Uncovering Genomic Features and Maternal Origin of Korean Native Chicken by Whole Genome Sequencing

The Korean Native Chicken (KNC) is an important endemic biological resource in Korea. While numerous studies have been conducted exploring this breed, none have used next-generation sequencing to identify its specific genomic features. We sequenced five strains of KNC and identified 10.9 million SNVs and 1.3 million InDels. Through the analysis, we found that the highly variable region common to all 5 strains had genes like PCHD15, CISD1, PIK3C2A, and NUCB2 that might be related to the phenotypic traits of the chicken such as auditory sense, growth rate and egg traits. In addition, we assembled unaligned reads that could not be mapped to the reference genome. By assembling the unaligned reads, we were able to present genomic sequences characteristic to the KNC. Based on this, we also identified genes related to the olfactory receptors and antigen that are common to all 5 strains. Finally, through the reconstructed mitochondrial genome sequences, we performed phylogenomic analysis and elucidated the maternal origin of the artificially restored KNC. Our results revealed that the KNC has multiple maternal origins which are in agreement with Korea''s history of chicken breed imports. The results presented here provide a valuable basis for future research on genomic features of KNC and further understanding of KNC''s origin.     

The Role of Heme Binding by DNA-protective Protein from Starved Cells (Dps) in the Tolerance of Porphyromonas gingivalis to Heme Toxicity

The widely expressed DNA-protective protein from starved-cells (Dps) family proteins are considered major contributors to prokaryotic resistance to stress. We show here that Porphyromonas gingivalis Dps (PgDps), previously described as an iron-storage and DNA-binding protein, also mediates heme sequestration. We determined that heme binds strongly to PgDps with an apparent K_d of 3.7 × 10⁻⁸ m and is coordinated by a single surface-located cysteine at the fifth axial ligand position. Heme and iron sequestered in separate sites by PgDps provide protection of DNA from H₂O₂-mediated free radical damage and were found to be important for growth of P. gingivalis under excess heme as the only iron source. Conservation of the heme-coordinating cysteine among Dps isoforms from the Bacteroidales order suggests that this function may be a common feature within these anaerobic bacteria.     

Calcium Regulates the Activity and Structural Stability of Tpr,a Bacterial Calpain-like Peptidase

Porphyromonas gingivalis is a peptide-fermenting asaccharolytic periodontal pathogen. Its genome contains several genes encoding cysteine peptidases other than gingipains. One of these genes (PG1055) encodes a protein called Tpr (thiol protease) that has sequence similarity to cysteine peptidases of the papain and calpain families. In this study we biochemically characterize Tpr. We found that the 55-kDa Tpr inactive zymogen proteolytically processes itself into active forms of 48, 37, and 33 kDa via sequential truncations at the N terminus. These processed molecular forms of Tpr are associated with the bacterial outer membrane where they are likely responsible for the generation of metabolic peptides required for survival of the pathogen. Both autoprocessing and activity were dependent on calcium concentrations >1 mm, consistent with the protein''s activity within the intestinal and inflammatory milieus. Calcium also stabilized the Tpr structure and rendered the protein fully resistant to proteolytic degradation by gingipains. Together, our findings suggest that Tpr is an example of a bacterial calpain, a calcium-responsive peptidase that may generate substrates required for the peptide-fermenting metabolism of P. gingivalis. Aside from nutrient generation, Tpr may also be involved in evasion of host immune response through degradation of the antimicrobial peptide LL-37 and complement proteins C3, C4, and C5. Taken together, these results indicate that Tpr likely represents an important pathogenesis factor for P. gingivalis.     

