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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

Genome-wide analysis of methyl jasmonate-regulated isoform expression in the medicinal plant Andrographis paniculata

Alternative splicing can increase the complexity of the transcriptome and proteome. The most common mechanism of alternative splicing in plants is intron retention (IR), and the expression levels of IR isoforms can be differentially regulated when facing abiotic stress. The full-length transcriptome of the medicinal plant Andrographis paniculata was sequenced using both Illumina- and SMRT-based RNA-seq and a total of 4846 IR isoforms were identified. The expression levels of 310/296 IR isoforms were up-regulated, and 629/659 IR isoforms were down-regulated at 24?h/48?h after methyl jasmonate (MeJA) treatment, respectively. In the (E,E,E)-geranylgeranyl diphosphate (GGPP) biosynthesis pathway which contributes to the andrographolide biosynthesis, eight genes were alternatively spliced, resulting in a total of 25 isoforms, of which 12 are IR isoforms. After MeJA treatment, four of these IR isoforms showed significant differential expression. RT-PCR and qRT-PCR experiments confirmed the existence of five IR isoforms. This research deepens our understanding of the A. paniculata transcriptome and can assist in the future study of andrographolide biosynthesis.


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

Potential use of the Pteris vittata arsenic hyperaccumulation-regulation network for phytoremediation.

Arsenic accumulation in soil is a global problem typically addressed using phytoremediation methods. Pteris vittata, a model arsenic hyperaccumulator, has great potential as a genetically engineered plant for phytoremediation. However, the lack of omic information on this species has severely limited the identification and application of its arsenic hyperaccumulation and regulation components. In this study, we used an optimized single-molecular real-time (SMRT) strategy to create a de novo full-length transcriptomic-tonoplast proteomic database for this unsequenced fern and to determine the genetic components underlying its arsenic hyperaccumulation-regulation mechanisms. We established a comprehensive network consisting of six major transporter families, two novel resistance pathways, and a regulatory system by examining alternative splicing (AS) and long non-coding RNA (lncRNA) in different tissues following As(III) and As(V) treatment. The database and network established in this study will deepen our understanding of the unique hyperaccumulation and regulation mechanisms of P. vittata, ultimately providing a valuable resource for futher research on phytoremediation of arsenic-contaminated soil. Copyright © 2019 Elsevier B.V. All rights reserved.


April 21, 2020

Long-Read Annotation: Automated Eukaryotic Genome Annotation Based on Long-Read cDNA Sequencing.

Single-molecule full-length complementary DNA (cDNA) sequencing can aid genome annotation by revealing transcript structure and alternative splice forms, yet current annotation pipelines do not incorporate such information. Here we present long-read annotation (LoReAn) software, an automated annotation pipeline utilizing short- and long-read cDNA sequencing, protein evidence, and ab initio prediction to generate accurate genome annotations. Based on annotations of two fungal genomes (Verticillium dahliae and Plicaturopsis crispa) and two plant genomes (Arabidopsis [Arabidopsis thaliana] and Oryza sativa), we show that LoReAn outperforms popular annotation pipelines by integrating single-molecule cDNA-sequencing data generated from either the Pacific Biosciences or MinION sequencing platforms, correctly predicting gene structure, and capturing genes missed by other annotation pipelines. © 2019 American Society of Plant Biologists. All Rights Reserved.


April 21, 2020

Neopinone isomerase is involved in codeine and morphine biosynthesis in opium poppy.

The isomerization of neopinone to codeinone is a critical step in the biosynthesis of opiate alkaloids in opium poppy. Previously assumed to be spontaneous, the process is in fact catalyzed enzymatically by neopinone isomerase (NISO). Without NISO the primary metabolic products in the plant, in engineered microbes and in vitro are neopine and neomorphine, which are structural isomers of codeine and morphine, respectively. Inclusion of NISO in yeast strains engineered to convert thebaine to natural or semisynthetic opiates dramatically enhances formation of the desired products at the expense of neopine and neomorphine accumulation. Along with thebaine synthase, NISO is the second member of the pathogenesis-related 10 (PR10) protein family recently implicated in the enzymatic catalysis of a presumed spontaneous conversion in morphine biosynthesis.


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

Nodule bacteria from the cultured legume Phaseolus dumosus (belonging to the Phaseolus vulgaris cross-inoculation group) with common tropici phenotypic characteristics and symbiovar but distinctive phylogenomic position and chromid.

