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The complete chloroplast genomes of three Betulaceae species: implications for molecular phylogeny and historical biogeography.

ABSTRACT: Background:Previous phylogenetic conclusions on the family Betulaceae were based on either morphological characters or traditional single loci, which may indicate some limitations. The chloroplast genome contains rich polymorphism information, which is very suitable for phylogenetic studies. Thus, we sequenced the chloroplast genome sequences of three Betulaceae species and performed multiple analyses to investigate the genome variation, resolve the phylogenetic relationships, and clarify the divergence history. Methods:Chloroplast genomes were sequenced using the high-throughput sequencing. A comparative genomic analysis was conducted to examine the global genome variation and screen the hotspots. Three chloroplast partitions were used to reconstruct the phylogenetic relationships using Maximum Likelihood and Bayesian Inference approaches. Then, molecular dating and biogeographic inferences were conducted based on the whole chloroplast genome data. Results:Betulaceae chloroplast genomes consisted of a small single-copy region and a large single copy region, and two copies of inverted repeat regions. Nine hotspots can be used as potential DNA barcodes for species delimitation. Phylogenies strongly supported the division of Betulaceae into two subfamilies: Coryloideae and Betuloideae. The phylogenetic position of Ostryopsis davidiana was controversial among different datasets. The divergence time between subfamily Coryloideae and Betuloideae was about 70.49 Mya, and all six extant genera were inferred to have diverged fully by the middle Oligocene. Betulaceae ancestors were probably originated from the ancient Laurasia. Discussions:This research elucidates the potential of chloroplast genome sequences in the application of developing molecular markers, studying evolutionary relationships and historical dynamic of Betulaceae.It also reveals the advantages of using chloroplast genome data to illuminate those phylogenies that have not been well solved yet by traditional approaches in other plants.

SUBMITTER: Yang Z

PROVIDER: S-EPMC6348958 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature

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Project description:BackgroundSparganium (Typhaceae) is a widespread temperate genus of ecologically important aquatic plants. Previous reconstructions of the phylogenetic relationships among Sparganium species are incompletely resolved partly because they were based on molecular markers comprising < 7,000 bp. Here, we sequenced and assembled the complete chloroplast genomes from 19 Sparganium samples representing 15 putative species and three putative subspecies in order to explore chloroplast genome evolution in this genus, clarify taxonomic lineages, estimate the divergence times of Sparganium species, and reconstruct aspects of the biogeographic history of the genus.ResultsThe 19 chloroplast genomes shared a conserved genome structure, gene content, and gene order. Our phylogenomic analysis presented a well-resolved phylogeny with robust support for most clades. Non-monophyly was revealed in three species: S. erectum, S. eurycarpum, and S. stoloniferum. Divergence time estimates suggest that the two subgenera of Sparganium split from each other ca. 30.67 Ma in the middle Oligocene. The subgenus Xanthosparganium diversified in the late Oligocene and Miocene, while the subgenus Sparganium diversified in the late Pliocene and Pleistocene. Ancestral area reconstruction suggested that the two subgenera may have originated in East Eurasia and North America.ConclusionThe non-monophyletic nature of three putative species underscores the necessity of taxonomic revision for Sparganium: S. stoloniferum subsp. choui may be more appropriately identified as S. choui, and subspecies of S. erectum may be in fact distinct species. The estimated diversification times of the two subgenera correspond to their species and nucleotide diversities. The likely ancestral area for most of subgenus Xanthosparganium was East Eurasia and North America from where it dispersed into West Eurasia and Australia. Most of subgenus Sparganium likely originated in North America and then dispersed into Eurasia. Our study demonstrates some of the ways in which complete chloroplast genome sequences can provide new insights into the evolution, phylogeny, and biogeography of the genus Sparganium.

