Comparative Chloroplast Genomics of Dipsacales Species: Insights Into Sequence Variation, Adaptive Evolution, and Phylogenetic Relationships.
ABSTRACT: In general, the chloroplast genomes of angiosperms are considered to be highly conserved and affected little by adaptive evolution. In this study, we tested this hypothesis based on sequence differentiation and adaptive variation in the plastid genomes in the order Dipsacales. We sequenced the plastid genomes of one Adoxaceae species and six Caprifoliaceae species, and together with seven previously released Dipsacales chloroplasts, we determined the sequence variations, evolutionary divergence of the plastid genomes, and phylogeny of Dipsacales species. The chloroplast genomes of Adoxaceae species ranged in size from 157,074 bp (Sinadoxa corydalifolia) to 158,305 bp (Sambucus williamsii), and the plastid genomes of Caprifoliaceae varied from 154,732 bp (Lonicera fragrantissima var. lancifolia) to 156,874 bp (Weigela florida). The differences in the number of genes in Caprifoliaceae and Adoxaceae species were largely due to the expansion and contraction of inverted repeat regions. In addition, we found that the number of dispersed repeats (Adoxaceae = 37; Caprifoliaceae = 384) was much higher than that of tandem repeats (Adoxaceae = 34; Caprifoliaceae = 291) in Dipsacales species. Interestingly, we determined 19 genes with positive selection sites, including three genes encoding ATP protein subunits (atpA, atpB, and atpI), four genes for ribosome protein small subunits (rps3, rps7, rps14, and rps15), four genes for photosystem protein subunits (psaA, psaJ, psbC, and pabK), two genes for ribosome protein large subunits (rpl22 and rpl32), and the clpP, infA, matK, rbcL, ycf1, and ycf2 genes. These gene regions may have played key roles in the adaptation of Dipsacales to diverse environments. In addition, phylogenetic analysis based on the plastid genomes strongly supported the division of 14 Dipsacales species into two previously recognized sections. The diversification of Adoxaceae and Caprifoliaceae was dated to the late Cretaceous and Tertiary periods. The availability of these chloroplast genomes provides useful genetic information for studying taxonomy, phylogeny, and species evolution in Dipsacales.
Project description:The wax-leafed <i>Viburnum japonicum</i> (Adoxaceae) is an evergreen shrub distributed in Japan, Korea, and Taiwan. We sequenced its complete chloroplast (cp) genome to examine its phylogenetic relationship within Dipsacales. This genome is 158,614?bp long and features a large single-copy region (87,059?bp) and a small single-copy region (18,523?bp), separated by two inverted-repeat regions (26,516?bp each). It contains 128 genes, including 84 coding genes, eight rRNAs, and 36 tRNAs. The overall GC content is 38.1%. Our phylogenetic tree showed that <i>V</i>. <i>japonicum</i> is closely related to <i>V</i>. <i>utile</i> and is clustered together with four species in the family Adoxaceae.
Project description:<i>Linnaea chinensis</i> (Caprifoliaceae), which inhabits in China and Japan, is commonly cultivated as an ornamental shrub. The complete chloroplast genome of <i>L. chinensis</i> was newly assembled in this study based on Illumina pair-end sequencing data. The full length of <i>L. chinensis</i> plastome is 155,813?bp. In total, 124 genes were identified, including 75 protein-coding genes, 8 rRNA genes, and 42 tRNA genes. The overall GC content of this genome was 38.4%. A further phylogenomic analysis including16 species from Adoxaceae and Caprifoliaceae was constructed.
Project description:Phylogenetic analyses of complete chloroplast genome sequences have yielded significant improvements in our understanding of relationships in the woody flowering genus Viburnum (Adoxaceae, Dipsacales); however, these relationships were evaluated focusing only on Viburnum species within Central and South America and Southeast Asia. By contrast, despite being a hotspot of Viburnum diversity, phylogenetic relationships of Viburnum species in China are less well known. Here, we characterized the complete chloroplast (cp) genomes of 21 Viburnum species endemic to China, as well as three Sambucus species. These 24 plastomes were highly conserved in genomic structure, gene order and content, also when compared with other Adoxaceae. The identified repeat sequences, simple sequence repeats (SSRs) and highly variable plastid regions will provide potentially valuable genetic resources for further population genetics and phylogeographic studies on Viburnum and Sambucus. Consistent with previous combined phylogenetic analyses of 113 Viburnum species, our phylogenomic analyses based on the complete cp genome sequence dataset confirmed the sister relationship between Viburnum and the Sambucus-Adoxa-Tetradoxa-Sinadoxa group, the monophyly of four recognized sections in Flora of China (i.e., Viburnum sect. Tinus, Viburnum sect. Solenotinus, Viburnum sect. Viburnum and Viburnum sect. Pseudotinus) and the nonmonophyly of Viburnum sect. Odontotinus and Viburnum sect. Megalotinus. Additionally, our study confirmed the sister relationships between the clade Valvatotinus and Viburnum sect. Pseudotinus, as well as between Viburnum sect. Opulus and the Odontotinus-Megalotinus group. Overall, our results clearly document the power of the complete cp genomes in improving phylogenetic resolution, and will contribute to a better understanding of plastome evolution in Chinese Adoxaceae.
