As the costs for genome sequencing have decreased the number of “genome” sequences have increased at a rapid pace. Unfortunately, the quality and completeness of these so–called “genome” sequences have suffered enormously. We prefer to call such genome assemblies as “gene assembly space” (GAS). We believe it is important to distinguish GAS assemblies from reference genome assemblies (RGAs) as all subsequent research that depends on accurate genome assemblies can be highly compromised if the only assembly available is a GAS assembly.
The free-living flatworm, Macrostomum lignano, much like its better known planarian relative, Schmidtea mediterranea, has an impressive regenerative capacity. Following injury, this species has the ability to regenerate almost an entirely new organism. This is attributable to the presence of an abundant somatic stem cell population, the neoblasts. These cells are also essential for the ongoing maintenance of most tissues, as their loss leads to irreversible degeneration of the animal. This set of unique properties makes a subset of flatworms attractive organisms for studying the evolution of pathways involved in tissue self-renewal, cell fate specification, and regeneration. The use of…
Transmission of arboviruses such as Dengue Virus by Aedes aegypti causes debilitating disease across the globe. Disease in humans can include severe acute symptoms such as hemorrhagic fever and organ failure, but mosquitoes tolerate high titers of virus in a persistent infection. The mechanisms responsible for this viral tolerance are unclear. Recent publications highlighted the integration of genetic material from non-retroviral RNA viruses into the genome of the host during infection that relies upon endogenous retro-transcriptase activity from transposons. These endogenous viral elements (EVEs) found in the genome are predicted to be ancient, and at least some EVEs are under…
Transmission of arboviruses such as Dengue and Zika viruses by Aedes aegypti causes widespread and debilitating disease across the globe. Disease in humans can include severe acute symptoms such as hemorrhagic fever, organ failure, and encephalitis; and yet, mosquitoes tolerate high titers of virus in a persistent infection. The mechanisms responsible for tolerance to viral infection in mosquitoes are still unclear. Recent publications have highlighted the integration of genetic material from non-retroviral RNA viruses into the genome of the host during infection that relies upon endogenous retro-transcriptase activity from transposons. These endogenous viral elements (EVEs) found in the genome are…
PacBio Sequencing is characterized by very long sequence reads (averaging > 10,000 bases), lack of GC-bias, and high consensus accuracy. These features have allowed the method to provide a new gold standard in de novo genome assemblies, producing highly contiguous (contig N50 > 1 Mb) and accurate (> QV 50) genome assemblies. We will briefly describe the technology and then highlight the full workflow, from sample preparation through sequencing to data analysis, on examples of insect genome assemblies, and illustrate the difference these high-quality genomes represent with regard to biological insights, compared to fragmented draft assemblies generated by short-read sequencing.
In this PAG 2018 presentation, Tanya Renner of Pennsylvania State University shares research using PacBio SMRT Sequencing to understand the genomes and transcriptomes of carnivorous plants. She describes the humped bladderwort, Utricularia gibba, as having an extreme genome due to its small size (100 Mbp) despite containing numerous tandem gene duplications and having undergone two whole genome duplications. Renner shares ongoing research into two Drosera species, commonly known as sundews, which through whole genome sequencing are illuminating carnivorous plant genome structural evolution including the transition from monocentric to holocentric chromosomes.
