Evolutionary dynamics of chloroplast genomes in subfamily Aroideae (Araceae)

Complete chloroplast genome and phylogenetic analysis of Amorphophallus paeoniifolius (Araceae)

Amorphophallus paeoniifolius (Dennst.) Nicolson, 1885, often known as elephant foot yam, is a tropical tuber crop that originates from south-east Asia and belongs to the Araceae family. It is known for its high production potential and popularity as a medicinal plant. However, the phylogeny and genes for this species are still unavailable. In this study, the first complete chloroplast genome of A. paeoniifolius was reported and phylogenetic analysis was conducted with Araceae species. The chloroplast genome was 176,258 bp in length with 34.80% overall GC content and includes a large single-copy (LSC) region (93,951 bp), a small single-copy (SSC) region (15,013 bp), and a pair of inverted repeat (IRs) regions (33,647 bp). The chloroplast genome has 130 genes, which include 85 protein-coding genes, 37 tRNA genes, and eight rRNA genes. A maximum-likelihood (ML) phylogenetic analysis indicated that all Amorphophallus species formed a single monophyletic clade with a high bootstrap value and A. paeoniifolius was closely related to A. konjac, A. albus, A. krausei, and A. titanum. The chloroplast genome reported in this study will be useful for further taxonomic and evolutionary studies of Amorphophallus.

Genetic characterization and phylogenetic analysis of the Nigella sativa (black seed) plastome

In this study, the complete plastome sequence of Nigella sativa (black seed), was analyzed for the first time. The plastome spans approximately 154,120 bp, comprising four sections: the Large Single-Copy (LSC) (85,538 bp), the Small Single-Copy (SSC) (17,984 bp), and two Inverted Repeat (IR) regions (25,299 bp). A comparative study of N. sativa's plastome with ten other species from various genera in the Ranunculaceae family reveals substantial structural variations. The contraction of the inverted repeat region in N. sativa influences the boundaries of single-copy regions, resulting in a shorter plastome size than other species. When comparing the plastome of N. sativa with those of its related species, significant divergence is observed, particularly except for N. damascena. Among these, the plastome of A. glaucifolium displays the highest average pairwise sequence divergence (0.2851) with N. sativa, followed by A. raddeana (0.2290) and A. coerulea (0.1222). Furthermore, the study identified 12 distinct hotspot regions characterized by elevated Pi values (> 0.1). These regions include trnH-GUG-psbA, matK-trnQ-UUG, psbK-trnR-UCU, atpF-atpI, rpoB-psbD, ycf3-ndhJ, ndhC-cemA, petA-psaJ, trnN-GUU-ndhF, trnV-GAC-rps12, ycf2-trnI-CAU, and ndhA-ycf1. Approximately, 24 tandem and 48 palindromic and forward repeats were detected in N. sativa plastome. The analysis revealed 32 microsatellites with the majority being mononucleotide repeats. In the N. sativa plastome, phenylalanine had the highest number of codons (1982 codons), while alanine was the least common amino acid with 260 codons. A phylogenetic tree, constructed using protein-coding genes, revealed a distinct monophyletic clade comprising N. sativa and N. damascene, closely aligned with the Cimicifugeae tribe and exhibiting robust support. This plastome provides valuable genetic information for precise species identification, phylogenetic resolution, and evolutionary studies of N. sativa.

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

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

Comparative genomics and phylogenetic analysis of chloroplast genomes of Asian Caryodaphnopsis taxa (Lauraceae)

The genus Caryodaphnopsis, a member of the Lauraceae family, is characterized by seeds that are rich in oil, as well as highly exploitable fruits and wood. The Asian taxa within this genus exhibit complex morphological variations, posing challenges to their accurate classification and impeding their effective use and development as a resource. In this study, we sequenced the chloroplast genomes of 31 individuals representing nine Asian taxa within the Caryodaphnopsis genus. Our primary objectives were to reveal structural variations in these chloroplast genomes through comparative analyses and to infer the species' phylogenetic relationships. Our findings revealed that all chloroplast genomes had a tetrad structure, ranged in length from 148,828 to 154,946 bp, and harbored 128-131 genes. Notably, contraction of the IR region led to the absence of some genes in eight taxa. A comprehensive analysis identified 1267 long repetitive sequences and 2176 SSRs, 286 SNPs, and 135 indels across the 31 chloroplast genomes. The Ka/Ks ratio analysis indicated potential positive selection on the matK, rpl22, and rpoC2 genes. Furthermore, we identified six variable regions as promising barcode regions. Phylogenetic analysis grouped the nine Asian taxa into six branches, with C. henryi forming the basal group from which three distinct complexes emerged. This study contributes significantly to the current understanding of the evolutionary dynamics and phylogenetic relationships within the genus Caryodaphnopsis. Furthermore, the identified molecular markers hold potential for molecular barcoding applications in population genetics, providing valuable tools for future research and conservation efforts within this diverse genus.

The first complete chloroplast genome of Thalictrum fargesii: insights into phylogeny and species identification

Introduction

Thalictrum fargesii is a medicinal plant belonging to the genus Thalictrum of the Ranunculaceae family and has been used in herbal medicine in the Himalayan regions of China and India. This species is taxonomically challenging because of its morphological similarities to other species within the genus. Thus, herbal drugs from this species are frequently adulterated, substituted, or mixed with other species, thereby endangering consumer safety.

Methods

The present study aimed to sequence and assemble the entire chloroplast (cp) genome of T. fargesii using the Illumina HiSeq 2500 platform to better understand the genomic architecture, gene composition, and phylogenetic relationships within the Thalictrum.

Results and discussion

The cp genome was 155,929 bp long and contained large single-copy (85,395 bp) and small single-copy (17,576 bp) regions that were segregated by a pair of inverted repeat regions (26,479 bp) to form a quadripartite structure. The cp genome contains 133 genes, including 88 protein-coding genes (PCGs), 37 tRNA genes, and 8 rRNA genes. Additionally, this genome contains 64 codons that encode 20 amino acids, the most preferred of which are alanine and leucine. We identified 68 SSRs, 27 long repeats, and 242 high-confidence C-to-U RNA-editing sites in the cp genome. Moreover, we discovered seven divergent hotspot regions in the cp genome of T. fargesii, among which ndhD-psaC and rpl16-rps3 may be useful for developing molecular markers for identifying ethnodrug species and their contaminants. A comparative study with eight other species in the genus revealed that pafI and rps19 had highly variable sites in the cp genome of T. fargesii. Additionally, two special features, (i) the shortest length of the ycf1 gene at the IRA-SSC boundary and (ii) the distance between the rps19 fragment and trnH at the IRA-LSC junction, distinguish the cp genome of T. fargesii from those of other species within the genus. Furthermore, phylogenetic analysis revealed that T. fargesii was closely related to T. tenue and T. petaloidium.

Conclusion

Considering all these lines of evidence, our findings offer crucial molecular and evolutionary information that could play a significant role in further species identification, evolution, and phylogenetic studies on T. fargesii.

Phylogenomics and plastomics offer new evolutionary perspectives on Kalanchoideae (Crassulaceae)

BACKGROUND AND AIMS

Kalanchoideae is one of three subfamilies within Crassulaceae and contains four genera. Despite previous efforts, the phylogeny of Kalanchoideae remains inadequately resolved with persistent issues including low support, unstructured topologies and polytomies. This study aimed to address two central objectives: (1) resolving the pending phylogenetic questions within Kalanchoideae by using organelle-scale 'barcodes' (plastomes) and nuclear data; and (2) investigating interspecific diversity patterns among Kalanchoideae plastomes.

METHODS

To explore the plastome evolution in Kalanchoideae, we newly sequenced 38 plastomes representing all four constituent genera (Adromischus, Cotyledon, Kalanchoe and Tylecodon). We performed comparative analyses of plastomic features, including GC and gene contents, gene distributions at the IR (inverted repeat) boundaries, nucleotide divergence, plastomic tRNA (pttRNA) structures and codon aversions. Additionally, phylogenetic inferences were inferred using both the plastomic dataset (79 genes) and nuclear dataset (1054 genes).

