ResearchPad - chloroplast-genome https://www.researchpad.co Default RSS Feed en-us © 2020 Newgen KnowledgeWorks <![CDATA[Chloroplast genomes of Rubiaceae: Comparative genomics and molecular phylogeny in subfamily Ixoroideae]]> https://www.researchpad.co/article/elastic_article_11231 In Rubiaceae phylogenetics, the number of markers often proved a limitation with authors failing to provide well-supported trees at tribal and generic levels. A robust phylogeny is a prerequisite to study the evolutionary patterns of traits at different taxonomic levels. Advances in next-generation sequencing technologies have revolutionized biology by providing, at reduced cost, huge amounts of data for an increased number of species. Due to their highly conserved structure, generally recombination-free, and mostly uniparental inheritance, chloroplast DNA sequences have long been used as choice markers for plant phylogeny reconstruction. The main objectives of this study are: 1) to gain insight in chloroplast genome evolution in the Rubiaceae (Ixoroideae) through efficient methodology for de novo assembly of plastid genomes; and, 2) to test the efficiency of mining SNPs in the nuclear genome of Ixoroideae based on the use of a coffee reference genome to produce well-supported nuclear trees. We assembled whole chloroplast genome sequences for 27 species of the Rubiaceae subfamily Ixoroideae using next-generation sequences. Analysis of the plastid genome structure reveals a relatively good conservation of gene content and order. Generally, low variation was observed between taxa in the boundary regions with the exception of the inverted repeat at both the large and short single copy junctions for some taxa. An average of 79% of the SNP determined in the Coffea genus are transferable to Ixoroideae, with variation ranging from 35% to 96%. In general, the plastid and the nuclear genome phylogenies are congruent with each other. They are well-resolved with well-supported branches. Generally, the tribes form well-identified clades but the tribe Sherbournieae is shown to be polyphyletic. The results are discussed relative to the methodology used and the chloroplast genome features in Rubiaceae and compared to previous Rubiaceae phylogenies.

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<![CDATA[Detecting useful genetic markers and reconstructing the phylogeny of an important medicinal resource plant, Artemisia selengensis, based on chloroplast genomics]]> https://www.researchpad.co/article/5c61e90ed5eed0c48496f746

Artemisia selengenesis is not only a health food, but also a well-known traditional Chinese medicine. Only a fraction of the chloroplast (cp) genome data of Artemisia has been reported and chloroplast genomic materials have been widely used in genomic evolution studies, molecular marker development, and phylogenetic analysis of the genus Artemisia, which makes evolutionary studies, genetic improvement, and phylogenetic identification very difficult. In this study, the complete chloroplast genome of A. selengensis was compared with that of other species within Artemisia and phylogenetic analyses was conducted with other genera in the Asteraceae family. The results showed that A. selengensis is an AT-rich species and has a typical quadripartite structure that is 151,215 bp in length. Comparative genome analyses demonstrated that the available chloroplast genomes of species of Artemisia were well conserved in terms of genomic length, GC contents, and gene organization and order. However, some differences, which may indicate evolutionary events, were found, such as a re-inversion event within the Artemisia genus, an unequal duplicate phenomenon of the ycf1 gene because of the expansion and contraction of the IR region, and the fast-evolving regions. Repeated sequences analysis showed that Artemisia chloroplast genomes presented a highly similar pattern of SSR or LDR distribution. A total of 257 SSRs and 42 LDRs were identified in the A. selengensis chloroplast genome. The phylogenetic analysis showed that A. selengensis was sister to A. gmelinii. The findings of this study will be valuable in further studies to understand the genetic diversity and evolutionary history of Asteraceae.

