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July 7, 2019

Complete genome sequencing of Arachidicoccus ginsenosidimutans sp. nov., and its application for production of minor ginsenosides by finding a novel ginsenoside-transforming beta-glucosidase

A novel bacterial strain (BS20T), which has ginsenoside-transforming ability, was whole genome sequenced for the identification of a target gene. After complete genome sequencing, phylogenetic, phenotypic and chemotaxonomic analyses, the strain BS20T (Arachidicoccus ginsenosidimutans sp. nov.) was placed within the genus Arachidicoccus of family Chitinophagaceae. The complete genome of strain BS20T comprised a circular chromosome of 4[thin space (1/6-em)]138[thin space (1/6-em)]017 bp. To find the target functional gene, 17 sets of four different glycoside hydrolases were cloned in E. coli BL21 (DE3) using the pGEX4T-1 vector and were characterized. Among these 17 sets of clones, only one, BglAg-762, exhibited ginsenoside-conversion ability. The BglAg-762 comprised 762 amino acid residues and belonged to the glycoside hydrolase family 3. The recombinant enzyme (GST-BglAg-762) was able to convert major ginsenosides Rb1 to F2 via gypenoside-XVII (Gyp-XVII), Rb2 to C-O, and Rb3, Rc, Rd, and Gyp-XVII to C-Mx1, C-Mc1, and F2, respectively. Finally, ginsenoside F2 was transformed into compound K (C-K). Besides, these pilot data demonstrate the identification of 17 sets of target/functional genes of 4 different glycoside hydrolases from a novel bacterial species via whole genome sequencing. Our results have shown that the recombinant BglAg-762 very quickly converts the major ginsenosides into minor ginsenosides, which can be used for the enhanced production of target minor ginsenosides. Furthermore, the web service of NCBI is suitable for any targeted gene identification, but based on our experimental analysis we concluded that the hypothetical protein present in NCBI should be considered as a putative or uncharacterized protein.


July 7, 2019

Repetitive sequences in malaria parasite proteins.

Five species of parasite cause malaria in humans with the most severe disease caused by Plasmodium falciparum. Many of the proteins encoded in the P. falciparum genome are unusually enriched in repetitive low-complexity sequences containing a limited repertoire of amino acids. These repetitive sequences expand and contract dynamically and are among the most rapidly changing sequences in the genome. The simplest repetitive sequences consist of single amino acid repeats such as poly-asparagine tracts that are found in approximately 25% of P. falciparum proteins. More complex repeats of two or more amino acids are also common in diverse parasite protein families. There is no universal explanation for the occurrence of repetitive sequences and it is possible that many confer no function to the encoded protein and no selective advantage or disadvantage to the parasite. However, there are increasing numbers of examples where repetitive sequences are important for parasite protein function. We discuss the diverse roles of low-complexity repetitive sequences throughout the parasite life cycle, from mediating protein-protein interactions to enabling the parasite to evade the host immune system.© FEMS 2017. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.


July 7, 2019

Efficient transgenesis and annotated genome sequence of the regenerative flatworm model Macrostomum lignano.

Regeneration-capable flatworms are informative research models to study the mechanisms of stem cell regulation, regeneration, and tissue patterning. However, the lack of transgenesis methods considerably hampers their wider use. Here we report development of a transgenesis method for Macrostomum lignano, a basal flatworm with excellent regeneration capacity. We demonstrate that microinjection of DNA constructs into fertilized one-cell stage eggs, followed by a low dose of irradiation, frequently results in random integration of the transgene in the genome and its stable transmission through the germline. To facilitate selection of promoter regions for transgenic reporters, we assembled and annotated the M. lignano genome, including genome-wide mapping of transcription start regions, and show its utility by generating multiple stable transgenic lines expressing fluorescent proteins under several tissue-specific promoters. The reported transgenesis method and annotated genome sequence will permit sophisticated genetic studies on stem cells and regeneration using M. lignano as a model organism.


July 7, 2019

Integrating transcriptomic and proteomic data for accurate assembly and annotation of genomes.

Complementing genome sequence with deep transcriptome and proteome data could enable more accurate assembly and annotation of newly sequenced genomes. Here, we provide a proof-of-concept of an integrated approach for analysis of the genome and proteome of Anopheles stephensi, which is one of the most important vectors of the malaria parasite. To achieve broad coverage of genes, we carried out transcriptome sequencing and deep proteome profiling of multiple anatomically distinct sites. Based on transcriptomic data alone, we identified and corrected 535 events of incomplete genome assembly involving 1196 scaffolds and 868 protein-coding gene models. This proteogenomic approach enabled us to add 365 genes that were missed during genome annotation and identify 917 gene correction events through discovery of 151 novel exons, 297 protein extensions, 231 exon extensions, 192 novel protein start sites, 19 novel translational frames, 28 events of joining of exons, and 76 events of joining of adjacent genes as a single gene. Incorporation of proteomic evidence allowed us to change the designation of more than 87 predicted “noncoding RNAs” to conventional mRNAs coded by protein-coding genes. Importantly, extension of the newly corrected genome assemblies and gene models to 15 other newly assembled Anopheline genomes led to the discovery of a large number of apparent discrepancies in assembly and annotation of these genomes. Our data provide a framework for how future genome sequencing efforts should incorporate transcriptomic and proteomic analysis in combination with simultaneous manual curation to achieve near complete assembly and accurate annotation of genomes.© 2017 Prasad et al.; Published by Cold Spring Harbor Laboratory Press.