KEY RESULTS

Significant heterogeneities were observed in plastome lengths among Kalanchoideae, strongly correlated with LSC (large single copy) lengths. Informative diversities existed in the gene content at SSC/IRa (small single copy/inverted repeat a), with unique patterns individually identified in Adromischus leucophyllus and one major Kalanchoe clade. The ycf1 gene was assessed as a shared hypervariable region among all four genera, containing nine lineage-specific indels. Three pttRNAs exhibited unique structures specific to Kalanchoideae and the genera Adromischus and Kalanchoe. Moreover, 24 coding sequences revealed a total of 41 lineage-specific unused codons across all four constituent genera. The phyloplastomic inferences clearly depicted internal branching patterns in Kalanchoideae. Most notably, by both plastid- and nuclear-based phylogenies, our research offers the first evidence that Kalanchoe section Eukalanchoe is not monophyletic.

CONCLUSIONS

This study conducted comprehensive analyses on 38 newly reported Kalanchoideae plastomes. Importantly, our results not only reconstructed well-resolved phylogenies within Kalanchoideae, but also identified highly informative unique markers at the subfamily, genus and species levels. These findings significantly enhance our understanding of the evolutionary history of Kalanchoideae.

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 assembly of Amorphophallus kiusianus makino 1913 (araceae) from Southern China

The mountainous region of southern China has been characterized by its complicated environment and topography. Amorphophallus kiusianus Makino 1913 is a representative species of extreme habitat preference that resides mainly in this region. To help study the genetic differentiation mechanisms of A. kiusianus populations, we sequenced the first chloroplast genome of this species using next-generation sequencing. The chloroplast genome was 166,269 bp in length with an average GC content of 36% (GenBank accession number: PP072243). The lengths of the large single-copy region (LSC), small single-copy region (SSC), and two inverted repeats (IRs) were 90,701 bp, 14,802 bp, 31,383 bp, and 31,383 bp, respectively. One hundred and twenty-nine genes were annotated in the chloroplast genome, including 84 protein-coding genes, 8 rRNA genes, and 37 tRNA genes. The phylogenetic tree suggested a close relationship among A. kiusianus, A. yunnanensis, and A. coaetaneus. The chloroplast genome reported in this study provides valuable genomic resources for the future phylogeographic research of A. kiusianus.

Assembly and analysis of the chloroplast genome of Amorphophallus kachinensis Engler & Gehrmann (Araceae) from Southwestern China: implications for conservation and utilization

Konjac glucomannan consists of D-mannose and D-glucose units and is a hydrocolloid obtained from the corm of Amorphophallus species. Due to its bioactive properties, biodegradability, and hydrophilic ability, glucomannan is widely used in the fields of food, medicine, and industry. Amorphophallus species have been cultivated as cash crops in many Asian countries. Amorphophallus kachinensis Engler & Gehrmann 1911 is naturally distributed in southwestern China, Laos, and northern Thailand. To help the genetic assessment and conservation of this species, the first chloroplast genome of A. kachinensis was sequenced on the Illumina sequencing platform. We assembled the chloroplast genome using the software GetOrganelle and annotated the genome by Geseq and Cpgavas 2. The assembled chloroplast genome was 173,330 bp long, and the average GC content was 35% (GenBank accession number: PP072244). The chloroplast genome of A. kachinensis contained one large single copy, one small single copy, and two inverted repeats, with lengths of 92,030 bp, 15,118 bp, 33,091 bp, and 33,091 bp, respectively. We successfully annotated 132 genes across the genome, which was consistent with other Amorphophallus species. The phylogenetic tree indicates a sub-divergence in the Amorphophallus genus with two main genetic groups detected among eight species. The two genetic groups should be treated as distinct evolutionarily significant units when making conservation strategies. Our study enriched the chloroplast genome resources of the Amorphophallus genus and could help future phylogeographic studies, protection, and utilization of wild resources.

Plastid genome data provide new insights into the dynamic evolution of the tribe Ampelopsideae (Vitaceae)

BACKGROUND

Ampelopsideae J. Wen & Z.L. Nie is a small-sized tribe of Vitaceae Juss., including ca. 47 species from four genera showing a disjunct distribution worldwide across all the continents except Antarctica. There are numerous species from the tribe that are commonly used as medicinal plants with immune-modulating, antimicrobial, and anti-hypertensive properties. The tribe is usually recognized into three clades, i.e., Ampelopsis Michx., Nekemias Raf., and the Southern Hemisphere clade. However, the relationships of the three clades differ greatly between the nuclear and the plastid topologies. There has been limited exploration of the chloroplast phylogenetic relationships within Ampelopsideae, and studies on the chloroplast genome structure of this tribe are only available for a few individuals. In this study, we aimed to investigate the evolutionary characteristics of plastid genomes of the tribe, including their genome structure and evolutionary insights.

RESULTS

We sequenced, assembled, and annotated plastid genomes of 36 species from the tribe and related taxa in the family. Three main clades were recognized within Ampelopsideae, corresponding to Ampelopsis, Nekemias, and the Southern Hemisphere lineage, respectively, and all with 100% bootstrap supports. The genome sequences and content of the tribe are highly conserved. However, comparative analyses suggested that the plastomes of Nekemias demonstrate a contraction in the large single copy region and an expansion in the inverted repeat region, and possess a high number of forward and palindromic repeat sequences distinct from both Ampelopsis and the Southern Hemisphere taxa.

CONCLUSIONS

Our results highlighted plastome variations in genome length, expansion or contraction of the inverted repeat region, codon usage bias, and repeat sequences, are corresponding to the three lineages of the tribe, which probably faced with different environmental selection pressures and evolutionary history. This study provides valuable insights into understanding the evolutionary patterns of plastid genomes within the Ampelopsideae of Vitaceae.

The evolution of ephemeral flora in Xinjiang, China: insights from plastid phylogenomic analyses of Brassicaceae

BACKGROUND

The ephemeral flora of northern Xinjiang, China, plays an important role in the desert ecosystems. However, the evolutionary history of this flora remains unclear. To gain new insights into its origin and evolutionary dynamics, we comprehensively sampled ephemeral plants of Brassicaceae, one of the essential plant groups of the ephemeral flora.

RESULTS

We reconstructed a phylogenetic tree using plastid genomes and estimated their divergence times. Our results indicate that ephemeral species began to colonize the arid areas in north Xinjiang during the Early Miocene and there was a greater dispersal of ephemeral species from the surrounding areas into the ephemeral community of north Xinjiang during the Middle and Late Miocene, in contrast to the Early Miocene or Pliocene periods.

CONCLUSIONS

Our findings, together with previous studies, suggest that the ephemeral flora originated in the Early Miocene, and species assembly became rapid from the Middle Miocene onwards, possibly attributable to global climate changes and regional geological events.

The complete chloroplast genome of Philodendron hederaceum (Jacq.) Schott 1829 (Alismatales: Araceae)

Philodendron hederaceum (Jacq.) Schott 1829, a species of the Araceae family, is a foliage plant of ornamental value. The complete chloroplast genome sequence of Philodendron hederaceum was obtained by the de novo assembly of NovaSeq 6000 (Illumina Co., San Diego, CA) paired-end short reads and Oxford Nanopore long reads. The complete chloroplast genome of P. hederaceum was 168,609 bp in length, with a large single-copy (LSC) region of 94,393 bp, a small single-copy (SSC) region of 25,774 bp, and a pair of identical inverted repeat regions (IRs) of 24,221 bp. The genome contained a total of 129 genes, including 85 protein-coding genes, 36 transfer RNA (tRNA) genes, and eight ribosomal RNA (rRNA) genes. The phylogenetic analysis of P. hederaceum with 19 related species and two outgroup species revealed the closest taxonomical relationship with Philodendron lanceolatum in the Araceae family.

