Chromosomal Level Research Articles

The genomes of the most diverse AA genome rice species provide a resource for rice improvement and studies of rice evolution and domestication

Rice (Oryza sativa) is a staple food crop globally, with origins in wild progenitors within the AA genome group of Oryza species. Oryza rufipogon and Oryza meridionalis are native to tropical Asia and Northern Australia and offer unique genetic reservoirs. Here we explored the relationships of the genomes of these wild rice species with the domesticated rice genome. We utilized long read sequencing (PacBio HiFi) and chromatin mapping (Hi-C) to produce de novo chromosomal level genomes of Oryza meridionalis, the most divergent AA gnome species, and the unique Australian Oryza rufipogon like taxon that is a sister to the clade of domesticated and wild AA genome rice species of Asia and Africa. Comparative genomic analyses were conducted to identify structural variations and syntenic relationships between these wild taxa and the domesticated rice variety Nipponbare. The genome assemblies of the wild rice species achieved high completeness and contiguity, revealing the shared and unique genes in each species. Both wild species uniquely shared some genes with domesticated rice many of which were associated with disease resistance and stress tolerance. Structural differences included the large 6 Mb inversion on chromosome 6 specific to Japonica rice. Functional annotation highlighted conserved biological functions and novel genes unique to the wild taxa. These findings provide a deeper understanding of rice domestication and highlight the genetic contributions of wild species to enhancing the genetic diversity and ecological adaptability of modern rice varieties. Our study emphasizes the importance of conserving wild rice populations as genetic resources for breeding and adaptation in changing environments.

Dynamic Genomic Imaging and Tracking in Living Cells by a DNA Origami-Based CRISPR‒dCas9 System.

The clustered regularly interspaced short palindromic repeat (CRISPR)-associated system has displayed promise in visualizing the dynamics of target loci in living cells, which is important for studying genome regulation. However, developing a cell-friendly and rapid transfection method for achieving dynamic and long-term genomic imaging in living cells with high specificity and accuracy is still challenging. Herein, a robust and versatile method is presented that employs a barrel-shaped DNA nanostructure (TUBE) modified with aptamers for loading, protecting, and delivering CRISPR-Cas9 to visualize specific genomic loci in living cells. This approach enables dynamic tracking of target genomic regions (Chr3q29, a repetitive region of chromosome 3) throughout the mitotic process and captures variations in their spatial distribution and quantity accurately. Distinct dynamic behaviors between the Chr3q29 and telomeres are observed, which are linked to their unique chromosomal positions and levels of mobility. High-resolution multicolor labeling of the target genes is achieved, with a high degree of colocalization between the enhanced green fluorescent protein and cyanine-5 channels, facilitating precise imaging of target loci. This method not only supports dynamic genomic imaging but also enables multiplexed tracking, providing a powerful visualization tool for studying cellular processes and genetic interactions in real time within living cells.

A Chromosome level assembly of pomegranate (Punica granatum L.) variety grown in arid environment

The pomegranate (Punica granatum L.) is an ancient fruit-bearing tree known for its nutritional and antioxidant properties. They originated from the Middle East in regions having large farms including mountainous regions of Al-Baha in Saudi Arabia. Pomegranates can tolerate arid climates and are considered among the fruits that will play a major role in food security. However, the genomics resources of pomegranate growing in arid regions are scarce. Here, we present a high-quality chromosome-level reference genome using PacBio HiFi long reads. The final assembly was 384.65 Mb with N50 contig size of 43.11 Mb, with 353.42 Mb being anchored on the eight pseudo chromosomes. Annotation revealed that 48.79% of the genome comprises repetitive elements and contains 21,620 protein-coding genes. The new reference genome will contribute to identifying stress resistance traits in pomegranates thriving in arid environments as well as new dietary antioxidants and antimicrobial peptides with pharmaceutical and therapeutic applications.

