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Auto Tag: diploid genome assembly

April 21, 2020  |  

Finding Nemo’s Genes: A chromosome-scale reference assembly of the genome of the orange clownfish Amphiprion percula.

The iconic orange clownfish, Amphiprion percula, is a model organism for studying the ecology and evolution of reef fishes, including patterns of population connectivity, sex change, social organization, habitat selection and adaptation to climate change. Notably, the orange clownfish is the only reef fish for which a complete larval dispersal kernel has been established and was the first fish species for which it was demonstrated that antipredator responses of reef fishes could be impaired by ocean acidification. Despite its importance, molecular resources for this species remain scarce and until now it lacked a reference genome assembly. Here, we present a de novo chromosome-scale assembly of the genome of the orange clownfish Amphiprion percula. We utilized single-molecule real-time sequencing technology from Pacific Biosciences to produce an initial polished assembly comprised of 1,414 contigs, with a contig N50 length of 1.86 Mb. Using Hi-C-based chromatin contact maps, 98% of the genome assembly were placed into 24 chromosomes, resulting in a final assembly of 908.8 Mb in length with contig and scaffold N50s of 3.12 and 38.4 Mb, respectively. This makes it one of the most contiguous and complete fish genome assemblies currently available. The genome was annotated with 26,597 protein-coding genes and contains 96% of the core set of conserved actinopterygian orthologs. The availability of this reference genome assembly as a community resource will further strengthen the role of the orange clownfish as a model species for research on the ecology and evolution of reef fishes. © 2018 The Authors. Molecular Ecology Resources Published by John Wiley & Sons Ltd.

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April 21, 2020  |  

Genome sequence of Jatropha curcas L., a non-edible biodiesel plant, provides a resource to improve seed-related traits.

Jatropha curcas (physic nut), a non-edible oilseed crop, represents one of the most promising alternative energy sources due to its high seed oil content, rapid growth and adaptability to various environments. We report ~339 Mbp draft whole genome sequence of J. curcas var. Chai Nat using both the PacBio and Illumina sequencing platforms. We identified and categorized differentially expressed genes related to biosynthesis of lipid and toxic compound among four stages of seed development. Triacylglycerol (TAG), the major component of seed storage oil, is mainly synthesized by phospholipid:diacylglycerol acyltransferase in Jatropha, and continuous high expression of homologs of oleosin over seed development contributes to accumulation of high level of oil in kernels by preventing the breakdown of TAG. A physical cluster of genes for diterpenoid biosynthetic enzymes, including casbene synthases highly responsible for a toxic compound, phorbol ester, in seed cake, was syntenically highly conserved between Jatropha and castor bean. Transcriptomic analysis of female and male flowers revealed the up-regulation of a dozen family of TFs in female flower. Additionally, we constructed a robust species tree enabling estimation of divergence times among nine Jatropha species and five commercial crops in Malpighiales order. Our results will help researchers and breeders increase energy efficiency of this important oil seed crop by improving yield and oil content, and eliminating toxic compound in seed cake for animal feed. © 2018 The Authors. Plant Biotechnology Journal published by Society for Experimental Biology and The Association of Applied Biologists and John Wiley & Sons Ltd.

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April 21, 2020  |  

The red bayberry genome and genetic basis of sex determination.

Morella rubra, red bayberry, is an economically important fruit tree in south China. Here, we assembled the first high-quality genome for both a female and a male individual of red bayberry. The genome size was 313-Mb, and 90% sequences were assembled into eight pseudo chromosome molecules, with 32 493 predicted genes. By whole-genome comparison between the female and male and association analysis with sequences of bulked and individual DNA samples from female and male, a 59-Kb region determining female was identified and located on distal end of pseudochromosome 8, which contains abundant transposable element and seven putative genes, four of them are related to sex floral development. This 59-Kb female-specific region was likely to be derived from duplication and rearrangement of paralogous genes and retained non-recombinant in the female-specific region. Sex-specific molecular markers developed from candidate genes co-segregated with sex in a genetically diverse female and male germplasm. We propose sex determination follow the ZW model of female heterogamety. The genome sequence of red bayberry provides a valuable resource for plant sex chromosome evolution and also provides important insights for molecular biology, genetics and modern breeding in Myricaceae family. © 2018 The Authors. Plant Biotechnology Journal published by Society for Experimental Biology and The Association of Applied Biologists and John Wiley & Sons Ltd.