Chloroplast genome analyses of Caragana arborescens and Caragana opulens

BACKGROUND

Numerous species within the genus Caragana have high ecological and medicinal value. However, species identification based on morphological characteristics is quite complicated in the genus. To address this issue, we analyzed complete plastid genome data for the genus.

RESULTS

We obtained chloroplast genomes of two species, Caragana arborescens and Caragana opulens, using Illumina sequencing technology, with lengths of 129,473 bp and 132,815 bp, respectively. The absence of inverted repeat sequences in the two species indicated that they could be assigned to the inverted repeat-lacking clade (IRLC). The genomes included 111 distinct genes (4 rRNA genes, 31 tRNA genes, and 76 protein-coding genes). In addition, 16 genes containing introns were identified in the two genomes, the majority of which contained a single intron. Repeat analyses revealed 129 and 229 repeats in C. arborescens and C. opulens, respectively. C. arborescens and C. opulens genomes contained 277 and 265 simple sequence repeats, respectively. The two Caragana species exhibited similar codon usage patterns. rpl20-clpP, rps19-rpl2, and rpl23-ycf2 showed the highest nucleotide diversity (pi). In an analysis of sequence divergence, certain intergenic regions (matK-rbcL, psbM-petN, atpA-psbI, petA-psbL, psbE-petL, and rps7-rps12) were highly variable. A phylogenetic analysis showed that C. arborescens and C. opulens were related and clustered together with four other Caragana species. The genera Astragalus and Caragana were relatively closely related.

CONCLUSIONS

The present study provides valuable information about the chloroplast genomes of C. arborescens and C. opulens and lays a foundation for future phylogenetic research and molecular marker development.

A new perspective on codon usage, selective pressure, and phylogenetic implications of the plastomes in the Telephium clade (Crassulaceae)

The Telephium clade of the Crassulaceae family contains many medicinal, ornamental, and ecologically restorative plants. However, the phylogenetic relationships within the clade remain debated, and comprehensive analyses of codon usage and selection pressure in Telephium plastomes are limited. In this study, we assembled and annotated four plastomes and performed extensive analyses. The plastomes exhibited a typical quadripartite structure and high conservation. The lengths ranged from 151,357 bp to 151,641 bp with 134 genes identified. The GC content was the highest within IR, followed by LSC, and lowest in the SSC region. Meanwhile, a unique inversion was observed within the LSC region of Meterostachys sikokianus. Polymorphisms analysis revealed minimum nucleotide diversity in the IR regions, with over ten highly polymorphic regions identified. Phylogenetically, two subclades formed within the monophyletic Telephium clade, with Umbilicus as the sister group to the remaining Hylotelephium subclade members. Notably, no significant positive selection was found among the 79 plastid genes, which showed varying evolutionary patterns. However, 19 genes contained codons under positive selection. The specific functions of these sites require further investigation. Synonymous codon usage was biased and conserved across the tested plastomes, shaped by natural selection, mutations and other factors of varying influence. We also identified 34 taxon-specific codon aversion motifs from 49 plastid genes. Our plastomic analyses elucidate phylogenetic relationships and evolutionary patterns in this medicinal clade, providing a foundation for further research on these ecologically and pharmaceutically important plants.

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

BACKGROUND

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

RESULT

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

CONCLUSION

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

The complete chloroplast genome sequence of Amorphophallus konjac (Araceae) from Yunnan, China and its phylogenetic analysis in the family Araceae

This work determined and analyzed the complete chloroplast genome sequence of Amorphophallus konjac K. Koch ex N.E.Br 1858 from Yunnan, China. The genome size was 167,470 bp, of which contains a large single-copy region (LSC 93,443 bp), a small single-copy region (SSC 21,575 bp), and a pair of inverted repeat regions (IR 26,226 bp). The chloroplast genome has 131 genes, including 86 protein-coding genes, 37 tRNAs, and eight rRNAs. A previous study reported deletion of accD, psbE, and trnG-GCC genes in the A. konjac chloroplast genome. Our study supports the conservative structure of A. konjac and does not support the gene deletion mentioned above. Phylogenetic analysis indicated that A. konjac shares a close relationship with another A. konjac (collected from Guizhou) and A. titanium by forming a clade in the genus Amorphophallus. Our results provide some useful information to the evolution of the family Araceae.

Comprehensive analysis of complete chloroplast genome sequence of Plantago asiatica L. (Plantaginaceae)

Plantago asiatica L. is a representative individual species of Plantaginaceae, whose high reputation is owed to its edible and medicinal values. However, the phylogeny and genes of the P. asiatica chloroplast have not yet been well described. Here we report the findings of a comprehensive analysis of the P. asiatica chloroplast genome. The P. asiatica chloroplast genome is 164,992 bp, circular, and has a GC content of 37.98%. The circular genome contains 141 genes, including 8 rRNAs, 38 tRNAs, and 95 protein-coding genes. Seventy-two simple sequence repeats are detected. Comparative chloroplast genome analysis of six related species suggests that a higher similarity exists in the coding region than the non-coding region, and differences in the degree of preservation is smaller between P. asiatica and Plantago depressa than among others. Our phylogenetic analysis illustrates P. asiatica has a relatively close relationship with P. depressa, which was also divided into different clades with Plantago ovata and Plantago lagopus in the genus Plantago. This analysis of the P. asiatica chloroplast genome contributes to an improved deeply understanding of the evolutionary relationships among Plantaginaceae.

Characterization of the complete chloroplast genome assembly of Amorphophallus yunnanensis Engler, Pflanzenr (Araceae) from southwestern China

Southwestern China is a biodiversity hotspot due to its diverse topography and environment. Amorphophallus yunnanensis is a species of perennial herb that is mainly distributed throughout southwestern China. The genetic diversity and divergence in this species have not been assessed largely due to a lack of genomic resources. To help with the phylogeographic study, we sequenced and assembled the first complete chloroplast genome sequence of A. yunnanensis. The length of the chloroplast genome was 164,417 bp, with an average GC content of 36% (GenBank accession no. OR400247). The genome possessed a typical quadripartite structure, and the lengths of the large single-copy (LSC), small single-copy (SSC), and two inverted repeat (IR) regions were 92,149 bp, 15,182 bp, 28,543bp, and 28,543bp, respectively. A total of 128 genes were annotated across the genome, including 82 protein-coding genes, 8 rRNAs, and 38 tRNAs. The maximum likelihood (ML) phylogeny confirmed the phylogenetic position of Amorphophallus within Araceae, with the Amorphophallus species forming a single monophyletic clade with a high bootstrap value. The ML tree also indicated that A. yunnanensis was most closely related to A. coaetaneus. This newly sequenced chloroplast genome assembly will aid in future studies of genetic diversity, historical population dynamics, and geographic differentiation patterns of A. yunnanensis.

The complete chloroplast genome assembly of Amorphophallus krausei Engler, Pflanzenr 1911 (Araceae) from southwestern China

Plants in the genus Amorphophallus, many of which possess high konjac glucomannan content, are considered important cash crops in many Asian countries. Wild relatives of cultivated Amorphophallus species are valuable resources for the genetic improvement of these crops. To aid in future genetic research of wild germplasm resources of Amorphophallus, a single individual of Amorphophallus krausei Engler, Pflanzenr 1911 was collected from southwestern China, and its chloroplast genome was sequenced using next-generation sequencing technologies. The assembled chloroplast genome was 172,418 bp in length with a GC content of 35.23% (GenBank accession no. OR416863). A typical quadripartite structure was found in the genome, which was comprised of one large single-copy (LSC), one small single-copy (SSC), and two inverted repeats (IRs), with lengths of 91,983 bp, 15,591 bp, 32,422 bp, and 32,422 bp, respectively. A total of 132 genes were annotated in the genome, including 86 protein-coding genes, 38 tRNAs, and 8 rRNAs. A maximum likelihood (ML) tree of A. krausei and 17 other species in the family Araceae suggested that all Amorphophallus species formed a single monophyletic clade. A close relationship among A. konjac, A. albus, and A. krausei was also revealed by the phylogenetic tree. The newly sequenced chloroplast genome of A. krausei will support future genetic studies, particularly the assessment of genetic diversity, resource conservation, and phylogeographic research.