Resequencing the Mycobacterium avium subsp. paratuberculosis K10 Genome: Improved Annotation and Revised Genome Sequence

We report the resequencing and revised annotation of the Mycobacterium avium subsp. paratuberculosis K10 genome. A total of 90 single-nucleotide errors and a 51-bp indel in the original K10 genome were corrected, and the whole genome annotation was revised. Correction of these sequencing errors resulted in 28 frameshift alterations. The amended genome sequence is accessible via the supplemental section of study SRR060191 in the NCBI Sequence Read Archive and will serve as a valuable reference genome for future studies.The American bovine isolate K10 remains the only Mycobacterium avium subsp. paratuberculosis genome to be fully sequenced and published to date (1). Although this 4.8-Mbp genome likely contains some assembly errors (3), it has provided, and will continue to provide, an invaluable resource for Mycobacterium research. The assembly errors were identified through optical mapping of related M. avium subsp. paratuberculosis strain ATCC 19698, which revealed a 648-kb inversion around the origin of replication and two additional copies of the insertion sequences IS1311 and IS_MAP03 (3). These findings were subsequently validated via PCR, Southern blotting, and (Sanger) sequence analysis in ATCC 19698 and were also confirmed to be present in K10 (3). We designate this interim corrected genome M. avium subsp. paratuberculosis K10′. To further improve this resource, we undertook a resequencing project of the original M. avium subsp. paratuberculosis K10 genome.Whole-genome sequencing was performed on the Illumina GAIIx platform using one flow cell lane with 36-cycle paired-end chemistry. Reads were variably trimmed at the 3′ end based on the Illumina Read Segment Quality Indicator (Illumina manual), and read pairs containing ambiguous bases were removed. Read mapping onto the K10′ genome sequence was performed using SHRiMP (ver. 1.3.2) (2), and single-nucleotide polymorphisms and indels (deletion and insertion polymorphisms [DIPs]) were called using Nesoni (ver. 0.29; Monash University Victorian Bioinformatics Consortium) with default parameters. Read mapping determined that the data set comprised an average sequence coverage of 72.6 across the K10′ genome. This high sequence coverage allowed differences between K10\K10′ and the resequenced version of the genome, designated K10", to be identified with high confidence.Ninety single-nucleotide differences and one 51-bp indel were identified in the K10" genome. As confirmation that these differences are likely to represent errors in the original genome sequence, we have also detected these polymorphisms in two additional bovine M. avium subsp. paratuberculosis genomes recently sequenced and assembled within our laboratory (data not shown). Seven of the 90 differences and the 51-bp indel were subjected to PCR and Sanger sequencing for verification. All of the polymorphisms were confirmed to be present in K10" compared to the original genome sequence.Thirty-six single-nucleotide deletions and four nucleotide insertions were identified in K10" compared to the reference. These DIPs resulted in 27 frameshift mutations of protein coding loci. As a consequence of these frameshifts, one complete coding sequence (CDS) feature was removed (MAPK_3751), one novel CDS was created (MAPK_2081b), and one pseudogene was repaired (MAPK_4158-4159). In almost all of the other cases, the frameshifts resulted in proteins which more closely resembled their orthologs in M. avium subsp. hominissuis and M. intracellulare. Other frameshifts of biological interest include the truncation of a PPE family protein (MAPK_1173) and the extension of an MCE (mammalian cell entry) family protein (MAPK_4086). Compared to the reference, K10" also had a 51-bp indel within a possible MCE family protein (MAPK_1575). This indel consisted of an 11-bp deletion (bases 2436510 to 2436520 in the original K10 sequence) and an insertion of 51 bp. The resulting protein sequence now more closely resembles orthologs of the MCE family in other Mycobacterium spp. In conclusion, the fact that so many of the amended bases have resulted in revised coding regions indicates the underlying importance of this exercise.     