Genotoxicity of Microplastics on Living Organisms: Effects on Chromosomes, DNA and Gene Expression

Microplastic exposure has become unavoidable, leading to their presence in living organisms. One area of particular concern is the genotoxicity of microplastics, which has implications for reproductive health and cancer development. This review aims to highlight the genotoxic effects of microplastics on different organisms, focusing on their impacts on chromosomes, DNA, and gene expression. More than 85 papers, primarily published in the last five years, have been reviewed. This review indicates that microplastics can cause clastogenesis and aneugenesis at the chromosome level. Clastogenesis results in chromosome damage, while aneugenesis leads to failures in chromosome segregation without causing direct damage. Additionally, microplastics can fracture and damage DNA. These effects arise from (1) the direct genotoxicity of microplastics through interactions with chromosomes, DNA, and associated proteins; and (2) their indirect genotoxicity due to the production of reactive oxygen species (ROS) by oxidative stress induced by microplastics. Microplastics can trigger the activation of genes related to oxidative stress and the inflammatory response, leading to increased ROS production. Furthermore, they may alter gene expression in other biological processes. The genotoxicity linked to microplastics can stem from the particles themselves and their associated chemicals, and it appears to be both size- and dose-dependent.

Efficient Multiplex Genome Editing of the Cyanobacterium Synechocystis sp. PCC6803 via CRISPR-Cas12a.

Cyanobacteria have been genetically modified to convert CO2 into biochemical products, but efficient genetic engineering tools, including CRISPR-Cas systems, remain limited. This is primarily due to the polyploid nature of cyanobacteria, which hinders their effectiveness. Here, we address the latter by specifically (i) modifying the RSF1010-based replicative plasmid to simplify cloning efforts while maintaining high conjugation efficiency; (ii) improving the design of the guide RNA (gRNA) to facilitate chromosomal cleavage; (iii) introducing template DNA fragments as pure plasmids via natural transformation; and (iv) using sacB to facilitate replicative plasmid curing. With this system, the replicative plasmid containing both Cas12a and gRNA is introduced to Synechocystis sp. PCC6803 cells via conjugation to cleave the circular chromosomes. Template DNA plasmid that has meanwhile been assimilated will then repair it achieving the desired genetic modifications. This system was validated by successfully deleting various "neutral" chromosomal loci, both individually and collectively, as well as targeting an essential gene, sll1797. With the sacB-sucrose counter-selection, all deletions were simultaneously made markerless in < 4 weeks. Moreover, we also integrate YFP with various protein degradation tags into the chromosome, allowing for their characterization at the chromosomal level. We foresee this system will greatly facilitate future genome engineering in cyanobacteria.

A haplotype-resolved and chromosome-scale genome assembly of Hainan muntjac (Muntiacus nigripes)

The Hainan muntjac (Muntiacus nigripes) is a wild animal endemic to Hainan, China. Its species distribution and the diversity of muntjac karyotypes have attracted much attention. Although genomic resources have increased in recent years, relevant genome assembly data of Hainan muntjac are still lacking. Meanwhile, molecular evidence for the taxonomic units of this species remains lacking. In this study, we successfully assembled the Hainan muntjac haplotype genome at the chromosome level using Pacbio long read and long sequencing technologies and Hi-C data. The final assembly size was 2.66 Gb, with allele and scaffold N50 values of 29.27 and 700.27 Mb, respectively, and we scaffolded the genome sequence onto three chromosomes. The genome contains a total of 21,451 genes and 10,056 gene families. Phylogenetic analysis using single-copy gene families revealed that Hainan muntjac is most closely related to red muntjac, with a divergence time of 8–11 Ma. This new genomic resource of Hainan muntjac will be crucial for future comparative genomic analyses and genetic evolutionary studies.

Genome sequencing and assembly of near threatened Clarias dussumieri (Valenciennes, 1840), an endemic catfish of peninsular India

Clarias dussumieri, a near threatened freshwater catfish, is endemic to peninsular India and has aquaculture potential. Unlike its sister species, C. magur, the male fish needs not be sacrificed during captive breeding. Thus, the generation of genomic information of this species becomes significant for effective genome mining through the bioprospecting of novel genes for important production traits. In this study, the genome assembly was undertaken to address this gap by generating high quality chromosome level genome assembly using PacBio long reads and Hi-C scaffolding. The total assembled genome was found to be 918.72 Mb in size and showed 95.23% completeness. Its characterization exhibited 41.46% repeats, 1,174,725 SSRs and 25,369 predicted genes with functional annotations. The Single copy orthologs analysis placed C. dussumieri in a distinct position with C. magur. The comprehensive genomic information offers resources for comparative genomics with other Clarias species for improvement of economic traits.