The complete plastome sequence of Monstera deliciosa (Araceae), an ornamental foliage plant

In the current study, we sequenced the complete plastome of Monstera deliciosa Liebm. (1849), an attractive foliage plant. The total length of the plastome of M. deliciosa is 163,499 bp and it consists of three distinct regions: a large single-copy (90,092 bp), a small single-copy (21,737 bp), and a pair of inverted repeats (IRs, 25,835 bp). The overall GC content is 36.2%, and the genome contains 110 functional genes, excluding pseudogenes. These functional genes encompass 77 protein-coding genes, 29 transfer RNA genes, and four ribosomal RNA genes. Notably, both the infA and rpl23 genes have been identified as pseudogenes. Phylogenetic analysis based on 14 representative plastomes from seven subfamilies indicates that Monsteroideae is monophyletic and sister to Pothoideae. Furthermore, M. deliciosa and M. adansonii were shown to share a recent common ancestor, the finding for which is supported by a strong bootstrap value. The sequenced plastome of M. deliciosa can serve as a valuable resource for establishing phylogenetic relationships and enhancing species identification within the genus Monstera. In addition, it can facilitate investigations into the genetic characteristics of this plant.

Comparative analysis of chloroplast genome and new insights into phylogenetic relationships of Ajuga and common adulterants

Introduction

The potential contamination of herbal medicinal products poses a significant concern for consumer health. Given the limited availability of genetic information concerning Ajuga species, it becomes imperative to incorporate supplementary molecular markers to enhance and ensure accurate species identification.

Methods

In this study, the chloroplast (cp) genomes of seven species of the genus Ajuag were sequenced, de novo assembled and characterized.

Results

exhibiting lengths ranging from 150,342 bp to 150,472 bp, encompassing 86 - 88 protein-coding genes (PCGs), 35 - 37 transfer RNA, and eight ribosomal RNA. The repetitive sequences, codon uses, and cp genomes of seven species were highly conserved, and PCGs were the reliable molecular markers for investigating the phylogenetic relationship within the Ajuga genus. Moreover, four mutation hotspot regions (accD-psaI, atpH-atpI, ndhC-trnV(UAC), and ndhF-rpl23) were identified within cp genomes of Ajuga, which could help distinguish A. bracteosa and its contaminants. Based on cp genomes and PCGs, the phylogenetic tree preliminary confirmed the position of Ajuga within the Lamiaceae family. It strongly supported a sister relationship between Subsect. Genevense and Subsect. Biflorae, suggesting the merger of Subsect. Biflorae and Subsect. Genevenses into one group rather than maintaining separate categorizations. Additionally, molecular clock analysis estimated the divergence time of Ajuga to be around 7.78 million years ago.

Discussion

The species authentication, phylogeny, and evolution analyses of the Ajuga species may benefit from the above findings.

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.

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.

Chloroplast genome analysis of three Acanthus species reveal the adaptation of mangrove to intertidal habitats

Acanthus is a distinctive genus that covers three species with different ecological niches including Acanthus mollis (arid terrestrial), Acanthus leucostachyus (damp forest) and Acanthus ilicifolius (coastal intertidal). It is an intriguing question how these species evolved from terrestrial to coastal intertidal. In the present study, we assembled chloroplast genomes of A. ilicifolius, A. leucostachyus and A. mollis, which exhibited typical quadripartite structures. The sizes were 150,758, 154,686 and 150,339 bp that comprised a large single copy (LSC, 82,963, 86,461 and 82,612 bp), a small single copy (SSC, 17,191, 17,511 and 17,019 bp), and a pair of inverted repeats (IRs, 25,302, 25,357 and 25,354 bp), respectively. Gene annotation revealed that A. ilicifolius, A. leucostachyus and A. mollis contained 113, 112 and 108 unique genes, each of which contained 79, 79 and 74 protein-coding genes, 30, 29 and 30 tRNAs, and 4 rRNA genes, respectively. Differential gene analysis revealed plenty of ndhs gene deletions in the terrestrial plant A. mollis. Nucleotide diversity analysis showed that the psbK, ycf1, ndhG, and rpl22 have the highest nucleotide variability. Compared to A. leucostachyus and A. mollis, seven genes in A. ilicifolius underwent positive selection. Among them, the atpF gene showed a strong positive selection throughout terrestrial to marine evolution and was important for adaptation to coastal intertidal habitats. Phylogenetic analysis indicated that A. ilicifolius has a closer genetic relationship with A. leucostachyus than A. mollis which further confirmed the evolutionary direction of Acanthus going from terrestrial to coastal intertidal zones.

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

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

Pinellia genus: A systematic review of active ingredients, pharmacological effects and action mechanism, toxicological evaluation, and multi-omics application

The dried tuber of Pinellia ternata (Thunb.) Breit, Pinelliae Rhizoma (PR, also named 'Banxia' in Chinese), is widely used in traditional medicine. This review aims to provide detail summary of active ingredients, pharmacological effects, toxic ingredients, detoxification strategies, and omic researches, etc. Pharmacological ingredients from PR are mainly classified into six categories: alkaloids, amino acids, polysaccharides, phenylpropanoids, essential oils, and glucocerebrosides. Diversity of chemical composition determines the broad-spectrum efficacy and gives a foundation for the comprehensive utilization of P. ternata germplasm resources. The pharmacological compounds are involved in inhibition of cancer cells by targeting various pathways, including activation of immune system, inhibition of proliferation and cycle, induction of apoptosis, and inhibition of angiogenesis. The pharmacological components of PR act on nervous system by targeting neurotransmitters, activating immune system, decreasing apoptosis, and increasing redox system. Lectins, one major class of the toxic ingredients extracted from raw PR, possess significant toxic effects on human cells. Inflammatory factors, cytochrome P450 proteins (CYP) family enzymes, mammalian target of rapamycin (mTOR) signaling factors, transforming growth factor-β (TGF-β) signaling factors, and nervous system, are considered to be the target sites of lectins. Recently, omic analysis is widely applied in Pinellia genus studies. Plastome genome-based molecular markers are deeply used for identifying and resolving phylogeny of Pinellia genus plants. Various omic works revealed and functional identified a series of environmental stress responsive factors and active component biosynthesis-related genes. Our review summarizes the recent progress in active and toxic ingredient evaluation, pharmacological effects, detoxification strategies, and functional gene identification and accelerates efficient utilization of this traditional herb.

Identification of three cultivated varieties of Scutellaria baicalensis using the complete chloroplast genome as a super-barcode

Scutellaria baicalensis has been one of the most commonly used traditional Chinese medicinal plants in China for more than 2000 years. The three new varieties cultivated could not be distinguished by morphology before flowering. It will hinder the promotion of later varieties. Chloroplast DNA has been widely used in species identification. Moreover, previous studies have shown that complete chloroplast genome sequences have been suggested as super barcodes for identifying plants. Therefore, we sequenced and annotated the complete chloroplast genomes of three cultivated varieties. The chloroplast genomes of SBW, SBR, and SBP were 151,702 bp, 151,799 bp, and 151,876 bp, which contained 85 protein-coding genes, 36 tRNA genes, and 8 rRNA genes. The analysis of the repeat sequences, codon usage, and comparison of chloroplast genomes shared a high degree of conservation. However, the sliding window results show significant differences among the three cultivated varieties in matK-rps16 and petA-psbJ. And we found that the matK-rps16 sequence can be used as a barcode for the identification of three varieties. In addition, the complete chloroplast genome contains more variations and can be used as a super-barcode to identify these three cultivated varieties. Based on the protein-coding genes, the phylogenetic tree demonstrated that SBP was more closely related to SBW, in the three cultivated varieties. Interestingly, we found that S. baicalensis and S. rehderiana are closely related, which provides new ideas for the development of S. baicalensis. The divergence time analysis showed that the three cultivated varieties diverged at about 0.10 Mya. Overall, this study showed that the complete chloroplast genome could be used as a super-barcode to identify three cultivated varieties of S. baicalensis and provide biological information, and it also contributes to bioprospecting.

