GenomeScope: fast reference-free genome profiling from short reads

A chromosomal-level genome assembly of Begonia fimbristipula (Begoniaceae)

Begonia fimbristipula Hance (Begoniaceae) is a valuable medicinal herb that is classified as a protected species in Guangdong Province, China. In this study, we present a chromosome-level genome assembly of B. fimbristipula, aiming to facilitate its conservation and utilization. The genome was assembled using a combination of Oxford Nanopore long-read data and Illumina short-read data. The assembled genome size of B. fimbristipula is 462.11 Mb, with a scaffold N50 of 38.22 Mb. A total of 91.96% (424.94 Mb) of the sequences were anchored to 11 pseudochromosomes using Hi-C technology. The genome assembly exhibits a BUSCO completeness of 90.3% and an LTR Assembly Index (LAI) of 17.73. Genome annotation revealed 25,563 protein-coding genes and 274 tRNA genes. The high-quality chromosome-level assembly and annotation provide valuable insights into the genomic characteristics of B. fimbristipula, thereby offering essential resources for its conservation and economic utilization.

Chromosome-level genome assembly of the clam, Xishi tongue Coelomactra antiquata

Xishi tongue (Coelomactra antiquata), a commercially valuable marine bivalve, is distributed along the coastal waters of East Asia. In China, significant morphological and genetic differences have been observed between northern and southern populations. Overfishing and pollution have caused a severe decline in its natural populations, rendering the species endangered. In this study, we constructed the first chromosome-level genome of C. antiquata based on PacBio HiFi and Hi-C sequencing data. The assembled genome was 791.83 Mb in size, with the scaffold N50 of 44.05 Mb, and 99.79% of the sequences (790.13 Mb) were anchored to 19 chromosomes. A total of 24,592 protein-coding genes were predicted in the final assembly, of which 89.88% were functionally annotated. The BUSCO analysis revealed a genome completeness of 97.69%. The high-quality genome serves as a critical resource for advancing research on population genetics and germplasm conservation of this commercial shellfish, thereby facilitating sustainable management and conservation efforts.

Chromosome-level genome assembly and annotation of pawak croaker (Pennahia pawak)

The diversity of fish coloration is a fascinating scientific question. The pawak croaker (Pennahia pawak) is distinguished by its silver-white colour, setting it apart from other Sciaenidae species. However, the genomic information of this genus remains largely unexplored. This study aims to advance our understanding by assembling and annotating the genome of P. pawak at the chromosome level using multi-platform sequencing data. The assembled genome size of P. pawak is 613.02 Mb, closely matching the estimated size of 570.32 Mb from 21-mer analysis. The assembly features a scaffold N50 of 27.09 Mb, with 24 chromosomes successfully constructed using Hi-C technology, achieving a mounting rate of 99.31%. Genome annotation revealed that 26.20% of the genome consists of repetitive sequences and identified 26,361 protein-coding genes, of which 25,885 have functional annotations. This chromosome-level genome assembly of P. pawak provides valuable resources for comparative genomic studies within the Sciaenidae family and offers foundational data for researchers to understand its unique silver-white pigmentation.

Chromosome-Level Genome Assembly of the Heptageniid Mayfly Parafronurus youi (Ephemeroptera), and Its Annotation

As a group of winged insects (Pterygota) retaining many primitive characteristics, genomic research on mayflies remains highly limited, posing challenges to the study of their origin and evolution. In this study, we present the first chromosome-level genome assembly of the Chinese endemic mayfly Parafronurus youi utilizing Illumina short-read, PacBio long-read, and Hi-C sequencing technologies. The high-quality genome is 412.90 Mb in size with 99.07% of the sequences anchored to 11 chromosomes (ranging from 24.88 to 45.89 Mb). Genome annotation predicted 15,647 protein-coding genes with an average length of 9,934.7 bp, of which 85.9% were functionally annotated in the UniProtKB database. Repetitive elements accounted for 32.83% of the genome, including 27.33% transposable elements and 4.07% simple repeats. This study not only enriches genomic resources for mayflies but also establishes a foundation for investigating molecular mechanisms underlying ecological adaptation and evolutionary traits, contributing to the conservation of freshwater ecosystems.

Pervasive Conservation of Intron Number and Other Genetic Elements Revealed by a Chromosome-level Genome Assembly of the Hyper-polymorphic Nematode Caenorhabditis brenneri

With within-species genetic diversity estimates that span the gamut of that seen across the entirety of animals, the Caenorhabditis genus of nematodes holds unique potential to provide insights into how population size and reproductive strategies influence gene and genome organization and evolution. Our study focuses on Caenorhabditis brenneri, currently known as one of the most genetically diverse nematodes within its genus and, notably, across Metazoa. Here, we present a high-quality, gapless genome assembly and annotation for C. brenneri, revealing a common nematode chromosome arrangement characterized by gene-dense central regions and repeat-rich arms. A comparison of C. brenneri with other nematodes from the "Elegans" group revealed conserved macrosynteny but a lack of microsynteny, characterized by frequent rearrangements and low correlation of orthogroup size, indicative of high rates of gene turnover, consistent with previous studies. We also assessed genome organization within corresponding syntenic blocks in selfing and outcrossing species, affirming that selfing species predominantly experience loss of both genes and intergenic DNA. A comparison of gene structures revealed a strikingly small number of shared introns across species, yet consistent distributions of intron number and length, regardless of population size or reproductive mode, suggesting that their evolutionary dynamics are primarily reflective of functional constraints. Our study provides valuable insights into genome evolution and expands the nematode genome resources with the highly genetically diverse C. brenneri, facilitating research into various aspects of nematode biology and evolutionary processes.

Chromosome-scale haploid genome assembly of Durio zibethinus KanYao

Durian (Durio zibethinus) is a tropical fruit valued for its nutritional and commercial significance. In this study, we generated two high-quality, haplotype-resolved, chromosome-level genomes of the durian cultivar 'Kan Yao', each with 28 chromosomes. The total genome lengths were 737.2 Mb and 763.8 Mb, with contig N50 values of 22.9 Mb and 21.5 Mb, and scaffold N50 values of 25.9 Mb and 26.7 Mb, respectively. Nineteen chromosomes were assembled without gaps, while the remaining nine contained 1 to 10 gaps. Genome annotation identified 53,125 and 53,101 functional genes, as well as 5,254 and 5,496 non-coding RNAs. The high-quality assembled genomes will aid in the molecular breeding of durian.

K-mer-based Approaches to Bridging Pangenomics and Population Genetics

Many commonly studied species now have more than one chromosome-scale genome assembly, revealing a large amount of genetic diversity previously missed by approaches that map short reads to a single reference. However, many species still lack multiple reference genomes and correctly aligning references to build pangenomes can be challenging for many species, limiting our ability to study this missing genomic variation in population genetics. Here, we argue that k-mers are a very useful but underutilized tool for bridging the reference-focused paradigms of population genetics with the reference-free paradigms of pangenomics. We review current literature on the uses of k-mers for performing three core components of most population genetics analyses: identifying, measuring, and explaining patterns of genetic variation. We also demonstrate how different k-mer-based measures of genetic variation behave in population genetic simulations according to the choice of k, depth of sequencing coverage, and degree of data compression. Overall, we find that k-mer-based measures of genetic diversity scale consistently with pairwise nucleotide diversity (π) up to values of about π=0.025 (R2=0.97) for neutrally evolving populations. For populations with even more variation, using shorter k-mers will maintain the scalability up to at least π=0.1. Furthermore, in our simulated populations, k-mer dissimilarity values can be reliably approximated from counting bloom filters, highlighting a potential avenue to decreasing the memory burden of k-mer-based genomic dissimilarity analyses. For future studies, there is a great opportunity to further develop methods to identifying selected loci using k-mers.