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April 21, 2020  |  

The CF Canada-Sick Kids Program in individual CF therapy: A resource for the advancement of personalized medicine in CF.

Therapies targeting certain CFTR mutants have been approved, yet variations in clinical response highlight the need for in-vitro and genetic tools that predict patient-specific clinical outcomes. Toward this goal, the CF Canada-Sick Kids Program in Individual CF Therapy (CFIT) is generating a “first of its kind”, comprehensive resource containing patient-specific cell cultures and data from 100 CF individuals that will enable modeling of therapeutic responses.The CFIT program is generating: 1) nasal cells from drug naïve patients suitable for culture and the study of drug responses in vitro, 2) matched gene expression data obtained by sequencing the RNA from the primary nasal tissue, 3) whole genome sequencing of blood derived DNA from each of the 100 participants, 4) induced pluripotent stem cells (iPSCs) generated from each participant’s blood sample, 5) CRISPR-edited isogenic control iPSC lines and 6) prospective clinical data from patients treated with CF modulators.To date, we have recruited 57 of 100 individuals to CFIT, most of whom are homozygous for F508del (to assess in-vitro: in-vivo correlations with respect to ORKAMBI response) or heterozygous for F508del and a minimal function mutation. In addition, several donors are homozygous for rare nonsense and missense mutations. Nasal epithelial cell cultures and matched iPSC lines are available for many of these donors.This accessible resource will enable development of tools that predict individual outcomes to current and emerging modulators targeting F508del-CFTR and facilitate therapy discovery for rare CF causing mutations.Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.

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April 21, 2020  |  

A prophage and two ICESa2603-family integrative and conjugative elements (ICEs) carrying optrA in Streptococcus suis.

To investigate the presence and transfer of the oxazolidinone/phenicol resistance gene optrA and identify the genetic elements involved in the horizontal transfer of the optrA gene in Streptococcus suis.A total of 237 S. suis isolates were screened for the presence of the optrA gene by PCR. Whole-genome DNA of three optrA-positive strains was completely sequenced using the Illumina MiSeq and Pacbio RSII platforms. MICs were determined by broth microdilution. Transferability of the optrA gene in S. suis was investigated by conjugation. The presence of circular intermediates was examined by inverse PCR.The optrA gene was present in 11.8% (28/237) of the S. suis strains. In three strains, the optrA gene was flanked by two copies of IS1216 elements in the same orientation, located either on a prophage or on ICESa2603-family integrative and conjugative elements (ICEs), including one tandem ICE. In one isolate, the optrA-carrying ICE transferred with a frequency of 2.1?×?10-8. After the transfer, the transconjugant displayed elevated MICs of the respective antimicrobial agents. Inverse PCRs revealed that circular intermediates of different sizes were formed in the three optrA-carrying strains, containing one copy of the IS1216E element and the optrA gene alone or in combination with other resistance genes.A prophage and two ICESa2603-family ICEs (including one tandem ICE) associated with the optrA gene were identified in S. suis. The association of the optrA gene with the IS1216E elements and its location on either a prophage or ICEs will aid its horizontal transfer. © The Author(s) 2019. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For permissions, please email: journals.permissions@oup.com.

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April 21, 2020  |  

Multiple modes of convergent adaptation in the spread of glyphosate-resistant Amaranthus tuberculatus.