Molecular structure, comparative and phylogenetic analysis of the complete chloroplast genome sequences of weedy rye Secale cereale ssp. segetale

The complete chloroplast genome of Secale cereale ssp. segetale (Zhuk.) Roshev. (Poaceae: Triticeae) was sequenced and analyzed to better use its genetic resources to enrich rye and wheat breeding. The study was carried out using the following methods: DNA extraction, sequencing, assembly and annotation, comparison with other complete chloroplast genomes of the five Secale species, and multigene phylogeny. As a result of the study, it was determined that the chloroplast genome is 137,042 base pair (bp) long and contains 137 genes, including 113 unique genes and 24 genes which are duplicated in the IRs. Moreover, a total of 29 SSRs were detected in the Secale cereale ssp. segetale chloroplast genome. The phylogenetic analysis showed that Secale cereale ssp. segetale appeared to share the highest degree of similarity with S. cereale and S. strictum. Intraspecific diversity has been observed between the published chloroplast genome sequences of S. cereale ssp. segetale. The genome can be accessed on GenBank with the accession number (OL688773).

New insights into the phylogenetic relationships among wild onions (Allium, Amaryllidaceae), with special emphasis on the subgenera Anguinum and Rhizirideum, as revealed by plastomes

The genus Allium, with over 900 species, is one of the largest monocotyledonous genera and is widely accepted with 15 recognized subgenera and 72 sections. The robust subgeneric and sectional relationships within Allium have long been not resolved. Based on 76 species of Allium (a total of 84 accessions), we developed a highly resolved plastome phylogenetic framework by integrating 18 newly sequenced species (20 accessions) in this study and assessed their subgeneric and sectional relationships, with special emphasis on the two subgenera Anguinum and Rhizirideum. We retrieved the three major evolutionary lines within Allium and found that the two subgenera Anguinum and Rhizirideum are monophyletic whereas others are highly polyphyletic (e.g., Allium, Cepa, Polyprason, and Melanocrommyum). Within the subgenus Anguinum, two strongly supported sublineages in East Asian and Eurasian-American were found. Allium tricoccum in North America belonged to the Eurasian clade. The distinct taxonomic status of A. ulleungense and its sister taxon were further determined. In subg. Rhizirideum, the Ulleung Island endemic A. dumebuchum shared its most recent common ancestor with the species from Mongolia and the narrow Korean endemic A. minus. Two Ulleung Island endemics were estimated to originate independently during the Pleistocene. In addition, a separate monotypic sectional treatment of the east Asian A. macrostemon (subg. Allium) and sister relationship between A. condensatum and A. chinense was suggested.

Characterization and phylogenetic analyses of ten complete plastomes of Spiraea species

BACKGROUND

Spiraea is a genus of deciduous shrubs that contains 80-120 species, is mainly distributed in the Northern Hemisphere and has diversified in East Asia. Spiraea species are cultivated as ornamental plants and some are used in traditional herbal medicine. Based on morphological characteristics and genetic markers, phylogenetic classification exhibits low discriminatory power.

RESULTS

In present study, we assembled and characterized the chloroplast (cp) genomes of ten Spiraea species and comparatively analysed with five reported cp genomes of this genus. The cp genomes of the fifteen Spiraea species, ranging from 155,904 to 158,637 bp in length, were very conserved and no structural rearrangements occurred. A total of 85 protein-coding genes (PCGs), 37 tRNAs and 8 rRNAs were annotated. We also examined 1,010 simple sequence repeat (SSR) loci, most of which had A/T base preference. Comparative analysis of cp genome demonstrated that single copy and non-coding regions were more divergent than the inverted repeats (IRs) and coding regions and six mutational hotspots were detected. Selection pressure analysis showed that all PCGs were under purifying selection. Phylogenetic analysis based on the complete cp genome data showed that Spiraea formed a monophyletic group and was further divided into two major clades. Infrageneric classification in each clade was supported with a high resolution value. Moreover, the phylogenetic trees based on each individual mutational hotspot segment and their combined dataset also consisted of two major clades, but most of the phylogenetic relationships of interspecies were not well supported.

CONCLUSIONS

Although the cp genomes of Spiraea species exhibited high conservation in genome structure, gene content and order, a large number of polymorphism sites and several mutation hotspots were identified in whole cp genomes, which might be sufficiently used as molecular markers to distinguish Spiraea species. Phylogenetic analysis based on the complete cp genome indicated that infrageneric classification in two major clades was supported with high resolution values. Therefore, the cp genome data of the genus Spiraea will be effective in resolving the phylogeny in this genus.

The dynamic history of plastome structure across aquatic subclass Alismatidae

BACKGROUND

The rapidly increasing availability of complete plastomes has revealed more structural complexity in this genome under different taxonomic levels than expected, and this complexity provides important evidence for understanding the evolutionary history of angiosperms. To explore the dynamic history of plastome structure across the subclass Alismatidae, we sampled and compared 38 complete plastomes, including 17 newly assembled, representing all 12 recognized families of Alismatidae.

RESULT

We found that plastomes size, structure, repeat elements, and gene content were highly variable across the studied species. Phylogenomic relationships among families were reconstructed and six main patterns of variation in plastome structure were revealed. Among these, the inversion from rbcL to trnV-UAC (Type I) characterized a monophyletic lineage of six families, but independently occurred also in Caldesia grandis. Three independent ndh gene loss events were uncovered across the Alismatidae. In addition, we detected a positive correlation between the number of repeat elements and the size of plastomes and IR in Alismatidae.

CONCLUSION

In our study, ndh complex loss and repeat elements likely contributed to the size of plastomes in Alismatidae. Also, the ndh loss was more likely related to IR boundary changes than the adaptation of aquatic habits. Based on existing divergence time estimation, the Type I inversion may have occurred during the Cretaceous-Paleogene in response to the extreme paleoclimate changes. Overall, our findings will not only allow exploring the evolutionary history of Alismatidae plastome, but also provide an opportunity to test if similar environmental adaptations result in convergent restructuring in plastomes.

Comparative chloroplast genome analyses of diverse Phoebe (Lauraceae) species endemic to China provide insight into their phylogeographical origin

The genus Phoebe (Lauraceae) includes about 90 evergreen tree species that are an ideal source of timber. Habitat destruction and deforestation have resulted in most of them being endemic to China. The accurate identification of endangered Phoebe species in China is necessary for their conservation. Chloroplast genome sequences can play an important role in species identification. In this study, comparative chloroplast genome analyses were conducted on diverse Phoebe species that are primarily distributed in China. Despite the conserved nature of chloroplast genomes, we detected some highly divergent intergenic regions (petA-psbE, ndhF-rpl32, and psbM-trnD-GUC) as well as three highly divergent genes (rbcL, ycf1, and ycf2) that have potential applications in phylogenetics and evolutionary analysis. The phylogenetic analysis indicated that various Phoebe species in China were divided into three clades. The complete chloroplast genome was better suited for phylogenetic analysis of Phoebe species. In addition, based on the phylogeographical analysis of Phoebe species in China, we inferred that the Phoebe species in China first originated in Yunnan and then spread to other southern areas of the Yangtze River. The results of this research will add to existing case studies on the phylogenetic analysis of Phoebe species and have the potential to contribute to the conservation of Phoebe species that are in danger of extinction.

The complete chloroplast genome of Hibiscus syriacus using long-read sequencing: Comparative analysis to examine the evolution of the tribe Hibisceae

Hibiscus syriacus, a member of the tribe Hibisceae, is considered an important ornamental and medicinal plant in east Asian countries. Here, we sequenced and assembled the complete chloroplast genome of H. syriacus var. Baekdansim using the PacBio long-read sequencing platform. A quadripartite structure with 161,026 base pairs was obtained, consisting of a pair of inverted repeats (IRA and IRB) with 25,745 base pairs, separated by a large single-copy region of 89,705 base pairs and a short single-copy region of 19,831 base pairs. This chloroplast genome had 79 protein-coding genes, 30 transfer RNA genes, 4 ribosomal RNA genes, and 109 simple sequence repeat regions. Among them, ndhD and rpoC1, containing traces of RNA-editing events associated with adaptive evolution, were identified by analysis of putative RNA-editing sites. Codon usage analysis revealed a preference for A/U-terminated codons. Furthermore, the codon usage pattern had a clustering tendency similar to that of the phylogenetic analysis of the tribe Hibisceae. This study provides clues for understanding the relationships and refining the taxonomy of the tribe Hibisceae.

