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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.


April 21, 2020

Draft Genome of Burkholderia cenocepacia TAtl-371, a Strain from the Burkholderia cepacia Complex Retains Antagonism in Different Carbon and Nitrogen Sources.

Burkholderia cenocepacia TAtl-371 was isolated from the rhizosphere of a tomato plant growing in Atlatlahucan, Morelos, Mexico. This strain exhibited a broad antimicrobial spectrum against bacteria, yeast, and fungi. Here, we report and describe the improved, high-quality permanent draft genome of B. cenocepacia TAtl-371, which was sequenced using a combination of PacBio RS and PacBio RS II sequencing methods. The 7,496,106 bp genome of the TAtl-371 strain is arranged in three scaffolds, contains 6722 protein-coding genes, and 99 RNA only-encoding genes. Genome analysis revealed genes related to biosynthesis of antimicrobials such as non-ribosomal peptides, siderophores, chitinases, and bacteriocins. Moreover, analysis of bacterial growth on different carbon and nitrogen sources shows that the strain retains its antimicrobial ability.


April 21, 2020

An open resource for accurately benchmarking small variant and reference calls.

Benchmark small variant calls are required for developing, optimizing and assessing the performance of sequencing and bioinformatics methods. Here, as part of the Genome in a Bottle (GIAB) Consortium, we apply a reproducible, cloud-based pipeline to integrate multiple short- and linked-read sequencing datasets and provide benchmark calls for human genomes. We generate benchmark calls for one previously analyzed GIAB sample, as well as six genomes from the Personal Genome Project. These new genomes have broad, open consent, making this a ‘first of its kind’ resource that is available to the community for multiple downstream applications. We produce 17% more benchmark single nucleotide variations, 176% more indels and 12% larger benchmark regions than previously published GIAB benchmarks. We demonstrate that this benchmark reliably identifies errors in existing callsets and highlight challenges in interpreting performance metrics when using benchmarks that are not perfect or comprehensive. Finally, we identify strengths and weaknesses of callsets by stratifying performance according to variant type and genome context.


April 21, 2020

The Isolation and Characterization of Kronos, a Novel Caulobacter Rhizosphere Phage that is Similar to Lambdoid Phages.

Despite their ubiquity, relatively few bacteriophages have been characterized. Here, we set out to explore Caulobacter bacteriophages (caulophages) in the rhizosphere and characterized Kronos, the first caulophage isolated from the rhizosphere. Kronos is a member of the Siphoviridae family since it has a long flexible tail. In addition, an analysis of the Kronos genome indicated that many of the predicted proteins were distantly related to those of bacteriophages in the lambdoid family. Consistent with this observation, we were able to demonstrate the presence of cos sites that are similar to those found at the ends of lambdoid phage genomes. Moreover, Kronos displayed a relatively rare head and tail morphology compared to other caulophages but was similar to that of the lambdoid phages. Taken together, these data indicate that Kronos is distantly related to lambdoid phages and may represent a new Siphoviridae genus.


April 21, 2020

Mitochondrial genome characterization of Melipona bicolor: Insights from the control region and gene expression data.

The stingless bee Melipona bicolor is the only bee in which true polygyny occurs. Its mitochondrial genome was first sequenced in 2008, but it was incomplete and no information about its transcription was known. We combined short and long reads of M. bicolor DNA with RNASeq data to obtain insights about mitochondrial evolution and gene expression in bees. The complete genome has 15,001?bp, including a control region of 255?bp that contains all conserved structures described in honeybees with the highest AT content reported so far for bees (98.1%), displaying a compact but functional region. Gene expression control is similar to other insects however unusual patterns of expression may suggest the existence of different isoforms for the mitochondrially encoded 12S rRNA. Results reveal unique and shared features of the mitochondrial genome in terms of sequence evolution and gene expression making M. bicolor an interesting model to study mitochondrial genomic evolution. Copyright © 2019 Elsevier B.V. All rights reserved.


April 21, 2020

Genomic sequence and copy number evolution during hybrid crop development in sunflowers.

