the chloroplast genomes of Achillea millefolium. These sequencing results showed that the plastid genome is 149,078 bp in size and possesses a typical quadripartite structure containing one large single copy (LSC) with 82,352 bp, one small single copy (SSC) with 18,426 bp, and a pair of inverted repeat (IR) regions with 24,150 bp in Achillea millefolium. The chloroplast genome encodes a common number of genes, of which 88 are protein-coding genes, 37 transfer ribonucleic acid genes, and 8 ribosomal ribonucleic acid genes, which are highly similar in overall size, genome structure, gene content, and sequence. The exact similarity was observed when compared to other Asteraceae species. However, there were structural differences due to the restriction or extension of the inverted repeat (IR) regions-the palindromic repeats being the most prevalent form. Based on 12 whole-plastomes, 3 hypervariable regions (rpoB, rbcL, and petL-trnP-UGG) were discovered, which could be used as potential molecular markers.

Analysis of the complete plastomes of Bidens pilosa L. 1753 (Asteraceae, Coreopsideae) from Beijing, China reveals high genetic diversity and possible misidentifications

Bidens pilosa L. 1753 is a perennial herbaceous flowering plant, traditionally used in foods and medicines. In this study, we sequenced, assembled, and characterized the complete plastome of B. pilosa from Beijing, China. The plastome (MN385242) is circularized with a conservative quadripartite structure. Its length is 150,524 bp, including a large single-copy region (83,535 bp), a small single-copy region (17,627 bp), and a pair of inverted repeat regions (each 24,681 bp). The plastome consists of 128 genes, including 78 unique protein-coding, 28 unique tRNA, and 4 unique rRNA genes. Phylogenetic analyses showed all five B. pilosa plants couldn't form a monophyletic clade and were separated into three clades. The results of K2P distance and molecular markers were all consistent with those of phylogenetic analysis, revealing high genetic diversity and even possible misidentifications of the B. pilosa. Our results highlighted the importance of correct species identification of materials in medicinal products.

Progress, challenge and prospect of plant plastome annotation

The plastome (plastid genome) represents an indispensable molecular data source for studying phylogeny and evolution in plants. Although the plastome size is much smaller than that of nuclear genome, and multiple plastome annotation tools have been specifically developed, accurate annotation of plastomes is still a challenging task. Different plastome annotation tools apply different principles and workflows, and annotation errors frequently occur in published plastomes and those issued in GenBank. It is therefore timely to compare available annotation tools and establish standards for plastome annotation. In this review, we review the basic characteristics of plastomes, trends in the publication of new plastomes, the annotation principles and application of major plastome annotation tools, and common errors in plastome annotation. We propose possible methods to judge pseudogenes and RNA-editing genes, jointly consider sequence similarity, customed algorithms, conserved domain or protein structure. We also propose the necessity of establishing a database of reference plastomes with standardized annotations, and put forward a set of quantitative standards for evaluating plastome annotation quality for the scientific community. In addition, we discuss how to generate standardized GenBank annotation flatfiles for submission and downstream analysis. Finally, we prospect future technologies for plastome annotation integrating plastome annotation approaches with diverse evidences and algorithms of nuclear genome annotation tools. This review will help researchers more efficiently use available tools to achieve high-quality plastome annotation, and promote the process of standardized annotation of the plastome.

Genetic diversity and population divergence of Leonurus japonicus and its distribution dynamic changes from the last interglacial to the present in China

BACKGROUND

Leonurus japonicus, a significant medicinal plant known for its therapeutic effects on gynecological and cardiovascular diseases, has genetic diversity that forms the basis for germplasm preservation and utilization in medicine. Despite its economic value, limited research has focused on its genetic diversity and divergence.

RESULTS

The avg. nucleotide diversity of 59 accessions from China were 0.00029 and hotspot regions in petN-psbM and rpl32-trnL_(UAG) spacers, which can be used for genotype discrimination. These accessions divided into four clades with significant divergence. The four subclades, which split at approximately 7.36 Ma, were likely influenced by the Hengduan Mountains uplift and global temperature drop. The initial divergence gave rise to Clade D, with a crown age estimated at 4.27 Ma, followed by Clade C, with a crown age estimated at 3.39 Ma. The four clades were not showed a clear spatial distribution. Suitable climatic conditions for the species were identified, including warmest quarter precipitation 433.20 mm ~ 1,524.07 mm, driest month precipitation > 12.06 mm, and coldest month min temp > -4.34 °C. The high suitability distribution showed contraction in LIG to LGM, followed by expansion from LGM to present. The Hengduan Mountains acted as a glacial refuge for the species during climate changes.

