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

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

Untying the Gordian knot of plastid phylogenomic conflict: A case from ferns.

Phylogenomic studies based on plastid genome have resolved recalcitrant relationships among various plants, yet the phylogeny of Dennstaedtiaceae at the level of family and genera remains unresolved due to conflicting plastid genes, limited molecular data and incomplete taxon sampling of previous studies. The present study generated 30 new plastid genomes of Dennstaedtiaceae (9 genera, 29 species), which were combined with 42 publicly available plastid genomes (including 24 families, 27 genera, 42 species) to explore the evolution of Dennstaedtiaceae. In order to minimize the impact of systematic errors on the resolution of phylogenetic inference, we applied six strategies to generate 30 datasets based on CDS, intergenic spacers, and whole plastome, and two tree inference methods (maximum-likelihood, ML; and multispecies coalescent, MSC) to comprehensively analyze the plastome-scale data. Besides, the phylogenetic signal among all loci was quantified for controversial nodes using ML framework, and different topologies hypotheses among all datasets were tested. The species trees based on different datasets and methods revealed obvious conflicts at the base of the polypody ferns. The topology of the "CDS-codon-align-rm3" (CDS with the removal of the third codon) matrix was selected as the primary reference or summary tree. The final phylogenetic tree supported Dennstaedtiaceae as the sister group to eupolypods, and Dennstaedtioideae was divided into four clades with full support. This robust reconstructed phylogenetic backbone establishes a framework for future studies on Dennstaedtiaceae classification, evolution and diversification. The present study suggests considering plastid phylogenomic conflict when using plastid genomes. From our results, reducing saturated genes or sites can effectively mitigate tree conflicts for distantly related taxa. Moreover, phylogenetic trees based on amino acid sequences can be used as a comparison to verify the confidence of nucleotide-based trees.

Population Diversity Analysis Provide Insights into Provenance Identification of Dendrobium catenatum.

Dendrobium catenatum (Dendrobium officinale) is a valuable genuine herb. The source of this species is difficult to be identified by traditional methods including morphology, spectroscopy, and chromatography. We used the restriction site-associated DNA sequencing (RAD-seq) approach to perform the high-throughput sequencing of 24 D. catenatum provenances. In this study, 371.18 Gb clean data were obtained, and 655,057 high-quality SNPs were selected after their filtration. We used phylogenetic tree, genetic structure, and principal component analyses to examine the genetic diversities and genetic relationships of the 109 accessions. We found that D. catenatum could be divided into two groups, and each group was closely related to the distribution of the sampling sites. At the population level, the average nucleotide diversity (π) of the D. catenatum population mutation parameters was 0.1584 and the expected heterozygosity (HE) was 0.1575. The GXLPTP07 accessions showed the highest genetic diversity in terms of the private allele number, observed heterozygosity, and nucleotide diversity. The Mantel test showed a significant positive correlation between the genetic and geographic distances among the overall distribution. A genetic information database of D. catenatum was established, which confirmed that RAD-seq technology has the potential to be applied in the identification of medicinal Dendrobium of different origins.

The complete chloroplast genome sequence of Thrixspermum amplexicaule (Orchidaceae, Aeridinae).

The complete chloroplast genome sequence of Thrixspermum amplexicaule was assembled and analyzed in this work. The total chloroplast genome size of T. amplexicaule was 148,124 bp in length, containing a large single-copy (LSC) region of 86,079 bp, a small single-copy (SSC) region of 10,799 bp, and a pair of inverted repeat (IR) regions of 25,623 bp. The GC content of T. amplexicaule was 36.4%. It encoded a total of 120 unique genes, including 75 protein-coding genes, 37 tRNA genes, and eight rRNA genes. The results of phylogenetic analysis strongly supported that all four samples of Thrixspermum are monophyletic and T. amplexicaule was closely related to T. centipeda.

The complete chloroplast genome of Geodorum eulophioides (Orchidaceae).