Phaseolus dumosus is an endemic species from mountain tops in Mexico that was found in traditional agriculture areas in Veracruz, Mexico. P. dumosus plants were identified by ITS sequences and their nodules were collected from agricultural fields or from trap plant experiments in the laboratory. Bacteria from P. dumosus nodules were identified as belonging to the phaseoli-etli-leguminosarum (PEL) or to the tropici group by 16S rRNA gene sequences. We obtained complete closed genomes from two P. dumosus isolates CCGE531 and CCGE532 that were phylogenetically placed within the tropici group but with a distinctive phylogenomic position and low average nucleotide identity (ANI). CCGE531 and CCGE532 had common phenotypic characteristics with tropici type B rhizobial symbionts. Genome synteny analysis and ANI showed that P. dumosus isolates had different chromids and our analysis suggests that chromids have independently evolved in different lineages of the Rhizobium genus. Finally, we considered that P. dumosus and Phaseolus vulgaris plants belong to the same cross-inoculation group since they have conserved symbiotic affinites for rhizobia.Copyright © 2018 Elsevier GmbH. All rights reserved.


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

Secretion of an Argonaute protein by a parasitic nematode and the evolution of its siRNA guides.

Extracellular RNA has been proposed to mediate communication between cells and organisms however relatively little is understood regarding how specific sequences are selected for export. Here, we describe a specific Argonaute protein (exWAGO) that is secreted in extracellular vesicles (EVs) released by the gastrointestinal nematode Heligmosomoides bakeri, at multiple copies per EV. Phylogenetic and gene expression analyses demonstrate exWAGO orthologues are highly conserved and abundantly expressed in related parasites but highly diverged in free-living genus Caenorhabditis. We show that the most abundant small RNAs released from the nematode parasite are not microRNAs as previously thought, but rather secondary small interfering RNAs (siRNAs) that are produced by RNA-dependent RNA Polymerases. The siRNAs that are released in EVs have distinct evolutionary properties compared to those resident in free-living or parasitic nematodes. Immunoprecipitation of exWAGO demonstrates that it specifically associates with siRNAs from transposons and newly evolved repetitive elements that are packaged in EVs and released into the host environment. Together this work demonstrates molecular and evolutionary selectivity in the small RNA sequences that are released in EVs into the host environment and identifies a novel Argonaute protein as the mediator of this. © The Author(s) 2019. Published by Oxford University Press on behalf of Nucleic Acids Research.


April 21, 2020

Dynamic virulence-related regions of the plant pathogenic fungus Verticillium dahliae display enhanced sequence conservation.

Plant pathogens continuously evolve to evade host immune responses. During host colonization, many fungal pathogens secrete effectors to perturb such responses, but these in turn may become recognized by host immune receptors. To facilitate the evolution of effector repertoires, such as the elimination of recognized effectors, effector genes often reside in genomic regions that display increased plasticity, a phenomenon that is captured in the two-speed genome hypothesis. The genome of the vascular wilt fungus Verticillium dahliae displays regions with extensive presence/absence polymorphisms, so-called lineage-specific regions, that are enriched in in planta-induced putative effector genes. As expected, comparative genomics reveals differential degrees of sequence divergence between lineage-specific regions and the core genome. Unanticipated, lineage-specific regions display markedly higher sequence conservation in coding as well as noncoding regions than the core genome. We provide evidence that disqualifies horizontal transfer to explain the observed sequence conservation and conclude that sequence divergence occurs at a slower pace in lineage-specific regions of the V. dahliae genome. We hypothesize that differences in chromatin organisation may explain lower nucleotide substitution rates in the plastic, lineage-specific regions of V. dahliae. © 2019 The Authors. Molecular Ecology Published by John Wiley & Sons Ltd.


April 21, 2020

Full-length transcriptome analysis of Litopenaeus vannamei reveals transcript variants involved in the innate immune system.

