Menu

Auto Tag: Genome assembly

September 22, 2019

Comparative genomics of Czech vaccine strains of Bordetella pertussis.

Bordetella pertussis is a strictly human pathogen causing the respiratory infectious disease called whooping cough or pertussis. B. pertussis adaptation to acellular pertussis vaccine pressure has been repeatedly highlighted, but recent data indicate that adaptation of circulating strains started already in the era of the whole cell pertussis vaccine (wP) use. We sequenced the genomes of five B. pertussis wP vaccine strains isolated in the former Czechoslovakia in the pre-wP (1954-1957) and early wP (1958-1965) eras, when only limited population travel into and out of the country was possible. Four isolates exhibit a similar genome organization and form a distinct phylogenetic cluster with a geographic signature. The fifth strain is rather distinct, both in genome organization and SNP-based phylogeny. Surprisingly, despite isolation of this strain before 1966, its closest sequenced relative appears to be a recent isolate from the US. On the genome content level, the five vaccine strains contained both new and already described regions of difference. One of the new regions contains duplicated genes potentially associated with transport across the membrane. The prevalence of this region in recent isolates indicates that its spread might be associated with selective advantage leading to increased strain fitness.

Read more
September 22, 2019

High genomic variability in the plant pathogenic bacterium Pectobacterium parmentieri deciphered from de novo assembled complete genomes.

Pectobacterium parmentieri is a newly established species within the plant pathogenic family Pectobacteriaceae. Bacteria belonging to this species are causative agents of diseases in economically important crops (e.g. potato) in a wide range of different environmental conditions, encountered in Europe, North America, Africa, and New Zealand. Severe disease symptoms result from the activity of P. parmentieri virulence factors, such as plant cell wall degrading enzymes. Interestingly, we observe significant phenotypic differences among P. parmentieri isolates regarding virulence factors production and the abilities to macerate plants. To establish the possible genomic basis of these differences, we sequenced 12 genomes of P. parmentieri strains (10 isolated in Poland, 2 in Belgium) with the combined use of Illumina and PacBio approaches. De novo genome assembly was performed with the use of SPAdes software, while annotation was conducted by NCBI Prokaryotic Genome Annotation Pipeline.The pan-genome study was performed on 15 genomes (12 de novo assembled and three reference strains: P. parmentieri CFBP 8475T, P. parmentieri SCC3193, P. parmentieri WPP163). The pan-genome includes 3706 core genes, a high number of accessory (1468) genes, and numerous unique (1847) genes. We identified the presence of well-known genes encoding virulence factors in the core genome fraction, but some of them were located in the dispensable genome. A significant fraction of horizontally transferred genes, virulence-related gene duplications, as well as different CRISPR arrays were found, which can explain the observed phenotypic differences. Finally, we found also, for the first time, the presence of a plasmid in one of the tested P. parmentieri strains isolated in Poland.We can hypothesize that a large number of the genes in the dispensable genome and significant genomic variation among P. parmentieri strains could be the basis of the potential wide host range and widespread diffusion of P. parmentieri. The obtained data on the structure and gene content of P. parmentieri strains enabled us to speculate on the importance of high genomic plasticity for P. parmentieri adaptation to different environments.

Read more
September 22, 2019

The sequence of a male-specific genome region containing the sex determination switch in Aedes aegypti.

Aedes aegypti is the principal vector of several important arboviruses. Among the methods of vector control to limit transmission of disease are genetic strategies that involve the release of sterile or genetically modified non-biting males, which has generated interest in manipulating mosquito sex ratios. Sex determination in Ae. aegypti is controlled by a non-recombining Y chromosome-like region called the M locus, yet characterisation of this locus has been thwarted by the repetitive nature of the genome. In 2015, an M locus gene named Nix was identified that displays the qualities of a sex determination switch.With the use of a whole-genome bacterial artificial chromosome (BAC) library, we amplified and sequenced a ~200 kb region containing the male-determining gene Nix. In this study, we show that Nix is comprised of two exons separated by a 99 kb intron primarily composed of repetitive DNA, especially transposable elements.Nix, an unusually large and highly repetitive gene, exhibits features in common with Y chromosome genes in other organisms. We speculate that the lack of recombination at the M locus has allowed the expansion of repeats in a manner characteristic of a sex-limited chromosome, in accordance with proposed models of sex chromosome evolution in insects.