Geodorum eulophioides Schltr., is a critically Endangered orchid (IUCN). In this study, we report the first complete chloroplast (cp) genome of G. eulophioides to provide the underlying information for genetic breeding and conservation studies of this species. The cp genome sequence of G. eulophioides is 149,466 bp in length, which contains one large single-copy region (LSC, 85,436 bp), one small single-copy region (SSC, 14,086 bp), and two inverted repeat regions (IRs, 24,972 bp). The cp genome encoded 177 genes, of which 106 were unique genes (78 protein-coding genes, 24 tRNAs, and 4 rRNAs). Phylogenetic analysis showed that G. eulophioides is closely related to the genera Eulophia.

The complete chloroplast genome sequence of monotypic Cyphotheca (Melastomataceae), an endemic genus in China.

Cyphotheca, a shrub narrowly endemic to Yunnan, southwest China, is a monotypic genus of Sonerileae in Melastomataceae. The species, Cyphotheca montana, is dwindling and is listed as 'Near Threatened (NT)' by IUCN Red List of China. Herein, we report the complete chloroplast genome (cpDNA) sequence assembled from Illumina pair-end sequencing data. The complete chloroplast genome was 156,424 bp in length, which includes two inverted repeat regions (IRs) of 26,776 bp each, which were separated by a large single copy region (LSC) 85,900 bp and a small single copy region (SSC) 16,972 bp. The chloroplast genome contained 130 genes, including 85 protein-coding genes, 37 tRNA genes, and 8 rRNA genes. The overall GC content in the chloroplast genome of C. montana was 37.0%. The phylogenomic analysis showed that C. montana is sister to Barthea barthei.

The complete chloroplast genome of an Endangered species Cymbidium Nanulum (Orchidaceae).

Cymbidium nanulum Y.S.Wu & S.C.Chen is an IUCN Red listed Endangered species and distributes in South-Central China and Hainan. Here, we report the complete chloroplast (cp) genome sequence and the cp genome features of C. nanulum. The complete chloroplast (cp) genome sequence of C. nanulum was 149,776 bp in length. It presented a typical quadripartite structure including one large single-copy region (LSC, 85,392 bp), one small single-copy region (SSC, 14,210 bp), and two inverted repeat regions (IRs, 25,087 bp). The cp genome encoded 133 genes, of which 104 were unique genes (77 protein-coding genes, 23 tRNAs, and 4 rRNAs). The maximum-likelihood phylogenetic analysis showed that C. nanulum was closely related to other species of genus Cymbidium.

The complete chloroplast genome of Cymbidium erythraeum (Orchidaceae).

Cymbidium erythraeum Lindl. is an endangered species of Orchidaceae and distributed in China and Bhutan, India, Myanmar, Nepal, and Vietnam. Here, we report the complete chloroplast (cp) genome sequence and the cp genome features of C. erythraeum. The complete chloroplast (cp) genome sequence of C. erythraeum is 156,327 bp in length and including one large single-copy region (LSC, 85,404 bp), one small single-copy region (SSC, 20,021 bp), and two inverted repeat regions (IRs, 25,426 bp). The cp genome encoded 136 genes, of which 107 were unique genes (80 protein-coding genes, 23 tRNAs, and four rRNAs). The phylogenetic relationships show that C. erythraeum is closely related to other species in the genus Cymbidium and is sister with C. tracyanum.

The complete chloroplast genome of Vanilla shenzhenica (Orchidaceae).

Vanilla shenzhenica Z.J.Liu & S.C.Chen is a new species of orchid found in Shenzhen, South China for the first time. Here we report the complete chloroplast (cp) genome sequence and the features of V. shenzhenica. Its cp genome sequence was 151,537 bp, including one large single-copy region (LSC, 87,487 bp), one small single-copy region (SSC, 19,172 bp), and two inverted repeat regions (IRs, 22,439 bp). It encoded 123 genes, of which 104 were unique genes (69 protein-coding genes, 31 tRNAs and 4 rRNAs). The phylogenetic relationships show that V. shenzhenica is sister with V. aphylla.