Chromosome-scale genome assembly and gene annotation of the Alligator Gar (Atractosteus spatula)

Given the aggressive nature and robust survival capabilities of the alligator gar (Atractosteus spatula), if it was to exist in a new environment as an invasive species, it could cause significant disruption to the invaded ecosystem. Building on the continuity and completeness of the existing draft genome were not optimal, this study has updated a high-quality genome of the alligator gar at the chromosome level, which was assembled using Oxford Nanopore Technology and chromatin interaction mapping (Hi-C) sequencing techniques. In summary, the alligator gar genome in this study was 1.05 Gb in size with a contig N50 of 15.7 Mb and scaffold N50 of 56.8 Mb. We captured 98.26% of assembled bases in 28 pseudochromosomes. The completeness of the final chromosome-level genome reached 96.7%. Meanwhile, a total of 19,103 protein-coding genes were predicted, of which 99.83% could be predicted with functions. Taken together, the present high-quality alligator gar chromosome-level genome provides a valuable resource for exploring the underlying genomic basis to comprehend the functional genomics, chromosome evolution, and population management of this species.

Chromosome-level genome assembly of Phortica okadai, a vector of Thelazia callipaeda

Phortica okadai, known as the vector of Thelazia callipaeda in Asia, is of concern to public health in the past few decades. We generated a high-quality chromosome-level genome assembly of P. okadai with a size of 263.82 Mb and a contig N50 of 15 Mb, scaffold N50 of 47.45 Mb, combining PacBio HiFi, Illumina short-reads, and Hi-C sequencing data. Approximately 98.5% of 100 contigs could be properly ordered and oriented into 6 pseudo-chromosomes and a total of 15,052 protein-coding genes were obtained from the P. okadai genome, of which 91.76% were functionally annotated. BUSCO analysis revealed that 96.20% of 1315 predicted genes were clearly covered the conserved invertebrate genes within the database. Additionally, 302 rRNAs, 377 tRNAs, 52 miRNAs, 40 snRNAs and 21 snoRNAs were detected. In conclusion, this high-quality chromosome level reference genome will be a valuable resource for furthering the fields of ecology, genetics, evolution and functional genomics of P. okadai.

Nanopore Data-Driven T2T Genome Assemblies of Colletotrichum lini Strains.

Colletotrichum lini is a pathogenic fungus that infects flax and causes significant yield losses. In this study, we assembled the genomes of four highly virulent C. lini strains using the Oxford Nanopore Technologies (ONT, R10.4.1 flow cells) and Illumina platforms. The performance of two tools developed for telomere-to-telomere (T2T) genome assembly was compared: Verkko and Hifiasm. Prior to the assembly, ONT reads were corrected using the HERRO algorithm. Verkko generated genome assemblies of high completeness but low contiguity, while Hifiasm allowed the generation of T2T assemblies. Despite significantly different genome coverage with ONT data (25-100×), four assemblies of equal contiguity were obtained: 53.6-54.7 Mb, ten core chromosomes, and two or three accessory chromosomes. A comparative analysis of different polishing tools showed that at a certain genome coverage with the corrected ONT data (≥35×), the additional polishing of the assembly did not improve its accuracy, even with the Illumina data. An analysis of the genome structures of the four C. lini strains revealed a high similarity between the core chromosomes. Thus, our approach enabled assembling T2T Colletotrichum genomes only from the ONT data obtained using R10.4.1 flow cells and may be promising for other fungal genera. These assemblies will allow the accurate identification of strain-specific differences at the chromosome level and will aid in the development of effective strategies to protect flax from anthracnose.

Mycological and Genomic Characterization of Fusarium vorosii, a Potentially Pathogenic Fungus, Isolated from Field Crops and Weeds in Korea.