Complete Genome Sequence of the Plant Pathogen Erwinia amylovora Strain ATCC 49946

Erwinia amylovora causes the economically important disease fire blight that affects rosaceous plants, especially pear and apple. Here we report the complete genome sequence and annotation of strain ATCC 49946. The analysis of the sequence and its comparison with sequenced genomes of closely related enterobacteria revealed signs of pathoadaptation to rosaceous hosts.Erwinia amylovora, a plant-associated member of the Enterobacteriaceae, causes fire blight, a devastating disease of rosaceous plants, especially pear and apple (6). The complete genome of Ea273 (ATCC 49946), a virulent strain isolated from an infected apple tree in New York State, was sequenced. Total DNA was extracted and prepared in pMAQ1 shotgun libraries. The complete shotgun sequence was obtained by using dye terminator chemistry in ABI 3730 automated sequencers and contains 88,457 reads (11.12-fold coverage), yielding a theoretical coverage of the genome of 99.99%. The sequence was assembled, finished, and annotated as described previously (1, 5), using Artemis (4) to collate data and facilitate annotation.The genome of E. amylovora consists of a circular chromosome of 3,805,874 bp and two plasmids, AMYP1 (28,243 bp) and AMYP2 (71,487 bp). Coding regions in the chromosome account for 85.1% of the total sequence, with 3,483 identified coding sequences (CDS). Two hundred fifty-four (7%) of the CDSs do not have any matches in current NCBI databases; 114 (3.3%) correspond to conserved hypothetical proteins. Forty-nine CDSs (1.4%) are similar to genes from mobile elements such as integrases, transposases, and bacteriophages, and 110 CDSs (3.2%) were classified as pseudogenes due to interruptions or truncations of the CDSs. The remaining 2,956 annotated CDSs include among other categories genes involved in biosynthesis of the cellular envelope and modifications of surface proteins (299 CDSs [11%]) and genes involved in signal transduction and regulation (228 CDSs [8%]). Seven rRNA operons and 78 tRNA sequences were identified in the chromosome; two new clusters were identified (AMY1550-1575 and AMY2648-2676) that resemble the T3SS-encoding SSR-1 island of Sodalis glossinidius (2), and four clusters that contain genes for biosynthesis of flagella, which based on their location might be regulated independently.The smaller plasmid, AMYP1, had been reported as pEA29 (3); its sequence is nearly identical to the one reported here. The larger plasmid, AMYP2, renamed pEA72 for consistency in nomenclature, contains 87 predicted CDSs, with two predicted mobile-element-related CDSs and one pseudogene. Among the CDSs with annotated functions are a cluster of genes (AMYP2_49 to AMYP2_62) that encode a putative type IV fimbrial system (pil genes).The genome of E. amylovora is only 3.8 Mb long, whereas most free-living enterobacteria, including plant pathogens, have genomes of 4.5 Mb to 5.5 Mb. Comparison of the genome of Ea273 with the sequenced genomes of 15 closely related enterobacteria identified 21 lineage-specific regions, which might be considered genomic islands. E. amylovora has many more predicted pseudogenes, relative to other enterobacteria with similar lifestyles. Given its size and the preponderance of pseudogenes, genome reduction may have occurred via mutational inactivation and subsequent deletion with the following consequences: E. amylovora has fewer genes involved in anaerobic respiration and fermentation than are found in typical related enterobacteria; this likely result in a reduced capacity to live in anaerobic environments.The genome sequence of E. amylovora has revealed clear signs of pathoadaptation to the rosaceous plant environment. For example, T3SS-related proteins are present that are more similar to proteins of other plant pathogens than to proteins of closely related enterobacteria. These include type III effectors, homologous to those of plant-pathogenic pseudomonads, which confer virulence to E. amylovora in plants, and a sorbitol-metabolizing cluster that may confer a competitive advantage for survival in rosaceous plants. The reduced genome size and erosion or loss of genes involved in anaerobic respiration and nitrate assimilation are remarkable, relative to other plant- and animal-pathogenic members of the Enterobacteriaceae.     

