Genome Assembly Research Articles

A chromosome-level genome assembly of the aphid Semiaphis heraclei (Takahashi)

The S. heraclei (Takahashi) (Hemiptera: Aphididae) is a destructive pest of cultivated insectary plant Cnidium monnieri (L.) Cuss. However, to date, no S. heraclei-related genomic information has been reported. Here, we present the first chromosomal-scale genome assembly of S. heraclei approximately 440.3 Mb with contig N50 of 81.7 Mb. Using PacBio long-read sequencing, Illumina sequencing, and Hi-C scaffolding techniques, 94.24% of the assembled sequences were successfully anchored to the four pseudochromosomes. BUSCO assessment showed a completeness score of 95.4%. The S. heraclei genome consisted of 32.02% repetitive elements and 13,983 predicted protein-coding genes. Phylogenetic analysis showed that S. heraclei was closely related to Diuraphis noxia. This high-quality genome assembly of S. heraclei will serve as a genomic resource for aphid evolution and pave the way for deciphering the tri-trophic interaction mechanisms between plants, herbivores, and natural enemies.

The unexplored diversity of rough-seeded lupins provides rich genomic resources and insights into lupin evolution

Lupin crops provide nutritious seeds as an excellent source of dietary protein. However, extensive genomic resources are needed for crop improvement, focusing on key traits such as nutritional value and climate resiliency, to ensure global food security based on sustainable and healthy diets for all. Such resources can be derived either from related lupin species or crop wild relatives, which represent a large and untapped source of genetic variation for crop improvement. Here, we report genome assemblies of the cross-compatible species Lupinus cosentinii (Mediterranean) and its pan-Saharan wild relative L. digitatus, which are well adapted to drought-prone environments and partially domesticated. We show that both species are tetraploids, and their repetitive DNA content differs considerably from that of the main lupin crops L. angustifolius and L. albus. We present the complex evolutionary process within the rough-seeded lupins as a species-based model involving polyploidization and rediploidization. Our data also provide the foundation for a systematic analysis of genomic diversity among lupin species to promote their exploitation for crop improvement and sustainable agriculture.

AmrProfiler: a comprehensive tool for identifying antimicrobial resistance genes and mutations across species.

Antimicrobial resistance (AMR) remains a critical challenge in public health and research. AmrProfiler is a comprehensive tool with three specialized modules: identifying acquired AMR genes, resistance-associated mutations, and ribosomal RNA (rRNA) gene mutations across nearly 18 000 bacterial species. By integrating and refining data from established databases, it provides a robust framework for AMR analysis. AmrProfiler is the first to systematically report mutations in rRNA genes, offering in-depth analysis of rRNA copy numbers and mutations-key for identifying potential rRNA-associated resistance mechanisms. Its curated database includes 7600 unique AMR gene entries and over 4300 resistance-related mutations. Supporting genome assemblies in multiple formats, AmrProfiler allows users to customize detection thresholds for AMR genes, mutations, and rRNA analysis. Validation with Acinetobacter baumannii,Escherichia coli,Klebsiella pneumoniae,Staphylococcus aureus, and Staphylococcus epidermidis demonstrated that AmrProfiler accurately identified all AMR genes and mutations reported by other tools while also detecting additional resistance markers and mutations not previously recognized. By bridging AMR genotypes and phenotypes, AmrProfiler provides actionable insights that advance both research and clinical applications in AMR. AmrProfiler is freely available as an open-access web server without login at https://dianalab.e-ce.uth.gr/amrprofiler.

Chromosome-level genome assembly of the doctor fish (Garra rufa)

Garra rufa, or doctor fish, is a small cyprinid known for its high-temperature tolerance and its use in ichthyotherapy. Recently, this trait has gained interest as a model for human diseases, including infections and cancer xenografts, though limited genomic resources hinder experimental use. In this study, we have generated a high-quality, chromosome-level genome assembly of G. rufa using PacBio HiFi long-read sequencing and Hi-C technology. The genome is 1.38 Gb in size, with 25 chromosomes and a scaffold N50 of 49.3 Mb. Approximately 59% of the genome consists of repetitive elements, while 27,352 protein-coding genes were annotated, with 98.3% being functionally characterized. BUSCO analysis revealed 94.5% and 94.7% completeness for the genome assembly and annotated protein sequences, respectively. Notably, we identified two heat shock transcription factor (HSF) genes, 239 heat shock protein (HSP)-related genes, and 1,036 heat shock elements (HSEs) in regulatory regions. Phylogenetic analysis supports the placement of G. rufa within the Labeoninae subfamily. This genome assembly provides a valuable resource for advancing G. rufa as a model organism.