Fusarium vorosii (Fv) is one of the least studied species of the Fusarium graminearum species complex, a major plant pathogen causing Fusarium head blight (FHB) in a variety of crops. In this study, we isolated 12 strains of Fv from cereal samples with FHB symptoms and gramineous weeds. Trichothecene genotyping of Fv strains showed that 10 strains were nivalenol (NIV) type and 2 strains were 15-acetyldeoxynivalenol (15ADON) type. Fv strains have similar mycological characteristics to Fusarium asiaticum, a major FHB pathogen of rice in Asia, however, asexual sporulation was at least 100 to 1,000 times higher in Fv. In comparison of pathogenicity, the Fv-15ADON type was more pathogenic than the NIV type in both rice and wheat, and had a similar level of pathogenicity as the F. asiaticum-NIV type. Among the 12 Fv strains, two representative ones, Fv-NIV type RN1 and Fv-15ADON type W15A1, were selected and their whole genomes were sequenced and analyzed. Complete genome sequences of two Fv strains, RN1 and W15A1, were assembled at the chromosome level with high quality compared to known Fv genomes. The genome data of the two Fv strains were compared with the reference strains already known. As a result of comparative genome analysis, it was found that they are phylogenetically related according to the trichothecene biosynthetic gene cluster, that is, toxin chemotype. Through this study, we provided important information about Fv species that can be potential pathogens in domestic crops about biological and genomic characteristics.

Targeting Chromosome 21 Gene Over-Expression: A Novel Approach to Prevent Health Complications in Individuals with Down Syndrome.

Background: Down Syndrome (DS), caused by an extra copy of chromosome 21, leads to over-expression of 200–300 genes. This genetic imbalance contributes to various health complications, including an elevated risk of blood cancers. Modulating gene expression is vital to mitigating these risks. Methodology: This study focused on reducing the over-expression of genes on chromosome 21 by inhibiting the proteins they encode. Potential inhibitors were identified and evaluated using electrostatic interaction scoring and protein docking simulations. The goal was to reduce gene expression by 50%, thereby mitigating the harmful effects of over-expressed proteins. Results: Analysis confirmed significantly higher expression levels of chromosome 21 genes in DS individuals. Targeting the encoded proteins successfully reduced gene expression by 50%. Protein docking studies identified a promising inhibitor that effectively blocked over-expressed proteins, demonstrating potential to prevent blood cancer by mitigating the effects of the extra genetic material. Conclusion: This study proposes a novel therapeutic strategy for DS by focusing on inhibiting the over-expressed proteins linked to blood cancer. The identified drug candidates hold promise for improving health outcomes and quality of life in individuals with DS by reducing the risk of blood cancers and other complications.

Advances and Perspectives of Genetic Pathologies in the 21st century.

Introduction: The discovery of deoxyribonucleic acid in 1953 marks the difference between classical genetics that was based on clinical observation to make diagnoses and perform genomic modifications empirically, which triggered a series of genetic aberrations that compromise the dignity of the human being and the new genetics, an era that allowed understanding the starting point in the mechanisms of regulation and gene expression and its role when coding DNA which has allowed the study of diseases of genetic or hereditary origin and give a targeted treatment. The new genetics brings with it novel tools to objectify the alterations that occur either at the level of genes, chromosomes or multifactorial disorders and to be able to identify and classify them in a pertinent manner, simplifying the understanding of these pathologies. Objective: This article aims to keep the scientific community updated on the different genetic pathologies and their classification taking into account the nomenclature and key points of each one. Methodology: A review of scientific articles was performed in databases such as Pubmed, Web of Science, Dynamed and Uptodate, with search terms for artificial intelligence in medicine, clinical research, legal framework, bioethical principles, automated analysis, among others. No language restrictions were applied. Medical subject headings (MeSH) were used. Additionally, reference lists, review articles and grey literature were manually searched for relevant articles not captured in the electronic scan. Conclusion: Human genetics and its pathologies are of constant interest, since through its knowledge different DNA variants of the coding and replication process are explained, knowing the latest definitions covering the subject is of great importance for its understanding.

Investigation of Astyanax mexicanus (Characiformes, Characidae) chromosome 1 structure reveals unmapped sequences and suggests conserved evolution.

