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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

Assembly of long, error-prone reads using repeat graphs.

Accurate genome assembly is hampered by repetitive regions. Although long single molecule sequencing reads are better able to resolve genomic repeats than short-read data, most long-read assembly algorithms do not provide the repeat characterization necessary for producing optimal assemblies. Here, we present Flye, a long-read assembly algorithm that generates arbitrary paths in an unknown repeat graph, called disjointigs, and constructs an accurate repeat graph from these error-riddled disjointigs. We benchmark Flye against five state-of-the-art assemblers and show that it generates better or comparable assemblies, while being an order of magnitude faster. Flye nearly doubled the contiguity of the human genome assembly (as measured by the NGA50 assembly quality metric) compared with existing assemblers.


April 21, 2020

The Genome of Cucurbita argyrosperma (Silver-Seed Gourd) Reveals Faster Rates of Protein-Coding Gene and Long Noncoding RNA Turnover and Neofunctionalization within Cucurbita.

Whole-genome duplications are an important source of evolutionary novelties that change the mode and tempo at which genetic elements evolve within a genome. The Cucurbita genus experienced a whole-genome duplication around 30 million years ago, although the evolutionary dynamics of the coding and noncoding genes in this genus have not yet been scrutinized. Here, we analyzed the genomes of four Cucurbita species, including a newly assembled genome of Cucurbita argyrosperma, and compared the gene contents of these species with those of five other members of the Cucurbitaceae family to assess the evolutionary dynamics of protein-coding and long intergenic noncoding RNA (lincRNA) genes after the genome duplication. We report that Cucurbita genomes have a higher protein-coding gene birth-death rate compared with the genomes of the other members of the Cucurbitaceae family. C. argyrosperma gene families associated with pollination and transmembrane transport had significantly faster evolutionary rates. lincRNA families showed high levels of gene turnover throughout the phylogeny, and 67.7% of the lincRNA families in Cucurbita showed evidence of birth from the neofunctionalization of previously existing protein-coding genes. Collectively, our results suggest that the whole-genome duplication in Cucurbita resulted in faster rates of gene family evolution through the neofunctionalization of duplicated genes. Copyright © 2019 The Author. Published by Elsevier Inc. All rights reserved.


April 21, 2020

Endogenous pararetrovirus sequences are widely present in Citrinae genomes.

Endogenous pararetroviruses (EPRVs) are characterized in several plant genomes and their biological effects have been reported. In this study, hundreds of EPRV segments were identified in six Citrinae genomes. A total of 1034 EPRV segments were identified in the genomes of sweet orange, 2036 in pummelo, 598 in clementine mandarin, 752 in Ichang papeda, 2060 in citron and 245 in atalantia. Genomic analysis indicated that EPRV segments tend to cluster as hot spots in the genomes, particularly on chromosome 2 and 5. Large numbers of simple repeats and transposable elements were identified in the 2-kb flanking regions of the EPRV segments. Comparative genomic analysis and PCR experiments showed that there are highly conserved EPRV segments and species-specific EPRV segments between the Citrinae genomes. Phylogenetic analysis suggested that the integration events of EPRVs could initiate in a common progenitor of Citrinae species and repeatedly occur during the Citrinae divergence.Copyright © 2018 Elsevier B.V. All rights reserved.


April 21, 2020

Potential of TLR-gene diversity in Czech indigenous cattle for resistance breeding as revealed by hybrid sequencing

A production herd of Czech Simmental cattle (Czech Red Pied, CRP), the conserved subpopulation of this breed, and the ancient local breed Czech Red cattle (CR) were screened for diversity in the antibacterial toll-like receptors (TLRs), which are members of the innate immune system. Polymerase chain reaction (PCR) amplicons of TLR1, TLR2, TLR4, TLR5, and TLR6 from pooled DNA samples were sequenced with PacBio technology, with 3–5×?coverage per gene per animal. To increase the reliability of variant detection, the gDNA pools were sequenced in parallel with the Illumina X-ten platform at low coverage (60× per gene). The diversity in conserved CRP and CR was similar to the diversity in conserved and modern CRP, representing 76.4?% and 70.9?% of its variants, respectively. Sixty-eight (54.4?%) polymorphisms in the five TLR genes were shared by the two breeds, whereas 38 (30.4?%) were specific to the production herd of CRP; 4 (3.2?%) were specific to the broad CRP population; 7 (5.6?%) were present in both conserved populations; 5 (4.0?%) were present solely for the conserved CRP; and 3 (2.4?%) were restricted to CR. Consequently, gene pool erosion related to intensive breeding did not occur in Czech Simmental cattle. Similarly, no considerable consequences were found from known bottlenecks in the history of Czech Red cattle. On the other hand, the distinctness of the conserved populations and their potential for resistance breeding were only moderate. This relationship might be transferable to other non-abundant historical cattle breeds that are conserved as genetic resources. The estimates of polymorphism impact using Variant Effect Predictor and SIFT software tools allowed for the identification of candidate single-nucleotide polymorphisms (SNPs) for association studies related to infection resistance and targeted breeding. Knowledge of TLR-gene diversity present in Czech Simmental populations may aid in the potential transfer of variant characteristics from other breeds.