Read more
September 22, 2019

Genome sequence of the cauliflower mushroom Sparassis crispa (Hanabiratake) and its association with beneficial usage.

Sparassis crispa (Hanabiratake) is a widely used medicinal mushroom in traditional Chinese medicine because it contains materials with pharmacological activity. Here, we report its 39.0-Mb genome, encoding 13,157 predicted genes, obtained using next-generation sequencing along with RNA-seq mapping data. A phylogenetic analysis by comparison with 25 other fungal genomes revealed that S. crispa diverged from Postia placenta, a brown-rot fungus, 94 million years ago. Several features specific to the genome were found, including the A-mating type locus with the predicted genes for HD1 and HD2 heterodomain transcription factors, the mitochondrial intermediate peptidase (MIP), and the B-mating type locus with seven potential pheromone receptor genes and three potential pheromone precursor genes. To evaluate the benefits of the extract and chemicals from S. crispa, we adopted two approaches: (1) characterization of carbohydrate-active enzyme (CAZyme) genes and ß-glucan synthase genes and the clusters of genes for the synthesis of second metabolites, such as terpenes, indoles and polyketides, and (2) identification of estrogenic activity in its mycelial extract. Two potential ß-glucan synthase genes, ScrFKS1 and ScrFKS2, corresponding to types I and II, respectively, characteristic of Agaricomycetes mushrooms, were newly identified by the search for regions homologous to the reported features of ß-glucan synthase genes; both contained the characteristic transmembrane regions and the regions homologous to the catalytic domain of the yeast ß-glucan synthase gene FKS1. Rapid estrogenic cell-signaling and DNA microarray-based transcriptome analyses revealed the presence of a new category of chemicals with estrogenic activity, silent estrogens, in the extract. The elucidation of the S. crispa genome and its genes will expand the potential of this organism for medicinal and pharmacological purposes.

Read more
September 22, 2019

Convergent evolution of complex genomic rearrangements in two fungal meiotic drive elements.

Meiotic drive is widespread in nature. The conflict it generates is expected to be an important motor for evolutionary change and innovation. In this study, we investigated the genomic consequences of two large multi-gene meiotic drive elements, Sk-2 and Sk-3, found in the filamentous ascomycete Neurospora intermedia. Using long-read sequencing, we generated the first complete and well-annotated genome assemblies of large, highly diverged, non-recombining regions associated with meiotic drive elements. Phylogenetic analysis shows that, even though Sk-2 and Sk-3 are located in the same chromosomal region, they do not form sister clades, suggesting independent origins or at least a long evolutionary separation. We conclude that they have in a convergent manner accumulated similar patterns of tandem inversions and dense repeat clusters, presumably in response to similar needs to create linkage between genes causing drive and resistance.

Read more
September 22, 2019

Whole genome sequencing for investigations of meningococcal outbreaks in the United States: a retrospective analysis.

Although rare in the U.S., outbreaks due to Neisseria meningitidis do occur. Rapid, early outbreak detection is important for timely public health response. In this study, we characterized U.S. meningococcal isolates (N?=?201) from 15 epidemiologically defined outbreaks (2009-2015) along with temporally and geographically matched sporadic isolates using multilocus sequence typing, pulsed-field gel electrophoresis (PFGE), and six whole genome sequencing (WGS) based methods. Recombination-corrected maximum likelihood (ML) and Bayesian phylogenies were reconstructed to identify genetically related outbreak isolates. All WGS analysis methods showed high degree of agreement and distinguished isolates with similar or indistinguishable PFGE patterns, or the same strain genotype. Ten outbreaks were caused by a single strain; 5 were due to multiple strains. Five sporadic isolates were phylogenetically related to 2 outbreaks. Analysis of 9 outbreaks using timed phylogenies identified the possible origin and estimated the approximate time that the most recent common ancestor emerged for outbreaks analyzed. U.S. meningococcal outbreaks were caused by single- or multiple-strain introduction, with organizational outbreaks mainly caused by a clonal strain and community outbreaks by divergent strains. WGS can infer linkage of meningococcal cases when epidemiological links are uncertain. Accurate identification of outbreak-associated cases requires both WGS typing and epidemiological data.