Chromosome-level genome assembly of the short-faced mole (Scaptochirus moschatus)

The short-faced mole (Scaptochirus moschatus) belonging to the family Talpidae in the order Eulipotyphla is a good model for studying adaptive evolution of mammals because of its morphological and ecological characteristics. However, the lack of genome of short-faced mole has hindered previous studies. In this study, we assembled the genome of the short-faced mole based on Illumina, PacBio HiFi and Hi-C sequencing, and acquired the genome of the short-faced mole with the size of 2.17 Gb. 99.6% of the assembled genome were identified as complete BUSCOs, including 90.7% as complete single-copy BUSCOs and 8.9% as complete duplicated BUSCOs. The assembled genome was anchored to 24 chromosomes with an anchor rate of 94.33%, of which the 24th chromosome (Chr 24) probably contained the X and Y chromosomes. A total of 21,139 coding genes were predicted, and 8.58 exons per gene were predicted.

Chromosome-scale genome assembly of Phyllanthus emblica L. 'Yingyu'

Phyllanthus emblica L. is an edible plant with medicinal properties native to the dry-hot valley of Yunnan, China. Here, we report a de novo chromosome-scale genome of P. emblica wild type 'Yingyu'. 'Yingyu' is an octopoid plant with a total of 104 chromosomes. In total, we assembled and clustered 480 Mb of the genome and constructed 26 pseudochromosomes (haplotypes) of P. emblica wild type 'Yingyu' that encompass 97.9% of the genome and demonstrate to have relatively high integrity. We annotated 31,111 genes found in the genome of P. emblica. We screened 5 different tissues for searching the tissue-specific expression candidate genes. Four unknown function candidate genes were expressed at high levels in the flowers while genes relating to the biosynthesis of gibberellins and cellulose were specifically expressed in the fruits. The ascorbate biosynthesis-related genes were screened on P. emblica 'Yingyu' genome. The high expression level of 2 GDP-mannose epimerases and one L-galactono-1,4- lactone dehydrogenases in the fruit may be related to the activity of absorbate biosynthesis in the fruit. The chromosome-level genomic data for P. emblica we report will be important for the development of molecular markers to facilitate the selection of superior cultivars for processing and pharmaceuticals.

Chromosome-level genome assembly of Z strain European corn borer Ostrinia nubilalis (Lepidoptera: Crambidae)

European corn borer Ostrinia nubilalis (Hübner) is the most important pest of maize around world, and an ideal model for the sympatric host races, evolutionary and speciation research. In this study, we assembled a chromosome-level genome of Z strain O. nubilalis by the integrated Illumina short reads, PacBio Revio long reads, and Hi-C sequencing data. The chromosome-level genome was 480.04 Mb in total length with a contig N50 length of 16.51 Mb, which 98.59% genome anchored into 31 chromosomes. For the annotation, 1,046,695 repeat sequences in length of 212.07 Mb, 1,550 non-coding RNAs (including 1,208 tRNAs, 179 rRNAs, 62 miRNAs, 81 snRNAs, and 20 snoRNAs), and 17,145 protein-coding genes were identified. And 100% genes were functional annotated by SwissProt, NR, eggNOG, Go, and KEGG database. This genome provides a valuable genomics resource to elucidate the host plant adaptation, thermal adaptation, diapause induction, Bacillus thuringiensis toxin resistance, sexual communication, sympatric host races, and speciation process of O. nubilalis.

Genome and Tissue-Specific Transcriptome of the Tropical Milkweed (Asclepias curassavica)

Tropical milkweed (Asclepias curassavica) serves as a host plant for monarch butterflies (Danaus plexippus) and other insect herbivores that can tolerate the abundant cardiac glycosides that are characteristic of this species. Cardiac glycosides, along with additional specialized metabolites, also contribute to the ethnobotanical uses of A. curassavica. To facilitate further research on milkweed metabolism, we assembled the 197-Mbp genome of a fifth-generation inbred line of A. curassavica into 619 contigs, with an N50 of 10 Mbp. Scaffolding resulted in 98% of the assembly being anchored to 11 chromosomes, which are mostly colinear with the previously assembled common milkweed (A. syriaca) genome. Assembly completeness evaluations showed that 98% of the BUSCO gene set is present in the A. curassavica genome assembly. The transcriptomes of six tissue types (young leaves, mature leaves, stems, flowers, buds, and roots), with and without defense elicitation by methyl jasmonate treatment, showed both tissue-specific gene expression and induced expression of genes that may be involved in cardiac glycoside biosynthesis. Expression of a CYP87A gene, the predicted first gene in the cardiac glycoside biosynthesis pathway, was observed only in the stems and roots and was induced by methyl jasmonate. Together, this genome sequence and transcriptome analysis provide important resources for further investigation of the ecological and medicinal uses of A. curassavica.

Super pangenome of Vitis empowers identification of downy mildew resistance genes for grapevine improvement

Grapevine (Vitis) is one of the oldest domesticated fruit crops with great cultural and economic importance. Here we assembled and annotated haplotype-resolved genomes of 72 global Vitis accessions including 25 wild and 47 cultivated grapevines, among which genomes for 60 grapevines are newly released. Haplotype-aware phylogenomics disentangled the mysterious hybridization history of grapevines, revealing the enormous genetic diversity of the Vitis genus. Pangenomic analysis reveals that European cultivars, more susceptible to the destructive disease downy mildew (DM), have a smaller repertoire of resistance genes in the NLR family encoding the TIR-NBARC-LRR domain. Through extensive structural variation (SV) characterization, phenotyping, DM-infection transcriptome profiling of 113 Vitis accessions, and SV-expression quantitative trait loci analysis, we have identified over 63 SVs and their relevant genes significantly associated with DM resistance, exemplified by a lysine histidine transporter, VvLHT8. This haplotype-resolved super pangenome of the Vitis genus will accelerate breeding and enrich our understanding of the evolution and biology of grapevines.