Natural selection in the cave habitat has resulted in unique phenotypic traits (including pigmentation loss and ocular degeneration) in the Mexican tetra Astyanax mexicanus, considered a model species for evolutionary research. A. mexicanus has a karyotype of 2n = 50 chromosomes, and long-read sequencing and quantitative trait linkage maps (QTLs) have completely reconstructed the reference genome at the chromosomal level. In the current work, we performed whole chromosome isolation by microdissection and total amplification using DOP-PCR and Whole Chromosome Painting (WCP), followed by sequencing on the Illumina NextSeq platform, to investigate the microstructure of the large and conserved metacentric chromosome 1 of A. mexicanus. The sequences aligned to linkage block 3 of the reference genome, as determined by processing the reads with the DOPseq pipeline and characterizing the satellites with the TAREAN program. In addition, part of the sequences was anchored in linkage blocks that have not yet been assigned to the chromosomes. Furthermore, fluorescence in situ hybridization using WCP 1 carried out in other nearby species revealed a high degree of chromosome conservation, which allows us to hypothesize a common origin of this element. The physical mapping of the repetitive marker sequences provided a micro- and macrostructural overview and confirmed their position in chromosome pair 1. These sequences can serve as comparative tools for understanding the evolution and organization of this chromosome in other species of the family in future studies.

Chromosome-level genome assembly of the smallscale yellowfin (Plagiognathops microlepis)

The small-scale yellowfin (Plagiognathops microlepis) is a highly valued species in East Asian aquaculture due to its adaptability and high yield. However, the lack of genomic data has impeded genetic research and breeding efforts. In this study, we utilize PacBio Hifi long-read sequencing and Hi-C technologies to construct a highly detailed genome of P. microlepis at the chromosomal level. The assembly encompasses 976.41 Mb, with an exceptional 99.84% distribution across 24 chromosomes. Notably, the contig N50 was 34.41 Mb and scaffold N50 was 38.38 Mb. The completeness of the P. microlepis genome assembly is underscored by a BUSCO score of 98.08%. A total of 25,389 protein-coding genes were identified, with a BUSCO score of 96.98%, and 99.85% of these genes were functionally annotated. Synteny relationships at the chromosome level with Danio rerio and Chanodichthys erythropterus genomes uncover small-scale chromosomal rearrangements. This high-fidelity genome assembly serves as a pivotal resource for forthcoming endeavors such as the genome structure, functional elements, comparative genomics, and evolutionary characteristics of P. microlepis and its relative species.

Chromosome-level genome assembly of banaba (Lagerstroemia speciosa L.)

Lagerstroemia speciosa is a famous medicinal and ornamental plant of the Lagerstroemia genus, with large and gorgeous flowers and a flowering period of 3 to 5 months. L. speciosa extracts have been used for many years in folk medicine to treat diabetes. Here, we used PacBio and Hi-C sequencing technologies to obtain a high-quality whole genome map of L. speciosa at chromosome level. The assembled genome is 306.76 Mb, with a scaffold N50 of 13.03 Mb. 98.75% of contigs were anchored to 24 pseudochromosomes, and 38.58% of the contigs (118.11 Mb) were identified as repeats. 93.54% of the 29,351 protein-coding genes were annotated. In addition, 146 miRNAs, 511 tRNAs, 2,733 rRNAs and 679 snRNAs were annotated. This high-quality genome assembly provides a valuable resource for understanding the species evolution in the Lythraceae family and promoting the study of important traits of L. speciosa.

Chromosome-level genome assembly of Indo-Pacific king mackerel (Scomberomorus guttatus)

The Indo-Pacific king mackerel, scientifically known as Scomberomorus guttatus, is a valued marine species that holds significant commercial importance in the Indo-Pacific region. However, the lack of genomic resources has hindered a comprehensive understanding of this species. In this study, we constructed a genome of Indo-Pacific king mackerel at the chromosome level using a combination of PacBio HiFi reads and a chromosome contact map (Hi-C). The resulting genome had high contig and scaffold N50 values of 8.84 Mb and 32.9 Mb, respectively. In the genome assembly, which is 797.66 Mb in size and consists of 24 chromosomes, we also identified 35.89% repetitive elements and predicted 25,886 protein-coding genes. Our study not only benefits to reveal the possible mechanism of adaptive evolution in this fish, but also offers insight for the future sustainable management of these valuable biological resources.