Long-read sequencing reveals absence of 5mC in Ogataea parapolymorpha DL-1 genome and introduces telomere-to-telomere assembly

BackgroundOgataea parapolymorpha DL-1 is a versatile thermotolerant organism with numerous applications in biotechnology, particularly in the production of recombinant proteins and the study of methanol metabolism and peroxisome functions. This study presents a comprehensive genome and methylome analysis of Ogataea parapolymorpha DL-1 using long-read sequencing technology. The research builds upon previous short-read sequencing efforts, revealing enhancements in genome assembly and epigenomic insights.MethodsWe used long-read sequencing technology to achieve a telomere-to-telomere (T2T) genome assembly of Ogataea parapolymorpha DL-1. High-quality reads were obtained and assembled de novo, followed by polishing to enhance accuracy. The genome was analyzed to identify coding genes, telomeric motifs, rRNA genes, and methylation patterns, including the detection of 5mC and 6 mA modifications. Epigenetic features were further assessed and validated through liquid chromatography-mass spectrometry.ResultsKey findings include the absence of 5 mC DNA modification and the presence of 6 mA in the genome, unusual telomere regulation mechanism based on the addition of non-telomeric dT and the introduction of long-read enhanced telomere-to-telomere assembly.ConclusionThis work provides deeper insights into the yeast’s genome organization and methylation patterns, contributing to the understanding of its genetics and therefore potential biotechnological applications.

Chromosome-level genome assemblies of five Sinocyclocheilus species

Sinocyclocheilus, a genus of tetraploid fishes endemic to Southwest China’s karst regions, are classified as second-class nationally protected species due to their fragile habitat. Limited high-quality genomic resources have hampered studies on their phylogenetic relationships and the origin of their polyploidy. Here, we present a high-quality genome assembly of the most abundant Sinocyclocheilus species, the golden-line barbel (Sinocyclocheilus grahami), by integrating PacBio long-read and Hi-C sequencing. The resulting scaffold-level genome-assembly is 1.6 Gb long, with a scaffold N50 of up to 30.7 Mb. We annotated 42,806 protein-coding genes. Also, 93.1% of the assembled genome sequences (about 1.5 Gb) and 93.8% of the total predicted genes were successfully anchored onto 48 chromosomes. Furthermore, we obtained chromosome-level genome assemblies for four other Sinocyclocheilus species (S. anophthalmus, S. maitianheensis, S. anshuiensis, and S. rhinocerous) based on homologous comparisons. These genomic resources will enable in-depth investigations on cave adaptation, improvement of economic values, and conservation of diverse Sinocyclocheilus fishes.

Genome of the enigmatic watering-pot shell and morphological adaptations for anchoring in sediment

BackgroundIn this study, we present the first chromosome-scale genome of Verpa penis (Linnaeus, 1758), and the first for the bivalve clade Anomalodesmata. The present study has two separate foci. Primarily, we provide the genetic resource to bridge further studies from genome to phenome and propose hypotheses to guide future empirical investigations. Secondarily, based on morphology, we outline a conceptual exploration to address their adaptation. Watering-pot shells have been called “the weirdest bivalves” for their fused tubular shell resembling the spout of a watering can. This adventitious tube arose twice convergently in clavagelloidean bivalves. However, previous literature has never provided a convincing adaptive pathway.ResultsThe genome assembly of V. penis was about 507 Mb, with contig N50 of 5.33 Mb, and has 96.5% of sequences anchored onto 19 pseudochromosomes. Phylogenomic analyses of this new genome in context of other bivalves confirms the placement for Anomalodesmata as sister to the clade Imparidentia. Contrary to expectations from its highly modified body plan, there is no evidence of chromosome reduction compared to the ancestral karyotype of heterodont bivalves (1 N = 19). Drawing on established principles from engineering as well as morphology, the thought experiment about the adventitious tube seeks to extend current understanding by exploring parallels with other built structures. A new hypothesis explains one possible interpretation of the adaptive significance of this body form: it is potentially structurally optimised for vertical stability in relatively soft sediments, with parallels to the engineering principles of a suction anchor.ConclusionsWhile the conclusions presented here on morphological interpretations are theoretical, this serves as a foundation for further empirical validation and refinement. Our study offers new insights to a long-standing mystery in molluscan body forms and provides genomic resources that are relevant to understanding molluscan evolution, biomineralisation, and biomimetic design.