July 7, 2019

Insights into adaptations to a near-obligate nematode endoparasitic lifestyle from the finished genome of Drechmeria coniospora.

Nematophagous fungi employ three distinct predatory strategies: nematode trapping, parasitism of females and eggs, and endoparasitism. While endoparasites play key roles in controlling nematode populations in nature, their application for integrated pest management is hindered by the limited understanding of their biology. We present a comparative analysis of a high quality finished genome assembly of Drechmeria coniospora, a model endoparasitic nematophagous fungus, integrated with a transcriptomic study. Adaptation of D. coniospora to its almost completely obligate endoparasitic lifestyle led to the simplification of many orthologous gene families involved in the saprophytic trophic mode, while maintaining orthologs of most known fungal pathogen-host interaction proteins, stress response circuits and putative effectors of the small secreted protein type. The need to adhere to and penetrate the host cuticle led to a selective radiation of surface proteins and hydrolytic enzymes. Although the endoparasite has a simplified secondary metabolome, it produces a novel peptaibiotic family that shows antibacterial, antifungal and nematicidal activities. Our analyses emphasize the basic malleability of the D. coniospora genome: loss of genes advantageous for the saprophytic lifestyle; modulation of elements that its cohort species utilize for entomopathogenesis; and expansion of protein families necessary for the nematode endoparasitic lifestyle.


July 7, 2019

No evidence for extensive horizontal gene transfer in the genome of the tardigrade Hypsibius dujardini.

Tardigrades are meiofaunal ecdysozoans that are key to understanding the origins of Arthropoda. Many species of Tardigrada can survive extreme conditions through cryptobiosis. In a recent paper [Boothby TC, et al. (2015) Proc Natl Acad Sci USA 112(52):15976-15981], the authors concluded that the tardigrade Hypsibius dujardini had an unprecedented proportion (17%) of genes originating through functional horizontal gene transfer (fHGT) and speculated that fHGT was likely formative in the evolution of cryptobiosis. We independently sequenced the genome of H. dujardini As expected from whole-organism DNA sampling, our raw data contained reads from nontarget genomes. Filtering using metagenomics approaches generated a draft H. dujardini genome assembly of 135 Mb with superior assembly metrics to the previously published assembly. Additional microbial contamination likely remains. We found no support for extensive fHGT. Among 23,021 gene predictions we identified 0.2% strong candidates for fHGT from bacteria and 0.2% strong candidates for fHGT from nonmetazoan eukaryotes. Cross-comparison of assemblies showed that the overwhelming majority of HGT candidates in the Boothby et al. genome derived from contaminants. We conclude that fHGT into H. dujardini accounts for at most 1-2% of genes and that the proposal that one-sixth of tardigrade genes originate from functional HGT events is an artifact of undetected contamination.


July 7, 2019

Haemonchus contortus: genome structure, organization and comparative genomics

One of the first genome sequencing projects for a parasitic nematode was that for Haemonchus contortus. The open access data from the Wellcome Trust Sanger Institute provided a valuable early resource for the research community, particularly for the identification of specific genes and genetic markers. Later, a second sequencing project was initiated by the University of Melbourne, and the two draft genome sequences for H. contortus were published back-to-back in 2013. There is a pressing need for long-range genomic information for genetic mapping, population genetics and functional genomic studies, so we are continuing to improve the Wellcome Trust Sanger Institute assembly to provide a finished reference genome for H. contortus. This review describes this process, compares the H. contortus genome assemblies with draft genomes from other members of the strongylid group and discusses future directions for parasite genomics using the H. contortus model. Copyright © 2016 Elsevier Ltd. All rights reserved.


July 7, 2019

OPERA-LG: efficient and exact scaffolding of large, repeat-rich eukaryotic genomes with performance guarantees.

The assembly of large, repeat-rich eukaryotic genomes represents a significant challenge in genomics. While long-read technologies have made the high-quality assembly of small, microbial genomes increasingly feasible, data generation can be expensive for larger genomes. OPERA-LG is a scalable, exact algorithm for the scaffold assembly of large, repeat-rich genomes, out-performing state-of-the-art programs for scaffold correctness and contiguity. It provides a rigorous framework for scaffolding of repetitive sequences and a systematic approach for combining data from different second-generation and third-generation sequencing technologies. OPERA-LG provides an avenue for systematic augmentation and improvement of thousands of existing draft eukaryotic genome assemblies.


July 7, 2019

Population scale mapping of transposable element diversity reveals links to gene regulation and epigenomic variation.