Genome assembly of the temporary socially parasitic spiny ant Polyrhachis lamellidens and its host Camponotus japonicus

Polyrhachis lamellidens is a temporary socially parasitic ant. The newly mated P. lamellidens queen takes over a colony of several Camponotus ant species and uses the labour of the host workers in the early stages of social parasitism. To facilitate genomic resources for these species, we assembled and annotated the chromosomal genome of P. lamellidens using the 10× Genomics linked-read and Hi-C sequencing, and the draft genome of its host, Camponotus japonicus, using long-read sequencing with the Revio system. The P. lamellidens chromosomal genome assembly is 214.1 Mb, 95.5% BUSCO completeness, and contains 13,703 protein-coding genes. The C. japonicus draft genome assembly is 314.2 Mb, 99.0% BUSCO completeness, and contains 11,207 protein-coding genes. Genome-wide phylogeny and synteny analysis confirmed the phylogenetic position of P. lamellidens and C. japonicus, and a high level of synteny with the genome of both ant species. In addition, P. lamellidens possesses nearly identical chemosensory proteins to its host, C. japonicus, and these genes tended to exhibit higher expression levels in the newly mated queen. The genome assemblies of P. lamellidens and its host C. japonicus provide a valuable resource for the molecular biological and bioinformatic basis for studying the strategy of social parasitism in ants.

Chromosome-level genome assembly and improved annotation of onion genome (Allium cepa L.)

Onion (Allium cepa L.) is an economically valuable crop, but its large, repeat-enriched genome makes genome assembly difficult and limits molecular breeding and biological studies. Herein, we present a chromosomal-level reference genome assembly of the double-haploid onion line DHW30006, constructed by combining PacBio, Illumina, and Hi-C sequencing approaches. The assembled genome totaled 12.77 Gb, with 65,730 gene models, and was anchored to eight pseudo-chromosomes covering 12.07 Gb (94.5%), with a scaffold N50 of 1.40 Gb. DHW30006 onion genome contained improved gene models covering approximately 580 Mb (4.54%) of the genic regions with an average gene length of 8,827 bp and 5.48 exons per gene. These gene models represented the most improved annotation among Allium genomes. This onion genome will serve as a valuable resource for breeding and biological research in Allium plants.

Chromosome-level genome assembly of Phytoseiulus persimilis Athias-Henriot

As a globally recognized predatory mite, Phytoseiulus persimilis Athias-Henriot is known for its highly effective control of pest mites. Also, as a model species in Phytoseiidae, P. persimilis possesses unique biological characteristics, such as the first offspring developing into a male with a strict sex sequence. However, the genetic mechanisms have not been fully unrevealed yet. To lay the groundwork for genetic research, we presented a high-quality chromosomal genome of P. persimilis with PacBio HiFi and Hi-C data. The total length of genome is 214.23 Mb, of which 190.48 (88.91%) is anchored on 4 chromosomes. The scaffold N50 is 57.95 Mb and the BUSCO (Benchmarking Universal Single-Copy Orthologs) completeness is 98.3%. Repeat elements comprise 27.59% (59.10 Mb) of the genome. The genome contained 15,847 predicted protein-coding genes, 12,344 of which were annotated for function. This high-quality genome of P. persimilis would allow us to explore the genetic mechanism underlying the biological characteristics of the Phytoseiidae species, and provide possibilities for the industrial optimization of commercial predatory mites in the future.

IMA GENOME - F20 A draft genome assembly of Agroatheliarolfsii, Ceratobasidiumpapillatum, Pyrenopezizabrassicae, Neopestalotiopsismacadamiae, Sphaerellopsisfilum and genomic resources for Colletotrichumspaethianum and Colletotrichumfructicola

This is a genome announacment there is no abstract

A chromosome-level genome assembly of Mylabris sibirica Fischer von Waldheim, 1823 (Coleoptera, Meloidae)

Mylabris sibirica is a hypermetamorphic insect that primarily feeds on oilseed rape during the adult stage. However, the limited availability of genomic resources hinders our understanding of the gene function, medical use, and ecological adaptation in M. sibirica. Here, a high-quality chromosome-level genome of M. sibirica was generated by PacBio, Illumina, and Hi-C technologies. Its genome size was 138.45 Mb, with a scaffold N50 of 13.84 Mb and 99.85% (138.25 Mb) of the assembly anchors onto 10 pseudo-chromosomes. BUSCO analysis showed this genome assembly had a high-level completeness of 100% (n = 1,367), containing 1,358 (99.4%) single-copy BUSCOs and 8 (0.6%) duplicated BUSCOs. In addition, a total of 11,687 protein-coding genes and 35.46% (49.10 Mb) repetitive elements were identified. The high-quality genome assembly offers valuable genomic resources for exploring gene function, medical use, and ecology.

k-mer approaches for biodiversity genomics

The wide array of currently available genomes displays a wonderful diversity in size, composition, and structure and is quickly expanding thanks to several global biodiversity genomics initiatives. However, sequencing of genomes, even with the latest technologies, can still be challenging for both technical (e.g., small physical size, contaminated samples, or access to appropriate sequencing platforms) and biological reasons (e.g., germline-restricted DNA, variable ploidy levels, sex chromosomes, or very large genomes). In recent years, k-mer-based techniques have become popular to overcome some of these challenges. They are based on the simple process of dividing the analyzed sequences (e.g., raw reads or genomes) into a set of subsequences of length k, called k-mers, and then analyzing the frequency or sequences of those k-mers. Analyses based on k-mers allow for a rapid and intuitive assessment of complex sequencing data sets. Here, we provide a comprehensive review to the theoretical properties and practical applications of k-mers in biodiversity genomics with a special focus on genome modeling.

De novo genome hybrid assembly and annotation of the endangered and euryhaline fish Aphanius iberus (Valenciennes, 1846) with identification of genes potentially involved in salinity adaptation

BACKGROUND

The sequencing of non-model species has increased exponentially in recent years, largely due to the advent of novel sequencing technologies. In this study, we construct the Reference Genome of the Spanish toothcarp (Aphanius iberus (Valenciennes, 1846)), a renowned euryhaline fish species. This species is native to the marshes along the Mediterranean coast of Spain and has been threatened with extinction as a result of habitat modification caused by urbanization, agriculture, and its popularity among aquarium hobbyists since the mid-twentieth century. It is also one of the first Reference Genome for Euro-Asian species within the globally distributed order Cyprinodontiformes. Additionally, this effort aims to enhance our comprehension of the species' evolutionary ecology and history, particularly its remarkable adaptations that enable it to thrive in diverse and constantly changing inland aquatic environments.

RESULTS

A hybrid assembly approach was employed, integrating PacBio long-read sequencing with Illumina short-read data. In addition to the assembly, an extensive functional annotation of the genome is provided by using AUGUSTUS, and two different approaches (InterProScan and Sma3s). The genome size (1.15 Gb) is consistent with that of the most closely related species, and its quality and completeness, as assessed with various methods, exceeded the suggested minimum thresholds, thus confirming the robustness of the assembly. When conducting an orthology analysis, it was observed that nearly all genes were grouped in orthogroups that included genes of genetically similar species. GO Term annotation revealed, among others, categories related with salinity regulation processes (ion transport, transmembrane transport, membrane related terms or calcium ion binding).

CONCLUSIONS

The integration of genomic data with predicted genes presents future research opportunities across multiple disciplines, such as physiology, reproduction, disease, and opens up new avenues for future studies in comparative genomic studies. Of particular interest is the investigation of genes potentially associated with salinity adaptation, as identified in this study. Overall, this study contributes to the growing database of Reference Genomes, provides valuable information that enhances the knowledge within the order Cyprinodontiformes, and aids in improving the conservation status of threatened species by facilitating a better understanding of their behavior in nature and optimizing resource allocation towards their preservation.

