The genome contains 127 genes, including 85 protein-coding genes, 34 tRNA genes and 8 rRNA genes. For the first time, we describe the sequencing and assembly of the chloroplast genomes of two American elm genotypes (RV16 and Am57845). Our study constitutes the first investigation on the sequence and structural variation, phylogenetic utility and positive selection of plastomes of Dolomiaea, which will facilitate further studies of its taxonomy, evolution and conservation.Īmerican elm, Ulmus americana L., was cultivated widely in USA and Canada as a landscape tree, but the genome of this important species is poorly characterized. These genes may play important roles in the adaptation of Dolomiaea to alpine environments. Analysis for signatures of selection identified four genes that contain sites undergoing positive selection (atpA, ndhF, rbcL, and ycf4). Our analysis also revealed that the plastid genes, rpoC2 and ycf1, which are rarely used in Asteraceae phylogenetic inference, exhibit great phylogenetic informativeness and promise in further phylogenetic studies of tribe Cardueae. Phylogenetic analyses confirmed the evolutionary position of Dolomiaea as a clade within the subtribe Saussureinae, while revealing the discordance between the molecular phylogeny and morphological treatment. Eight highly divergent regions (rps16-trnQ, trnC-petN, trnE-rpoB, trnT-trnL-trnF, psbE-petL, ndhF-rpl32-trnL, rps15-ycf1, and ycf1), along with a total of 51-61 simple sequence repeats (SSRs) were identified as valuable molecular markers for further species delimitation and population genetic studies. All analyzed plastomes share the gene content and structure of most Asteraceae plastomes, indicating the conservation of plastome evolutionary history of Dolomiaea. Here, we sequenced and annotated plastomes of four Dolomiaea species. Despite significant medicinal value, genomic resources of Dolomiaea are still lacking, impeding our understanding of its evolutionary history. ![]() Genetic mutations of the following genes might have contributed to the survival and better adaptation during the evolutionary history of tobacco species.ĭolomiaea is a medicinally important genus of Asteraceae endemic to alpine habitats of the Qinghai-Tibet Plateau (QTP) and adjacent areas. These analyses indicated that four genes involved in different plastid functions, such as DNA replication (rpoA) and photosynthesis (atpB, ndhD and ndhF), came under positive selective pressure as a result of specific environmental conditions. We further inspected selective pressure on protein-coding genes among tobacco species to determine if this adaptation process affected the evolution of plastid genes. knightiana, which adapted to the Southern coastal climatic regimes. rustica developed in Southern Peru and separated from N. paniculata evolved in North/Central Peru, while N. The biogeographical analysis showed a south-to-north range expansion and diversification for N. rustica and knightiana appeared 0.56 Ma (HPD 0.65–0.46). The relaxed molecular clock analyses estimated that the speciation event between N. knightiana, and the later species is more closely related to N. Our comparative plastid genome analysis revealed that the maternal parent of the tetraploid N. We identified twenty highly polymorphic regions mostly belonging to intergenic spacer regions (IGS), which could be appropriate for the development of robust and cost-effective markers to infer the phylogeny of genus Nicotiana and family Solanaceae. ![]() Comparative analyses of Nicotiana plastid genomes showed similar GC content, gene content, codon usage, simple sequence repeats, oligonucleotide repeats, RNA editing sites and substitutions with currently available Solanaceae genomes sequences. De novo assembled tobacco plastid genomes showed typical quadripartite structure, consisting of a pair of inverted repeats (IR) regions (25,323–25,369 bp each) separated by a large single copy (LSC) region (86,510 –86,716 bp) and a small single copy (SSC) region (18,441–18,555 bp). Here, we assembled the plastid genomes of five tobacco species, namely N. Besides their use in the worldwide production of tobacco leaves, they are also used as evolutionary model systems due to their complex development history, which is tangled by polyploidy and hybridization. The genus Nicotiana of the family Solanaceae, commonly referred to as tobacco plants, are a group cultivated as garden ornamentals.
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