The selection pressure exerted by herbicides has led to the repeated evolution of herbicide resistance in weeds. The evolution of herbicide resistance on contemporary timescales in turn provides an outstanding opportunity to investigate key questions about the genetics of adaptation, in particular the relative importance of adaptation from new mutations, standing genetic variation, or geographic spread of adaptive alleles through gene flow. Glyphosate-resistant Amaranthus tuberculatus poses one of the most significant threats to crop yields in the Midwestern United States, with both agricultural populations and herbicide resistance only recently emerging in Canada. To understand the evolutionary mechanisms driving the spread of resistance, we sequenced and assembled the A. tuberculatus genome and investigated the origins and population genomics of 163 resequenced glyphosate-resistant and susceptible individuals from Canada and the United States. In Canada, we discovered multiple modes of convergent evolution: in one locality, resistance appears to have evolved through introductions of preadapted US genotypes, while in another, there is evidence for the independent evolution of resistance on genomic backgrounds that are historically nonagricultural. Moreover, resistance on these local, nonagricultural backgrounds appears to have occurred predominantly through the partial sweep of a single haplotype. In contrast, resistant haplotypes arising from the Midwestern United States show multiple amplification haplotypes segregating both between and within populations. Therefore, while the remarkable species-wide diversity of A. tuberculatus has facilitated geographic parallel adaptation of glyphosate resistance, more recently established agricultural populations are limited to adaptation in a more mutation-limited framework.Copyright © 2019 the Author(s). Published by PNAS.

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April 21, 2020  |  

A physical and genetic map of Cannabis sativa identifies extensive rearrangements at the THC/CBD acid synthase loci.

Cannabis sativa is widely cultivated for medicinal, food, industrial, and recreational use, but much remains unknown regarding its genetics, including the molecular determinants of cannabinoid content. Here, we describe a combined physical and genetic map derived from a cross between the drug-type strain Purple Kush and the hemp variety “Finola.” The map reveals that cannabinoid biosynthesis genes are generally unlinked but that aromatic prenyltransferase (AP), which produces the substrate for THCA and CBDA synthases (THCAS and CBDAS), is tightly linked to a known marker for total cannabinoid content. We further identify the gene encoding CBCA synthase (CBCAS) and characterize its catalytic activity, providing insight into how cannabinoid diversity arises in cannabis. THCAS and CBDAS (which determine the drug vs. hemp chemotype) are contained within large (>250 kb) retrotransposon-rich regions that are highly nonhomologous between drug- and hemp-type alleles and are furthermore embedded within ~40 Mb of minimally recombining repetitive DNA. The chromosome structures are similar to those in grains such as wheat, with recombination focused in gene-rich, repeat-depleted regions near chromosome ends. The physical and genetic map should facilitate further dissection of genetic and molecular mechanisms in this commercially and medically important plant. © 2019 Laverty et al.; Published by Cold Spring Harbor Laboratory Press.

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April 21, 2020  |  

Construction of full-length Japanese reference panel of class I HLA genes with single-molecule, real-time sequencing.

Human leukocyte antigen (HLA) is a gene complex known for its exceptional diversity across populations, importance in organ and blood stem cell transplantation, and associations of specific alleles with various diseases. We constructed a Japanese reference panel of class I HLA genes (ToMMo HLA panel), comprising a distinct set of HLA-A, HLA-B, HLA-C, and HLA-H alleles, by single-molecule, real-time (SMRT) sequencing of 208 individuals included in the 1070 whole-genome Japanese reference panel (1KJPN). For high-quality allele reconstruction, we developed a novel pipeline, Primer-Separation Assembly and Refinement Pipeline (PSARP), in which the SMRT sequencing and additional short-read data were used. The panel consisted of 139 alleles, which were all extended from known IPD-IMGT/HLA sequences, contained 40 with novel variants, and captured more than 96.5% of allelic diversity in 1KJPN. These newly available sequences would be important resources for research and clinical applications including high-resolution HLA typing, genetic association studies, and analyzes of cis-regulatory elements.

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April 21, 2020  |  

Diploid Genome Assembly of the Wine Grape Carménère.

