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April 21, 2020  |  

deSALT: fast and accurate long transcriptomic read alignment with de Bruijn graph-based index

Long-read RNA sequencing (RNA-seq) is promising to transcriptomics studies, however, the alignment of the reads is still a fundamental but non-trivial task due to the sequencing errors and complicated gene structures. We propose deSALT, a tailored two-pass long RNA-seq read alignment approach, which constructs graph-based alignment skeletons to sensitively infer exons, and use them to generate spliced reference sequence to produce refined alignments. deSALT addresses several difficult issues, such as small exons, serious sequencing errors and consensus spliced alignment. Benchmarks demonstrate that this approach has a better ability to produce high-quality full-length alignments, which has enormous potentials to transcriptomics studies.

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April 21, 2020  |  

Full-length mRNA sequencing and gene expression profiling reveal broad involvement of natural antisense transcript gene pairs in pepper development and response to stresses.

Pepper is an important vegetable with great economic value and unique biological features. In the past few years, significant development has been made towards understanding the huge complex pepper genome; however, pepper functional genomics has not been well studied. To better understand the pepper gene structure and pepper gene regulation, we conducted full-length mRNA sequencing by PacBio sequencing and obtained 57862 high-quality full-length mRNA sequences derived from 18362 previously annotated and 5769 newly detected genes. New gene models were built that combined the full-length mRNA sequences and corrected approximately 500 fragmented gene models from previous annotations. Based on the full-length mRNA, we identified 4114 and 5880 pepper genes forming natural antisense transcript (NAT) genes in-cis and in-trans, respectively. Most of these genes accumulate small RNAs in their overlapping regions. By analyzing these NAT gene expression patterns in our transcriptome data, we identified many NAT pairs responsive to a variety of biological processes in pepper. Pepper formate dehydrogenase 1 (FDH1), which is required for R-gene-mediated disease resistance, may be regulated by nat-siRNAs and participate in a positive feedback loop in salicylic acid biosynthesis during resistance responses. Several cis-NAT pairs and subgroups of trans-NAT genes were responsive to pepper pericarp and placenta development, which may play roles in capsanthin and capsaicin biosynthesis. Using a comparative genomics approach, the evolutionary mechanisms of cis-NATs were investigated, and we found that an increase in intergenic sequences accounted for the loss of most cis-NATs, while transposon insertion contributed to the formation of most new cis-NATs. This article is protected by copyright. All rights reserved.This article is protected by copyright. All rights reserved.

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April 21, 2020  |  

Microbial diversity in the tick Argas japonicus (Acari: Argasidae) with a focus on Rickettsia pathogens.

The soft tick Argas japonicus mainly infests birds and can cause human dermatitis; however, no pathogen has been identified from this tick species in China. In the present study, the microbiota in A. japonicus collected from an epidemic community was explored, and some putative Rickettsia pathogens were further characterized. The results obtained indicated that bacteria in A. japonicus were mainly ascribed to the phyla Proteobacteria, Firmicutes and Actinobacteria. At the genus level, the male A. japonicus harboured more diverse bacteria than the females and nymphs. The bacteria Alcaligenes, Pseudomonas, Rickettsia and Staphylococcus were common in nymphs and adults. The abundance of bacteria belonging to the Rickettsia genus in females and males was 7.27% and 10.42%, respectively. Furthermore, the 16S rRNA gene of Rickettsia was amplified and sequenced, and phylogenetic analysis revealed that 13 sequences were clustered with the spotted fever group rickettsiae (Rickettsia heilongjiangensis and Rickettsia japonica) and three were clustered with Rickettsia limoniae, which suggested that the characterized Rickettsia in A. japonicus were novel putative pathogens and also that the residents were at considerable risk for infection by tick-borne pathogens. © 2019 The Royal Entomological Society.

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April 21, 2020  |  

Pandemic spread of blaKPC-2 among Klebsiella pneumoniae ST11 in China is associated with horizontal transfer mediated by IncFII-like plasmids.