Genome assembly of Hawaiian flower thrips Thrips hawaiiensis (Thysanoptera: Thripidae)

The Hawaiian flower thrips, Thrips hawaiiensis, is a common flower inhabiting pest of various horticultural plant species. It damages flowers and fruits by puncturing. T. hawaiiensis shows a rapidly developed resistance to chemical control. The lack of a high-quality reference genome limits our understanding of the genetics of T. hawaiiensis. Here, we sequenced the genome of T. hawaiiensis using Oxford Nanopore sequencing technology, Illumina, and Hi-C technology, yielding a genome assembly of 287.59 Mb with scaffold N50 of 13.84 Mb. BUSCO analysis demonstrated the T. hawaiiensis genome assembly has a high-level completeness of 98.7%. In total, 18,289 protein-coding genes were annotated and 26.69% of the genome were annotated as repeats. Our study presents the first high-quality genome assembly of T. hawaiiensis and lays the foundation for further studies on thrips genetic characteristics and pest management.

Novel insight of the SVP gene involved in pedicel length based on genomics analysis in cherry

KEY MESSAGE

PcSVP was identified based on Prunus conradinae genome and was further overexpressed in A. thaliana to comfirm it was a key factor in flower development, causing the pedicels elongation. Prunus conradinae is an endemic plant resource in China with high ornamental and economic values. To generate useful genomic resources for expanding insights into the evolutionary history of this important plant, the chromosome-level genome and organelle genomes of P. conradinae are de novo assembled and functionally annotated. The chromosome-level haploid genome of autotetraploid P. conradinae was assembled with 262.79 Mb with 27,802 protein-coding genes annotated. The complete chloroplast and mitochondrial genome of P. conradinae are found to be 157,715 bp and 434,334 bp, respectively. According to evolutionary analysis, P. conradinae was closely related to P. serrulata and P. yedoensis, and they diverged from their common ancestor approximately 6.0 million years ago. There were 108 gene families that significantly expanded during P. conradinae evolution and 56 shared positively selected genes. Selective sweep analysis based on the whole-genome resequencing of wild cherries from Fujian and Zhejiang indicated that genes involved in flower development and stress responses were potentially under selection. Pedicel length varied greatly among Prunus species and was a significant identifying characteristic. Ectopic overexpression of PcSVP in Arabidopsis thaliana suggested that it was a key factor in flower development, causing the sepals curling and pedicels elongation. These findings will contribute to the discovery of key functional genes involved in the agronomic or biological traits of P. conradinae, as well as the future development, utilisation and germplasm conservation of wild cherries.

High-quality genome assembly and annotation of the crested gecko (Correlophus ciliatus)

Correlophus ciliatus, or the crested gecko, is widely kept as a pet in many countries around the world due to its ease to care and bred and its high survival rate. However, there is limited number of genomic studies on the crested gecko. In this study, we generated a high-quality chromosome-level genome assembly of the crested gecko by combining Nanopore, Illumina, and Hi-C data. The genome assemble has a size of 1.66 Gb, with scaffold N50 of 109.97 Mb, and 99.52% of the scaffold anchored on 19 chromosomes. The BUSCO analysis indicated a gene completeness of 90.3% (n = 7,480), including 6,673 (89.2%) single-copy genes and 84 (1.1%) duplicated genes. Additionally, we identified 21,065 protein-coding genes using the MAKER3 annotation toolkit, with 41.98% (697.51 Mb) consisting of repetitive elements. Among these, 21,037 genes were validated through InterProScan5. Our study is the first to report a chromosome-level genome for the crested gecko. It provides valuable genomic resources for understanding molecular mechanisms under many interesting traits of the species.

A chromosome-level genome assembly of the Peruvian Algarrobo (Neltuma pallida) provides insights on its adaptation to its unique ecological niche

The dry forests of northern Peru are dominated by the legumous tree Neltuma pallida which is adapted to hot arid and semiarid conditions in the tropics. Despite having been successfully introduced in multiple other areas around the world, N. pallida is currently threatened in its native area, where it is invaluable for the dry forest ecosystem and human subsistence. A major tool for enhancing ecosystem conservation and understanding the adaptive properties of N. pallida to dry forest ecosystems is the construction of a reference genome sequence. Here, we report on a high-quality reference genome for N. pallida. The final genome assembly size is 403.7 Mb, consisting of 14 pseudochromosomes and 63 scaffolds with an N50 size of 26.2 Mb and a 34.3% GC content. Use of Benchmarking Universal Single Copy Orthologs revealed 99.2% complete orthologs. Long terminal repeat elements dominated the repetitive sequence content which was 51.2%. Genes were annotated using N. pallida transcripts, plant protein sequences, and ab initio predictions resulting in 22,409 protein-coding genes encoding 24,607 gene models. Comparative genomic analysis showed evidence of rapidly evolving gene families related to disease resistance, transcription factors, and signaling pathways. The chromosome-scale N. pallida reference genome will be a useful resource for understanding plant evolution in extreme and highly variable environments.

Genomic Resources for the Scuttle Fly Megaselia abdita: A Model Organism for Comparative Developmental Studies in Flies

The order Diptera (true flies) holds promise as a model taxon in evolutionary developmental biology due to the inclusion of the model organism, Drosophila melanogaster, and the ability to cost-effectively rear many species in laboratories. One of them, the scuttle fly Megaselia abdita (Phoridae) has been used in evolutionary developmental biology for 30 years and is an excellent phylogenetic intermediate between fruit flies and mosquitoes but remains underdeveloped in genomic resources. Here, we present a de novo chromosome-level assembly and annotation of M. abdita and transcriptomes of 9 embryonic and 4 postembryonic stages. We also compare 9 stage-matched embryonic transcriptomes between M. abdita and D. melanogaster. Our analysis of these resources reveals extensive chromosomal synteny with D. melanogaster, 28 orphan genes with embryo-specific expression including a novel F-box LRR gene in M. abdita, and conserved and diverged features of gene expression dynamics between M. abdita and D. melanogaster. Collectively, our results provide a new reference for studying the diversification of developmental processes in flies.

A Near Complete Genome Assembly of the Oshima Cherry Cerasus speciosa

The Oshima cherry (Cerasus speciosa), which is endemic to Japan, has significant cultural and horticultural value. In this study, we present a near complete telomere-to-telomere genome assembly for C. speciosa, derived from the old growth "Sakurakkabu" tree on Izu Oshima Island. Using Illumina short-read, PacBio long-read, and Hi-C sequencing, we constructed a 269.3 Mbp genome assembly with a contig N50 of 32.0 Mbp. We examined the distribution of repetitive sequences in the assembled genome and identified regions that appeared to be centromeric. Detailed structural analysis of these putative centromeric regions revealed that the centromeric regions of C. speciosa comprised repetitive sequences with monomer lengths of 166 or 167 bp. Comparative genomic analysis with Prunus sensu lato genome revealed structural variations and conserved syntenic regions. This high-quality reference genome provides a crucial tool for studying the genetic diversity and evolutionary history of Cerasus species, facilitating advancements in horticultural research and the preservation of this iconic species.