In this genome report, we describe the sequencing and annotation of the genome of the wine grape Carménère (clone 02, VCR-702). Long considered extinct, this old French wine grape variety is now cultivated mostly in Chile where it was imported in the 1850s just before the European phylloxera epidemic. Genomic DNA was sequenced using Single Molecule Real Time technology and assembled with FALCON-Unzip, a diploid-aware assembly pipeline. To optimize the contiguity and completeness of the assembly, we tested about a thousand combinations of assembly parameters, sequencing coverage, error correction and repeat masking methods. The final scaffolds provide a complete and phased representation of the diploid genome of this wine grape. Comparison of the two haplotypes revealed numerous heterozygous variants, including loss-of-function ones, some of which in genes associated with polyphenol biosynthesis. Comparisons with other publicly available grape genomes and transcriptomes showed the impact of structural variation on gene content differences between Carménère and other wine grape cultivars. Among the putative cultivar-specific genes, we identified genes potentially involved in aroma production and stress responses. The genome assembly of Carménère expands the representation of the genomic variability in grapes and will enable studies that aim to understand its distinctive organoleptic and agronomical features and assess its still elusive extant genetic variability. A genome browser for Carménère, its annotation, and an associated blast tool are available at http://cantulab.github.io/data.Copyright © 2019 Minio et al.

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April 21, 2020  |  

Accurate circular consensus long-read sequencing improves variant detection and assembly of a human genome.

The DNA sequencing technologies in use today produce either highly accurate short reads or less-accurate long reads. We report the optimization of circular consensus sequencing (CCS) to improve the accuracy of single-molecule real-time (SMRT) sequencing (PacBio) and generate highly accurate (99.8%) long high-fidelity (HiFi) reads with an average length of 13.5?kilobases (kb). We applied our approach to sequence the well-characterized human HG002/NA24385 genome and obtained precision and recall rates of at least 99.91% for single-nucleotide variants (SNVs), 95.98% for insertions and deletions <50 bp (indels) and 95.99% for structural variants. Our CCS method matches or exceeds the ability of short-read sequencing to detect small variants and structural variants. We estimate that 2,434 discordances are correctable mistakes in the 'genome in a bottle' (GIAB) benchmark set. Nearly all (99.64%) variants can be phased into haplotypes, further improving variant detection. De novo genome assembly using CCS reads alone produced a contiguous and accurate genome with a contig N50 of >15?megabases (Mb) and concordance of 99.997%, substantially outperforming assembly with less-accurate long reads.

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April 21, 2020  |  

Metagenomic assembly through the lens of validation: recent advances in assessing and improving the quality of genomes assembled from metagenomes.

Metagenomic samples are snapshots of complex ecosystems at work. They comprise hundreds of known and unknown species, contain multiple strain variants and vary greatly within and across environments. Many microbes found in microbial communities are not easily grown in culture making their DNA sequence our only clue into their evolutionary history and biological function. Metagenomic assembly is a computational process aimed at reconstructing genes and genomes from metagenomic mixtures. Current methods have made significant strides in reconstructing DNA segments comprising operons, tandem gene arrays and syntenic blocks. Shorter, higher-throughput sequencing technologies have become the de facto standard in the field. Sequencers are now able to generate billions of short reads in only a few days. Multiple metagenomic assembly strategies, pipelines and assemblers have appeared in recent years. Owing to the inherent complexity of metagenome assembly, regardless of the assembly algorithm and sequencing method, metagenome assemblies contain errors. Recent developments in assembly validation tools have played a pivotal role in improving metagenomics assemblers. Here, we survey recent progress in the field of metagenomic assembly, provide an overview of key approaches for genomic and metagenomic assembly validation and demonstrate the insights that can be derived from assemblies through the use of assembly validation strategies. We also discuss the potential for impact of long-read technologies in metagenomics. We conclude with a discussion of future challenges and opportunities in the field of metagenomic assembly and validation. © The Author 2017. Published by Oxford University Press.

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April 21, 2020  |  

Genome assembly of a tropical maize inbred line provides insights into structural variation and crop improvement.