Project description:BACKGROUND:Lethal amanitas (Amanita section Phalloideae) are a group of wild, fatal mushrooms causing many poisoning cases worldwide. However, the diversity and evolutionary history of these lethal mushrooms remain poorly known due to the limited sampling and insufficient gene fragments employed for phylogenetic analyses. In this study, five gene loci (nrLSU, ITS, rpb2, ef1-? and ?-tubulin) with a widely geographic sampling from East and South Asia, Europe, North and Central America, South Africa and Australia were analysed with maximum-likelihood, maximum-parsimony and Bayesian inference methods. Biochemical analyses were also conducted with intention to detect amatoxins and phalloidin in 14 representative samples. RESULT:Lethal amanitas were robustly supported to be a monophyletic group after excluding five species that were provisionally defined as lethal amanitas based on morphological studies. In lethal amanitas, 28 phylogenetic species were recognised by integrating molecular phylogenetic analyses with morphological studies, and 14 of them represented putatively new species. The biochemical analyses indicated a single origin of cyclic peptide toxins (amatoxins and phalloidin) within Amanita and suggested that this kind of toxins seemed to be a synapomorphy of lethal amanitas. Molecular dating through BEAST and biogeographic analyses with LAGRANGE and RASP indicated that lethal amanitas most likely originated in the Palaeotropics with the present crown group dated around 64.92 Mya in the early Paleocene, and the East Asia-eastern North America or Eurasia-North America-Central America disjunct distribution patterns were primarily established during the middle Oligocene to Miocene. CONCLUSION:The cryptic diversity found in this study indicates that the species diversity of lethal amanitas is strongly underestimated under the current taxonomy. The intercontinental sister species or sister groups relationships among East Asia and eastern North America or Eurasia-North America-Central America within lethal amanitas are best explained by the diversification model of Palaeotropical origin, dispersal via the Bering Land Bridge, followed by regional vicariance speciation resulting from climate change during the middle Oligocene to the present. These findings indicate the importance of both dispersal and vicariance in shaping the intercontinental distributions of these ectomycorrhizal fungi.

Project description:BackgroundThe suamc genus Rhus (sensu stricto) includes two subgenera, Lobadium (ca. 25 spp.) and Rhus (ca. 10 spp.). Their members, R. glabra and R. typhina (Rosanae: Sapindales: Anacardiaceae), are two economic important species. Chloroplast genome information is of great significance for the study of plant phylogeny and taxonomy.ResultsThe three complete chloroplast genomes from two Rhus glabra and one R. typhina accessions were obtained with a total of each about 159k bp in length including a large single-copy region (LSC, about 88k bp), a small single-copy regions (SSC, about 19k bp) and a pair of inverted repeats regions (IRa/IRb, about 26k bp), to form a canonical quadripartite structure. Each genome contained 88 protein-coding genes, 37 transfer RNA genes, eight ribosomal RNA genes and two pseudogenes. The overall GC content of the three genomes all were same (37.8%), and RSCU values showed that they all had the same codon prefers, i.e., to use codon ended with A/U (93%) except termination codon. Three variable hotspots, i.e., ycf4-cemA, ndhF-rpl32-trnL and ccsA-ndhD, and a total of 152-156 simple sequence repeats (SSR) were identified. The nonsynonymous (Ka)/synonymous (Ks) ratio was calculated, and cemA and ycf2 genes are important indicators of gene evolution. The phylogenetic analyses of the family Anacardiaceae showed that the eight genera were grouped into three clusters, and supported the monophyly of the subfamilies and all the genera. The accessions of five Rhus species formed four clusters, while, one individual of R. typhina grouped with the R. glabra accessions instead of clustering into the two other individuals of R. typhina in the subgenus Rhus, which showed a paraphyletic relationship.ConclusionsComparing the complete chloroplast genomes of the Rhus species, it was found that most SSRs were A/T rich and located in the intergenic spacer, and the nucleotide divergence exhibited higher levels in the non-coding region than in the coding region. The Ka/Ks ratio of cemA gene was > 1 for species collected in America, while it was < 1 for other species in China, which dedicated that the Rhus species from North America and East Asia have different evolutionary pressure. The phylogenetic analysis of the complete chloroplast genome clarified the Rhus placement and relationship. The results obtained in this study are expected to provide valuable genetic resources to perform species identification, molecular breeding, and intraspecific diversity of the Rhus species.

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The complete chloroplast genomes of three Betulaceae species: implications for molecular phylogeny and historical biogeography.

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