The complete chloroplast genome of an endangered species Cymbidium mastersii (Orchidaceae).

Cymbidium mastersii Griff. & Lindl. is an endangered orchid. In this study, we report the complete chloroplast (cp) genome sequence and the cp genome features of C. mastersii. The cp genome sequence of C. mastersii was 155,362 bp in length. It included one large single-copy region (LSC, 84,465 bp), one small single-copy region (SSC, 20,647 bp), and two inverted repeat regions (IRs, 25,125 bp). The cp genome encoded 130 genes, of which 107 were unique genes (80 protein-coding genes, 23 tRNAs, and 4 rRNAs). The maximum-likelihood phylogenetic analysis showed that C. mastersii was a sister of C. erythraeum and C. nanulum.

Complete chloroplast genome of Dendrobium thyrsiflorum (Orchidaceae).

Dendrobium thyrsiflorum H. G. Reichenbach ex André is an endemic herb with ornamental and medicinal orchid value distributed in Southeast of Yunnan of China. Here, we report and characterize the complete chloroplast (cp) genome sequence of D. thyrsiflorum in order to provide genomic resources helpful for its identification, conservation and utilization. The complete cp genome of D. thyrsiflorum is 160,123 bp, including one large single-copy region (LSC, 88,001), one small single-copy region (SSC, 21,142), and two inverted repeat regions (IRs, 25,490). The cp genome contains 143 genes, consisting of 110 unique genes (80 protein-coding genes, 26 tRNAs, and 4 rRNAS). The phlyogenetic relationships show that D. thyrsiflorum is closely related to other species of Dendrobium.

The complete chloroplast genome of Pholidota imbricata (Orchidaceae).

Pholidota imbricata belongs to tribe Coelogninae in Orchidaceae distributed in Sichuan, Xizang, and Yunnan. Here, we report the first complete chloroplast (cp) genome and the cp genome features of P. imbricata. The complete cp genome sequence of P. imbricata is 159,292 bp in length and presented a typical quadripartite structure including one large single-copy region (LSC, 87,515 bp), one small single-copy region (SSC, 20,999 bp), and two inverted repeat regions (IRs, 25,389 bp each). The cp genome encoded 141 genes, of which 108 were unique genes (80 protein-coding genes, 24 tRNAs, and 4 rRNAs). The phylogenetic relationships show that P. imbricata is sister to the species of the genus Pleione in tribe Coelogninae.

The complete chloroplast genome of Dendrobium longicornu (Orchidaceae).

Dendrobium longicornu Lindl is an epiphytic orchid with significant ornamental values. Here, we report the first complete chloroplast genome of D. longicornu. The complete chloroplast (cp) genome sequence of D. longicornu is 160,024 bp in length and consisted of two inverted repeats (IRs, 25,403 bp), which were separated by a large single copy region (LSC, 88,075 bp) and a small single copy region (SSC, 21,143 bp). The cp genome encoded 142 genes, of which 110 were unique genes (80 protein-coding genes, 26 tRNAs and 4 rRNAs). Phylogenetic analysis showed that D. longicornu clustered together with D. ellipsophy.

The complete chloroplast genome of Cymbidium changningense (Orchidaceae).

Cymbidium changningense is an ornamental orchid and endemic specie in China. Here, we report the complete chloroplast (cp) genome sequence and the cp genome features of C. changningense. The cp genome was 155,388 bp in length with a typical quadripartite structure, which was comprised of one large single copy (LSC, 84,522 bp) region and one small single copy (SSC, 20,622 bp) region separated by two inverted repeat (IR, 25,122 bp) regions. The cp genome encoded 132 genes, of which 108 were unique genes (80 protein-coding genes, 24 tRNAs, and four rRNAs). The phylogenetic analysis showed that C. changningense was sister with C. erythraeum.