Target sequence data shed new light on the infrafamilial classification of Araceae

PREMISE

Recent phylogenetic studies of the Araceae have confirmed the position of the duckweeds nested within the aroids, and the monophyly of a clade containing all the unisexual flowered aroids plus the bisexual-flowered Calla palustris. The main objective of the present study was to better resolve the deep phylogenetic relationships among the main lineages within the family, particularly the relationships between the eight currently recognized subfamilies. We also aimed to confirm the phylogenetic position of the enigmatic genus Calla in relation to the long-debated evolutionary transition between bisexual and unisexual flowers in the family.

METHODS

Nuclear DNA sequence data were generated for 128 species across 111 genera (78%) of Araceae using target sequence capture and the Angiosperms 353 universal probe set.

RESULTS

The phylogenomic data confirmed the monophyly of the eight Araceae subfamilies, but the phylogenetic position of subfamily Lasioideae remains uncertain. The genus Calla is included in subfamily Aroideae, which has also been expanded to include Zamioculcadoideae. The tribe Aglaonemateae is newly defined to include the genera Aglaonema and Boycea.

CONCLUSIONS

Our results strongly suggest that new research on African genera (Callopsis, Nephthytis, and Anubias) and Calla will be important for understanding the early evolution of the Aroideae. Also of particular interest are the phylogenetic positions of the isolated genera Montrichardia, Zantedeschia, and Anchomanes, which remain only moderately supported here.

Complete chloroplast genome molecular structure, comparative and phylogenetic analyses of Sphaeropteris lepifera of Cyatheaceae family: a tree fern from China

Sphaeropteris lepifera is a tree fern in the Cyatheaceae, a family that has played an important role in the evolution of plant systems. This study aimed to analyze the complete chloroplast genome of S. lepifera and compared it with previously published chloroplast genomes Cyatheaceae family. The chloroplast genome of S. lepifera comprised 162,114 bp, consisting of a large single copy (LSC) region of 86,327 bp, a small single copy (SSC) region of 27,731 bp and a pair of inverted repeats (IRa and IRb) of 24,028 bp each. The chloroplast genome encoded 129 genes, comprising 32 transfer RNAs, 8 ribosomal RNAs, and 89 protein-coding genes. Comparison of the genomes of 7 Cyatheaceae plants showed that the chloroplast genome of S. lepifera was missing the gene trnV-UAC. Expansion of the SSC region led to the difference in the chloroplast genome size of S. lepifera. Eight genes, atpI, ccsA, petA, psaB, rpl16, rpoA, rpoC1, and ycf2 have high nucleic acid diversity and can be regarded as potential molecular markers. The genes trnG-trnR and atpB were suitable for DNA barcodes between different communities of S. lepifera. The S. lepifera groups in Zhejiang Province probably diffused from Pingtan and Ningde, Fujian. The results will provide a basis for species identification, biological studies, and endangerment mechanism of S. lepifera.

Application of chloroplast genome in the identification of Phyllanthus urinaria and its common adulterants

BACKGROUND

Phyllanthus urinaria L. is extensively used as ethnopharmacological material in China. In the local marketplace, this medicine can be accidentally contaminated, deliberately substituted, or mixed with other related species. The contaminants in herbal products are a threat to consumer safety. Due to the scarcity of genetic information on Phyllanthus plants, more molecular markers are needed to avoid misidentification.

METHODS

In this study, the complete chloroplast genome of nine species of the genus Phyllanthus was de novo assembled and characterized.

RESULTS

This study revealed that all of these species exhibited a conserved quadripartite structure, which includes a large single copy (LSC) region and small single copy (SSC) region, and two copies of inverted repeat regions (IRa and IRb), which separate the LSC and SSC regions. And the genome structure, codon usage, and repeat sequences were highly conserved and showed similarities among the nine species. Three highly variable regions (trnS-GCU-trnG-UCC, trnT-UGU-trnL-UAA, and petA-psbJ) might be helpful as potential molecular markers for identifying P. urinaria and its contaminants. In addition, the molecular clock analysis results showed that the divergence time of the genus Phyllanthus might occur at ~ 48.72 Ma.

CONCLUSION

This study provides valuable information for further species identification, evolution, and phylogenetic research of Phyllanthus.

Molecular characterizations of genes in chloroplast genomes of the genus Arachis L. (Fabaceae) based on the codon usage divergence

Studies on the molecular characteristics of chloroplast genome are generally important for clarifying the evolutionary processes of plant species. The base composition, the effective number of codons, the relative synonymous codon usage, the codon bias index, and their correlation coefficients of a total of 41 genes in 21 chloroplast genomes of the genus Arachis were investigated to further perform the correspondence and clustering analyses, revealing significantly higher variations in genomes of wild species than those of the cultivated taxa. The codon usage patterns of all 41 genes in the genus Arachis were AT-rich, suggesting that the natural selection was the main factor affecting the evolutionary history of these genomes. Five genes (i.e., ndhC, petD, atpF, rpl14, and rps11) and five genes (i.e., atpE, psbD, psaB, ycf2, and rps12) showed higher and lower base usage divergences, respectively. This study provided novel insights into our understanding of the molecular evolution of chloroplast genomes in the genus Arachis.

Distinctive origin and evolution of endemic thistle of Korean volcanic island: Structural organization and phylogenetic relationships with complete chloroplast genome

Unlike other Cirsium in Korea, Cirsium nipponicum (Island thistle) is distributed only on Ulleung Island, a volcanic island off the east coast of the Korean Peninsula, and a unique thistle with none or very small thorns. Although many researchers have questioned the origin and evolution of C. nipponicum, there is not much genomic information to estimate it. We thus assembled the complete chloroplast of C. nipponicum and reconstructed the phylogenetic relationships within the genus Cirsium. The chloroplast genome was 152,586 bp, encoding 133 genes consisting of 8 rRNA genes, 37 tRNA genes, and 88 protein-coding genes. We found 833 polymorphic sites and eight highly variable regions in chloroplast genomes of six Cirsium species by calculating nucleotide diversity, as well as 18 specific variable regions distinguished C. nipponicum from other Cirsium. As a result of phylogenetic analysis, C. nipponicum was closer to C. arvense and C. vulgare than native Cirsium in Korea: C. rhinoceros and C. japonicum. These results indicate that C. nipponicum is likely introduced through the north Eurasian root, not the mainland, and evolved independently in Ulleung Island. This study contributes to further understanding the evolutionary process and the biodiversity conservation of C. nipponicum on Ulleung Island.

Comparative and phylogenetic analysis based on chloroplast genome of Heteroplexis (Compositae), a protected rare genus

BACKGROUND

Heteroplexis Chang is an endangered genus endemic to China with important ecological and medicinal value. However, due to the lack of genetic data, our conservation strategies have repeatedly been delayed by controversial phylogenetic (molecular) relationships within the genera. In this study, we reported three new Heteroplexis chloroplast (cp.) genomes (H. vernonioides, H. impressinervia and H. microcephala) to clarify phylogenetic relationships between species allocated in this genus and other related Compositae.

RESULTS

All three new cp. genomes were highly conserved, showing the classic four regions. Size ranged from 152,984 - 153,221 bp and contained 130 genes (85 protein-coding genes, 37 tRNA, eight rRNA) and two pseudogenes. By comparative genomic and phylogenetic analyses, we found a large-scale inversion of the entire large single-copy (LSC) region in H. vernonioides, H. impressinervia and H. microcephala, being experimentally verified by PCR. The inverted repeat (IR) regions showed high similarity within the five Heteroplexis plastomes, showing small-size contractions. Phylogenetic analyses did not support the monophyly of Heteroplexis genus, whereas clustered the five species within two differentiated clades within Aster genus. These phylogenetic analyses suggested that the five Heteroplexis species might be subsumed into the Aster genus.