Long-term human influence on the demography and genetic diversity of the hyperdominant Bertholletia excelsa in the Amazon Basin

The Amazon rainforest is characterized by a limited number of hyperdominant trees that play an oversized role in its ecosystems, nutrient cycle, and rainfall production. Some of these, such as the Brazil nut, appear to have been intensively exploited and dispersed by Indigenous populations since their earliest arrival in this part of South America around 13,000 years ago. However, the genetic diversity-and geographic structure-of these species remains poorly understood, as does their exact relationship with past human land use. We use a new genome assembly for Brazil nut to analyze 270 individuals sampled at areas with varying intensities of archaeological evidence. We demonstrate that overall low genetic diversity, with a notable decrease since the Late Pleistocene, is accompanied by significant geographic structure, where evidence for improved gene flow and regeneration by long-term traditional human management is linked to increased genetic diversity. We argue that historical perspectives on the genetic diversity of key tree species, such as the Brazil nut, can support the development of more active management strategies today.

A fully phased octoploid strawberry genome reveals the evolutionary dynamism of centromeric satellites

We systematically examine the application of different phasing strategies to decrypt strawberry genome organization and produce a fully phased and accurate reference genome for Fragaria x ananassa cv. "EA78" (2n = 8x = 56). We identify 147 bp canonical centromeric repeats across 50 strawberry chromosomes and uncover the formation of six neocentromeres through centromere turnover. Our findings indicate strawberry genomes have diverged centromeric satellite arrays among chromosomes, particularly across homoeologs, while maintaining high sequence similarity between homologs. We trace the evolutionary dynamics of centromeric repeats and find substantial centromere size expansion in wild and cultivated octoploids compared to the diploid ancestor, F. vesca.

Transposon proliferation drives genome architecture and regulatory evolution in wild and domesticated peppers

Pepper (Capsicum spp.) is a widely consumed vegetable with exceptionally large genomes in Solanaceae, yet its genomic evolutionary history remains largely unknown. Here we present 11 high-quality Capsicum genome assemblies, including two gap-free genomes, covering four wild and all five domesticated pepper species. We reconstructed the ancestral karyotype and inferred the evolutionary trajectory of peppers. The expanded and variable genome sizes were attributed to differential transposable element accumulations, which shaped 3D chromatin architecture and introduced mutations associated with traits such as fruit orientation and colour. Using a chromatin accessibility atlas of Capsicum, we highlight the influence of transposable elements on regulatory element evolution. Furthermore, by constructing a haploblock map of 124 pepper core germplasms, we uncover frequent introgressions that facilitate the formation of sweet blocky pepper and the acquisition of important traits such as resistance to pepper mild mottle virus. These findings on the genomic and functional evolution of Capsicum will benefit pepper breeding.

The first engkabang jantong (Rubroshorea macrophylla) genome survey data

The engkabang jantong (Rubroshorea macrophylla) is one of the most indispensable tree species for reforestation due to its high survival rate and rapid growth rate. Due to relatively low genetic interest of this tree species, its genomic landscape has since faced scarcity, impeding our further elucidation on genes that are involved in expressing its aforementioned superior properties. In this study, we performed genome survey and microsatellite analysis of engkabang jantong. Based on the results, the estimated genome size of this species is 312,071,515 bp with 18.43 % repeated sequences and 1.16 % heterozygosity. BUSCO analysis unearthed that 83.5 % of the contigs are single-copy genes whereas 12.7 % of them are duplicated. Only 2.8 % and 1 % of them are fragmented and missing respectively. The short-read sequencing results obtained from the Illumina platform in this study will be essential to complement the Nanopore long-read sequencing results in hybrid genome assembly endeavors in the near future.

Genome of tropical bed bug Cimex hemipterus (Cimicidae, Hemiptera) reveals tetraspanin expanded in bed bug ancestor

Cimex species are ectoparasites that exclusively feed on warm-blooded animals such as birds and mammals. Three cimicid species are known to be persistent pests for humans, including the tropical bed bug Cimex hemipterus, common bed bug Cimex lectularius, and Eastern bat bug Leptocimex boueti. To date, genomic information is restricted to the common bed bug C. lectularius, which limits understanding their biology and to provide controls of bed bug infestations. Here, a chromosomal-level genome assembly of C. hemipterus (495 Mb [megabase pairs]) contained on 16 pseudochromosomes (scaffold N50 = 34 Mb), together with 9 messenger RNA and small RNA transcriptomes were obtained. In comparison between hemipteran genomes, we found that the tetraspanin superfamily was expanded in the Cimex ancestor. This study provides the first genome assembly for the tropical bed bug C. hemipterus, and offers an unprecedented opportunity to address questions relating to bed bug infestations, as well as genomic evolution to hemipterans more widely.

A high-quality chromosome-level genome assembly of the mulberry looper, Phthonandria atrilineata

The mulberry looper (Phthonandria atrilineata), a geometrid moth, plays a pivotal role in the destruction of mulberry trees (Morus spp.). In China, P. atrilineata is the most significant insect pest to sericulture, as it feeds on mulberry leaves and spreads diseases. The outbreak trend of P. atrilineata has been expanding yearly, causing substantial economic losses. Despite its ecological and economic importance, knowledge about the genomic background of P. atrilineata remains limited. Here, we report a chromosome-level reference genome of P. atrilineata, with a total size of 336.55 Mb, containing 15,026 protein-coding genes and 39.72% repeat sequences. These findings have the potential to shed light on the genetic basis of the destructive nature and environmental adaptation of P. atrilineata, offering valuable genomic resources for understanding genome evolution and pest management within this Lepidopteran pest.

Chromosome-Level Genome Assembly and Comparative Genomic Analysis of Planiliza haematocheilus: Insights into Environmental Adaptation and Hypoxia Tolerance Mechanisms

Planiliza haematocheilus, a teleostan species noted for its ecological adaptability and economic significance, thrives in both freshwater and marine environments. This study presents a novel chromosome-level genome assembly through Hi-C, PacBio CCS, and Illumina sequencing methods. The assembled genome has a final size of 651.58 Mb, with 24 chromosomes anchoring 91.94% of contigs. Contig N50 and scaffold N50 are respectively measured at 25.52 Mb and 28.59 Mb. Of the 22,476 protein-coding genes identified in the genome, 21,834 have functional annotations. BUSCO (Benchmarking Universal Single-Copy Orthologs) genome and gene annotation assessments yielded scores of 96% and 96.6%, respectively. The genome of P. haematocheilus revealed 228 expanded and 1433 contracted gene families. Comparative genomic analyses highlight adaptations and hypoxia tolerance, linked to protein synthesis, immune response, and metabolic regulation. The high-quality genome assembly supports advanced studies on gene expression patterns under different environmental stressors, contributing to genetic enhancement efforts for this economically important aquaculture species.