Read more
September 22, 2019

The pathogenic mechanisms of Tilletia horrida as revealed by comparative and functional genomics.

Tilletia horrida is a soil-borne, mononucleate basidiomycete fungus with a biotrophic lifestyle that causes rice kernel smut, a disease that is distributed throughout hybrid rice growing areas worldwide. Here we report on the high-quality genome sequence of T. horrida; it is composed of 23.2?Mb that encode 7,729 predicted genes and 6,973 genes supported by RNA-seq. The genome contains few repetitive elements that account for 8.45% of the total. Evolutionarily, T. horrida lies close to the Ustilago fungi, suggesting grass species as potential hosts, but co-linearity was not observed between T. horrida and the barley smut Ustilago hordei. Genes and functions relevant to pathogenicity were presumed. T. horrida possesses a smaller set of carbohydrate-active enzymes and secondary metabolites, which probably reflect the specific characteristics of its infection and biotrophic lifestyle. Genes that encode secreted proteins and enzymes of secondary metabolism, and genes that are represented in the pathogen-host interaction gene database genes, are highly expressed during early infection; this is consistent with their potential roles in pathogenicity. Furthermore, among the 131 candidate pathogen effectors identified according to their expression patterns and functionality, we validated two that trigger leaf cell death in Nicotiana benthamiana. In summary, we have revealed new molecular mechanisms involved in the evolution, biotrophy, and pathogenesis of T. horrida.

Read more
September 22, 2019

First draft genome sequence of the rock bream in the family Oplegnathidae.

The rock bream (Oplegnathus fasciatus) is one of the most economically valuable marine fish in East Asia, and due to various environmental factors, there is substantial revenue loss in the production sector. Therefore, knowledge of its genome is required to uncover the genetic factors and the solutions to these problems. In this study, we constructed the first draft genome of O. fasciatus as a reference for the family Oplegnathidae. The genome size is estimated to be 749?Mb, and it was assembled into 766?Mb by combining Illumina and PacBio sequences. A total of 24,053 transcripts (23,338 genes) are predicted, and among those transcripts, 23,362 (97%), are annotated with functional terms. Finally, the completeness of the genome assembly was assessed by CEGMA, which resulted in the complete mapping of 220 (88.7%) core genes in the genome. To the best of our knowledge, this is the first draft genome for the family Oplegnathidae.

Read more
September 22, 2019

Whole genome sequencing and microsatellite analysis of the Plasmodium falciparum E5 NF54 strain show that the var, rifin and stevor gene families follow Mendelian inheritance.

Plasmodium falciparum exhibits a high degree of inter-isolate genetic diversity in its variant surface antigen (VSA) families: P. falciparum erythrocyte membrane protein 1, repetitive interspersed family (RIFIN) and subtelomeric variable open reading frame (STEVOR). The role of recombination for the generation of this diversity is a subject of ongoing research. Here the genome of E5, a sibling of the 3D7 genome strain is presented. Short and long read whole genome sequencing (WGS) techniques (Ilumina, Pacific Bioscience) and a set of 84 microsatellites (MS) were employed to characterize the 3D7 and non-3D7 parts of the E5 genome. This is the first time that VSA genes in sibling parasites were analysed with long read sequencing technology.Of the 5733 E5 genes only 278 genes, mostly var and rifin/stevor genes, had no orthologues in the 3D7 genome. WGS and MS analysis revealed that chromosomal crossovers occurred at a rate of 0-3 per chromosome. var, stevor and rifin genes were inherited within the respective non-3D7 or 3D7 chromosomal context. 54 of the 84 MS PCR fragments correctly identified the respective MS as 3D7- or non-3D7 and this correlated with var and rifin/stevor gene inheritance in the adjacent chromosomal regions. E5 had 61 var and 189 rifin/stevor genes. One large non-chromosomal recombination event resulted in a new var gene on chromosome 14. The remainder of the E5 3D7-type subtelomeric and central regions were identical to 3D7.The data show that the rifin/stevor and var gene families represent the most diverse compartments of the P. falciparum genome but that the majority of var genes are inherited without alterations within their respective parental chromosomal context. Furthermore, MS genotyping with 54 MS can successfully distinguish between two sibling progeny of a natural P. falciparum cross and thus can be used to investigate identity by descent in field isolates.