April 21, 2020

Efficiency of PacBio long read correction by 2nd generation Illumina sequencing.

Long sequencing reads offer unprecedented opportunities in analysis and reconstruction of complex genomic regions. However, the gain in sequence length is often traded for quality. Therefore, recently several approaches have been proposed (e.g. higher sequencing coverage, hybrid assembly or sequence correction) to enhance the quality of long sequencing reads. A simple and cost-effective approach includes use of the high quality 2nd generation sequencing data to improve the quality of long reads. We designed a dedicated testing procedure and selected universal programs for long read correction, which provide as the output sequences that can be used in further genomic and transcriptomic studies. Our results show that HALC is the best choice for correction of long PacBio reads, when both, read size and quality, are the main focus of the analysis. However, the tested tools show some unexpected behaviors, including read trimming and fragmentation.Copyright © 2017 Elsevier Inc. All rights reserved.


April 21, 2020

An Annotated Genome for Haliotis rufescens (Red Abalone) and Resequenced Green, Pink, Pinto, Black, and White Abalone Species.

Abalone are one of the few marine taxa where aquaculture production dominates the global market as a result of increasing demand and declining natural stocks from overexploitation and disease. To better understand abalone biology, aid in conservation efforts for endangered abalone species, and gain insight into sustainable aquaculture, we created a draft genome of the red abalone (Haliotis rufescens). The approach to this genome draft included initial assembly using raw Illumina and PacBio sequencing data with MaSuRCA, before scaffolding using sequencing data generated from Chicago library preparations with HiRise2. This assembly approach resulted in 8,371 scaffolds and total length of 1.498?Gb; the N50 was 1.895?Mb, and the longest scaffold was 13.2?Mb. Gene models were predicted, using MAKER2, from RNA-Seq data and all related expressed sequence tags and proteins from NCBI; this resulted in 57,785 genes with an average length of 8,255?bp. In addition, single nucleotide polymorphisms were called on Illumina short-sequencing reads from five other eastern Pacific abalone species: the green (H. fulgens), pink (H. corrugata), pinto (H. kamtschatkana), black (H. cracherodii), and white (H. sorenseni) abalone. Phylogenetic relationships largely follow patterns detected by previous studies based on 1,784,991 high-quality single nucleotide polymorphisms. Among the six abalone species examined, the endangered white abalone appears to harbor the lowest levels of heterozygosity. This draft genome assembly and the sequencing data provide a foundation for genome-enabled aquaculture improvement for red abalone, and for genome-guided conservation efforts for the other five species and, in particular, for the endangered white and black abalone.


April 21, 2020

Bioinformatic analysis of the complete genome sequence of Pectobacterium carotovorum subsp. brasiliense BZA12 and candidate effector screening

AbstractPectobacterium carotovorum subsp. brasiliense (Pcb) is a gram-negative, plant pathogenic bacterium of the soft rot Enterobacteriaceae (SRE) family. We present the complete genome sequence of Pcb strain BZA12, which reveals that Pcb strain BZA12 carries a single 4,924,809 bp chromosome with 51.97% GC content and comprises 4508 predicted protein-coding genes.Geneannotationofthese genes utilizedGO, KEGG,and COG databases.Incomparison withthree closely related soft-rot pathogens, strain BZA12 has 3797 gene families, among which 3107 gene families are identified as orthologous with those of both P. carotovorum subsp. carotovorum PCC21 and P. carotovorum subsp. odoriferum BCS7, as well as 36 putative Unique Gene Families. We selected five putative effectors from the BZA12 genome and transiently expressed them in Nicotiana benthamiana. Candidate effector A12GL002483 was localized in the cell nucleus and induced cell death. This study provides a foundation for a better understanding of the genomic structure and function of Pcb, particularly in the discovery of potential pathogenic factors and for the development of more effective strategies against this pathogen.


April 21, 2020

Physiological properties and genetic analysis related to exopolysaccharide (EPS) production in the fresh-water unicellular cyanobacterium Aphanothece sacrum (Suizenji Nori).