Hybrid crops, an important part of modern agriculture, rely on the development of male and female heterotic gene pools. In sunflowers, heterotic gene pools were developed through the use of crop-wild relatives to produce cytoplasmic male sterile female and branching, fertility restoring male lines. Here, we use genomic data from a diversity panel of male, female, and open-pollinated lines to explore the genetic changes brought during modern improvement. We find the male lines have diverged most from their open-pollinated progenitors and that genetic differentiation is concentrated in chromosomes, 8, 10 and 13, due to introgressions from wild relatives. Ancestral variation from open-pollinated varieties almost universally evolved in parallel for both male and female lines suggesting little or no selection for heterotic overdominance. Furthermore, we show that gene content differs between the male and female lines and that differentiation in gene content is concentrated in high FST regions. This means that the introgressions that brought branching and fertility restoration to the male lines, brought with them different gene content from the ancestral haplotypes, including the removal of some genes. Although we find no evidence that gene complementation genomewide is responsible for heterosis between male and female lines, several of the genes that are largely absent in either the male or female lines are associated with pathogen defense, suggesting complementation may be functionally relevant for crop breeders.


April 21, 2020

Genomic analysis provides insights into the transmission and pathogenicity of Talaromyces marneffei.

Talaromyces marneffei (T. marneffei) is a medically important opportunistic dimorphic fungus that infects both humans and bamboo rats. However, the mechanisms of transmission and pathogenicity of T. marneffei are poorly understood. In our study, we combined Illumina and PacBio sequencing technologies to sequence and assemble a complete genome of T. marneffei. To elucidate the transmission route and source, we sequenced three additional T. marneffei isolates using Illumina sequencing technology. Variations among isolates were used to develop a multilocus sequence typing (MLST) system comprising five housekeeping genes that can be used to discriminate between isolates derived from different sources. Our analysis revealed that human and bamboo rat share identical genotypes in these five loci. Thus, we hypothesized that T. marneffei is transmitted to humans through inhalation of spores in the surrounding environment into the lungs and that the bamboo rat can serve as an important natural reservoir for pathogens. Furthermore, we also identified temperature-dependent polyketide synthases, non-ribosomal peptide synthetases and secreted proteins as putative pathogenicity-related factors. In addition, we identified antifungal drug targets that can be investigated in future studies to elucidate the mechanisms underlying drug resistance. In summary, our study presents the basic features of the T. marneffei genome and provides insights into the transmission and pathogenicity of T. marneffei, which warrant fundamental experimental research.Copyright © 2019 Elsevier Inc. All rights reserved.


April 21, 2020

Complete genome of Pseudoalteromonas atlantica ECSMB14104, a Gammaproteobacterium inducing mussel settlement

Pseudoalteromonas is widely distributed in the marine environments and the biofilms formed by Pseudoalteromonas promote settlement of many species of invertebrates. Here, we show the complete genome of Pseudoalteromonas atlantica ECSMB14104, which was isolated from biofilms formed in the East China Sea and exhibited inducing activity on the Mytilus coruscus settlement. Complete genome of this strain containsa total of 3325 genes and the GC content of 41.02%. This genomic information is contributed to molecular mechanism of P. atlantica ECSMB14104 regulating mussel settlement.


April 21, 2020

A full-length transcriptome of Sepia esculenta using a combination of single-molecule long-read (SMRT) and Illumina sequencing

As an economically important cephalopods species, wild-caught Sepia esculenta fishery has suffered a server decline due to over-fishing and ocean environmental damage. To restore this seriously declining fishery resource, we should understand the genetic foundation and molecular mechanism of spawning, reproduction and mortal of golden cuttlefish. In this study, we generated the full-length transcriptome of S. esculenta based on the total RNA of tissue samples (brain, optic gland, nidamental gland, ovary and muscle at different developmental stages) using a combination of single-molecule real-time (SMRT) and Illumina RNA-seq technology. A total of 14.16 Gb SMRT sequencing data were assembled into 94,635 transcripts. Meanwhile, 35.15 Gb Illumina HiSeq data were assembled into 177,226 non-redundant transcripts. Then, we merged SMRT and Illumina assembled data to generate a more complete/full-length S. esculenta transcriptome with 177,951 high-quality transcripts. Based on the obtained transcriptome data, total 81,459 transcripts were annotated in at least one of seven functional databases and 49,189 nucleotide sequences of coding regions were identified. Additionally, 161,327 SSRs distributed in 64,933 transcripts were identified based on SSR analysis. This full-length and high-quality transcriptome of S. esculenta can provide an important foundation for future genomic research on growth and development, reproduction and mortal of cephalopod and further recovery of this recessionary fisheries resources.