CONCLUSION

Our results enrich the data on the cp. genomes of the genus Heteroplexis, providing valuable genetic resources for future studies on the taxonomy, phylogeny, and evolution of Aster genus.

The whole chloroplast genome of Mesua ferrea: Insight into the dynamic pattern of evolution and its comparison with species from recently diverged families

Mesua ferrea is an important source of timber, oil and herbal medicines. In the present investigation, we assembled the whole chloroplast genome of M. ferrea of size 161.4 kb. The genome contained 86 protein-coding genes, 38 tRNAs, 8 rRNA genes and exhibited a characteristic quadripartite structural orientation, with two inverted repeats (27,614 bp) separated by an LSC (88,746 bp) region and an SSC (27,614 bp) (17,470 bp). Interestingly, no gene loss was identified in the M. ferrea genome, contrary to what has been observed in other Clusioid species. We compared the chloroplast genome of M. ferrea with the chloroplast genome of Bonnetia and Garcinia belonging to Bonnetiaceae and Clusiaceae families. Overall, the compared genomes possess a similar synteny of gene order except for a small inversion in Garcinia species. M. ferrea has the largest chloroplast genome size in Clusioid clade owing to the lengthening of the LSC, IR, and non-coding regions. Substantial differences were observed in population of simple sequence repeats (SSRs) and RNA editing sites among the studied genomes. A comparative assessment of chloroplast genomes revealed five highly divergence regions: rpl32, trnS-GCU_trnG-UCC, petN-psbM, psbZ_trnG-GCC and ccsA_ndhD among the analyzed sequences. Phylogenetic analyses and sequence homology search indicate that M. ferrea is closely related to the Garcinia species.

Structural Diversities and Phylogenetic Signals in Plastomes of the Early-Divergent Angiosperms: A Case Study in Saxifragales

As representative of the early-divergent groups of angiosperms, Saxifragales is extremely divergent in morphology, comprising 15 families. Within this order, our previous case studies observed significant structural diversities among the plastomes of several lineages, suggesting a possible role in elucidating their deep phylogenetic relationships. Here, we collected 208 available plastomes from 11 constituent families to explore the evolutionary patterns among Saxifragales. With thorough comparisons, the losses of two genes and three introns were found in several groups. Notably, 432 indel events have been observed from the introns of all 17 plastomic intron-containing genes, which could well play an important role in family barcoding. Moreover, numerous heterogeneities and strong intrafamilial phylogenetic implications were revealed in pttRNA (plastomic tRNA) structures, and the unique structural patterns were also determined for five families. Most importantly, based on the well-supported phylogenetic trees, evident phylogenetic signals were detected in combinations with the identified pttRNAs features and intron indels, demonstrating abundant lineage-specific characteristics for Saxifragales. Collectively, the results reported here could not only provide a deeper understanding into the evolutionary patterns of Saxifragales, but also provide a case study for exploring the plastome evolution at a high taxonomic level of angiosperms.

Comparative analysis of medicinal plant Isodon rubescens and its common adulterants based on chloroplast genome sequencing

Isodon rubescens (Hemsley) H. Hara is the source of Donglingcao under the monograph Rabdosiae Rubescentis Herba in Chinese Pharmacopoeia. In the local marketplace, this medicine can be accidentally contaminated, deliberately substituted, or mixed with other related species. The contaminants of herbal products are a threat to consumer safety. Due to the scarcity of genetic information on Isodon plants, more molecular markers are needed to avoid misidentification. In the present study, the complete chloroplast (cp) genome of seven species of Isodon was sequenced, de novo assembled and characterized. The cp genomes of these species universally exhibited a conserved quadripartite structure, i.e., two inverted repeats (IRs) containing most of the ribosomal RNA genes and two unique regions (large single copy and small single copy). Moreover, the genome structure, codon usage, and repeat sequences were highly conserved and showed similarities among the seven species. Five highly variable regions (trnS-GCU-trnT-CGU, atpH-atpI, trnE-UUC-trnT-GGU, ndhC-trnM-CAU, and rps15-ycf1) might be potential molecular markers for identifying I. rubescens and its contaminants. These findings provide valuable information for further species identification, evolution, and phylogenetic research of Isodon.

Comparative Analyses of Plastomes of Four Anubias (Araceae) Taxa, Tropical Aquatic Plants Endemic to Africa

Anubias Schott (Araceae) have high ornamental properties as aquarium plants. However, the genus has difficulties in species identification, and the mechanism of its adaptation to the aquatic environment is unknown. To better identify species and understand the evolutionary history of Anubias, the plastomes of Anubias barteri Schott, A. barteri var. nana (Engl.) Crusio, and A. hastifolia Engl., were sequenced. The sizes of the plastomes of Anubias ranged from 169,841 bp to 170,037 bp. These plastomes were composed of conserved quadripartite circular structures and comprised 112 unique genes, including 78 protein-coding genes, 30 transfer RNA genes, and 4 ribosomal RNA genes. The comparative analysis of genome structure, repeat sequences, codon usage and RNA editing sites revealed high similarities among the Anubias plastomes, indicating the conservation of plastomes of Anubias. Three spacer regions with relatively high nucleotide diversity, trnL-CAA-ndhB, ycf1-ndhF, and rps15-ycf1, were found within the plastomes of Anubias. Phylogenetic analysis, based on 75 protein-coding genes, showed that Anubias was sister to Montrichardia arborescens (L.) Schott (BS = 99). In addition, four genes (ccsA, matK, ndhF, and ycf4) that contain sites undergoing positive selection were identified within the Anubias plastomes. These genes may play an important role in the adaptation of Anubias to the aquatic environment. The present study provides a valuable resource for further studies on species identification and the evolutionary history of Anubias.

Comprehensive Comparative Analysis and Development of Molecular Markers for Dianthus Species Based on Complete Chloroplast Genome Sequences

Dianthus spp. is a genus with high economic and ornamental value in the Caryophyllaceae, which include the famous fresh-cut carnation and the traditional Chinese herbal medicine, D. superbus. Despite the Dianthus species being seen everywhere in our daily lives, its genome information and phylogenetic relationships remain elusive. Thus, we performed the assembly and annotation of chloroplast genomes for 12 individuals from seven Dianthus species. On this basis, we carried out the first comprehensive and systematic analysis of the chloroplast genome sequence characteristics and the phylogenetic evolution of Dianthus. The chloroplast genome of 12 Dianthus individuals ranged from 149,192 bp to 149,800 bp, containing 124 to 126 functional genes. Sequence repetition analysis showed the number of simple sequence repeats (SSRs) ranged from 75 to 80, tandem repeats ranged from 23 to 41, and pair-dispersed repeats ranged from 28 to 43. Next, we calculated the synonymous nucleotide substitution rates (Ks) of all 76 protein coding genes to obtain the evolution rate of these coding genes in Dianthus species; rpl22 showed the highest Ks (0.0471), which suggested that it evolved the swiftest. By reconstructing the phylogenetic relationships within Dianthus and other species of Caryophyllales, 16 Dianthus individuals (12 individuals reported in this study and four individuals downloaded from NCBI) were divided into two strongly supported sister clades (Clade A and Clade B). The Clade A contained five species, namely D. caryophyllus, D. barbatus, D. gratianopolitanus, and two cultivars (‘HY’ and ‘WC’). The Clade B included four species, in which D. superbus was a sister branch with D. chinensis, D. longicalyx, and F1 ‘87M’ (the hybrid offspring F1 from D. chinensis and ‘HY’). Further, based on sequence divergence analysis and hypervariable region analysis, we selected several regions that had more divergent sequences, to develop DNA markers. Additionally, we found that one DNA marker can be used to differentiate Clade A and Clade B in Dianthus. Taken together, our results provide useful information for our understanding of Dianthus classification and chloroplast genome evolution.