The clonal strains, phycoerythrin(PE)-rich- and PE-poor strains, of the unicellular, fresh water cyanobacterium Aphanothece sacrum (Suringar) Okada (Suizenji Nori, in Japanese) were isolated from traditional open-air aquafarms in Japan. A. sacrum appeared to be oligotrophic on the basis of its growth characteristics. The optimum temperature for growth was around 20°C. Maximum growth and biomass increase at 20°C was obtained under light intensities between 40 to 80 µmol m-2 s-1 (fluorescent lamps, 12 h light/12 h dark cycles) and between 40 to 120 µmol m-2 s-1 for PE-rich and PE-poor strains, respectively, of A. sacrum . Purified exopolysaccharide (EPS) of A. sacrum has a molecular weight of ca. 104 kDa with five major monosaccharides (glucose, xylose, rhamnose, galactose and mannose; =85 mol%). We also deciphered the whole genome sequence of the two strains of A. sacrum. The putative genes involved in the polymerization, chain length control, and export of EPS would contribute to understand the biosynthetic process of their extremely high molecular weight EPS. The putative genes encoding Wzx-Wzy-Wzz- and Wza-Wzb-Wzc were conserved in the A. sacrum strains FPU1 and FPU3. This result suggests that the Wzy-dependent pathway participates in the EPS production of A. sacrum.


April 21, 2020

Discovery of tandem and interspersed segmental duplications using high-throughput sequencing.

Several algorithms have been developed that use high-throughput sequencing technology to characterize structural variations (SVs). Most of the existing approaches focus on detecting relatively simple types of SVs such as insertions, deletions and short inversions. In fact, complex SVs are of crucial importance and several have been associated with genomic disorders. To better understand the contribution of complex SVs to human disease, we need new algorithms to accurately discover and genotype such variants. Additionally, due to similar sequencing signatures, inverted duplications or gene conversion events that include inverted segmental duplications are often characterized as simple inversions, likewise, duplications and gene conversions in direct orientation may be called as simple deletions. Therefore, there is still a need for accurate algorithms to fully characterize complex SVs and thus improve calling accuracy of more simple variants.We developed novel algorithms to accurately characterize tandem, direct and inverted interspersed segmental duplications using short read whole genome sequencing datasets. We integrated these methods to our TARDIS tool, which is now capable of detecting various types of SVs using multiple sequence signatures such as read pair, read depth and split read. We evaluated the prediction performance of our algorithms through several experiments using both simulated and real datasets. In the simulation experiments, using a 30× coverage TARDIS achieved 96% sensitivity with only 4% false discovery rate. For experiments that involve real data, we used two haploid genomes (CHM1 and CHM13) and one human genome (NA12878) from the Illumina Platinum Genomes set. Comparison of our results with orthogonal PacBio call sets from the same genomes revealed higher accuracy for TARDIS than state-of-the-art methods. Furthermore, we showed a surprisingly low false discovery rate of our approach for discovery of tandem, direct and inverted interspersed segmental duplications prediction on CHM1 (<5% for the top 50 predictions).TARDIS source code is available at https://github.com/BilkentCompGen/tardis, and a corresponding Docker image is available at https://hub.docker.com/r/alkanlab/tardis/.Supplementary data are available at Bioinformatics online. © The Author(s) 2019. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.


April 21, 2020

Genome assembly and gene expression in the American black bear provides new insights into the renal response to hibernation.

The prevalence of chronic kidney disease (CKD) is rising worldwide and 10-15% of the global population currently suffers from CKD and its complications. Given the increasing prevalence of CKD there is an urgent need to find novel treatment options. The American black bear (Ursus americanus) copes with months of lowered kidney function and metabolism during hibernation without the devastating effects on metabolism and other consequences observed in humans. In a biomimetic approach to better understand kidney adaptations and physiology in hibernating black bears, we established a high-quality genome assembly. Subsequent RNA-Seq analysis of kidneys comparing gene expression profiles in black bears entering (late fall) and emerging (early spring) from hibernation identified 169 protein-coding genes that were differentially expressed. Of these, 101 genes were downregulated and 68 genes were upregulated after hibernation. Fold changes ranged from 1.8-fold downregulation (RTN4RL2) to 2.4-fold upregulation (CISH). Most notable was the upregulation of cytokine suppression genes (SOCS2, CISH, and SERPINC1) and the lack of increased expression of cytokines and genes involved in inflammation. The identification of these differences in gene expression in the black bear kidney may provide new insights in the prevention and treatment of CKD. © The Author(s) 2018. Published by Oxford University Press on behalf of Kazusa DNA Research Institute.


April 21, 2020

Genome-Scale Sequence Disruption Following Biolistic Transformation in Rice and Maize.