Salivary mycobiome alterations in HIV-infected MSM: dominance of Pseudogymnoascus and functional shifts across disease stages

BackgroundOral health is increasingly recognized as a crucial determinant of overall health in people living with HIV/AIDS (PLWHA). Specifically, the oral mycobiome may play a pivotal role in HIV-associated oral complications. However, the fungal species involved and their potential as biomarkers for HIV-related oral conditions remain poorly understood. This study investigates salivary fungal profiles in PLWHA who have sex with men (MSM), focusing on diversity, functional shifts, and correlations with disease progression.MethodsA cross-sectional study included 25 MSM participants divided into five groups: HIV-negative controls (n = 5) and four HIV-positive groups stratified by CD4 count: Stage 0 (HIV RNA-positive/antibody-negative; n = 5), Stage 1 (CD4 ≥500 cells/μL; n = 5), Stage 2 (CD4 200–499 cells/μL; n = 5), and Stage 3 (CD4 <200 cells/μL or opportunistic infections; n = 5). Saliva samples were collected and analyzed using metagenomic sequencing (Illumina NovaSeq platform). Bioinformatic analyses included genome assembly (MEGAHIT), gene clustering (CD-HIT), gene abundance calculation (SOAPaligner), species annotation (BLASTP), and KEGG pathway annotation (KOBAS 2.0). Statistical analyses (Kruskal-Wallis tests, Spearman’s correlation) assessed associations between fungal profiles, CD4 count, and viral loads.ResultsA total of 51 fungal genera were identified, with Pseudogymnoascus being the most abundant. Functional analysis revealed 113 shared KEGG pathways, of which 69 were unique to Stage 3, primarily related to metabolic and disease-related processes. Notably, Auricularia exhibited a positive correlation with CD4 count (P ≤ 0.01), while Mucor showed a negative correlation (P = 0.0299).ConclusionsSalivary mycobiome composition and function shift significantly across HIV stages, reflecting immune decline. Pseudogymnoascus dominance challenges conventional views of oral fungal ecology in immunocompromised hosts. These findings highlight the mycobiome’s diagnostic potential for monitoring HIV-related oral health. Longitudinal studies are needed to validate clinical relevance.

Reconstruction of the X and Y haplotypes in the genetically improved Abbassa nile tilapia genome assembly

The success of the Nile tilapia (Oreochromis niloticus) as an aquaculture species is partly the result of continuous selective breeding leading to high performing strains. These elite strains have been derived from breeding populations of diverse origins and crosses with other Oreochromis species. Owing to the complex and unique evolutionary histories of each strain, existing reference genomes of wild populations are unsuitable to implement genomic selection for beneficial traits such as growth or environmental resilience in aquaculture programmes. Here we generated a high-quality genome assembly and annotation of the WorldFish Genetically Improved Abbassa Nile tilapia (GIANT) elite strain using a combination of PacBio HiFi, and Omni-C Illumina sequencing. As a male Abbassa Nile tilapia was used for the generation of the genome assembly, we reconstructed both X and Y haplotypes, identifying both amhY and amhΔy on LG23 indicating that Abbassa likely shares the same sex determination system as GIFT, and thereby differs from the existing reference genome, whose sex determination loci are located on LG1.

A Chromosome-level Genome Assembly of the Beavertail Cactus, Opuntia basilaris.

Few genomic resources currently exist for the American endemic family Cactaceae, a group of around 1850 species, which are world renowned for their amazing growth forms and succulent habits. These icons of arid landscapes across the Americas are threatened in many parts of their range, including in parts of California, and developing more comprehensive genomic data will aid efforts to better understand and preserve these plants. We sequenced and assembled the genome of the beavertail cactus, Opuntia basilaris, which is represented by three varieties in California, one of which is threatened, and another endangered. The genome assembly has a BUSCO complete score of 98.1%, and a total scaffold length of 980Mb, with a scaffold N50 length of 83Mb. The genome size of diploid O. basilaris is markedly smaller than other diploid members of Cactaceae that have been assembled to date. This is the first nuclear genome sequenced in subfamily Opuntioideae and the most complete nuclear genome for Cactaceae to date and will lay the foundation for future genomic work across the biologically and taxonomically complicated prickly pear cacti.