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<![CDATA[Quillworts from the Amazon: A multidisciplinary populational study on Isoetes serracarajensis and Isoetes cangae]]> https://www.researchpad.co/article/5b87837240307c3c45097671

Isoetes are ancient quillworts members of the only genus of the order Isoetales. The genus is slow evolving but is resilient, and widespread worldwide. Two recently described species occur in the Eastern Brazilian Amazon, Isoetes serracarajensis and Isoetes cangae. They are found in the ironstone grasslands known as Canga. While I. serracarajensis is present mostly in seasonal water bodies, I. cangae is known to occur in a single permanent lake at the South mountain range. In this work, we undertake an extensive morphological, physiological and genetic characterization of both species to establish species boundaries and better understand the morphological and genetic features of these two species. Our results indicate that the morphological differentiation of the species is subtle and requires a quantitative assessment of morphological elements of the megaspore for diagnosis. We did not detect differences in microspore output, but morphological peculiarities may establish a reproductive barrier. Additionally, genetic analysis using DNA barcodes and whole chloroplast genomes indicate that although the plants are genetically very similar both approaches provide diagnostic characters. There was no indication of population structuring I. serracarajensis. These results set the basis for a deeper understanding of the evolution of the Isoetes genus.

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<![CDATA[Chloroplast Genome Evolution in Actinidiaceae: clpP Loss, Heterogenous Divergence and Phylogenomic Practice]]> https://www.researchpad.co/article/5989db28ab0ee8fa60bd0a20

Actinidiaceae is a well-known economically important plant family in asterids. To elucidate the chloroplast (cp) genome evolution within this family, here we present complete genomes of three species from two sister genera (Clematoclethra and Actinidia) in the Actinidiaceae via genome skimming technique. Comparative analyses revealed that the genome structure and content were rather conservative in three cp genomes in spite of different inheritance pattern, i.e.paternal in Actinidia and maternal in Clematoclethra. The clpP gene was lacked in all the three sequenced cp genomes examined here indicating that the clpP gene loss is likely a conspicuous synapomorphic characteristic during the cp genome evolution of Actinidiaceae. Comprehensive sequence comparisons in Actinidiaceae cp genomes uncovered that there were apparently heterogenous divergence patterns among the cpDNA regions, suggesting a preferred data-partitioned analysis for cp phylogenomics. Twenty non-coding cpDNA loci with fast evolutionary rates are further identified as potential molecular markers for systematics studies of Actinidiaceae. Moreover, the cp phylogenomic analyses including 31 angiosperm plastomes strongly supported the monophyly of Actinidia, being sister to Clematoclethra in Actinidiaceae which locates in the basal asterids, Ericales.

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<![CDATA[Assembly of the Complete Sitka Spruce Chloroplast Genome Using 10X Genomics’ GemCode Sequencing Data]]> https://www.researchpad.co/article/5989da88ab0ee8fa60b9cea1

The linked read sequencing library preparation platform by 10X Genomics produces barcoded sequencing libraries, which are subsequently sequenced using the Illumina short read sequencing technology. In this new approach, long fragments of DNA are partitioned into separate micro-reactions, where the same index sequence is incorporated into each of the sequencing fragment inserts derived from a given long fragment. In this study, we exploited this property by using reads from index sequences associated with a large number of reads, to assemble the chloroplast genome of the Sitka spruce tree (Picea sitchensis). Here we report on the first Sitka spruce chloroplast genome assembled exclusively from P. sitchensis genomic libraries prepared using the 10X Genomics protocol. We show that the resulting 124,049 base pair long genome shares high sequence similarity with the related white spruce and Norway spruce chloroplast genomes, but diverges substantially from a previously published P. sitchensis- P. thunbergii chimeric genome. The use of reads from high-frequency indices enabled separation of the nuclear genome reads from that of the chloroplast, which resulted in the simplification of the de Bruijn graphs used at the various stages of assembly.

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<![CDATA[The first complete chloroplast genome sequences of Ulmus species by de novo sequencing: Genome comparative and taxonomic position analysis]]> https://www.researchpad.co/article/5989db4fab0ee8fa60bdba96