Chromosome-level genome assembly of Cyperus iria, an aggressive weed of rice

Cyperus iria is an aggressive weed of rice throughout the world. Until now, the reference genome of C. iria has not been published. Here, we completed the chromosome-level genome assembly of C. iria based on Illumina, PacBio and Hi-C reads. The assembled genome size of C. iria was 479.08 Mb with a contig N50 of 7.02 Mb. 68 pseudochromosomes were produced using Hi-C scaffolding, accounting for 99.65% of the assembled genome. The number of predicted protein-coding genes is 47,395, of which 93.26% were annotated, and 37.69% repetitive sequences were identified. Our study provided a valuable genomic resource for the molecular biology research and the management of C. iria.

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.

Comprehensive genome annotation of Trilocha varians, a new model species of Lepidopteran insects

Trilocha varians is a member of the bombycid moths. Since T. varians has a considerably shorter generation period than the prevailing model species, Bombyx mori, this species would be a novel model insect in Lepidoptera. To facilitate further use of T. varians, we developed genome annotation information on the chromosome-scale assembly of T. varians previously published by our group. 9 RNA-seq datasets and 2 Iso-seq datasets were submitted for transcriptome-based gene prediction. As a result, 16,266 protein-coding genes were predicted on the latest genome assembly, and 98.6% of BUSCO sequences were present in our gene models. ATAC-seq was also conducted to determine chromatin accessibility across the genome. Finally, piRNA-targeted small RNA-seq revealed T. varians genome harbours 517 piRNA clusters (piCs). This information will encourage and facilitate potential users who plan to use this species.

A chromosome-level genome assembly of Meteorus pulchricornis Wesmael (Hymenoptera: Braconidae)

Meteorus pulchricornis Wesmael (Hymenoptera: Braconidae) is an important parasitoid of lepidopteran insects. So far, only three scaffold-level genomes have been published for the genus Meteorus. In this study, we present a high-quality, chromosome-level genome assembly of M. pulchricornis, characterized by high accuracy and contiguity. This assembly was achieved using Oxford Nanopore Technologies long-read, MGI-SEQ short-read, and Hi-C sequencing methods. The final assembly was 158.5 Mb in genome size, with 153.8 Mb (97.03%) assigned to ten pseudochromosomes. The scaffold N50 length reached 17.51 Mb, and the complete Benchmarking Universal Single-Copy Orthologs (BUSCO) score was 99.3%. The genome contains 28.29 Mb of repetitive elements, accounting for 18.39% of the total genome size. We identified 12,342 protein-coding genes, of which 12,308 genes were annotated functionally. Our investigation into gene family evolution in M. pulchricornis showed that 563 gene families expanded, 1,739 contracted, and 58 underwent rapid evolution. The high-quality genome assembly we report here is advantageous for further research on parasitoid wasps and provides a foundational data resource for natural enemy studies.

A Chromosome-Scale Genome of Trametes versicolor and Transcriptome-Based Screening for Light-Induced Genes That Promote Triterpene Biosynthesis

Trametes versicolor is an important fungus with medicinal properties and a significant role in lignocellulose degradation. In this study, we constructed a high-quality chromosome-level genome of T. versicolor using Illumina, PacBio HiFi, and Hi-C sequencing technologies. The assembled genome is 47.42 Mb in size and contains 13,307 protein-coding genes. BUSCO analysis revealed genome and gene completeness results of 95.80% and 95.90%, respectively. Phylogenetic analysis showed that T. versicolor is most closely related to T. pubescens, followed by T. cinnabarina and T. coccinea. Comparative genomic analysis identified 266 syntenic blocks between T. versicolor and Wolfiporia cocos, indicating a conserved evolutionary pattern between the two species. Gene family analysis highlighted the expansion and contraction of genes in functional categories related to the biosynthesis of secondary metabolites, including several T. versicolor-specific genes. Key genes involved in lignocellulose degradation and triterpene production were identified within the CAZyme and CYP450 gene families. Transcriptomic analysis under dark and light conditions revealed significant changes in the expression of genes related to secondary metabolism, suggesting that light signals regulate metabolic pathways. A total of 2577 transporter proteins and 2582 membrane proteins were identified and mapped in the T. versicolor genome, and 33 secondary metabolite gene clusters were identified, including two light-sensitive triterpene biosynthesis clusters. This study offers a comprehensive genomic resource for further investigation into the functional genomics, metabolic regulation, and triterpene biosynthesis of T. versicolor, providing valuable insights into fungal evolution and biotechnological applications.

Complete genome sequence of a methanotrophic bacterium, Methylomicrobium lacus strain 22M6SE5-12 isolated from a freshwater sediment environment

We assembled the complete genome of Methylomicrobium lacus strain 22M6SE5-12 isolated from a freshwater sediment in South Korea. The genome consists of a 4.36-Mbp chromosome and two plasmids and has 3,961 coding sequences, 12 rRNA genes, and 55 tRNA genes. We identified a gene set encoding the particulate methane monooxygenase subunits.

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.

Global Invasion History and Genomic Signatures of Adaptation of the Highly Invasive Sycamore Lace Bug

Invasive species cause massive economic and ecological damages. Climate change has resulted in an unprecedented increase in the number and impact of invasive species; however, the mechanisms underlying these invasions are unclear. The sycamore lace bug, Corythucha ciliata, is a highly invasive species originating from North America and has expanded across the Northern Hemisphere since the 1960s. In this study, we assembled the C. ciliata genome using high-coverage Pacific Biosciences (PacBio), Illumina, and high-throughput chromosome conformation capture (Hi-C) sequencing. A total of 15,278 protein-coding genes were identified, and expansions of gene families with oxidoreductase and metabolic activities were observed. In-depth resequencing of 402 samples from native and nine invaded countries across three continents revealed 2.74 million single nucleotide polymorphisms. Two major invasion routes of C. ciliata were identified from North America to Europe and Japan, with a contact zone forming in East Asia. Genomic signatures of selection associated with invasion and long-term balancing selection in native ranges were identified. These genomic signatures overlapped with each other as well as with expanded genes, suggesting improvements in the oxidative stress and thermal tolerance of C. ciliata. These findings offer valuable insights into the genomic architecture and adaptive evolution underlying the invasive capabilities of species during rapid environmental changes.

Pan-genome analyses of 11 Fraxinus species provide insights into salt adaptation in ash trees

Ash trees (Fraxinus) exhibit rich genetic diversity and wide adaptation to various ecological environments, and several species are highly salt tolerant. Dissecting the genomic basis of salt adaptation in Fraxinus is vital for its resistance breeding. Here, we present 11 high-quality chromosome-level genome assemblies for Fraxinus species, which reveal two unequal subgenome compositions and two recent whole-genome triplication events in their evolutionary history. A Fraxinus pan-genome was constructed on the basis of structural variations and revealed that presence-absence variations (PAVs) of transmembrane transport genes have likely contributed to salt adaptation in Fraxinus. Through whole-genome resequencing of an F1 population from an interspecies cross of F. velutina 'Lula 3' (salt tolerant) with F. pennsylvanica 'Lula 5' (salt sensitive), we mapped salt-tolerance PAV-based quantitative trait loci (QTLs) and pinpointed two PAV-QTLs and candidate genes associated with Fraxinus salt tolerance. Mechanistically, FvbHLH85 enhances salt tolerance by mediating reactive oxygen species and Na+/K+ homeostasis, whereas FvSWEET5 enhances salt tolerance by mediating osmotic homeostasis. Collectively, these findings provide valuable genomic resources for Fraxinus salt-resistance breeding and the research community.