Molecular evolution of a reproductive barrier in maize and related species.

Three cross-incompatibility loci each control a distinct reproductive barrier in both domesticated maize (Zea mays ssp. mays) and its wild teosinte relatives. These three loci, Teosinte crossing barrier1 (Tcb1), Gametophytic factor1 (Ga1), and Ga2, each play a key role in preventing hybridization between incompatible populations and are proposed to maintain the barrier between domesticated and wild subspecies. Each locus encodes both a silk-active and a matching pollen-active pectin methylesterase (PMEs). To investigate the diversity and molecular evolution of these gametophytic factor loci, we identified existing and improved models of the responsible genes in a new genome assembly of maize line P8860 that contains active versions of all three loci. We then examined fifty-two assembled genomes from seventeen species to classify haplotype diversity and identify sites under diversifying selection during the evolution of these genes. We show that Ga2, the oldest of these three loci, was duplicated to form Ga1 at least 12 million years ago. Tcb1, the youngest locus, arose as a duplicate of Ga1 before or around the time of diversification of the Zea genus. We find evidence of positive selection during evolution of the functional genes at an active site in the pollen-expressed PME and predicted surface sites in both the silk- and pollen-expressed PMEs. The most common allele at the Ga1 locus is a conserved ga1 allele (ga1-Off), which is specific haplotype containing three full-length PME gene copies, all of which are non-coding due to conserved stop codons and are between 610 thousand and 1.5 million years old. We show that the ga1-Off allele is associated with and likely generates 24-nt siRNAs in developing pollen-producing tissue, and these siRNAs map to functional Ga1 alleles. In previously-published crosses, the ga1-Off allele was associated with reduced function of the typically dominant functional alleles for the Ga1 and Tcb1 barriers. Taken together, this seems to be an example of an allele at a reproductive barrier locus being associated with an as yet undetermined mechanism capable of silencing the reproductive barrier.

Optimizing genomic prediction for complex traits via investigating multiple factors in switchgrass.

Genomic prediction has accelerated breeding processes and provided mechanistic insights into the genetic bases of complex traits. To further optimize genomic prediction, we assess the impact of genome assemblies, genotyping approaches, variant types, allelic complexities, polyploidy levels, and population structures on the prediction of 20 complex traits in switchgrass (Panicum virgatum L.), a perennial biofuel feedstock. Surprisingly, short read-based genome assembly performs comparably to or even better than long read-based assembly. Due to higher gene coverage, exome capture and multi-allelic variants outperform genotyping-by-sequencing and bi-allelic variants, respectively. Tetraploid models show higher prediction accuracy than octoploid models for most traits, likely due to the greater genetic distances among tetraploids. Depending on the trait in question, different types of variants need to be integrated for optimal predictions. Our study provides insights into the factors influencing genomic prediction outcomes, guiding best practices for future studies and for improving agronomic traits in switchgrass and other species through selective breeding.

Chromosome-level genome assembly and annotation of the Amur rat snake Elaphe schrenckii.

The Amur rat snake (Elaphe schrenckii), a widely distributed colubrid species in Northeast Asia, plays a critical role in controlling rodent and mouse populations in the wild. Despite its ecological and evolutionary significance, genomic resources for this non-venomous species have been limited. In this study, we present a high-quality, chromosome-level genome assembly of E. schrenckii, generated by PacBio HiFi long-read sequencing and Hi-C chromatin interaction mapping. The assembled genome size comprises 1.69 Gb, with a scaffold N50 length of 215 Mb. Hi-C scaffolding anchored the genome into 18 chromosomes, including one that represents the conserved Z chromosome of snakes, consistent with karyotypic observations. This assembly enables further gene annotation and analysis of chromosomal synteny patterns. Repetitive elements account for 53.2% of the genome, with LINE retrotransposons being the predominant class (23.2%). We identified 18,529 protein-coding genes, with 90.6% functionally annotated through homology-based methods. The genome assembly is highly complete, with a BUSCO score of 97.4% (tetrapoda_odb10). This resource provides a foundation for comparative studies of colubrid genome evolution, which also serves as a crucial reference for conservation genomics, particularly for Asian snake populations facing habitat fragmentation.