Maize is one of the most important crops globally, and it shows remarkable genetic diversity. Knowledge of this diversity could help in crop improvement; however, gold-standard genomes have been elucidated only for modern temperate varieties. Here, we present a high-quality reference genome (contig N50 of 15.78?megabases) of the maize small-kernel inbred line, which is derived from a tropical landrace. Using haplotype maps derived from B73, Mo17 and SK, we identified 80,614 polymorphic structural variants across 521 diverse lines. Approximately 22% of these variants could not be detected by traditional single-nucleotide-polymorphism-based approaches, and some of them could affect gene expression and trait performance. To illustrate the utility of the diverse SK line, we used it to perform map-based cloning of a major effect quantitative trait locus controlling kernel weight-a key trait selected during maize improvement. The underlying candidate gene ZmBARELY ANY MERISTEM1d provides a target for increasing crop yields.

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April 21, 2020  |  

Chromosome-level genome assembly of Triplophysa tibetana, a fish adapted to the harsh high-altitude environment of the Tibetan Plateau.

Triplophysa is an endemic fish genus of the Tibetan Plateau in China. Triplophysa tibetana, which lives at a recorded altitude of ~4,000 m and plays an important role in the highland aquatic ecosystem, serves as an excellent model for investigating high-altitude environmental adaptation. However, evolutionary and conservation studies of T. tibetana have been limited by scarce genomic resources for the genus Triplophysa. In the present study, we applied PacBio sequencing and the Hi-C technique to assemble the T. tibetana genome. A 652-Mb genome with 1,325 contigs with an N50 length of 3.1 Mb was obtained. The 1,137 contigs were further assembled into 25 chromosomes, representing 98.7% and 80.47% of all contigs at the base and sequence number level, respectively. Approximately 260 Mb of sequence, accounting for ~39.8% of the genome, was identified as repetitive elements. DNA transposons (16.3%), long interspersed nuclear elements (12.4%) and long terminal repeats (11.0%) were the most repetitive types. In total, 24,372 protein-coding genes were predicted in the genome, and ~95% of the genes were functionally annotated via a search in public databases. Using whole genome sequence information, we found that T. tibetana diverged from its common ancestor with Danio rerio ~121.4 million years ago. The high-quality genome assembled in this work not only provides a valuable genomic resource for future population and conservation studies of T. tibetana, but it also lays a solid foundation for further investigation into the mechanisms of environmental adaptation of endemic fishes in the Tibetan Plateau. © 2019 John Wiley & Sons Ltd.

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April 21, 2020  |  

Recompleting the Caenorhabditis elegans genome.

Caenorhabditis elegans was the first multicellular eukaryotic genome sequenced to apparent completion. Although this assembly employed a standard C. elegans strain (N2), it used sequence data from several laboratories, with DNA propagated in bacteria and yeast. Thus, the N2 assembly has many differences from any C. elegans available today. To provide a more accurate C. elegans genome, we performed long-read assembly of VC2010, a modern strain derived from N2. Our VC2010 assembly has 99.98% identity to N2 but with an additional 1.8 Mb including tandem repeat expansions and genome duplications. For 116 structural discrepancies between N2 and VC2010, 97 structures matching VC2010 (84%) were also found in two outgroup strains, implying deficiencies in N2. Over 98% of N2 genes encoded unchanged products in VC2010; moreover, we predicted =53 new genes in VC2010. The recompleted genome of C. elegans should be a valuable resource for genetics, genomics, and systems biology. © 2019 Yoshimura et al.; Published by Cold Spring Harbor Laboratory Press.

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April 21, 2020  |  

The complete genome sequence of the denitrifying bacterium Marinobacter sp. Arc7-DN-1 isolated from Arctic Ocean sediment

The general features and genome characteristics of the denitrifying bacterium Marinobacter sp. Arc7-DN-1, isolated from Arctic Ocean sediment, are described. Marinobacter sp. Arc7-DN-1 uses NO3- or NH4+ as the sole nitrogen source to grow at low temperatures. The strain can grow at a wide range of temperatures (0–30?°C) and NaCl concentration (15–90‰). The genome has one circular chromosome of 4,300,456?bp (57.64?mol%?G?+?C content), consisting of 4012 coding genes, including 50 tRNAs and three rRNA operons as 16S-23S-5S rRNA. On the basis of the KEGG analysis, strain Arc7-DN-1 encodes 43 proteins related to nitrogen metabolism, including a complete denitrifying pathway and an assimilatory nitrate reduction pathway.

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