Elm (Ulmus) has a long history of use as a high-quality heavy hardwood famous for its resistance to drought, cold, and salt. It grows in temperate, warm temperate, and subtropical regions. This is the first report of Ulmaceae chloroplast genomes by de novo sequencing. The Ulmus chloroplast genomes exhibited a typical quadripartite structure with two single-copy regions (long single copy [LSC] and short single copy [SSC] sections) separated by a pair of inverted repeats (IRs). The lengths of the chloroplast genomes from five Ulmus ranged from 158,953 to 159,453 bp, with the largest observed in Ulmus davidiana and the smallest in Ulmus laciniata. The genomes contained 137–145 protein-coding genes, of which Ulmus davidiana var. japonica and U. davidiana had the most and U. pumila had the fewest. The five Ulmus species exhibited different evolutionary routes, as some genes had been lost. In total, 18 genes contained introns, 13 of which (trnL-TAA+, trnL-TAA, rpoC1-, rpl2-, ndhA-, ycf1, rps12-, rps12+, trnA-TGC+, trnA-TGC-, trnV-TAC-, trnI-GAT+, and trnI-GAT) were shared among all five species. The intron of ycf1 was the longest (5,675bp) while that of trnF-AAA was the smallest (53bp). All Ulmus species except U. davidiana exhibited the same degree of amplification in the IR region. To determine the phylogenetic positions of the Ulmus species, we performed phylogenetic analyses using common protein-coding genes in chloroplast sequences of 42 other species published in NCBI. The cluster results showed the closest plants to Ulmaceae were Moraceae and Cannabaceae, followed by Rosaceae. Ulmaceae and Moraceae both belonged to Urticales, and the chloroplast genome clustering results were consistent with their traditional taxonomy. The results strongly supported the position of Ulmaceae as a member of the order Urticales. In addition, we found a potential error in the traditional taxonomies of U. davidiana and U. davidiana var. japonica, which should be confirmed with a further analysis of their nuclear genomes. This study is the first report on Ulmus chloroplast genomes, which has significance for understanding photosynthesis, evolution, and chloroplast transgenic engineering.

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<![CDATA[Characterization of the whole chloroplast genome of Chikusichloa mutica and its comparison with other rice tribe (Oryzeae) species]]> https://www.researchpad.co/article/5989db5cab0ee8fa60bdffde

Chloroplast genomes are a significant genomic resource in plant species and have been used in many research areas. The complete genomic information from wild crop species could supply a valuable genetic reservoir for breeding. Chikusichloa mutica is one of the most important wild distant relatives of cultivated rice. In this study, we sequenced and characterized its complete chloroplast (cp) genome and compared it with other species in the same tribe. The whole cp genome sequence is 136,603 bp in size and exhibits a typical quadripartite structure with large and small single-copy regions (LSC, 82,327 bp; SSC, 12,598 bp) separated by a pair of 20,839-bp inverted repeats (IRA, B). A total of 110 unique genes are annotated, including 76 protein-coding genes, 4 ribosomal RNA genes and 30 tRNA genes. The genome structure, gene order, GC content, and other features are similar to those of other angiosperm cp genomes. When comparing the cp genomes between Oryzinae and Zizaniinae subtribes, the main differences were found between the junction regions and distribution of simple sequence repeats (SSRs). In comparing the two Chikusichloa species, the genomes were only 40 bp different in length and 108 polymorphic sites, including 83 single nucleotide substitutions (SNPs) and 25 insertion-deletions (Indels), were found between the whole cp genomes. The complete cp genome of C. mutica will be an important genetic tool for future breeding programs and understanding the evolution of wild rice relatives.

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<![CDATA[The First Chloroplast Genome Sequence of Boswellia sacra, a Resin-Producing Plant in Oman]]> https://www.researchpad.co/article/5989da2aab0ee8fa60b824ef

Boswellia sacra (Burseraceae), a keystone endemic species, is famous for the production of fragrant oleo-gum resin. However, the genetic make-up especially the genomic information about chloroplast is still unknown. Here, we described for the first time the chloroplast (cp) genome of B. sacra. The complete cp sequence revealed a circular genome of 160,543 bp size with 37.61% GC content. The cp genome is a typical quadripartite chloroplast structure with inverted repeats (IRs 26,763 bp) separated by small single copy (SSC; 18,962 bp) and large single copy (LSC; 88,055 bp) regions. De novo assembly and annotation showed the presence of 114 unique genes with 83 protein-coding regions. The phylogenetic analysis revealed that the B. sacra cp genome is closely related to the cp genome of Azadirachta indica and Citrus sinensis, while most of the syntenic differences were found in the non-coding regions. The pairwise distance among 76 shared genes of B. sacra and A. indica was highest for atpA, rpl2, rps12 and ycf1. The cp genome of B. sacra reveals a novel genome, which could be used for further studied to understand its diversity, taxonomy and phylogeny.