Degenerated vision, altered lipid metabolism, and expanded chemoreceptor repertoires enable Lindaspio polybranchiata to thrive in deep-sea cold seeps

BACKGROUND

Lindaspio polybranchiata, a member of the Spionidae family, has been reported at the Lingshui Cold Seep, where it formed a dense population around this nascent methane vent. We sequenced and assembled the genome of L. polybranchiata and performed comparative genomic analyses to investigate the genetic basis of adaptation to the deep sea. Supporting this, transcriptomic and fatty acid data further corroborate our findings.

RESULTS

We report the first genome of a deep-sea spionid, L. polybranchiata. Over long-term adaptive evolution, genes associated with vision and biological rhythmicity were lost, which may indirectly benefit oligotrophy by eliminating energetically costly processes. Compared to its shallow-sea relatives, L. polybranchiata has a significantly higher proportion of polyunsaturated fatty acids (PUFAs) and expanded gene families involved in the biosynthesis of unsaturated fatty acids and chromatin stabilization, possibly in response to high hydrostatic pressure. Additionally, L. polybranchiata has broad digestive scope, allowing it to fully utilize the limited food resources in the deep sea to sustain a large population. As a pioneer species, L. polybranchiata has an expanded repertoire of genes encoding potential chemoreceptor proteins, including ionotropic receptors (IRs) and gustatory receptor-like receptors (GRLs). These proteins, characterized by their conserved 3D structures, may enhance the organism's ability to detect chemical cues in chemosynthetic ecosystems, facilitating rapid settlement in suitable environments.

CONCLUSIONS

Our results shed light on the adaptation of Lindaspio to the darkness, high hydrostatic pressure, and food deprivation in the deep sea, providing insights into the molecular basis for L. polybranchiata becoming a pioneer species.

Population sequencing of cherry accessions unravels the evolution of Cerasus species and the selection of genetic characteristics in edible cherries

Cerasus is a subgenus of Prunus in the family Rosaceae that is popular owing to its ornamental, edible, and medicinal properties. Understanding the evolution of the Cerasus subgenus and identifying selective trait loci in edible cherries are crucial for the improvement of cherry cultivars to meet producer and consumer demands. In this study, we performed a de novo assembly of a chromosome-scale genome for the sweet cherry (Prunus avium L.) cultivar 'Burlat', covering 297.55 Mb and consisting of eight chromosomes with 33,756 protein-coding genes. The resequencing and population structural analysis of 384 Cerasus representative accessions revealed that they could be divided into four groups (Group 1, Group 2, Group 3, and Group 4). We inferred that Group 1 was the oldest population and Groups 2, 3, and 4 were clades derived from it. In addition, we found selective sweeps for fruit flavor and improved stress resistance in different varieties of edible cherries (P. avium, P. cerasus, and P. pseudocerasus). Transcriptome analysis revealed significant differential expression of genes associated with key pathways, such as sucrose starch and sucrose metabolism, fructose and mannose metabolism, and the pentose phosphate pathway, between the leaves and fruits of P. avium. This study enhances the understanding of the evolutionary processes of the Cerasus subgenus and provides resources for functional genomics research and the improvement of edible cherries.

Chromosome-level genome assembly of the seasonally polyphenic scorpionfly (Panorpa liui)

Mecoptera is a small relict order of insects within the Holometabola. Panorpidae is the most speciose family in Mecoptera. They are also known as scorpion flies due to the enlarged and upward recurved male genital bulb. Panorpa liui Hua, 1997, a member of Panorpidae, is a bivoltine species of seasonal color polyphenism in the lowland plain of northeastern China. In this study, we applied PacBio HiFi and Hi-C sequencing technologies to generate a chromosome-level genome reference of P. liui. The assembled genome is 678.26 Mbp in size, with 91.3% being anchored onto 23 pseudo-chromosomes. Benchmarking Universal Single-Copy Orthologs (BUSCO) estimation reveals the completeness of this assembly as 95.1%. By integrating full-length transcriptome and homologs of related species, we generated full annotation of this assembly, yielding a total of 15,960 protein-coding genes, of these, 15,892 genes were anchored on the 23 chromosomes. The high-quality genome provides critical genomic resources for population genetics and phylogenetic research on Mecoptera. It also offers valuable information for exploring the mechanisms underlying seasonal color polymorphism.

Chromosome-level haplotype-resolved genome of the tropical loach (Oreonectes platycephalus)

The flat-headed loach (Oreonectes platycephalus) is a small fish inhabiting headwaters of hillstreams of southern China. Its local populations are characterized by low genetic diversity and exceptionally high differentiation, making it an ideal model for studying small population isolates' persistence and adaptive potential. However, the lack of Oreonectes reference genomes limits endeavours toward these ambitions. We assembled the first haplotype-resolved chromosome-level genome of the genus Oreonectes using PacBio HiFi and Hi-C technologies. This genome consists of two haplotypes (24 pseudo-chromosomes in each), with sizes of 565.68 Mb (haplotype A) and 521.13 Mb (haplotype B) and scaffold N50 lengths of 22.80 Mb and 21.91 Mb, respectively. Chr01 was identified as the likely sex chromosome pair. After masking repetitive elements which accounted for 34.43% to 36.44% of the genome, there are 27,127 protein-coding genes in haplotype A and 25,576 in haplotype B. The availability of this haplotype-resolved chromosome-level reference genome will facilitate the study of population and conservation genetics of the flat-headed loach and other Oreonectes species.

The B Chromosome of Pseudococcus viburni: A Selfish Chromosome that Exploits Whole-Genome Meiotic Drive

Meiosis is generally a fair process: each chromosome has a 50% chance of being included into each gamete. However, meiosis can become aberrant with some chromosomes having a higher chance of making it into gametes than others. Yet, why and how such systems evolve remains unclear. Here, we study the unusual reproductive genetics of mealybugs, where only maternal-origin chromosomes are included in gametes during male meiosis, while paternal chromosomes are eliminated. One species-Pseudococcus viburni-has a segregating B chromosome that drives by escaping paternal genome elimination. We present whole genome and gene expression data from lines with and without B chromosomes. We identify B-linked sequences including 204 protein-coding genes and a satellite repeat that makes up a significant proportion of the chromosome. The few paralogs between the B and the core genome are distributed throughout the genome, arguing against a simple, or at least recent, chromosomal duplication of one of the autosomes to create the B. We do, however, find one 373 kb region containing 146 genes that appears to be a recent translocation. Finally, we show that while many B-linked genes are expressed during meiosis, most of these are encoded on the recently translocated region. Only a small number of B-exclusive genes are expressed during meiosis. Of these, only one was overexpressed during male meiosis, which is when the drive occurs: an acetyltransferase involved in H3K56Ac, which has a putative role in meiosis and is, therefore, a promising candidate for further studies.