Read more
September 22, 2019

Genome sequence of the brown rot fungal pathogen Monilinia fructigena.

Monilinia fructigena (phylum Ascomycota, family Sclerotiniaceae) is a plant pathogen that causes brown rot and blossom blight in pome fruit and stone fruit of the Rosaceae family, which can cause significant losses in the field and mainly postharvest. The aim of this study was to create a high-quality draft of the M. fructigena genome assembly and annotation that provides better understanding of the epidemiology of the pathogen and its interactions with the host(s) and will thus improve brown rot management.We report here on the genome sequence of M. fructigena strain Mfrg269 that was collected from plum in southern Italy. This is assembled into 131 scaffolds, with a total size of 43.125 Mb, with 9960 unique protein-coding genes. The novel genomic resources allow improved genomic comparisons among the most important pathogens belonging to the Monilinia genus, with the aim being to improve the knowledge of their plant-pathogen interactions, population biology, and control.

Read more
September 22, 2019

Genomic analysis of the Phalaenopsis pathogen Dickeya sp. PA1, representing the emerging species Dickeya fangzhongdai.

Dickeya sp. strain PA1 is the causal agent of bacterial soft rot in Phalaenopsis, an important indoor orchid in China. PA1 and a few other strains were grouped into a novel species, Dickeya fangzhongdai, and only the orchid-associated strains have been shown to cause soft rot symptoms.We constructed the complete PA1 genome sequence and used comparative genomics to explore the differences in genomic features between D. fangzhongdai and other Dickeya species.PA1 has a 4,979,223-bp circular genome with 4269 predicted protein-coding genes. D. fangzhongdai was phylogenetically similar to Dickeya solani and Dickeya dadantii. The type I to type VI secretion systems (T1SS-T6SS), except for the stt-type T2SS, were identified in D. fangzhongdai. The three phylogenetically similar species varied significantly in terms of their T5SSs and T6SSs, as did the different D. fangzhongdai strains. Genomic island (GI) prediction and synteny analysis (compared to D. fangzhongdai strains) of PA1 also indicated the presence of T5SSs and T6SSs in strain-specific regions. Two typical CRISPR arrays were identified in D. fangzhongdai and in most other Dickeya species, except for D. solani. CRISPR-1 was present in all of these Dickeya species, while the presence of CRISPR-2 varied due to species differentiation. A large polyketide/nonribosomal peptide (PK/NRP) cluster, similar to the zeamine biosynthetic gene cluster in Dickeya zeae rice strains, was discovered in D. fangzhongdai and D. solani. The D. fangzhongdai and D. solani strains might recently have acquired this gene cluster by horizontal gene transfer (HGT).Orchid-associated strains are the typical members of D. fangzhongdai. Genomic analysis of PA1 suggested that this strain presents the genomic characteristics of this novel species. Considering the absence of the stt-type T2SS, the presence of CRISPR loci and the zeamine biosynthetic gene cluster, D. fangzhongdai is likely a transitional form between D. dadantii and D. solani. This is supported by the later acquisition of the zeamine cluster and the loss of CRISPR arrays by D. solani. Comparisons of phylogenetic positions and virulence determinants could be helpful for the effective quarantine and control of this emerging species.

Read more
September 22, 2019

Assembling the genome of the African wild rice Oryza longistaminata by exploiting synteny in closely related Oryza species.

The African wild rice species Oryza longistaminata has several beneficial traits compared to cultivated rice species, such as resistance to biotic stresses, clonal propagation via rhizomes, and increased biomass production. To facilitate breeding efforts and functional genomics studies, we de-novo assembled a high-quality, haploid-phased genome. Here, we present our assembly, with a total length of 351?Mb, of which 92.2% was anchored onto 12 chromosomes. We detected 34,389 genes and 38.1% of the genome consisted of repetitive content. We validated our assembly by a comparative linkage analysis and by examining well-characterized gene families. This genome assembly will be a useful resource to exploit beneficial alleles found in O. longistaminata. Our results also show that it is possible to generate a high-quality, functionally complete rice genome assembly from moderate SMRT read coverage by exploiting synteny in a closely related Oryza species.