To better understand the immune system of shrimp, this study combined PacBio isoform sequencing (Iso-Seq) and Illumina paired-end short reads sequencing methods to discover full-length immune-related molecules of the Pacific white shrimp, Litopenaeus vannamei. A total of 72,648 nonredundant full-length transcripts (unigenes) were generated with an average length of 2545 bp from five main tissues, including the hepatopancreas, cardiac stomach, heart, muscle, and pyloric stomach. These unigenes exhibited a high annotation rate (62,164, 85.57%) when compared against NR, NT, Swiss-Prot, Pfam, GO, KEGG and COG databases. A total of 7544 putative long noncoding RNAs (lncRNAs) were detected and 1164 nonredundant full-length transcripts (449 UniTransModels) participated in the alternative splicing (AS) events. Importantly, a total of 5279 nonredundant full-length unigenes were successfully identified, which were involved in the innate immune system, including 9 immune-related processes, 19 immune-related pathways and 10 other immune-related systems. We also found wide transcript variants, which increased the number and function complexity of immune molecules; for example, toll-like receptors (TLRs) and interferon regulatory factors (IRFs). The 480 differentially expressed genes (DEGs) were significantly higher or tissue-specific expression patterns in the hepatopancreas compared with that in other four tested tissues (FDR <0.05). Furthermore, the expression levels of six selected immune-related DEGs and putative IRFs were validated using real-time PCR technology, substantiating the reliability of the PacBio Iso-seq results. In conclusion, our results provide new genetic resources of long-read full-length transcripts data and information for identifying immune-related genes, which are an invaluable transcriptomic resource as genomic reference, especially for further exploration of the innate immune and defense mechanisms of shrimp. Copyright © 2019 Elsevier Ltd. All rights reserved.


April 21, 2020

TranscriptClean: variant-aware correction of indels, mismatches and splice junctions in long-read transcripts.

Long-read, single-molecule sequencing platforms hold great potential for isoform discovery and characterization of multi-exon transcripts. However, their high error rates are an obstacle to distinguishing novel transcript isoforms from sequencing artifacts. Therefore, we developed the package TranscriptClean to correct mismatches, microindels and noncanonical splice junctions in mapped transcripts using the reference genome while preserving known variants.Our method corrects nearly all mismatches and indels present in a publically available human PacBio Iso-seq dataset, and rescues 39% of noncanonical splice junctions.All Python and R scripts used in this paper are available at https://github.com/dewyman/TranscriptClean.


April 21, 2020

Genome Sequence of Jaltomata Addresses Rapid Reproductive Trait Evolution and Enhances Comparative Genomics in the Hyper-Diverse Solanaceae.

Within the economically important plant family Solanaceae, Jaltomata is a rapidly evolving genus that has extensive diversity in flower size and shape, as well as fruit and nectar color, among its ~80 species. Here, we report the whole-genome sequencing, assembly, and annotation, of one representative species (Jaltomata sinuosa) from this genus. Combining PacBio long reads (25×) and Illumina short reads (148×) achieved an assembly of ~1.45?Gb, spanning ~96% of the estimated genome. Ninety-six percent of curated single-copy orthologs in plants were detected in the assembly, supporting a high level of completeness of the genome. Similar to other Solanaceous species, repetitive elements made up a large fraction (~80%) of the genome, with the most recently active element, Gypsy, expanding across the genome in the last 1-2 Myr. Computational gene prediction, in conjunction with a merged transcriptome data set from 11 tissues, identified 34,725 protein-coding genes. Comparative phylogenetic analyses with six other sequenced Solanaceae species determined that Jaltomata is most likely sister to Solanum, although a large fraction of gene trees supported a conflicting bipartition consistent with substantial introgression between Jaltomata and Capsicum after these species split. We also identified gene family dynamics specific to Jaltomata, including expansion of gene families potentially involved in novel reproductive trait development, and loss of gene families that accompanied the loss of self-incompatibility. This high-quality genome will facilitate studies of phenotypic diversification in this rapidly radiating group and provide a new point of comparison for broader analyses of genomic evolution across the Solanaceae.


April 21, 2020

Effective approaches to study the plant-root knot nematode interaction.

Plant-parasitic nematodes cause major agricultural losses worldwide. Examining the molecular mechanisms underlying plant-nematode interactions and how plants respond to different invading pathogens is attracting major attention to reduce the expanding gap between agricultural production and the needs of the growing world population. This review summarizes the most recent developments in plant-nematode interactions and the diverse approaches used to improve plant resistance against root knot nematode (RKN). We will emphasize the recent rapid advances in genome sequencing technologies, small interfering RNA techniques (RNAi) and targeted genome editing which are contributing to the significant progress in understanding the plant-nematode interaction mechanisms. Also, molecular approaches to improve plant resistance against nematodes are considered.Copyright © 2019 Elsevier Masson SAS. All rights reserved.


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