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<![CDATA[The complete chloroplast genome sequences of Lychnis wilfordii and Silene capitata and comparative analyses with other Caryophyllaceae genomes]]> https://www.researchpad.co/article/5989db4fab0ee8fa60bdbcb8

The complete chloroplast genomes of Lychnis wilfordii and Silene capitata were determined and compared with ten previously reported Caryophyllaceae chloroplast genomes. The chloroplast genome sequences of L. wilfordii and S. capitata contain 152,320 bp and 150,224 bp, respectively. The gene contents and orders among 12 Caryophyllaceae species are consistent, but several microstructural changes have occurred. Expansion of the inverted repeat (IR) regions at the large single copy (LSC)/IRb and small single copy (SSC)/IR boundaries led to partial or entire gene duplications. Additionally, rearrangements of the LSC region were caused by gene inversions and/or transpositions. The 18 kb inversions, which occurred three times in different lineages of tribe Sileneae, were thought to be facilitated by the intermolecular duplicated sequences. Sequence analyses of the L. wilfordii and S. capitata genomes revealed 39 and 43 repeats, respectively, including forward, palindromic, and reverse repeats. In addition, a total of 67 and 56 simple sequence repeats were discovered in the L. wilfordii and S. capitata chloroplast genomes, respectively. Finally, we constructed phylogenetic trees of the 12 Caryophyllaceae species and two Amaranthaceae species based on 73 protein-coding genes using both maximum parsimony and likelihood methods.

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<![CDATA[Characterization of the complete chloroplast genome of Arabis stellari and comparisons with related species]]> https://www.researchpad.co/article/5aafc695463d7e7d7e2e8758

Arabis stellari var. japonica is an ornamental plant of the Brassicaceae family, and is widely distributed in South Korea. However, no information is available about its molecular biology and no genomic study has been performed on A. stellari. In this paper, the authors report the complete chloroplast genome sequence of A. stellari. The plastome of A. stellari was 153,683 bp in length with 36.4% GC and included a pair of inverted repeats (IRs) of 26,423 bp that separated a large single-copy (LSC) region of 82,807 bp and a small single-copy (SSC) region of 18,030 bp. It was also found to contain 113 unique genes, of which 79 were protein-coding genes, 30 were transfer RNAs, and four were ribosomal RNAs. The gene content and organization of the A. stellari chloroplast genome were similar to those of other Brassicaceae genomes except for the absence of the rps16 protein-coding gene. A total of 991 SSRs were identified in the genome. The chloroplast genome of A. stellari was compared with closely related species of the Brassicaceae family. Comparative analysis showed a minor divergence occurred in the protein-coding matK, ycf1, ccsA, accD and rpl22 genes and that the KA/KS nucleotide substitution ratio of the ndhA genes of A. stellari and A. hirsuta was 1.35135. The genes infA and rps16 were absent in the Arabis genus and phylogenetic evolutionary studies revealed that these genes evolved independently. However, phylogenetic analysis showed that the positions of Brassicaceae species are highly conserved. The present study provides A. stellari genomic information that may be found useful in conservation and molecular phylogenetic studies on Brassicaceae.

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<![CDATA[Complete Chloroplast Genomes of Erianthus arundinaceus and Miscanthus sinensis: Comparative Genomics and Evolution of the Saccharum Complex]]> https://www.researchpad.co/article/5989db4fab0ee8fa60bdba0e