Characterization of Genomic Deletion Efficiency Mediated by Clustered Regularly Interspaced Palindromic Repeats (CRISPR)/Cas9 Nuclease System in Mammalian Cells

The clustered regularly interspaced palindromic repeats (CRISPR)/CRISPR-associated (Cas) 9 nuclease system has provided a powerful tool for genome engineering. Double strand breaks may trigger nonhomologous end joining repair, leading to frameshift mutations, or homology-directed repair using an extrachromosomal template. Alternatively, genomic deletions may be produced by a pair of double strand breaks. The efficiency of CRISPR/Cas9-mediated genomic deletions has not been systematically explored. Here, we present a methodology for the production of deletions in mammalian cells, ranging from 1.3 kb to greater than 1 Mb. We observed a high frequency of intended genomic deletions. Nondeleted alleles are nonetheless often edited with inversions or small insertion/deletions produced at CRISPR recognition sites. Deleted alleles also typically include small insertion/deletions at predicted deletion junctions. We retrieved cells with biallelic deletion at a frequency exceeding that of probabilistic expectation. We demonstrate an inverse relationship between deletion frequency and deletion size. This work suggests that CRISPR/Cas9 is a robust system to produce a spectrum of genomic deletions to allow investigation of genes and genetic elements.     

Pdsg1 and Pdsg2, Novel Proteins Involved in Developmental Genome Remodelling in Paramecium

The epigenetic influence of maternal cells on the development of their progeny has long been studied in various eukaryotes. Multicellular organisms usually provide their zygotes not only with nutrients but also with functional elements required for proper development, such as coding and non-coding RNAs. These maternally deposited RNAs exhibit a variety of functions, from regulating gene expression to assuring genome integrity. In ciliates, such as Paramecium these RNAs participate in the programming of large-scale genome reorganization during development, distinguishing germline-limited DNA, which is excised, from somatic-destined DNA. Only a handful of proteins playing roles in this process have been identified so far, including typical RNAi-derived factors such as Dicer-like and Piwi proteins. Here we report and characterize two novel proteins, Pdsg1 and Pdsg2 (Paramecium protein involved in Development of the Somatic Genome 1 and 2), involved in Paramecium genome reorganization. We show that these proteins are necessary for the excision of germline-limited DNA during development and the survival of sexual progeny. Knockdown of PDSG1 and PDSG2 genes affects the populations of small RNAs known to be involved in the programming of DNA elimination (scanRNAs and iesRNAs) and chromatin modification patterns during development. Our results suggest an association between RNA-mediated trans-generational epigenetic signal and chromatin modifications in the process of Paramecium genome reorganization.     

Novel cis-Acting Element within the Capsid-Coding Region Enhances Flavivirus Viral-RNA Replication by Regulating Genome Cyclization

cis-Acting elements in the viral genome RNA (vRNA) are essential for the translation, replication, and/or encapsidation of RNA viruses. In this study, a novel conserved cis-acting element was identified in the capsid-coding region of mosquito-borne flavivirus. The downstream of 5′ cyclization sequence (5′CS) pseudoknot (DCS-PK) element has a three-stem pseudoknot structure, as demonstrated by structure prediction and biochemical analysis. Using dengue virus as a model, we show that DCS-PK enhances vRNA replication and that its function depends on its secondary structure and specific primary sequence. Mutagenesis revealed that the highly conserved stem 1 and loop 2, which are involved in potential loop-helix interactions, are crucial for DCS-PK function. A predicted loop 1-stem 3 base triple interaction is important for the structural stability and function of DCS-PK. Moreover, the function of DCS-PK depends on its position relative to the 5′CS, and the presence of DCS-PK facilitates the formation of 5′-3′ RNA complexes. Taken together, our results reveal that the cis-acting element DCS-PK enhances vRNA replication by regulating genome cyclization, and DCS-PK might interplay with other cis-acting elements to form a functional vRNA cyclization domain, thus playing critical roles during the flavivirus life cycle and evolution.     

