Genome最新文献

We present the first genome of a Brazilian bumblebee species, the bellicose bumblebee (Bombus bellicosus). This is an endemic species in southern South America facing local extinction due to habitat loss and climate change. During the COVID-19 social distancing in Brazil, we launched a citizen science initiative via social media to locate remaining bellicose bumblebee populations, leading to the collection of a specimen for genome sequencing. Analysis of the novel genome revealed lower genetic diversity in the bellicose bumblebee compared to a widespread related species (Bombus pascuorum). However, the absence of extensive runs of homozygosity indicated a lack of recent inbreeding, offering a promising perspective for the conservation of this species. Furthermore, demographic history analysis indicates population expansion during past glacial periods, in contrast to Palearctic bumblebees that suffered a stark decline during glaciations. Our findings provide invaluable information for the conservation of this species and for further studies about its biology and evolution, particularly under a scenario of rapid environmental change.

Bacteria in the genus Staphylococcus include human and animal pathogens. Although the genomic diversity of these bacteria is increasingly well characterized, the rate of protein evolution in staphylococci remains poorly understood. In this study, the genomic sequences of one representative from each of the 63 Staphylococcus species were downloaded from the RefSeq database. Homologous protein sequences were identified, and their evolutionary rates were inferred using a phylogenetic approach. The results demonstrated that some proteins evolve significantly faster than others, with several being involved in DNA-mediated transformation. Further analyses of the genomic sequences revealed that the evolutionary rate of proteins is correlated with codon adaptation of their genes, and that certain protein regions are more prone to accumulating mutations. This study highlights the more rapid evolution of specific proteins in staphylococci, likely reflecting the host diversity of these bacteria and their high adaptive capacity.

India harbors a substantial population of 9.43 million dogs, showcasing diverse phenotypes and utility. Initiatives focusing on awareness, conservation, and informed breeding can greatly enhance the recognition and welfare of the unique Indian canine heritage. This study describes the design and development of a high-density SNP array for genomic characterization of Indian dogs. Paired-end (150 bp) DNA sequences of 48 samples from four diverse dog populations were generated with 10× coverage, following the standard pipeline of Axiom Array technology for chip design. More than 23 million raw SNPs were initially identified, with 629 597 SNP markers ultimately tiled on the Indian canine array (Axiom_Shwaan) after stringent filtering and processing. With an inter-marker distance of 3.8 kb the Axiom_Shwaan greatly increases the canine genome coverage. The array was validated by genotyping 186 samples representing 11 dog breeds/populations from India. The high call rate (99%) of SNPs on the designed chip indicates its suitability for use in Indian dog populations, reflecting sufficient genetic diversity. The principal component and phylogenetic analyses delineated the native dog breeds into discrete groups. This high-density SNP array will empower future applications in population genetics, breed/selection signature identification, development of trait-specific biomarkers, and genome-wide data mining for various canine abilities.

The domestication of emu (Dromaius novaehollandiae) began in the 1970s, but their productive characteristics have not undergone significant genetic enhancement. This study investigated the inbreeding and genetic diversity of 50 emus from various farms in Japan using Double digest restriction-site associated DNA sequencing (ddRAD-seq) markers. Single nucleotide polymorphism (SNP) calling revealed 171 975 high-quality SNPs while runs of homozygosity (ROH) analysis identified 1843 homozygous segments, with an average of 36.86 ROH per individual and a mean genome length of 27 Mb under ROH. The majority (86%) of ROH were short (0.5-1 Mb), indicating ancient or remote inbreeding. The average genomic inbreeding coefficient (F_ROH) was 0.0228, suggesting nearly no inbreeding. Overlapping ROH regions were identified, with top consensus regions found on chromosomes 8 and Z. Seven candidate genes related to egg production, feather development, and energy metabolism were annotated in these regions. The findings highlight the prevalence of genetic diversity and low inbreeding levels in the studied emu population. This research highlights the potentiality of random mating in genetic management and conservation of emus. Further studies should focus on enhancing productive traits through selective breeding while preserving genetic diversity to ensure the sustainable growth of the emu farming.

Recently developed hybrid assemblies can achieve telomere-to-telomere (T2T) completeness of some chromosomes. However, such approaches involve sequencing a large volume of both Pacific Biosciences high-fidelity (HiFi) and Oxford Nanopore Technologies (ONT) sequencing reads. Along with this, third-generation sequencing techniques are rapidly advancing, increasing the available length and accuracy. To reduce the final cost of genome assembly, here we investigated the possibility of assembly from low-coverage samples and with only ONT corrected by next-generation sequencing (NGS) sequencing reads. We demonstrated that haploid ONT-based assembly approaches corrected by NGS can achieve performance metrics comparable to more expensive hybrid approaches based on HiFi sequencing. We investigated the assembly of different chromosomes and the low-coverage performance of state-of-the-art hybrid assembly tools, including Verkko and Hifiasm, as well as ONT-based assemblers such as Shasta and Flye. We found that even with one-contig T2T assembly Verkko and Hifiasm still have numerous misassemblies within centromere. Therefore, we recommend using a combination of regular R9 or simplex R10 ONT reads and accurate NGS reads for assembly without aiming for T2T completeness. Additionally, we rigorously evaluated the performance of MGI, Illumina, and stLFR NGS technologies across various aspects of hybrid genome assembly, including pre-assembly correction, haplotype phasing, and polishing.