To track stepwise changes in genetic diversity and antimicrobial resistance in rapidly evolving OXA-232-producing Klebsiella pneumoniae ST14, an emerging carbapenem-resistant high-risk clone, in clinical settings.Twenty-six K. pneumoniae ST14 isolates were collected by the Korean Nationwide Surveillance of Antimicrobial Resistance system over the course of 1 year. Isolates were subjected to whole-genome sequencing and MIC determinations using 33 antibiotics from 14 classes.Single-nucleotide polymorphism (SNP) typing identified 72 unique SNP sites spanning the chromosomes of the isolates, dividing them into three clusters (I, II and III). The initial isolate possessed two plasmids with 18 antibiotic-resistance genes, including blaOXA-232, and exhibited resistance to 11 antibiotic…
Horizontal transfer of plasmids encoding antimicrobial-resistance and virulence determinants has been instrumental in Staphylococcus aureus evolution, including the emergence of community-associated methicillin-resistant S. aureus (CA-MRSA). In the early 1990s the first CA-MRSA isolated in Western Australia (WA), WA-5, encoded cadmium, tetracycline and penicillin-resistance genes on plasmid pWBG753 (~30 kb). WA-5 and pWBG753 appeared only briefly in WA, however, fusidic-acid-resistance plasmids related to pWBG753 were also present in the first European CA-MRSA at the time. Here we characterized a 72-kb conjugative plasmid pWBG731 present in multiresistant WA-5-like clones from the same period. pWBG731 was a cointegrant formed from pWBG753 and a…
Acinetobacter calcoaceticus-baumannii complex isolates have been frequently associated with hospital and community infections, with A. baumannii being the most common. Other Acinetobacter spp. not belonging to this complex also cause infections in hospital settings, and the incidence has increased over the past few years. Some species of the Acinetobacter genus possess a great diversity of antibiotic resistance mechanisms, such as efflux pumps, porins, and resistance genes that can be acquired and disseminated by mobilizable genetic elements. By means of whole-genome sequencing, we describe in the clinical Acinetobacter haemolyticus strain AN54 different mechanisms of resistance that involve blaOXA-265, blaNDM-1, aphA6, aac(6′)-Ig,…
Orchardgrass (Dactylis glomerata L.) is an important forage grass for cultivating livestock worldwide. Here, we report an ~1.84-Gb chromosome-scale diploid genome assembly of orchardgrass, with a contig N50 of 0.93 Mb, a scaffold N50 of 6.08 Mb and a super-scaffold N50 of 252.52 Mb, which is the first chromosome-scale assembled genome of a cool-season forage grass. The genome includes 40 088 protein-coding genes, and 69% of the assembled sequences are transposable elements, with long terminal repeats (LTRs) being the most abundant. The LTRretrotransposons may have been activated and expanded in the grass genome in response to environmental changes during the Pleistocene between 0 and…
Horizontal gene transfer (HGT), the movement and genomic integration of DNA across species boundaries, is commonly associated with bacteria and other microorganisms, but functional HGT (fHGT) is increasingly being recognized in heterotrophic parasitic plants that obtain their nutrients and water from their host plants through direct haustorial feeding. Here, in the holoparasitic stem parasite Cuscuta, we identify 108?transcribed and probably functional HGT events in Cuscuta campestris and related species, plus 42?additional regions with host-derived transposon, pseudogene and non-coding sequences. Surprisingly, 18?Cuscuta fHGTs were acquired from the same gene families by independent HGT events in Orobanchaceae parasites, and the majority are…
Lactic acid bacteria (LAB) confer health benefits to human when administered orally. We have recently isolated several species of LAB strains from plant sources, such as fruits, vegetables, flowers, and medicinal plants. Since antibiotics used to treat bacterial infection diseases induce the emergence of drug-resistant bacteria in intestinal microflora, it is important to evaluate the susceptibility of LAB strains to antibiotics to ensure the safety and security of processed foods. The aim of the present study is to determine the minimum inhibitory concentration (MIC) of antibiotics against several plant-derived LAB strains. When aminoglycoside antibiotics, such as streptomycin (SM), kanamycin (KM), and…
Over the past decade, RNA sequencing (RNA-seq) has become an indispensable tool for transcriptome-wide analysis of differential gene expression and differential splicing of mRNAs. However, as next-generation sequencing technologies have developed, so too has RNA-seq. Now, RNA-seq methods are available for studying many different aspects of RNA biology, including single-cell gene expression, translation (the translatome) and RNA structure (the structurome). Exciting new applications are being explored, such as spatial transcriptomics (spatialomics). Together with new long-read and direct RNA-seq technologies and better computational tools for data analysis, innovations in RNA-seq are contributing to a fuller understanding of RNA biology, from questions…
Forest tree species are increasingly subject to severe mortalities from exotic pests, diseases, and invasive organisms, accelerated by climate change. Forest health issues are threatening multiple species and ecosystem sustainability globally. While sources of resistance may be available in related species, or among surviving trees, introgression of resistance genes into threatened tree species in reasonable time frames requires genome-wide breeding tools. Asian species of chestnut (Castanea spp.) are being employed as donors of disease resistance genes to restore native chestnut species in North America and Europe. To aid in the restoration of threatened chestnut species, we present the assembly of…
Sequencing technology and assembly algorithms have matured to the point that high-quality de novo assembly is possible for large, repetitive genomes. Current assemblies traverse transposable elements (TEs) and allow for annotation of TEs. There are numerous methods for each class of elements with unknown relative performance metrics. We benchmarked existing programs based on a curated library of rice TEs. Using the most robust programs, we created a comprehensive pipeline called Extensive de-novo TE Annotator (EDTA) that produces a condensed TE library for annotations of structurally intact and fragmented elements. EDTA is open-source and freely available: https://github.com/oushujun/EDTA.List of abbreviationsTETransposable ElementsLTRLong Terminal…