Chromosome level assemblies of Nakaseomyces (Candida) bracarensis uncover two distinct clades and define its adhesin repertoire

BackgroundThe Nakaseomyces clade is formed by at least nine described species among which three can be pathogenic to humans, namely Nakaseomyces glabratus (Candida glabrata), the second most-common cause of candidiasis worldwide, and two rarer emerging pathogens: Nakaseomyces (Candida) nivarensis and Nakaseomyces (Candida) bracarensis. Early comparative genomics analyses identified parallel expansions of subtelomeric adhesin genes in N. glabratus and N. nivarensis/bracarensis, and suggested possible links with the emergence of the virulence potential in these species. However, as shown for N. glabratus, the proper assessment of subtelomeric genes is hindered by the use of incomplete assemblies and reliance on a single isolate.ResultsHere we sequenced seven N. bracarensis isolates and reconstructed chromosome level assemblies of two divergent strains. We show that N. bracarensis isolates belong to two diverging clades that have slightly different genomic structures. We identified the set of encoded adhesins in the two complete assemblies, and uncovered the presence of a novel adhesin motif, found mainly in N. bracarensis. Our analysis revealed a larger adhesin content in N. bracarensis than previously reported, and similar in size to that of N. glabratus. We confirm the independent adhesin expansion in these two species, which could relate to their different levels of virulence.ConclusionN. bracarensis clinical isolates belong to at least two differentiated clades. We describe a novel repeat motif found in N. bracarensis adhesins, which helps in their identification. Adhesins underwent independent expansions in N. glabratus and N. bracarensis, leading to repertoires that are qualitatively different but quantitatively similar. Given that adhesins are considered virulence factors, some of the observed differences could contribute to variations in virulence capabilities between N. glabratus and N. bracarensis.

Chromosome architecture as a determinant for biosynthetic diversity in Micromonospora.

Natural products - small molecules generated by organisms to facilitate ecological interactions - are of great importance to society and are used as antibacterial, antiviral, antifungal and anticancer drugs. However, the role and evolution of these molecules and the fitness benefits they provide to their hosts in their natural habitat remain an outstanding question. In bacteria, the genes that encode the biosynthetic proteins that generate these molecules are organised into discrete loci termed biosynthetic gene clusters (BGCs). In this work, we asked the following question: How are biosynthetic gene clusters organised at the chromosomal level? We sought to answer this using publicly available high-quality assemblies of Micromonospora, an actinomycete genus with members responsible for biosynthesizing notable natural products, such as gentamicin and calicheamicin. By orienting the Micromonospora chromosome around the origin of replication, we demonstrated that Micromonospora has a conserved origin-proximal region, which becomes progressively more disordered towards the antipodes of the origin. We then demonstrated through genome mining of these organisms that the conserved origin-proximal region and the origin-distal region of Micromonospora have distinct populations of BGCs and, in this regard, parallel the organization of Streptomyces, which possesses linear chromosomes. Specifically, the origin-proximal region contains highly syntenous, conserved BGCs predicted to biosynthesize terpenes and a type III polyketide synthase. In contrast, the ori-distal region contains a highly diverse population of BGCs, with many BGCs belonging to unique gene cluster families. These data highlight that genomic plasticity in Micromonospora is locus-specific, and highlight the importance of using high-quality genome assemblies for natural product discovery and guide future natural product discovery by highlighting that biosynthetic novelty may be enriched in specific chromosomal neighbourhoods.

Evolutionary history written in tandem arrays – satellite repeats in the Lagoseris lineage of Crepis sensu lato (Asteraceae)

Abstract Satellite DNA families are excellent markers in evolutionary studies of plant karyotypes. Together with phylogenetic background, they can provide additonal information on different scenarios accompanying the speciation and diversification of related species. The Lagoseris lineage of Crepis sensu lato constitutes an interesting model in such studies, mainly due to: (i) the presence of large chromosomes; (ii) several base chromosome numbers; and (iii) variation in genome sizes. We aimed to characterize the satellite families and compare their genomic and chromosomal organization to better understand the evolutionary pathways that shaped the genomes of the Lagoseris lineage. Eight different families of satellite repeats were identified in Crepis palaestina based on RepeatExplorer raw Illumina read analyses. Most of these satellites were present in five species studied from the Lagoseris lineage and organized in tandem arrays. If the particular repeat was present in the genome of the related species, its genomic organization showed similarity to the one observed in C. palaestina. This similar genomic organization was not often reflected at the chromosomal level, where many distinct distribution patterns were shown, from several major loci to numerous minor ones spread throughout the chromosomal arms. The evolution of satellite repeats is discussed in phylogenetic context.