Biolistic transformation delivers nucleic acids into plant cells by bombarding the cells with microprojectiles, which are micron-scale, typically gold particles. Despite the wide use of this technique, little is known about its effect on the cell’s genome. We biolistically transformed linear 48-kb phage lambda and two different circular plasmids into rice (Oryza sativa) and maize (Zea mays) and analyzed the results by whole genome sequencing and optical mapping. Although some transgenic events showed simple insertions, others showed extreme genome damage in the form of chromosome truncations, large deletions, partial trisomy, and evidence of chromothripsis and breakage-fusion bridge cycling. Several transgenic events contained megabase-scale arrays of introduced DNA mixed with genomic fragments assembled by nonhomologous or microhomology-mediated joining. Damaged regions of the genome, assayed by the presence of small fragments displaced elsewhere, were often repaired without a trace, presumably by homology-dependent repair (HDR). The results suggest a model whereby successful biolistic transformation relies on a combination of end joining to insert foreign DNA and HDR to repair collateral damage caused by the microprojectiles. The differing levels of genome damage observed among transgenic events may reflect the stage of the cell cycle and the availability of templates for HDR. © 2019 American Society of Plant Biologists. All rights reserved.


April 21, 2020

RADAR-seq: A RAre DAmage and Repair sequencing method for detecting DNA damage on a genome-wide scale.

RAre DAmage and Repair sequencing (RADAR-seq) is a highly adaptable sequencing method that enables the identification and detection of rare DNA damage events for a wide variety of DNA lesions at single-molecule resolution on a genome-wide scale. In RADAR-seq, DNA lesions are replaced with a patch of modified bases that can be directly detected by Pacific Biosciences Single Molecule Real-Time (SMRT) sequencing. RADAR-seq enables dynamic detection over a wide range of DNA damage frequencies, including low physiological levels. Furthermore, without the need for DNA amplification and enrichment steps, RADAR-seq provides sequencing coverage of damaged and undamaged DNA across an entire genome. Here, we use RADAR-seq to measure the frequency and map the location of ribonucleotides in wild-type and RNaseH2-deficient E. coli and Thermococcus kodakarensis strains. Additionally, by tracking ribonucleotides incorporated during in vivo lagging strand DNA synthesis, we determined the replication initiation point in E. coli, and its relation to the origin of replication (oriC). RADAR-seq was also used to map cyclobutane pyrimidine dimers (CPDs) in Escherichia coli (E. coli) genomic DNA exposed to UV-radiation. On a broader scale, RADAR-seq can be applied to understand formation and repair of DNA damage, the correlation between DNA damage and disease initiation and progression, and complex biological pathways, including DNA replication.Copyright © 2019 The Authors. Published by Elsevier B.V. All rights reserved.


April 21, 2020

Characterization and analysis of the transcriptome in Gymnocypris selincuoensis on the Qinghai-Tibetan Plateau using single-molecule long-read sequencing and RNA-seq.

The lakes on the Qinghai-Tibet Plateau (QTP) are the largest and highest lake group in the world. Gymnocypris selincuoensis is the only cyprinid fish living in lake Selincuo, the largest lake on QTP. However, its genetic resource is still blank, limiting studies on molecular and genetic analysis. In this study, the transcriptome of G. selincuoensis was first generated by using PacBio Iso-Seq and Illumina RNA-seq. A full-length (FL) transcriptome with 75,435 transcripts was obtained by Iso-Seq with N50 length of 3,870 bp. Among all transcripts, 75,016 were annotated to public databases, 64,710 contain complete open reading frames and 2,811 were long non-coding RNAs. Based on all- vs.-all BLAST, 2,069 alternative splicing events were detected, and 80% of them were validated by reverse transcription polymerase chain reaction (RT-PCR). Tissue gene expression atlas showed that the number of detected expressed transcripts ranged from 37,397 in brain to 19,914 in muscle, with 10,488 transcripts detected in all seven tissues. Comparative genomic analysis with other cyprinid fishes identified 77 orthologous genes with potential positive selection (Ka/Ks > 0.3). A total of 56,696 perfect simple sequence repeats were identified from FL transcripts. Our results provide valuable genetic resources for further studies on adaptive evolution, gene expression and population genetics in G. selincuoensis and other congeneric fishes. © The Author(s) 2019. Published by Oxford University Press on behalf of Kazusa DNA Research Institute.


April 21, 2020

rMETL: sensitive mobile element insertion detection with long read realignment.

Mobile element insertion (MEI) is a major category of structure variations (SVs). The rapid development of long read sequencing technologies provides the opportunity to detect MEIs sensitively. However, the signals of MEI implied by noisy long reads are highly complex due to the repetitiveness of mobile elements as well as the high sequencing error rates. Herein, we propose the Realignment-based Mobile Element insertion detection Tool for Long read (rMETL). Benchmarking results of simulated and real datasets demonstrate that rMETL enables to handle the complex signals to discover MEIs sensitively. It is suited to produce high-quality MEI callsets in many genomics studies.rMETL is available from https://github.com/hitbc/rMETL.Supplementary data are available at Bioinformatics online. © The Author(s) 2019. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.


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