Variation in the presence or absence of transposable elements (TEs) is a major source of genetic variation between individuals. Here, we identified 23,095 TE presence/absence variants between 216 Arabidopsis accessions. Most TE variants were rare, and we find these rare variants associated with local extremes of gene expression and DNA methylation levels within the population. Of the common alleles identified, two thirds were not in linkage disequilibrium with nearby SNPs, implicating these variants as a source of novel genetic diversity. Many common TE variants were associated with significantly altered expression of nearby genes, and a major fraction of inter-accession DNA methylation differences were associated with nearby TE insertions. Overall, this demonstrates that TE variants are a rich source of genetic diversity that likely plays an important role in facilitating epigenomic and transcriptional differences between individuals, and indicates a strong genetic basis for epigenetic variation.


July 7, 2019

SimLoRD: Simulation of Long Read Data.

Third generation sequencing methods provide longer reads than second generation methods and have distinct error characteristics. While there exist many read simulators for second generation data, there is a very limited choice for third generation data.We analyzed public data from Pacific Biosciences (PacBio) SMRT sequencing, developed an error model and implemented it in a new read simulator called SimLoRD. It offers options to choose the read length distribution and to model error probabilities depending on the number of passes through the sequencer. The new error model makes SimLoRD the most realistic SMRT read simulator available.SimLoRD is available open source at http://bitbucket.org/genomeinformatics/simlord/ and installable via Bioconda (http://bioconda.github.io).Bianca.Stoecker@uni-due.de or Sven.Rahmann@uni-due.deSupplementary data are available at Bioinformatics online. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.


July 7, 2019

Minimap and miniasm: fast mapping and de novo assembly for noisy long sequences.

Single Molecule Real-Time (SMRT) sequencing technology and Oxford Nanopore technologies (ONT) produce reads over 10?kb in length, which have enabled high-quality genome assembly at an affordable cost. However, at present, long reads have an error rate as high as 10-15%. Complex and computationally intensive pipelines are required to assemble such reads.We present a new mapper, minimap and a de novo assembler, miniasm, for efficiently mapping and assembling SMRT and ONT reads without an error correction stage. They can often assemble a sequencing run of bacterial data into a single contig in a few minutes, and assemble 45-fold Caenorhabditis elegans data in 9?min, orders of magnitude faster than the existing pipelines, though the consensus sequence error rate is as high as raw reads. We also introduce a pairwise read mapping format and a graphical fragment assembly format, and demonstrate the interoperability between ours and current tools.https://github.com/lh3/minimap and https://github.com/lh3/miniasmhengli@broadinstitute.orgSupplementary data are available at Bioinformatics online. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.


July 7, 2019

Reply to Bemm et al. and Arakawa: Identifying foreign genes in independent Hypsibius dujardini genome assemblies.

Our report (1) describing the discovery of extensive horizontal gene transfer in a tardigrade genome has raised questions from other groups who were sequencing the Hypsibius dujardini genome in parallel or who have done new experiments and analyses since our report (2??–5). Bemm et al. (2) now report filtering our data for likely contaminants, resulting in a new, prefiltered genome assembly. Arakawa (3) has sequenced genomes of starved, washed, individual animals that had been treated with antibiotics for 48 h, and used this genomic sequence and RNA-Seq data to identify likely bona fide tardigrade contigs. Two other reports have contributed data and analysis: Delmont and Eren (4) used a newly published analysis and visualization platform, Anvi’o (6), to identify likely contaminants in our genome assembly, and Koutsovoulos et al. (5) applied useful taxon-annotated GC coverage plots (Blobplots) (7) to our data and reported an independent genome assembly.


July 7, 2019

Comparative genomic and functional analyses: unearthing the diversity and specificity of nematicidal factors in Pseudomonas putida strain 1A00316.

We isolated Pseudomonas putida (P. putida) strain 1A00316 from Antarctica. This bacterium has a high efficiency against Meloidogyne incognita (M. incognita) in vitro and under greenhouse conditions. The complete genome of P. putida 1A00316 was sequenced using PacBio single molecule real-time (SMRT) technology. A comparative genomic analysis of 16 Pseudomonas strains revealed that although P. putida 1A00316 belonged to P. putida, it was phenotypically more similar to nematicidal Pseudomonas fluorescens (P. fluorescens) strains. We characterized the diversity and specificity of nematicidal factors in P. putida 1A00316 with comparative genomics and functional analysis, and found that P. putida 1A00316 has diverse nematicidal factors including protein alkaline metalloproteinase AprA and two secondary metabolites, hydrogen cyanide and cyclo-(l-isoleucyl-l-proline). We show for the first time that cyclo-(l-isoleucyl-l-proline) exhibit nematicidal activity in P. putida. Interestingly, our study had not detected common nematicidal factors such as 2,4-diacetylphloroglucinol (2,4-DAPG) and pyrrolnitrin in P. putida 1A00316. The results of the present study reveal the diversity and specificity of nematicidal factors in P. putida strain 1A00316.


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