High Contiguity Research Articles

Chromosomal-level genome assembly of the Antarctic sea urchin Sterechinus neumayeri, a model for Antarctic invertebrate biology.

The Antarctic sea urchin Sterechinus neumayeri (Echinoida;Echinidae) is routinely used as a model organism for Antarctic biology. Here, we present a high-quality genome of S. neumayeri. This chromosomal-level assembly was generated using PacBio long-read sequencing and HiC chromatin conformation capture sequencing. This 885.3 Mb assembly exhibits high contiguity with a scaffold length N50 of 36.7Mb assembled into 20 chromosomal length scaffolds. These putative chromosomes exhibit a high degree of synteny compared to other sea urchin models. We used transcript evidence gene modeling combined with sequence homology to identify 21,638 gene models that capture 97.4% of BUSCO orthologs. Among these, we were able to identify and annotate conserved developmental gene regulatory network orthologs, positioning S. neumayeri as a tractable model for comparative studies on evolution and development.

The genomes of Australian wild limes

Australian wild limes occur in highly diverse range of environments and are a unique genetic resource within the genus Citrus. Here we compare the haplotype-resolved genome assemblies of six Australian native limes, including four new assemblies generated using PacBio HiFi and Hi-C sequencing data. The size of the genomes was between 315 and 391 Mb with contig N50s from 29.5 to 35 Mb. Gene completeness of the assemblies was estimated to be from 98.4 to 99.3% and the annotations from 97.7 to 98.9% based upon BUSCO, confirming the high contiguity and completeness of the assembled genomes. High collinearity was observed among the genomes and the two haplotype assemblies for each species. Gene duplication and evolutionary analysis demonstrated that the Australian citrus have undergone only one ancient whole-genome triplication event during evolution. The highest number of species-specific and expanded gene families were found in C. glauca and they were primarily enriched in purine, thiamine metabolism, amino acids and aromatic amino acids metabolism which might help C. glauca to mitigate drought, salinity, and pathogen attacks in the drier environments in which this species is found. Unique genes related to terpene biosynthesis, glutathione metabolism, and toll-like receptors in C. australasica, and starch and sucrose metabolism genes in both C. australis and C. australasica might be important candidate genes for HLB tolerance in these species. Expanded gene families were not lineage specific, however, a greater number of genes related to plant-pathogen interactions, predominantly disease resistant protein, was found in C. australasica and C. australis.

Optimization of Ni-Cu binder composition and sintering time for enhanced mechanical properties of Mo alloys via liquid phase sintering

Liquid phase sintering of refractory alloys offers a promising approach to enhance mechanical properties while ensuring cost-effectiveness and near-net shaping capabilities. This study systematically explores the impact of sintering time and Ni-Cu binder composition on densification, shape retention, and mechanical properties of Mo alloys processed via liquid phase sintering. The aim is to identify optimal binder composition and sintering time for low-cost production of dense, near-net-shape Mo alloys with superior mechanical properties. The sinterability of Mo compacts is enhanced as the Ni-Cu ratio increases. However, excessive Ni content induces geometric distortion during sintering. Alloys with Ni-rich binders exhibit two liquids at the sintering temperature, each with differing Mo solubility, resulting in a dual-phase matrix on solidification. Both Cu-rich and Ni-rich binder compositions exhibit brittle δ-MoNi intermetallic compound formation, whose quantity increases with prolonged sintering times. Alloys characterized by low Mo solubility in the matrix, high Mo volume fraction, high Mo grain contiguity, and large dihedral angles demonstrate high structural integrity and resistance to geometric distortion. Conversely, alloys featuring high matrix volume fraction, low grain contiguity, elevated Mo solubility in the binder, and strong Mo-matrix interfaces exhibit enhanced strength, hardness, and ductility. Notably, an alloy with a Ni-Cu ratio of 3:1 sintered for just 30 min at 1420°C demonstrates outstanding mechanical properties—hardness of 410 HV, tensile strength of 920 MPa, and elongation of 9 %—comparable to or better than many previously reported refractory alloys.