A chromosome-level, haplotype-resolved genome assembly and annotation for the Eurasian minnow (Leuciscidae: Phoxinus phoxinus) provide evidence of haplotype diversity

BACKGROUND

In this study, we present an in-depth analysis of the Eurasian minnow (Phoxinus phoxinus) genome, highlighting its genetic diversity, structural variations, and evolutionary adaptations. We generated an annotated haplotype-phased, chromosome-level genome assembly (2n = 50) by integrating high-fidelity (HiFi) long reads and chromosome conformation capture data (Hi-C).

RESULTS

We achieved a haploid size of 940 megabase pairs (Mbp) for haplome 1 and 929 Mbp for haplome 2 with high scaffold N50 values of 36.4 Mb and 36.6 Mb and BUSCO scores of 96.9% and 97.2%, respectively, indicating a highly complete genome assembly. We detected notable heterozygosity (1.43%) and a high repeat content (approximately 54%), primarily consisting of DNA transposons, which contribute to genome rearrangements and variations. We found substantial structural variations within the genome, including insertions, deletions, inversions, and translocations. These variations affect genes enriched in functions such as dephosphorylation, developmental pigmentation, phagocytosis, immunity, and stress response. In the annotation of protein-coding genes, 30,980 messenger RNAs and 23,497 protein-coding genes were identified with a high completeness score, which further underpins the high contiguity of our genome assemblies. We performed a gene family evolution analysis by comparing our proteome to 10 other teleost species, which identified immune system gene families that prioritize histone-based disease prevention over NB-LRR-related-based immune responses. Additionally, demographic analysis indicates historical fluctuations in the effective population size of P. phoxinus, likely correlating with past climatic changes.

CONCLUSIONS

This annotated, phased reference genome provides a crucial resource for resolving the taxonomic complexity within the genus Phoxinus and highlights the importance of haplotype-phased assemblies in understanding haplotype diversity in species characterized by high heterozygosity.

The haplotype-resolved T2T genome for Bauhinia × blakeana sheds light on the genetic basis of flower heterosis

BACKGROUND

The Hong Kong orchid tree Bauhinia × blakeana Dunn has long been proposed to be a sterile interspecific hybrid exhibiting flower heterosis when compared to its likely parental species, Bauhinia purpurea L. and Bauhinia variegata L. Here, we report comparative genomic and transcriptomic analyses of the 3 Bauhinia species.

FINDINGS

We generated chromosome-level assemblies for the parental species and applied a trio-binning approach to construct a haplotype-resolved telomere-to-telomere (T2T) genome for B. blakeana. Comparative chloroplast genome analysis confirmed B. purpurea as the maternal parent. Transcriptome profiling of flower tissues highlighted a closer resemblance of B. blakeana to its maternal parent. Differential gene expression analyses revealed distinct expression patterns among the 3 species, particularly in biosynthetic and metabolic processes. To investigate the genetic basis of flower heterosis observed in B. blakeana, we focused on gene expression patterns within pigment biosynthesis-related pathways. High-parent dominance and overdominance expression patterns were observed, particularly in genes associated with carotenoid biosynthesis. Additionally, allele-specific expression analysis revealed a balanced contribution of maternal and paternal alleles in shaping the gene expression patterns in B. blakeana.

CONCLUSIONS

Our study offers valuable insights into the genome architecture of hybrid B. blakeana, establishing a comprehensive genomic and transcriptomic resource for future functional genetics research within the Bauhinia genus. It also serves as a model for exploring the characteristics of hybrid species using T2T haplotype-resolved genomes, providing a novel approach to understanding genetic interactions and evolutionary mechanisms in complex genomes with high heterozygosity.

Chromosome-scale assemblies of three Ormosia species: repetitive sequences distribution and structural rearrangement

BACKGROUND

The genus Ormosia belongs to the Fabaceae family; almost all Ormosia species are endemic to China, which is considered one of the centers of this genus. Thus, genomic studies on the genus are needed to better understand species evolution and ensure the conservation and utilization of these species. We performed a chromosome-scale assembly of O. purpureiflora and updated the chromosome-scale assemblies of O. emarginata and O. semicastrata for comparative genomics.

FINDINGS

The genome assembly sizes of the 3 species ranged from 1.42 to 1.58 Gb, with O. purpureiflora being the largest. Repetitive sequences accounted for 74.0-76.3% of the genomes, and the predicted gene counts ranged from 50,517 to 55,061. Benchmarking Universal Single-Copy Orthologs (BUSCO) analysis indicated 97.0-98.4% genome completeness, whereas the long terminal repeat (LTR) assembly index values ranged from 13.66 to 17.56, meeting the "reference genome" quality standard. Gene completeness, assessed using BUSCO and OMArk, ranged from 95.1% to 96.3% and from 97.1% to 98.1%, respectively.Characterizing genome architectures further revealed that inversions were the main structural rearrangements in Ormosia. In numbers, density distributions of repetitive elements revealed the types of Helitron and terminal inverted repeat (TIR) elements and the types of Gypsy and unknown LTR retrotransposons (LTR-RTs) concentrated in different regions on the chromosomes, whereas Copia LTR-RTs were generally evenly distributed along the chromosomes in Ormosia.Compared with the sister species Lupinus albus, Ormosia species had lower numbers and percentages of resistance (R) genes and transcription factor genes. Genes related to alkaloid, terpene, and flavonoid biosynthesis were found to be duplicated through tandem or proximal duplications. Notably, some genes associated with growth and defense were absent in O. purpureiflora.By resequencing 153 genotypes (∼30 Gb of data per sample) from 6 O. purpureiflora (sub)populations, we identified 40,146 single nucleotide polymorphisms. Corresponding to its very small populations, O. purpureiflora exhibited low genetic diversity.

CONCLUSIONS

The Ormosia genome assemblies provide valuable resources for studying the evolution, conservation, and potential utility of both Ormosia and Fabaceae species.

Chromosome-level genome assembly of Pinus massoniana provides insights into conifer adaptive evolution

Pinus massoniana, a conifer of significant economic and ecological value in China, is renowned for its wide adaptability and oleoresin production. We sequenced and assembled the chromosomal-level P. massoniana genome, revealing 80,366 protein-coding genes and significant gene family expansions associated with stress response and plant-pathogen interactions. Long-intron genes, which are predominantly presented in low-copy gene families, are strongly linked to the recent long terminal repeat burst in the Pinus genome. By reanalyzing population transcriptomic data, we identified genetic markers linked to oleoresin synthesis, including those within the CYP450 and TPS gene families. The results suggest that the genes of the resin terpene biosynthesis pathway can be activated in several cell types, and the oleoresin yield may depend on the rate-limiting enzymes. Using a multiomics algorithm, we identified several regulatory factors, including PmMYB4 and PmbZIP2, that interact with TPS and CYP450 genes, potentially playing a role in oleoresin production. This was further validated through molecular genetics analyses. We observed signatures of adaptive evolution in dispersed duplicates and horizontal gene transfer events that have contributed to the species adaptation. This study provides insights for further research into the evolutionary biology of conifers and lays the groundwork for genomic-assisted breeding and sustainable management of Masson pine.