This study aimed to investigate the spread of the blaKPC-2 gene among Klebsiella pneumoniae and to illustrate the mechanism of dissemination of KPC-producing K. pneumoniae (KPC-Kp) ST11 in China.A total of 354 K. pneumoniae isolates were collected from four hospitals in China and were characterized by Multilocus sequence typing (MLST). Mobile genetic elements (MGEs) and pulsed-field gel electrophoresis (PFGE) analysis were used to identify the subtypes of K. pneumoniae ST11. PCR-based amplification and sequencing were performed to analyze Tn1721 transposons and IncFII-like plasmids. Electroporation experiments and whole-genome sequencing (WGS) analysis were used to reveal the genetic environment of the blaKPC-2 gene.As the primary type(87.1%) of KPC-Kp, K. pneumoniae ST11 was not predominant in nonKPC-Kp(3.1%). ST11 KPC-Kp was clonally heterogeneous and could be further classified into eleven MGE types and fourteen PFGE subtypes. Five Tn1721-blaKPC-2 variants were identified on IncFII-like plasmids. The detection rate of IncFII-like plasmids was much higher in ST11 KPC-Kp (100%) compared with non-ST11 KPC-Kp (16.0%) and the nonKPC-Kp group (7.5%). Moreover, the IncFII plasmid (with IIa replicon) was primarily detected on the MGE-F type (61.7%). The IncFIIk plasmid (with IIk replicon) was clustered into two subtypes: MGE-A (28.3%) and -F (41.5%). The detection of the IncFII and IncFIIk plasmids on MGE-A was 57.1% (20/35) and 42.9% (15/35), respectively.We revealed a close correlation between ST11 KPC-Kp and IncFII-like plasmids. Horizontal transfer mediated by IncFII-like plasmids plays an important role in the pandemic expansion of blaKPC-2 among K. pneumoniae ST11 in China. Copyright © 2019. Published by Elsevier B.V.

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April 21, 2020  |  

Defining transgene insertion sites and off-target effects of homology-based gene silencing informs the use of functional genomics tools in Phytophthora infestans.

DNA transformation and homology-based transcriptional silencing are frequently used to assess gene function in Phytophthora. Since unplanned side-effects of these tools are not well-characterized, we used P. infestans to study plasmid integration sites and whether knockdowns caused by homology-dependent silencing spreads to other genes. Insertions occurred both in gene-dense and gene-sparse regions but disproportionately near the 5′ ends of genes, which disrupted native coding sequences. Microhomology at the recombination site between plasmid and chromosome was common. Studies of transformants silenced for twelve different gene targets indicated that neighbors within 500-nt were often co-silenced, regardless of whether hairpin or sense constructs were employed and the direction of transcription of the target. However, cis-spreading of silencing did not occur in all transformants obtained with the same plasmid. Genome-wide studies indicated that unlinked genes with partial complementarity with the silencing-inducing transgene were not usually down-regulated. We learned that hairpin or sense transgenes were not co-silenced with the target in all transformants, which informs how screens for silencing should be performed. We conclude that transformation and gene silencing can be reliable tools for functional genomics in Phytophthora but must be used carefully, especially by testing for the spread of silencing to genes flanking the target.

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April 21, 2020  |  

Complete genome sequence of Bacillus velezensis JT3-1, a microbial germicide isolated from yak feces

Bacillus velezensis JT3-1 is a probiotic strain isolated from feces of the domestic yak (Bos grunniens) in the Gansu province of China. It has strong antagonistic activity against Listeria monocytogenes, Staphylococcus aureus, Escherichia coli, Salmonella Typhimurium, Mannheimia haemolytica, Staphylococcus hominis, Clostridium perfringens, and Mycoplasma bovis. These properties have made the JT3-1 strain the focus of commercial interest. In this study, we describe the complete genome sequence of JT3-1, with a genome size of 3,929,799 bp, 3761 encoded genes and an average GC content of 46.50%. Whole genome sequencing of Bacillus velezensis JT3-1 will lay a good foundation for elucidation of the mechanisms of its antimicrobial activity, and for its future application.

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April 21, 2020  |  

Fast and accurate long-read assembly with wtdbg2

Existing long-read assemblers require tens of thousands of CPU hours to assemble a human genome and are being outpaced by sequencing technologies in terms of both throughput and cost. We developed a novel long-read assembler wtdbg2 that, for human data, is tens of times faster than published tools while achieving comparable contiguity and accuracy. It represents a significant algorithmic advance and paves the way for population-scale long-read assembly in future.

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April 21, 2020  |  

Genome-wide selection footprints and deleterious variations in young Asian allotetraploid rapeseed.