Telomere-to-telomere gap-free genome assembly of Euchiloglanis kishinouyei

Euchiloglanis kishinouyei is a typical endemic torrent catfish found in the Jinsha River system of the upper Yangtze River in China. It inhabits fast-flowing streams with steep elevation gradients and has evolved unique biological adaptations to thrive in these extreme environments. A high-quality genome provides key insights into the adaptive mechanisms driving its evolution in these harsh conditions. In this study, we successfully assembled the first telomere-to-telomere (T2T) genome of E. kishinouyei, marking the first T2T genome assembly of torrent catfish. The genome spans 886.74 Mb, anchored to 27 chromosomes, with over 99% coverage. The quality value (QV) and Benchmarking Universal Single-Copy Ortholog (BUSCO) scores were 46.96 and 98.50%, respectively, reflecting the high quality of the assembly. We identified repetitive elements accounting for 45.59% (404.23 Mb) of the genome and predicted 24,403 protein-coding genes, 94.37% of which were annotated. This high-fidelity genome assembly provides a valuable resource for future research and lays the foundation for exploring the ecological adaptation mechanisms and evolutionary biology of torrent catfish.

Telomere to telomere flax (Linum usitatissimum L.) genome assembly Unlocks insights beyond fatty acid metabolism pathways

Abstract One of China's most important resources is flax (Linum usitatissimum L.), an ancient crop with significant nutritional and therapeutic benefits. Despite its importance, existing flax reference genomes remain incomplete, with many unassembled sequences. Here, we report a gapless 482.51 Mb telomere-to-telomere (T2T) flax genome assembly, predicting 46,634 genes, of which 42,805 were functionally annotated. Repetitive sequences constitute 60.05% of the genome, and we identified 30 telomeres and 15 centromeres across the chromosomes. Whole-genome duplication (WGD) events were detected at approximately 11.5, 53.5, and 114 million years ago (MYA) based on synonymous substitution rates (Ks). The T2T assembly enabled the reconstruction of the fatty acid metabolic pathway, identifying 49 related genes, including 6 newly annotated ones. Furthermore, genomic co-localization was observed between fatty acid metabolism pathway-related genes and transposable elements, suggesting that functional differentiation of these genes in flax evolution may have occurred through transposon-mediated duplication events. Phylogenetic analysis of SAD and FAD gene families revealed that FAD genes segregate into FAD2 and FAD3/7/8 subfamilies. Gene structure and motif analyses demonstrated conserved exon-intron architectures and motif organization within each phylogenetic clade of SAD and FAD genes. Promoter region characterization identified numerous cis-acting elements responsive to phytohormones (MeJA and abscisic acid) and abiotic stresses (low temperature and anaerobic induction) in both SAD and FAD genes. Our knowledge of the evolution of the flax genome is improved by this excellent genome assembly, which also offers a strong basis for enhancing agricultural attributes and speeding up molecular breeding.

Characterization and De Novo Genome Assembly for New Rhizobium Ruizarguesonis Rhizobial Strain Vst36-3 Involved in Symbiosis with Pisum and Vicia Plants.

Pea and vetch are the important legume crops used as food, forage, and green manure in agriculture. Several new rhizobial isolates were obtained from vetch Vicia sativa root nodules. For one of them, Vst36-3, the nodulation test showed various specificity in relation to plant hosts from the Fabeae tribe, such as pea and vetch. It is in contrast to typical strains of the Rhizobium leguminosarum species complex (Rlc), which formed effective nodules as in pea and vetch. Here, whole genome sequencing was performed followed by de novo genome assembly for Vst36-3 strain. As a result of de novo genome assembly, seven contigs were generated using Oxford Nanopore Technology long reads and subsequently Illumina short reads. Phylogenetic analysis allowed us to identify this strain as Rhizobium ruizarguesonis Vst36-3. Analysis of the Sym plasmid containing the nod and nif genes revealed that R. ruizarguesonis Vst36-3 has a complete suite of essential genes for the development of symbiosis. Nevertheless, this new strain forms ineffective nodules in pea. This makes Rhizobium ruizarguesonis Vst36-3 attractive for the search and investigation of new factors of host specificity in future.