April 21, 2020

Transmission of ESBL-producing Escherichia coli between broilers and humans on broiler farms.

ESBL and AmpC ß-lactamases are an increasing concern for public health. Studies suggest that ESBL/pAmpC-producing Escherichia coli and their plasmids carrying antibiotic resistance genes can spread from broilers to humans working or living on broiler farms. These studies used traditional typing methods, which may not have provided sufficient resolution to reliably assess the relatedness of these isolates.Eleven suspected transmission events among broilers and humans living/working on eight broiler farms were investigated using whole-genome short-read (Illumina) and long-read sequencing (PacBio). Core genome MLST (cgMLST) was performed to investigate the occurrence of strain transmission. Horizontal plasmid and gene transfer were analysed using BLAST.Of eight suspected strain transmission events, six were confirmed. The isolate pairs had identical ESBL/AmpC genes and fewer than eight allelic differences according to the cgMLST, and five had an almost identical plasmid composition. On one of the farms, cgMLST revealed that the isolate pairs belonging to ST10 from a broiler and a household member of the farmer had 475 different alleles, but that the plasmids were identical, indicating horizontal transfer of mobile elements rather than strain transfer. Of three suspected horizontal plasmid transmission events, one was confirmed. In addition, gene transfer between plasmids was found.The present study confirms transmission of strains as well as horizontal plasmid and gene transfer between broilers and farmers and household members on the same farm. WGS is an important tool to confirm suspected zoonotic strain and resistance gene transmission. © 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.


April 21, 2020

Origin and evolution of the octoploid strawberry genome.

Cultivated strawberry emerged from the hybridization of two wild octoploid species, both descendants from the merger of four diploid progenitor species into a single nucleus more than 1 million years ago. Here we report a near-complete chromosome-scale assembly for cultivated octoploid strawberry (Fragaria?×?ananassa) and uncovered the origin and evolutionary processes that shaped this complex allopolyploid. We identified the extant relatives of each diploid progenitor species and provide support for the North American origin of octoploid strawberry. We examined the dynamics among the four subgenomes in octoploid strawberry and uncovered the presence of a single dominant subgenome with significantly greater gene content, gene expression abundance, and biased exchanges between homoeologous chromosomes, as compared with the other subgenomes. Pathway analysis showed that certain metabolomic and disease-resistance traits are largely controlled by the dominant subgenome. These findings and the reference genome should serve as a powerful platform for future evolutionary studies and enable molecular breeding in strawberry.


April 21, 2020

Immunogenetic factors driving formation of ultralong VH CDR3 in Bos taurus antibodies.

The antibody repertoire of Bos taurus is characterized by a subset of variable heavy (VH) chain regions with ultralong third complementarity determining regions (CDR3) which, compared to other species, can provide a potent response to challenging antigens like HIV env. These unusual CDR3 can range to over seventy highly diverse amino acids in length and form unique ß-ribbon ‘stalk’ and disulfide bonded ‘knob’ structures, far from the typical antigen binding site. The genetic components and processes for forming these unusual cattle antibody VH CDR3 are not well understood. Here we analyze sequences of Bos taurus antibody VH domains and find that the subset with ultralong CDR3 exclusively uses a single variable gene, IGHV1-7 (VHBUL) rearranged to the longest diversity gene, IGHD8-2. An eight nucleotide duplication at the 3′ end of IGHV1-7 encodes a longer V-region producing an extended F ß-strand that contributes to the stalk in a rearranged CDR3. A low amino acid variability was observed in CDR1 and CDR2, suggesting that antigen binding for this subset most likely only depends on the CDR3. Importantly a novel, potentially AID mediated, deletional diversification mechanism of the B. taurus VH ultralong CDR3 knob was discovered, in which interior codons of the IGHD8-2 region are removed while maintaining integral structural components of the knob and descending strand of the stalk in place. These deletions serve to further diversify cysteine positions, and thus disulfide bonded loops. Hence, both germline and somatic genetic factors and processes appear to be involved in diversification of this structurally unusual cattle VH ultralong CDR3 repertoire.