Project description:<i>Symphoricarpos sinensis</i> is an important ornamental plant in China. Due to the lack of efficient molecular markers, although recent studies supported that <i>Symphoricarpos</i> was phylogenetically closely related to <i>Lonicera</i>, <i>Triosteum</i>, <i>Heptacodium</i>, and <i>Leycesteria</i>, relationships among these taxa remained uncertain. To examine the phylogenetic position of <i>Symphoricarpos</i> within Caprifoliaceae, we characterized the complete chloroplast (cp) genome of <i>S. sinensis</i>. The results showed that <i>S. sinensis</i> shared a typical quadripartite structure as with most angiosperms. It was 155,738?bp in length, including two inverted repeat (IR) regions (24,010?bp), a small single-copy (SSC) region (18,942?bp) and a large single-copy (LSC) region (88,776?bp). Phylogenetic analysis demonstrated that Caprifoliaceae and Adoxaceae formed two distinct monophyletic clades, and <i>S. sinensis</i> was closely related to <i>lonicera</i> and <i>Triosteum</i>, albeit with low support. The whole cp genome of <i>S. sinensis</i> will be useful resources for future studies on phylogeny and conservation in <i>Symphoricarpos.</i>
Project description:Plastid genomes of parasitic plants represent apt systems, in which the effects of relaxed selective pressure on photosynthetic function are studied. The complete chloroplast genome sequence of nonphotosynthetic mycoheterotrophic plant <i>Monotropa hypopitys</i> was determined. With only 19 protein-coding, four rRNA and 17 tRNA genes in 34?800?bp long genome, it is one of the most reduced plastid genomes characterized until now. <i>Monotropa</i> chloroplast genome lacks all genes encoding photosynthetic functions and RNA polymerase subunits but retains most of the ribosomal protein genes and housekeeping genes infA and matK. <i>Monotropa</i> represents the late stages of chloroplast genome decay following the transition to heterotrophy.
Project description:BACKGROUND AND AIMS: The expression of floral symmetry genes is examined in the CYCLOIDEA lineage following duplication, and these are linked to changes in flower morphology. The study focuses on Dipsacales, comparing DipsCYC2 gene expression in Viburnum (radially symmetrical Adoxaceae) to members of early-diverging lineages of the bilaterally symmetrical Caprifoliaceae (Diervilla and Lonicera). METHODS: Floral tissue from six species, which included dorsal, lateral and ventral regions of the corolla, was dissected. RNA was extracted from these tissues and each copy of DipsCYC2 was amplified with reverse transcriptase PCR. KEY RESULTS: Members of DipsCYC2 were expressed across the corolla in the radially symmetrical Viburnum plicatum. A shift to bilaterally symmetrical flowers at the base of the Caprifoliaceae was accompanied by a duplication of the DipsCYC2 gene, resulting in DipsCYC2A and DipsCYC2B, and by loss of expression of both of these copies in the ventral petal. In Lonicera (Caprifolieae), there is a shift from flowers with two dorsally and three ventrally oriented corolla lobes to a clear differentiation of dorsal, lateral and ventral lobes. This shift entailed a decoupling of expression of DipsCYC2A and DipsCYC2B; DipsCYC2B continues to be expressed in the dorsal and lateral lobes, while DipsCYC2A expression is restricted to just the two dorsal lobes. A reversion to more radially symmetrical flowers within Lonicera was accompanied by a re-expansion of expression of both DipsCYC2A and DipsCYC2B. CONCLUSIONS: The transition to bilateral symmetry in Caprifoliaceae involved: (a) duplication of an ancestral DipsCYC2 gene; (b) the loss of expression of both of these copies in the ventral petal; and (c) changes in the zone of expression, with one copy continuing to be expressed across the dorsal and lateral petals, and the other copy becoming restricted in expression to the dorsal corolla lobes.