Brassica napus (AACC, 2n = 38) is an important oilseed crop grown worldwide. However, little is known about the population evolution of this species, the genomic difference between its major genetic groups, such as European and Asian rapeseed, and the impacts of historical large-scale introgression events on this young tetraploid. In this study, we reported the de novo assembly of the genome sequences of an Asian rapeseed (B. napus), Ningyou 7, and its four progenitors and compared these genomes with other available genomic data from diverse European and Asian cultivars. Our results showed that Asian rapeseed originally derived from European rapeseed but subsequently significantly diverged, with rapid genome differentiation after hybridization and intensive local selective breeding. The first historical introgression of B. rapa dramatically broadened the allelic pool but decreased the deleterious variations of Asian rapeseed. The second historical introgression of the double-low traits of European rapeseed (canola) has reshaped Asian rapeseed into two groups (double-low and double-high), accompanied by an increase in genetic load in the double-low group. This study demonstrates distinctive genomic footprints and deleterious SNP (single nucleotide polymorphism) variants for local adaptation by recent intra- and interspecies introgression events and provides novel insights for understanding the rapid genome evolution of a young allopolyploid crop. © 2019 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  |  

Large-scale ruminant genome sequencing provides insights into their evolution and distinct traits.

The ruminants are one of the most successful mammalian lineages, exhibiting morphological and habitat diversity and containing several key livestock species. To better understand their evolution, we generated and analyzed de novo assembled genomes of 44 ruminant species, representing all six Ruminantia families. We used these genomes to create a time-calibrated phylogeny to resolve topological controversies, overcoming the challenges of incomplete lineage sorting. Population dynamic analyses show that population declines commenced between 100,000 and 50,000 years ago, which is concomitant with expansion in human populations. We also reveal genes and regulatory elements that possibly contribute to the evolution of the digestive system, cranial appendages, immune system, metabolism, body size, cursorial locomotion, and dentition of the ruminants. Copyright © 2019 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

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April 21, 2020  |  

Draft Genome Sequence of Bifidobacterium longum ZJ1, Isolated from a Centenarian in Anhui, China.

Here, we present the complete genome sequence of a Bifidobacterium longum isolate, that of strain ZJ1, and this strain showed a cholesterol degradation ability that is greater than that of five strains we chose for comparison (Bifidobacterium longum 536, B. infantis 1912, B. longum 1941, B. breve ATCC 15698, B. infantis ATCC 17930). The draft genome of strain ZJ1 consists of 2,414,672?bp, with 2,042 protein-coding genes, 69 noncoding RNA genes, and 60.16% G+C content.Copyright © 2019 Jin et al.

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April 21, 2020  |  

Whole-Genome Sequencing of a Brucella melitensis Strain (BMWS93) Isolated from a Bank Clerk and Exhibiting Complete Resistance to Rifampin.

Human brucellosis has become the most severe public health problem in the Ulanqab region of Inner Mongolia, China. Brucella melitensis BMWS93 was obtained from a blood sample taken from a bank clerk in the Ulanqab region of Inner Mongolia, China, and antimicrobial susceptibility testing in vitro showed no zone of inhibition, which confirmed resistance to rifampin. Therefore, whole-genome sequencing of this isolate was performed to better understand the mechanism of this resistance.Copyright © 2019 Liu et al.

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April 21, 2020  |  

Complete Genome and Plasmid Sequences of Seven Isolates of Salmonella enterica subsp. enterica Harboring the mcr-1 Gene Obtained from Food in China.

Seven Salmonella enterica subsp. enterica isolates were identified as carrying the mcr-1 gene, by using a real-time fluorescence quantitative PCR method, from a total of 2,558 isolates which were cultured from various food origins in China between 2011 and 2016. Few complete genomes of Salmonella strains harboring the mcr-1 gene have been reported to date, so we report here the complete genome and plasmid sequences of all of these isolates to provide useful references for understanding the prevalence of foodborne Salmonella enterica subsp. enterica isolates carrying mcr-1.Copyright © 2019 Hu et al.

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April 21, 2020  |  

Complete Genome Sequence of Kosakonia sp. Strain CCTCC M2018092, a Fucose-Rich Exopolysaccharide Producer.

Kosakonia sp. strain CCTCC M2018092 is a fucose-rich exopolysaccharide producer that was isolated from spring water in Chongqing, Southwest China. In this study, the whole-genome sequence and genetic characteristics of this strain were elucidated. This genome contained 4,789,478 bp, with a G+C content of 56.08% (excluding the plasmid). The genome information in this study will facilitate understanding of the mechanism of high yield of fucose-rich exopolysaccharide produced by Kosakonia sp. CCTCC M2018092.Copyright © 2019 Niu et al.

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