Cold Resistance of Euonymus japonicus Beihaidao Leaves and Its Chloroplast Genome Structure and Comparison with Celastraceae Species

Euonymus japonicus Beihaidao is one of the most economically important ornamental species of the Euonymus genus. There are approximately 97 genera and 1194 species of plants worldwide in this family (Celastraceae). Using E. japonicus Beihaidao, we conducted a preliminary study of the cold resistance of this species, evaluated its performance during winter, assembled and annotated its chloroplast genome, and performed a series of analyses to investigate its gene structure GC content, sequence alignment, and nucleic acid diversity. Our objectives were to understand the evolutionary relationships of the genus and to identify positive selection genes that may be related to adaptations to environmental change. The results indicated that E. japonicus Beihaidao leaves have certain cold resistance and can maintain their viability during wintering. Moreover, the chloroplast genome of E. japonicus Beihaidao is a typical double-linked ring tetrad structure, which is similar to that of the other four Euonymus species, E. hamiltonianus, E. phellomanus, E. schensianus, and E. szechuanensis, in terms of gene structure, gene species, gene number, and GC content. Compared to other Celastraceae species, the variation in the chloroplast genome sequence was lower, and the gene structure was more stable. The phylogenetic relationships of 37 species inferred that members of the Euonymus genus do not form a clade and that E. japonicus Beihaidao is closely related to E. japonicus and E. fortunei. A total of 11 functional positive selected genes were identified, which may have played an important role in the process of Celastraceae species adapting to environmental changes. Our study provides important genetic information to support further investigations into the phylogenetic development and adaptive evolution of Celastraceae species.

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

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

Comparative Analysis of Complete Chloroplast Genomes of Nine Species of Litsea (Lauraceae): Hypervariable Regions, Positive Selection, and Phylogenetic Relationships

Litsea is a group of evergreen trees or shrubs in the laurel family, Lauraceae. Species of the genus are widely used for a wide range of medicinal and industrial aspects. At present, most studies related to the gene resources of Litsea are restricted to morphological analyses or features of individual genomes, and currently available studies of select molecular markers are insufficient. In this study, we assembled and annotated the complete chloroplast genomes of nine species in Litsea, carried out a series of comparative analyses, and reconstructed phylogenetic relationships within the genus. The genome length ranged from 152,051 to 152,747 bp and a total of 128 genes were identified. High consistency patterns of codon bias, repeats, divergent analysis, single nucleotide polymorphisms (SNP) and insertions and deletions (InDels) were discovered across the genus. Variations in gene length and the presence of the pseudogene ycf1^Ψ, resulting from IR contraction and expansion, are reported. The hyper-variable gene rpl16 was identified for its exceptionally high Ka/Ks and Pi values, implying that those frequent mutations occurred as a result of positive selection. Phylogenetic relationships were recovered for the genus based on analyses of full chloroplast genomes and protein-coding genes. Overall, both genome sequences and potential molecular markers provided in this study enrich the available genomic resources for species of Litsea. Valuable genomic resources and divergent analysis are also provided for further research of the evolutionary patterns, molecular markers, and deeper phylogenetic relationships of Litsea.

The chloroplast genome of Farsetia hamiltonii Royle, phylogenetic analysis, and comparative study with other members of Clade C of Brassicaceae

BACKGROUND

Farsetia hamiltonii Royle is a medicinally important annual plant from the Cholistan desert that belongs to the tribe Anastaticeae and clade C of the Brassicaceae family. We provide the entire chloroplast sequence of F.hamiltonii, obtained using the Illumina HiSeq2500 and paired-end sequencing. We compared F. hamiltonii to nine other clade C species, including Farsetia occidentalis, Lobularia libyca, Notoceras bicorne, Parolinia ornata, Morettia canescens, Cochlearia borzaeana, Megacarpaea polyandra, Biscutella laevigata, and Iberis amara. We conducted phylogenetic research on the 22 Brassicaceae species, which included members from 17 tribes and six clades.

RESULTS

The chloroplast genome sequence of F.hamiltonii of 154,802 bp sizes with 36.30% GC content and have a typical structure comprised of a Large Single Copy (LSC) of 83,906 bp, a Small Single Copy (SSC) of 17,988 bp, and two copies of Inverted Repeats (IRs) of 26,454 bp. The genomes of F. hamiltonii and F. occidentalis show shared amino acid frequencies and codon use, RNA editing sites, simple sequence repeats, and oligonucleotide repeats. The maximum likelihood tree revealed Farsetia as a monophyletic genus, closely linked to Morettia, with a bootstrap score of 100. The rate of transversion substitutions (Tv) was higher than the rate of transition substitutions (Ts), resulting in Ts/Tv less than one in all comparisons with F. hamiltonii, indicating that the species are closely related. The rate of synonymous substitutions (Ks) was greater than non-synonymous substitutions (Ka) in all comparisons with F. hamiltonii, with a Ka/Ks ratio smaller than one, indicating that genes underwent purifying selection. Low nucleotide diversity values range from 0.00085 to 0.08516, and IR regions comprise comparable genes on junctions with minimal change, supporting the conserved status of the selected chloroplast genomes of the clade C of the Brassicaceae family. We identified ten polymorphic regions, including rps8-rpl14, rps15-ycf1, ndhG-ndhI, psbK-psbI, ccsA-ndhD, rpl36-rps8, petA-psbJ, ndhF-rpl32, psaJ-rpl3, and ycf1 that might be exploited to construct genuine and inexpensive to solve taxonomic discrepancy and understand phylogenetic relationship amongst Brassicaceae species.

CONCLUSION

The entire chloroplast sequencing of F. hamiltonii sheds light on the divergence of genic chloroplast sequences among members of the clade C. When other Farsetia species are sequenced in the future, the full F. hamiltonii chloroplast will be used as a source for comprehensive taxonomical investigations of the genus. The comparison of F. hamiltonii and other clade C species adds new information to the phylogenetic data and evolutionary processes of the clade. The results of this study will also provide further molecular uses of clade C chloroplasts for possible plant genetic modifications and will help recognise more Brassicaceae family species.

Comparative chloroplast genomes and phylogenetic analyses of Pinellia

Background

Pinellia Tenore (Araceae) is a genus of perennial herbaceous plants, all of which have medicinal value. The chloroplast (cp) genome data of Pinellia are scarce, and the phylogenetic relationship and gene evolution remain unclear.

Methods and results

We sequenced and annotated the Pinellia pedatisecta cp genome and combined it with previously published genomes for other Pinellia species. We used bioinformatics methods to analyse the genomic structure, repetitive sequences, interspecific variation, divergence hotspots, phylogenetic relationships, divergence time estimation and selective pressure of four Pinellia plastomes. Results showed that the cp genomes of Pinellia varied in length between 168,178 (P. pedatisecta MN046890) and 164,013 bp (P. ternata KR270823). A total of 68–111 SSR loci were identified as candidate molecular markers for further genetic diversity study. Eight mutational hotspot regions were determined, including psbI-trnG-UCC, psbM-rpoB, ndhJ-trnT-UGU, trnP-UGG-trnW-CCA, ndhF-trnN-GUU, ndhG-ndhE, ycf1-rps15 and trnR-ycf1. Gene selection pressure suggested that four genes were subjected to positive selection. Phylogenetic inferences based on the complete cp genomes revealed a sister relationship between Pinellia and Arisaema plants whose divergence was estimated to occur around 22.48 million years ago. All Pinellia species formed a monophyletic evolutionary clade in which P. peltata, rather than P. pedatisecta, earlier diverged, indicating that P. pedatisecta is not the basal taxon of Pinellia but P. peltata may be.

Conclusions

The cp genomes of Pinellia will provide valuable information for species classification, identification, molecular breeding and evolutionary exploration of the genus Pinellia.

Supplementary Information

The online version of this article (10.1007/s11033-022-07617-5) contains supplementary material, which is available to authorized users.