Retraction Note: Genome assembly of M. spongiola and comparative genomics of the genus Morchella provide initial insights into taxonomy and adaptive evolution

Retraction Note: Genome assembly of M. spongiola and comparative genomics of the genus Morchella provide initial insights into taxonomy and adaptive evolution

An annotated near-complete sequence assembly of the Magnaporthe oryzae 70-15 reference genome

Magnaporthe oryzae is a devastating fungal pathogen that causes substantial yield losses in rice and other cereal crops worldwide. A high-quality genome assembly is critical for addressing challenges posed by this pathogen. However, the current widely used MG8 assembly of the M. oryzae strain 70-15 reference genome contains numerous gaps and unresolved repetitive regions. Here, we report a complete 44.82 Mb high-quality nuclear genome and a 35.95 kb circular mitochondrial genome for strain 70-15, generated using deep-coverage PacBio high-fidelity sequencing (HiFi) and high-resolution chromatin conformation capture (Hi-C) data. Notably, we successfully resolved one or both telomere sequences for all seven chromosomes and achieved telomere-to-telomere (T2T) assemblies for chromosomes 2, 3, 4, 6, and 7. Based on this T2T assembly, we predicted 12,100 protein-coding genes and 493 effectors. This high-quality T2T assembly represents a significant advancement in M. oryzae genomics and provides an enhanced reference for studies in genome biology, comparative genomics, and population genetics of this economically important plant pathogen.

Chromosome-level genome assembly of Parotis chlorochroalis (Lepidoptera: Crambidae: Spilomelinae)

Parotis Hübner, 1831 is a genus within the family Crambidae, which is recognized as one of the most diverse families of Lepidoptera. Species within the genus Parotis can be readily distinguished from other closely related genera by their distinctive green or yellow-green body coloration. However, the genus Parotis has received relatively limited research attention, and the scarcity of genome-wide molecular resources has impeded a more comprehensive understanding of its evolution, adaptation, and phylogenetic relationships. This study reports the first genome assembly for Parotis chlorochroalis (Hampson, 1912), generated through PacBio Hi-Fi and Hi-C sequencing technologies. The assembled genome has a size of 456.23 Mb, comprising 31 chromosomes. Approximately 181.82 Mb, which constitutes 39.85% of the genome, has been identified as repetitive sequences. The genome assembly includes 16,299 protein-coding genes, of which 94.82% have been functionally annotated. This chromosome-level genome assembly not only advance understanding of P. chlorochroalis but also has the potential to facilitate genomic studies of other lepidopteran species.

Where did the Y chromosome in the spiny rat go, and how did it get there?

The XX/XY sex chromosome system is highly conserved across mammals, with rare exceptions where males lack a Y chromosome. Among these is the genus Tokudaia, a group of spiny rats comprising three species with unique sex chromosome systems deviating from the typical XX/XY pattern. While T. osimensis and T. tokunoshimensis have completely lost the Y chromosome, they retain some Y-linked genes on the X chromosome. In contrast, T. muenninki retains large sex chromosomes where both the X and Y chromosomes have fused with an autosome pair, carrying multi-copied Y-linked genes, including Sry. In this study, we generated chromosome-level genome assemblies for male individuals of all three Tokudaia species. By investigating loci typically associated with rodent Y-linked genes, we characterized sequences derived from the Tokudaia Y-chromosomal most recent common ancestor (Tokudaia Y-MRCA) and traced their evolutionary trajectories. Our analyses revealed that an initial X-to-Y translocation of a sequence containing the Boundary-Associated Segmental Duplication (BASD) in a common ancestor of Tokudaia marked the beginning of their unique sex chromosome evolution. The BASD, uniquely multi-copied in Tokudaia, facilitated further rearrangements through non-allelic homologous recombination and duplications. These processes culminated in subsequent Y-to-X translocations and duplications, leading to the complete loss of the Y chromosome as a distinct entity while preserving Y-linked genes in a multicopy state on the X chromosome. These findings highlight Tokudaia's rapid sex chromosome evolution within three million years and provide insights into the mechanisms underlying Y chromosome loss, contributing to a broader understanding of sex chromosome evolution in rodents.