The genera Erianthus and Miscanthus, both members of the Saccharum complex, are of interest as potential resources for sugarcane improvement and as bioenergy crops. Recent studies have mainly focused on the conservation and use of wild accessions of these genera as breeding materials. However, the sequence data are limited, which hampers the studies of phylogenetic relationships, population structure, and evolution of these grasses. Here, we determined the complete chloroplast genome sequences of Erianthus arundinaceus and Miscanthus sinensis by using 454 GS FLX pyrosequencing and Sanger sequencing. Alignment of the E. arundinaceus and M. sinensis chloroplast genome sequences with the known sequence of Saccharum officinarum demonstrated a high degree of conservation in gene content and order. Using the data sets of 76 chloroplast protein-coding genes, we performed phylogenetic analysis in 40 taxa including E. arundinaceus and M. sinensis. Our results show that S. officinarum is more closely related to M. sinensis than to E. arundinaceus. We estimated that E. arundinaceus diverged from the subtribe Sorghinae before the divergence of Sorghum bicolor and the common ancestor of S. officinarum and M. sinensis. This is the first report of the phylogenetic and evolutionary relationships inferred from maternally inherited variation in the Saccharum complex. Our study provides an important framework for understanding the phylogenetic relatedness of the economically important genera Erianthus, Miscanthus, and Saccharum.

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<![CDATA[Complete chloroplast genome sequence of common bermudagrass (Cynodon dactylon (L.) Pers.) and comparative analysis within the family Poaceae]]> https://www.researchpad.co/article/5989db5fab0ee8fa60be10e7

Common bermudagrass (Cynodon dactylon (L.) Pers.) belongs to the subfamily Chloridoideae of the Poaceae family, one of the most important plant families ecologically and economically. This grass has a long connection with human culture but its systematics is relatively understudied. In this study, we sequenced and investigated the chloroplast genome of common bermudagrass, which is 134,297 bp in length with two single copy regions (LSC: 79,732 bp; SSC: 12,521 bp) and a pair of inverted repeat (IR) regions (21,022 bp). The annotation contains a total of 128 predicted genes, including 82 protein-coding, 38 tRNA, and 8 rRNA genes. Additionally, our in silico analyses identified 10 sets of repeats longer than 20 bp and predicted the presence of 36 RNA editing sites. Overall, the chloroplast genome of common bermudagrass resembles those from other Poaceae lineages. Compared to most angiosperms, the accD gene and the introns of both clpP and rpoC1 genes are missing. Additionally, the ycf1, ycf2, ycf15, and ycf68 genes are pseudogenized and two genome rearrangements exist. Our phylogenetic analysis based on 47 chloroplast protein-coding genes supported the placement of common bermudagrass within Chloridoideae. Our phylogenetic character mapping based on the parsimony principle further indicated that the loss of the accD gene and clpP introns, the pseudogenization of four ycf genes, and the two rearrangements occurred only once after the most recent common ancestor of the Poaceae diverged from other monocots, which could explain the unusual long branch leading to the Poaceae when phylogeny is inferred based on chloroplast sequences.

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<![CDATA[Comparative chloroplast genomes of eleven Schima (Theaceae) species: Insights into DNA barcoding and phylogeny]]> https://www.researchpad.co/article/5989db5cab0ee8fa60be02ec

Schima is an ecologically and economically important woody genus in tea family (Theaceae). Unresolved species delimitations and phylogenetic relationships within Schima limit our understanding of the genus and hinder utilization of the genus for economic purposes. In the present study, we conducted comparative analysis among the complete chloroplast (cp) genomes of 11 Schima species. Our results indicate that Schima cp genomes possess a typical quadripartite structure, with conserved genomic structure and gene order. The size of the Schima cp genome is about 157 kilo base pairs (kb). They consistently encode 114 unique genes, including 80 protein-coding genes, 30 tRNAs, and 4 rRNAs, with 17 duplicated in the inverted repeat (IR). These cp genomes are highly conserved and do not show obvious expansion or contraction of the IR region. The percent variability of the 68 coding and 93 noncoding (>150 bp) fragments is consistently less than 3%. The seven most widely touted DNA barcode regions as well as one promising barcode candidate showed low sequence divergence. Eight mutational hotspots were identified from the 11 cp genomes. These hotspots may potentially be useful as specific DNA barcodes for species identification of Schima. The 58 cpSSR loci reported here are complementary to the microsatellite markers identified from the nuclear genome, and will be leveraged for further population-level studies. Phylogenetic relationships among the 11 Schima species were resolved with strong support based on the cp genome data set, which corresponds well with the species distribution pattern. The data presented here will serve as a foundation to facilitate species identification, DNA barcoding and phylogenetic reconstructions for future exploration of Schima.

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