De Novo Assembly and Genome Analyses of the Marine-Derived Scopulariopsis brevicaulis Strain LF580 Unravels Life-Style Traits and Anticancerous Scopularide Biosynthetic Gene Cluster

The marine-derived Scopulariopsis brevicaulis strain LF580 produces scopularides A and B, which have anticancerous properties. We carried out genome sequencing using three next-generation DNA sequencing methods. De novo hybrid assembly yielded 621 scaffolds with a total size of 32.2 Mb and 16298 putative gene models. We identified a large non-ribosomal peptide synthetase gene (nrps1) and supporting pks2 gene in the same biosynthetic gene cluster. This cluster and the genes within the cluster are functionally active as confirmed by RNA-Seq. Characterization of carbohydrate-active enzymes and major facilitator superfamily (MFS)-type transporters lead to postulate S. brevicaulis originated from a soil fungus, which came into contact with the marine sponge Tethya aurantium. This marine sponge seems to provide shelter to this fungus and micro-environment suitable for its survival in the ocean. This study also builds the platform for further investigations of the role of life-style and secondary metabolites from S. brevicaulis.     

Porphyromonas gingivalis Strain Specific Interactions with Human Coronary Artery Endothelial Cells: A Comparative Study

Both epidemiologic and experimental findings suggest that infection with Porphyromonas gingivalis exacerbates progression of atherosclerosis. As P. gingivalis exhibits significant strain variation, it is reasonable that different strains possess different capabilities and/or mechanisms by which they promote atherosclerosis. Using P. gingivalis strains that have been previously evaluated in the ApoE null atherosclerosis model, we assessed the ability of W83, A7436, 381, and 33277 to adhere, invade, and persist in human coronary artery endothelial (HCAE) cells. W83 and 381 displayed an equivalent ability to adhere to HCAE cells, which was significantly greater than both A7436 and 33277 (P<0.01). W83, 381, and 33277 were more invasive than A7436 (P<0.0001). However, only W83 and A7436 were able to remain viable up to 48 hours in HCAE cell cultures, whereas 381 was cleared by 48 hours and 33277 was cleared by 24 hours. These differences in persistence were in part due to strain specific differences in intracellular trafficking. Both W83 and 381 trafficked through the autophagic pathway, but not A7436 or 33277. Internalized 381 was the only strain that was dependent upon the autophagic pathway for its survival. Finally, we assessed the efficacy of these strains to activate HCAE cells as defined by production of IL-6, IL-8, IL-12p40, MCP-1, RANTES, TNF-α, and soluble adhesion molecules (sICAM-1, sVCAM-1, and sE-selectin). Only moderate inflammation was observed in cells infected with either W83 or A7436, whereas cells infected with 381 exhibited the most profound inflammation, followed by cells infected with 33277. These results demonstrate that virulence mechanisms among different P. gingivalis strains are varied and that pathogenic mechanisms identified for one strain are not necessarily applicable to other strains.     

Carriage of stx2a Differentiates Clinical and Bovine-Biased Strains of Escherichia coli O157

Background

Shiga toxin (Stx) are cardinal virulence factors of enterohemorrhagic E. coli O157:H7 (EHEC O157). The gene content and genomic insertion sites of Stx-associated bacteriophages differentiate clinical genotypes of EHEC O157 (CG, typical of clinical isolates) from bovine-biased genotypes (BBG, rarely identified among clinical isolates). This project was designed to identify bacteriophage-mediated differences that may affect the virulence of CG and BBG.

Methods

Stx-associated bacteriophage differences were identified by whole genome optical scans and characterized among >400 EHEC O157 clinical and cattle isolates by PCR.

Results

Optical restriction maps of BBG strains consistently differed from those of CG strains only in the chromosomal insertion sites of Stx2-associated bacteriophages. Multiplex PCRs (stx1, stx2a, and stx2c as well as Stx-associated bacteriophage - chromosomal insertion site junctions) revealed four CG and three BBG that accounted for >90% of isolates. All BBG contained stx2c and Stx2c-associated bacteriophage – sbcB junctions. All CG contained stx2a and Stx2a-associated bacteriophage junctions in wrbA or argW.