Project description:<i>Triosteum himalayanum</i> is a perennial herb which is distributed in the eastern Himalayas, Hengduan Mountains, and central China. The complete chloroplast genome of <i>T. himalayanum</i> is studied for the first time, which is 154,579?bp in length and is divided into four regions: two inverted repeat (IRA and IRB) regions of 23,370?bp, a small single copy (SSC) region of 18,682?bp and a large single copy (LSC) region of 89,157?bp. The plastid genome contains 133 genes, including 86 protein-coding genes, 39 tRNA genes, and 8 rRNA genes. The overall CG content in the chloroplast genome of <i>T. himalayanum</i> is 38.38%. The phylogenetic analysis on the complete plastome sequence of <i>T. himalayanum</i> will help to show the intergeneric diversity of Caprifoliaceae.
Project description:Quercus is considered economically and ecologically one of the most important genera in the Northern Hemisphere. Oaks are taxonomically perplexing because of shared interspecific morphological traits and intraspecific morphological variation, which are mainly attributed to hybridization. Universal plastid markers cannot provide a sufficient number of variable sites to explore the phylogeny of this genus, and chloroplast genome-scale data have proven to be useful in resolving intractable phylogenetic relationships. In this study, the complete chloroplast genomes of four Quercus species were sequenced, and one published chloroplast genome of Quercus baronii was retrieved for comparative analyses. The five chloroplast genomes ranged from 161,072 bp (Q. baronii) to 161,237 bp (Q. dolicholepis) in length, and their gene organization and order, and GC content, were similar to those of other Fagaceae species. We analyzed nucleotide substitutions, indels, and repeats in the chloroplast genomes, and found 19 relatively highly variable regions that will potentially provide plastid markers for further taxonomic and phylogenetic studies within Quercus. We observed that four genes (ndhA, ndhK, petA, and ycf1) were subject to positive selection. The phylogenetic relationships of the Quercus species inferred from the chloroplast genomes obtained moderate-to-high support, indicating that chloroplast genome data may be useful in resolving relationships in this genus.
Project description:Campanulaceae species are known to have highly rearranged plastid genomes lacking the acetyl-CoA carboxylase (ACC) subunit D gene (accD), and instead have a nuclear (nr)-accD. Plastid genome information has been thought to depend on studies concerning Trachelium caeruleum and genome announcements for Adenophora remotiflora, Campanula takesimana, and Hanabusaya asiatica. RNA editing information for plastid genes is currently unavailable for Campanulaceae. To understand plastid genome evolution in Campanulaceae, we have sequenced and characterized the chloroplast (cp) genome and nr-accD of Platycodon grandiflorum, a basal member of Campanulaceae.We sequenced the 171,818 bp cp genome containing a 79,061 bp large single-copy (LSC) region, a 42,433 bp inverted repeat (IR) and a 7840 bp small single-copy (SSC) region, which represents the cp genome with the largest IR among species of Campanulaceae. The genome contains 110 genes and 18 introns, comprising 77 protein-coding genes, four RNA genes, 29 tRNA genes, 17 group II introns, and one group I intron. RNA editing of genes was detected in 18 sites of 14 protein-coding genes. Platycodon has an IR containing a 3' rps12 operon, which occurs in the middle of the LSC region in four other species of Campanulaceae (T. caeruleum, A. remotiflora, C. takesimana, and H. asiatica), but lacks accD, clpP, infA, and rpl23, as has been found in these four species. Platycodon nr-accD contains about 3.2 kb intron between nr-accD.e1 and nr-accD.e2 at the same insertion point as in other Campanulaceae. The phylogenies of the plastid genomes and accD show that Platycodon is basal in the Campanulaceae clade, indicating that IR disruption in Campanulaceae occurred after the loss of accD, clpP, infA, and rpl23 in the cp genome, which occurred during plastid evolution in Campanulaceae.The plastid genome of P. grandiflorum lacks the rearrangement of the IR found in T. caeruleum, A. remotiflora, C. takesimana, and H. asiatica. The absence of accD, clpP, infA, and rpl23 in the plastid genome is a synapomorphic characteristic of Campanulaceae. The chloroplast genome phylogeny supports the hypothesis that chloroplast genomic arrangement occurred after accD nuclear transfer and loss of the four genes in the plastid of early Campanulaceae as a lineage of asterids.
Project description:<i>Maytenus guangxiensis</i> (Celastraceae) is a rare and critically endangered species endemic to China. Here, we first report and characterize its complete chloroplast genome sequence based on Illumina paired-end sequencing data. The complete plastid genome was 157,102?bp, which contained inverted repeats (IR) of 26,476?bp separated by a large single-copy (LSC) and a small single copy (SSC) of 85,559?bp and 18,591?bp, respectively. The cpDNA contains 130 genes, comprising 85 protein-coding genes, 37 tRNA genes and 8 rRNA genes. The overall GC content of the plastome is 37.3%. The phylogenetic analysis of 19 selected chloroplast genomes demonstrated that <i>M. guangxiensis</i> was close to the species <i>Catha edulis.</i>