Our comprehension of avian karyotypes still needs to be improved, especially for Suliform birds. To enhance understanding of chromosomal evolution in this order, we conducted conventional and molecular cytogenetic analysis in five species, named Sula dactylatra, Sula leucogaster, Sula sula (Sulidae), Fregata magnificens (Fregatidae), and Nannopterum brasilianum (Phalacrocoracidae). The diploid chromosome number for S. dactylatra and S. leucogaster was established as 2n = 76 in males, and 2n = 75 in females, but S. sula displayed a karyotype of 2n = 76 chromosomes in males. The disparity in diploid chromosome numbers between male and female Sula is due to a multiple sex chromosome system of the Z₁Z₁Z₂Z₂/Z₁Z₂W type. We propose that the emergence of this multiple-sex chromosome system resulted from a Robertsonian translocation involving the W chromosome and the smallest microchromosome. Fregata magnificens exhibited a diploid number 76 (2n = 76), while N. brasilianum displayed a diploid number of 74 (2n = 74) in both sexes. The ribosomal cluster was located in one microchromosome pair in S. dactylatra, S. leucogaster, S. sula, and F. magnificens and in four pairs in N. brasilianum. Our findings provide evidence of a conserved multiple-sex chromosome system within the Sula genus, shedding light on the high karyotype diversity in Suliformes.

Mycoplasma mycoides subsp. mycoides (Mmm) is the causative agent of contagious bovine pleuropneumonia (CBPP), a severe respiratory disease affecting cattle mostly in sub-Saharan African countries. CBPP can cause significant economic losses, and there is a need for efficacious vaccines to help bring the disease under control. To that end, all publicly available non-redundant whole genome sequences of Mmm strains isolated from cattle (n = 15) were used to identify a 93% core genome of 806 genes, which included 86 of 208 genes encoding outer membrane and extracellular proteins identified from the literature. Many of them and their encoded protein products were found to be highly conserved at the sequence level, including at the sites of predicted epitope binding with bovine major histocompatibility complex (MHC) Class I and II molecules. Despite the high sequence conservation, multiple proteins had large differences in the numbers of MHC Class I and II epitopes and their predicted binding strengths. These results highlight several promising targets supporting the development of new recombinant protein vaccines for CBPP.

Significant structural and evolutionary aspects associated with satellite DNAs (satDNAs) have been uncovered through the combination of cytogenetic and genomic analysis in a wide variety of organisms. In the last few years, several complete catalogs of satDNAs (the so-called satellitomes) were characterized in fishes, and despite the presence of comparative analysis in Neotropical fishes, the order Gymnotiformes remains largely unexplored. Thus, this study aimed to present a comparative satellitome analysis for weakly electric fishes by investigating the richness of satDNA sequences in the genomes of two banded knifefishes: Gymnotus cuia and Gymnotus sylvius. Our investigations identified 72 and 66 satDNA families in G. cuia and G. sylvius, respectively, characterized by varied motif genomic expansion and a high abundance of monomers in both species. The comparative study revealed a widely shared satDNA library, identifying 40 pairwise correspondences of satDNA sequences among the species, exhibiting varied levels of sequence similarity. The chromosomal mapping of the main sequences common to the catalogs facilitated inferences regarding the structural dynamics of satDNA accumulation and distribution throughout Gymnotus. Furthermore, we incorporated a species identification method utilizing quick-FISH of GcuSat07|GSySat05, thereby facilitating the identification of these species. Our data demonstrate significant satDNA sharing between these species, reflecting the recent divergence between these two species.

Satellite DNA (satDNA) sequences are dynamic components of the eukaryotic genome that can play significant roles in species diversification. The Prochilodontidae family, which includes 21 Neotropical fish species, is characterized by a conserved karyotype of 2n = 54 biarmed chromosomes, with variation in some species and populations regarding the presence or absence of B chromosomes. This study aimed to investigate whether the chromosomal distribution of specific satDNA sequences is conserved among three Prochilodus species (Prochilodus lineatus, Prochilodus costatus, and Prochilodus argenteus) regarding organization and number of loci, and to compare their genomes using comparative genomic hybridization (CGH). Our results demonstrated that most satDNA sequences share a similar distribution pattern across the three species, and CGH analysis corroborated that their karyotypes are very similar in terms of repetitive DNA distribution. We also identified a potential CENP-B box sequence within PliSat01, a satDNA located in the pericentromeric region of all analyzed species. In contrast, PliSat04 and PliSat14 displayed differential locations and variations in the number of loci per genome, underscoring the dynamic nature of repetitive sequences even in species with otherwise highly conserved genomes. These findings represent the first evidence of karyotype diversification in Prochilodus, highlighting the evolutionary dynamism of satDNA sequences.

Aegilops speltoides (2n = 2x = 14, genome SS) is a wild relative of wheat and a donor of useful traits for wheat improvement. Several whole-genome studies compared genic regions of Aegilops from the Sitopsis section and wheat and found that Ae. speltoides is most closely related to the wheat B subgenome but is not its direct progenitor. The results showed that a B subgenome ancestor diverged from Ae. speltoides more than 4 MYA and either has not yet been discovered, or is extinct. To further explore the evolutionary relationship between wheat and Ae. speltoides and develop Ae. speltoides chromosome paints, we performed comparative analysis of repetitive fractions of the S genome and three subgenomes of hexaploid wheat. The low-coverage sequence data were analyzed with RepeatExplorer pipeline to annotate repeats and estimate their content. The LTR-retrotransposons comprised about 80% of repeats in Ae. speltoides and wheat datasets and about two-third of them were LTR/Ty3-Gypsy. Ae. speltoides had 1.5 times more LTR/Ty-Copia repeats and 1.5 times less DNA transposons than wheat subgenomes. Several S genome-specific dispersed repeats were found and annotated. Their sequences were used to develop S genome-specific paints for detecting Ae. speltoides chromatin in the wheat background using fluorescent in situ hybridization.