Conclusions

Presence or absence of stx2a (or another product encoded by the Stx2a-associated bacteriophage) is a parsimonious explanation for differential virulence of BBG and CG, as reflected in the distributions of these genotypes in humans and in the cattle reservoir.     

Intraspecies Variability Affects Heterotypic Biofilms of Porphyromonas gingivalis and Prevotella intermedia: Evidences of Strain-Dependence Biofilm Modulation by Physical Contact and by Released Soluble Factors

It is well known that strain and virulence diversity exist within the population structure of Porphyromonas gingivalis. In the present study we investigate intra- and inter-species variability in biofilm formation of Porphyromonas gingivalis and partners Prevotella intermedia and Prevotella nigrescens. All strains tested showed similar hydrophobicity, except for P. gingivalis W83 which has roughly half of the hydrophobicity of P. gingivalis ATCC33277. An intraspecies variability in coaggregation of P. gingivalis with P. intermedia was also found. The association P. gingivalis W83/P. intermedia 17 produced the thickest biofilm and strain 17 was prevalent. In a two-compartment system P. gingivalis W83 stimulates an increase in biomass of strain 17 and the latter did not stimulate the growth of P. gingivalis W83. In addition, P. gingivalis W83 also stimulates the growth of P. intermedia ATCC25611 although strain W83 was prevalent in the association with P. intermedia ATCC25611. P. gingivalis ATCC33277 was prevalent in both associations with P. intermedia and both strains of P. intermedia stimulate the growth of P. gingivalis ATCC33277. FISH images also showed variability in biofilm structure. Thus, the outcome of the association P. gingivalis/P. intermedia seems to be strain-dependent, and both soluble factors and physical contact are relevant. The association P. gingivalis-P. nigrescens ATCC33563 produced larger biomass than each monotypic biofilm, and P. gingivalis was favored in consortia, while no differences were found in the two-compartment system. Therefore, in consortia P. gingivalis-P. nigrescens physical contact seems to favor P. gingivalis growth. The intraspecies variability found in our study suggests strain-dependence in ability of microorganisms to recognize molecules in other bacteria which may further elucidate the dysbiosis event during periodontitis development giving additional explanation for periodontal bacteria, such as P. gingivalis and P. intermedia, among others, to persist and establish chronic infections in the host.     

Congenic Mapping and Allele-Specific Alteration Analysis of Stmm1 Locus Conferring Resistance to Early-Stage Chemically Induced Skin Papillomas

Genome-wide association studies have revealed that many low-penetrance cancer susceptibility loci are located throughout the genome; however, a very limited number of genes have been identified so far. Using a forward genetics approach to map such loci in a mouse skin cancer model, we previously identified strong genetic loci conferring resistance to early-stage chemically induced skin papillomas on chromosome 7 with a large number of [(FVB/N×MSM/Ms)×FVB/N] F1 backcross mice. In this report, we describe a combination of congenic mapping and allele-specific alteration analysis of the loci on chromosome 7. We used linkage analysis and congenic mouse strains to refine the location of Stmm1 (Skin tumor modifier of MSM 1) locus within a genetic interval of about 3 cM on proximal chromosome 7. In addition, we used patterns of allele-specific imbalances in tumors from F1 backcross and N10 congenic mice to narrow down further the region of Stmm1 locus to a physical distance of about 5.4 Mb. To gain the insight into the function of Stmm1 locus, we carried out a long term BrdU labelling experiments with congenic mice containing Stmm1 locus. Interestingly, we observed a decrease of BrdU-LRCs (Label Retaining Cells) in a congenic strain heterozygous or homozygous for MSM allele of Stmm1. These results suggest that Stmm1 responsible genes may have an influence on papillomagenesis in the two-stage skin carcinogenesis by regulating epidermal quiescent stem cells.