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Comparison of eight complete chloroplast genomes of the endangered Aquilaria tree species (Thymelaeaceae) and their phylogenetic relationships.

ABSTRACT: Aquilaria tree species are naturally distributed in the Indomalesian region and are protected against over-exploitation. They produce a fragrant non-timber product of high economic value, agarwood. Ambiguous species delimitation and limited genetic information within Aquilaria are among the impediments to conservation efforts. In this study, we conducted comparative analysis on eight Aquilaria species complete chloroplast (cp) genomes, of which seven were newly sequenced using Illumina HiSeq X Ten platform followed by de novo assembly. Aquilaria cp genomes possess a typical quadripartite structure including gene order and genomic structure. The length of each of the cp genome is about 174 kbp and encoded between 89 and 92 proteins, 38 tRNAs, and 8 rRNAs, with 27 duplicated in the IR (inverted repeat) region. Besides, 832 repeats (forward, reverse, palindrome and complement repeats) and nine highly variable regions were also identified. The phylogenetic analysis suggests that the topology structure of Aquilaria cp genomes were well presented with strong support values based on the cp genomes data set and matches their geographic distribution pattern. In summary, the complete cp genomes will facilitate development of species-specific molecular tools to discriminate Aquilaria species and resolve the evolutionary relationships of members of the Thymelaeaceae family.

SUBMITTER: Hishamuddin MS

PROVIDER: S-EPMC7400740 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundSorbus sensu stricto (Sorbus s.s.) is a genus with important economical values because of its beautiful leaves, and flowers and especially the colorful fruits. It belongs to the tribe Maleae of the family Rosaceae, and comprises about 90 species mainly distributed in China. There is on-going dispute about its infrageneric classification and species delimitation as the species are morphologically similar. With the aim of shedding light on the circumscription of taxa within the genus, phylogenetic analyses were performed using 29 Sorbus s.s. chloroplast (cp) genomes (16 newly sequenced) representing two subgenera and eight sections.ResultsThe 16 cp genomes newly sequenced range between 159,646 bp and 160,178 bp in length. All the samples examined and 22 taxa re-annotated in Sorbus sensu lato (Sorbus s.l.) contain 113 unique genes with 19 of these duplicated in the inverted repeat (IR). Six hypervariable regions including trnR-atpA, petN-psbM, rpl32-trnL, trnH-psbA, trnT-trnL and ndhC-trnV were screened and 44-53 SSRs and 14-31 dispersed repeats were identified as potential molecular markers. Phylogenetic analyses under ML/BI indicated that Sorbus s.l. is polyphyletic, but Sorbus s.s. and the other five segregate genera, Aria, Chamaemespilus, Cormus, Micromeles and Torminalis are monophyletic. Two major clades and four sub-clades resolved with full-support within Sorbus s.s. are not consistent with the existing infrageneric classification. Two subgenera, subg. Sorbus and subg. Albocarmesinae are supported as monophyletic when S. tianschanica is transferred to subg. Albocarmesinae from subg. Sorbus and S. hupehensis var. paucijuga transferred to subg. Sorbus from subg. Albocarmesinae, respectively. The current classification at sectional level is not supported by analysis of cp genome phylogeny.ConclusionPhylogenomic analyses of the cp genomes are useful for inferring phylogenetic relationships in Sorbus s.s. Though genome structure is highly conserved in the genus, hypervariable regions and repeat sequences used are the most promising molecule makers for population genetics, species delimitation and phylogenetic studies.

Project description:The genus Alchemilla L., known for its medicinal and ornamental value, is widely distributed in the Holarctic regions with a few species found in Asia and Africa. Delimitation of species within Alchemilla is difficult due to hybridization, autonomous apomixes, and polyploidy, necessitating efficient molecular-based characterization. Herein, we report the initial complete chloroplast (cp) genomes of Alchemilla. The cp genomes of two African (Afromilla) species Alchemilla pedata and Alchemilla argyrophylla were sequenced, and phylogenetic and comparative analyses were conducted in the family Rosaceae. The cp genomes mapped a typical circular quadripartite structure of lengths 152,438 and 152,427 base pairs (bp) in A. pedata and A. argyrophylla, respectively. Alchemilla cp genomes were composed of a pair of inverted repeat regions (IRa/IRb) of length 25,923 and 25,915 bp, separating the small single copy (SSC) region of 17,980 and 17,981 bp and a large single copy (LSC) region of 82,612 and 82,616 bp in A. pedata and A. argyrophylla, respectively. The cp genomes encoded 114 unique genes including 88 protein-coding genes, 37 transfer RNA (tRNA) genes, and 4 ribosomal RNA (rRNA) genes. Additionally, 88 and 95 simple sequence repeats (SSRs) and 37 and 40 tandem repeats were identified in A. pedata and A. argyrophylla, respectively. Significantly, the loss of group II intron in atpF gene in Alchemilla species was detected. Phylogenetic analysis based on 26 whole cp genome sequences and 78 protein-coding gene sequences of 27 Rosaceae species revealed a monophyletic clustering of Alchemilla nested within subfamily Rosoideae. Based on a protein-coding region, negative selective pressure (Ka/Ks < 1) was detected with an average Ka/Ks value of 0.1322 in A. argyrophylla and 0.1418 in A. pedata. The availability of complete cp genome in the genus Alchemilla will contribute to species delineation and further phylogenetic and evolutionary studies in the family Rosaceae.

Project description:We analyzed the complete chloroplast genomes of eight Orostachys species and compared the sequences to those of published chloroplast genomes of the congeneric and closely related genera, Meterostachys and Hylotelephium. The total chloroplast genome length of thirteen species, including the eight species analyzed in this study and the five species analyzed in previous studies, ranged from 149,860 (M. sikokianus) to 151,707 bp (H. verticillatum). The overall GC contents of the genomes were almost identical (37.6 to 37.8%). The thirteen chloroplast genomes each contained 113 unique genes comprising 79 protein-coding genes, 30 tRNA genes, and four rRNA genes. Among the annotated genes, sixteen genes contained one or two introns. Although the genome structures of all Orostachys and Hylotelephium species were identical, Meterostachys differed in structure due to a relatively large gene block (trnS-GCU-trnS-GGA) inversion. The nucleotide diversity among the subsect. Orostachys chloroplast genomes was extremely low in all regions, and among the subsect. Appendiculatae, genus Orostachys, and all thirteen chloroplast genomes showed high values of Pi (>0.03) in one, five, or three regions. The phylogenetic analysis showed that Orostachys formed polyphyly, and subsect. Orostachys and Appendiculatae were clustered with Hylotelephium and Meterostachys, respectively, supporting the conclusion that each subsection should be considered as an independent genus. Furthermore, the data supported the taxonomic position of O. margaritifolia and O. iwarenge f. magnus, which were treated as synonyms for O. iwarenge in a previous study, as independent taxa. Our results suggested that O. ramosa and O. japonica f. polycephala were individual variations of O. malacophylla and O. japonica, respectively. The exact taxonomic position of O. latielliptica and the phylogenetic relationship among the three species, O. chongsunensis, O. malacophylla and O. ramosa, should be a topic of future study.

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Comparison of eight complete chloroplast genomes of the endangered Aquilaria tree species (Thymelaeaceae) and their phylogenetic relationships.

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