Read more
September 22, 2019

Genomic structural variations within five continental populations of Drosophila melanogaster.

Chromosomal structural variations (SV) including insertions, deletions, inversions, and translocations occur within the genome and can have a significant effect on organismal phenotype. Some of these effects are caused by structural variations containing genes. Large structural variations represent a significant amount of the genetic diversity within a population. We used a global sampling of Drosophila melanogaster (Ithaca, Zimbabwe, Beijing, Tasmania, and Netherlands) to represent diverse populations within the species. We used long-read sequencing and optical mapping technologies to identify SVs in these genomes. Among the five lines examined, we found an average of 2,928 structural variants within these genomes. These structural variations varied greatly in size and location, included many exonic regions, and could impact adaptation and genomic evolution. Copyright © 2018 Long et al.

Read more
September 22, 2019

Genome-wide researches and applications on Dendrobium.

This review summarizes current knowledge of chromosome characterization, genetic mapping, genomic sequencing, quality formation, floral transition, propagation, and identification in Dendrobium. The widely distributed Dendrobium has been studied for a long history, due to its important economic values in both medicine and ornamental. In recent years, some species of Dendrobium and other orchids had been reported on genomic sequences, using the next-generation sequencing technology. And the chloroplast genomes of many Dendrobium species were also revealed. The chromosomes of most Dendrobium species belong to mini-chromosomes, and showed 2n?=?38. Only a few of genetic studies were reported in Dendrobium. After revealing of genomic sequences, the techniques of transcriptomics, proteomics and metabolomics could be employed on Dendrobium easily. Some other molecular biological techniques, such as gene cloning, gene editing, genetic transformation and molecular marker developing, had also been applied on the basic research of Dendrobium, successively. As medicinal plants, insights into the biosynthesis of some medicinal components were the most important. As ornamental plants, regulation of flower related characteristics was the most important. More, knowledge of growth and development, environmental interaction, evolutionary analysis, breeding of new cultivars, propagation, and identification of species and herbs were also required for commercial usage. All of these studies were improved using genomic sequences and related technologies. To answer some key scientific issues in Dendrobium, quality formation, flowering, self-incompatibility and seed germination would be the focus of future research. And genome related technologies and studies would be helpful.

Read more
September 22, 2019

Haematococcus lacustris: the makings of a giant-sized chloroplast genome.

Recent work on the chlamydomonadalean green alga Haematococcus lacustris uncovered the largest plastid genome on record: a whopping 1.35 Mb with >90 % non-coding DNA. A 500-word description of this genome was published in the journal Genome Announcements. But such a short report for such a large genome leaves many unanswered questions. For instance, the H. lacustris plastome was found to encode only 12 tRNAs, less than half that of a typical plastome, it appears to have a non-standard genetic code, and is one of only a few known plastid DNAs (ptDNAs), out of thousands of available sequences, not biased in adenine and thymine. Here, I take a closer look at the H. lacustris plastome, comparing its size, content and architecture to other large organelle DNAs, including those from close relatives in the Chlamydomonadales. I show that the H. lacustris plastid coding repertoire is not as unusual as initially thought, representing a standard set of rRNAs, tRNAs and protein-coding genes, where the canonical stop codon UGA appears to sometimes signify tryptophan. The intergenic spacers are dense with repeats, and it is within these regions where potential answers to the source of such extreme genomic expansion lie. By comparing ptDNA sequences of two closely related strains of H. lacustris, I argue that the mutation rate of the non-coding DNA is high and contributing to plastome inflation. Finally, by exploring publicly available RNA-sequencing data, I find that most of the intergenic ptDNA is transcriptionally active.

Read more

Subscribe for blog updates:

Talk with an expert

If you have a question, need to check the status of an order, or are interested in purchasing an instrument, we're here to help.