CONCLUSIONS

Our findings reflected a clear phylogenetic relationships and divergence within species L. japonicus and the identified hotspot regions could facilitate the genotype discrimination. The divergence time estimation and suitable area simulation revealed evolution dynamics of this species and may propose conservation suggestions and exploitation approaches in the future.

Complete Chloroplast Genome Determination of Ranunculus sceleratus from Republic of Korea (Ranunculaceae) and Comparative Chloroplast Genomes of the Members of the Ranunculus Genus

Ranunculus sceleratus (family: Ranunculaceae) is a medicinally and economically important plant; however, gaps in taxonomic and species identification limit its practical applicability. This study aimed to sequence the chloroplast genome of R. sceleratus from Republic of Korea. Chloroplast sequences were compared and analyzed among Ranunculus species. The chloroplast genome was assembled from Illumina HiSeq 2500 sequencing raw data. The genome was 156,329 bp and had a typical quadripartite structure comprising a small single-copy region, a large single-copy region, and two inverted repeats. Fifty-three simple sequence repeats were identified in the four quadrant structural regions. The region between the ndhC and trnV-UAC genes could be useful as a genetic marker to distinguish between R. sceleratus populations from Republic of Korea and China. The Ranunculus species formed a single lineage. To differentiate between Ranunculus species, we identified 16 hotspot regions and confirmed their potential using specific barcodes based on phylogenetic tree and BLAST-based analyses. The ndhE, ndhF, rpl23, atpF, rps4, and rpoA genes had a high posterior probability of codon sites in positive selection, while the amino acid site varied between Ranunculus species and other genera. Comparison of the Ranunculus genomes provides useful information regarding species identification and evolution that could guide future phylogenetic analyses.

The complete chloroplast genome sequence of Sedum bulbiferum (Crassulaceae)

Sedum bulbiferum is a traditional medicinal plant in China, with few reports on its chloroplast genome. In this study, the chloroplast genome of Sedum bulbiferum was characterized, and its phylogenetic position among other closely related species was studied. The results showed that the full length of the chloroplast genome was 150,074 bp, containing a large single-copy (LSC) region and a small single-copy (SSC) region of 81,730 and 16,726 bp, respectively, as well as two inverted repeat regions (IRs) of 25,809 bp like other plants. A total of 128 genes were found, including 83 protein-coding genes, 37 tRNA genes, and eight rRNA genes. Phylogenetic analysis showed that Sedum bulbiferum is closely related to Sedum emarginatum, Sedum alfredii, Sedum tricarpum, Sedum plumbizincicola, and Sedum sarmentosum.

Comparative plastome genomics, taxonomic delimitation and evolutionary divergences of Tetraena hamiensis var. qatarensis and Tetraena simplex (Zygophyllaceae)

The Zygophyllum and Tetraena genera are intriguingly important ecologically and medicinally. Based on morphological characteristics, T. hamiensis var. qatarensis, and T. simplex were transferred from Zygophyllum to Tetraena with the least genomic datasets available. Hence, we sequenced the T. hamiensis and T. simplex and performed in-depth comparative genomics, phylogenetic analysis, and estimated time divergences. The complete plastomes ranged between 106,720 and 106,446 bp-typically smaller than angiosperms plastomes. The plastome circular genomes are divided into large single-copy regions (~ 80,964 bp), small single-copy regions (~ 17,416 bp), and two inverted repeats regions (~ 4170 bp) in both Tetraena species. An unusual shrinkage of IR regions 16-24 kb was identified. This resulted in the loss of 16 genes, including 11 ndh genes which encode the NADH dehydrogenase subunits, and a significant size reduction of Tetraena plastomes compared to other angiosperms. The inter-species variations and similarities were identified using genome-wide comparisons. Phylogenetic trees generated by analyzing the whole plastomes, protein-coding genes, matK, rbcL, and cssA genes exhibited identical topologies, indicating that both species are sisters to the genus Tetraena and may not belong to Zygophyllum. Similarly, based on the entire plastome and proteins coding genes datasets, the time divergence of Zygophyllum and Tetraena was 36.6 Ma and 34.4 Ma, respectively. Tetraena stem ages were 31.7 and 18.2 Ma based on full plastome and protein-coding genes. The current study presents the plastome as a distinguishing and identification feature among the closely related Tetraena and Zygophyllum species. It can be potentially used as a universal super-barcode for identifying plants.