April 21, 2020

Complete genome sequence of an IMP-8, CTX-M-14, CTX-M-3 and QnrS1 co-producing Enterobacter asburiae isolate from a patient with wound infection.

The aim of this study was to investigate the characteristics and complete genome sequence of an IMP-8, CTX-M-14, CTX-M-3 and QnrS1 co-producing multidrug-resistant Enterobacter asburiae isolate (EN3600) from a patient with wound infection.Species identification was confirmed by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF/MS). Carbapenemase genes were identified by PCR and Sanger sequencing. The complete genome sequence of E. asburiae EN3600 was obtained using a PacBio RS II platform. Genome annotation was done by Rapid Annotation using Subsystem Technology (RAST) server. Acquired antimicrobial resistance genes (ARGs) and plasmid replicons were detected using ResFinder 2.1 and PlasmidFinder 1.3, respectively.The genome of E. asburiae EN3600 consists of a 4.8-Mbp chromosome and five plasmids. The annotated genome contains various ARGs conferring resistance to aminoglycosides, ß-lactams, fluoroquinolones, fosfomycin, macrolides, phenicols, rifampicin and sulfonamides. In addition, plasmids of incompatibility (Inc) groups IncHI2A, IncFIB(pECLA), IncFIB(pQil) and IncP1 were identified. The genes blaIMP-8, blaCTX-M-14 and blaCTX-M-3 were located on different plasmids. The blaIMP-8 gene was carried by an 86-kb IncFIB(pQil) plasmid. The blaCTX-M-3 and qnrS1 genes were co-harboured by an IncP1 plasmid. In addition, blaCTX-M-14 was associated with blaTEM-1B, blaOXA-1, catB3 and sul1 genes in a 116-kb non-typeable plasmid.To our knowledge, this is the first complete genome sequence of an E. asburiae isolate co-producing IMP-8, CTX-M-14, CTX-M-3 and QnrS1. This genome may facilitate the understanding of the resistome, pathogenesis and genomic features of Enterobacter cloacae complex (ECC) and will provide valuable information for accurate identification of ECC.Copyright © 2019 International Society for Antimicrobial Chemotherapy. Published by Elsevier Ltd. All rights reserved.


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.


April 21, 2020

Analysis of Chromosomal Numbers, Mitochondrial Genome, and Full-Length Transcriptome of Onychostoma brevibarba.

Onychostoma brevibarba is a new discovered species which is distributed in Xiang Jiang River of the middle Chang Jiang basin in Hunan Province, South China. In this study, the ploidy levels of O. brevibarba were confirmed by counting chromosomal numbers and analyzing karyotype. The complete mitochondrial genome of O. brevibarba was determined and analyzed. Besides, we firstly performed the full-length transcriptome of O. brevibarba derived from 5 different tissues using the PacBio SMRT sequencing. The result shows that O. brevibarba was a diploid with 48 chromosomes. The complete mitogenome of O. brevibarba was 16,602 bp in size and very similar (89.1-91.3%) to that of other Onychostoma species but was distinct from all congeners. The full-length transcriptome dataset of O. brevibarba comprised 120,239 unigenes. Among the unigenes, 91,542 were functionally annotated, whereas 26,794 were found to have two or more isoforms. This study could provide many new insights into cytology and molecular characteristics of O. brevibarba; it laid the foundation for further exploration of the genomic signatures of species of Onychostoma.


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