Synergistic Enhancement of Mechanical Properties and Electrical Conductivity of Immiscible Bimetal: A Case Study on W–Cu

Immiscible bimetal systems, of which tungsten–copper (W–Cu) is a typical representative, have crucial applications in fields requiring both mechanical and physical properties. Nevertheless, it is a major challenge to determine how to give full play to the advantages of the two phases of the bimetal and achieve outstanding comprehensive properties. In this study, an ultrafine-grained W–Cu bimetal with spatially connected Cu and specific W islands was fabricated through a designed powder-mixing process and subsequent rapid low-temperature sintering. The prepared bimetal concurrently has a high yield strength, large plastic strain, and high electrical conductivity. The stress distribution and strain response of individual phases in different types of W–Cu bimetals under loading were quantified by means of a simulation. The high yield strength of the reported bimetal results from the microstructure refinement and high contiguity of the grains in the W islands, which enhance the contribution of W to the total plastic deformation of the bimetal. The high electrical conductivity is attributed to the increased mean free path of the Cu and the reduced proportion of phase boundaries due to the specific phase combination of W islands and Cu. This work provides new insight into modulating phase configuration in immiscible metallic composites to achieve high-level multi-objective properties.

Relics of interspecific hybridization retained in the genome of a drought-adapted peanut cultivar.

Peanut (Arachis hypogaea L.) is a globally important oil and food crop frequently grown in arid, semi-arid, or dryland environments. Improving drought tolerance is a key goal for peanut crop improvement efforts. Here we present the genome assembly and gene model annotation for 'Line8', a peanut genotype bred from drought tolerant cultivars. Our assembly and annotation are the most contiguous and complete peanut genome resources currently available. The high contiguity of the Line8 assembly allowed us to explore structural variation both between peanut genotypes and subgenomes. We detect several large inversions between Line8 and other peanut genome assemblies, and there is a trend for the inversions between more genetically diverged genotypes to have higher gene content. We also relate patterns of subgenome exchange to structural variation between Line8 homeologous chromosomes. Unexpectedly, we discover that Line8 harbors an introgression from A.cardenasii, a diploid peanut relative and important donor of disease resistance alleles to peanut breeding populations. The fully resolved sequences of both haplotypes in this introgression provide the first in situ characterization of A.cardenasii candidate alleles that can be leveraged for future targeted improvement efforts. The completeness of our genome will support peanut biotechnology and broader research into the evolution of hybridization and polyploidy.

Distributions, interactions, and dynamics of prokaryotes and phages in a hybrid biological wastewater treatment system

BackgroundUnderstanding the interactions and dynamics of microbiotas within biological wastewater treatment systems is essential for ensuring their stability and long-term sustainability. In this study, we developed a systematic framework employing multi-omics and Hi-C sequencing to extensively investigate prokaryotic and phage communities within a hybrid biofilm and activated sludge system.ResultsWe uncovered distinct distribution patterns, metabolic capabilities, and activities of functional prokaryotes through the analysis of 454 reconstructed prokaryotic genomes. Additionally, we reconstructed a phage catalog comprising 18,645 viral operational taxonomic units (vOTUs) with high length and contiguity using hybrid assembly, and a distinct distribution of phages was depicted between activated sludge (AS) and biofilm. Importantly, 1340 host-phage pairs were established using Hi-C and conventional in silico methods, unveiling the host-determined phage prevalence. The majority of predicted hosts were found to be involved in various crucial metabolic processes, highlighting the potential vital roles of phages in influencing substance metabolism within this system. Moreover, auxiliary metabolic genes (AMGs) related to various categories (e.g., carbohydrate degradation, sulfur metabolism, transporter) were predicted. Subsequent activity analysis emphasized their potential ability to mediate host metabolism during infection. We also profiled the temporal dynamics of phages and their associated hosts using 13-month time-series metagenomic data, further demonstrating their tight interactions. Notably, we observed lineage-specific infection patterns, such as potentially host abundance- or phage/host ratio-driven phage population changes.ConclusionsThe insights gained from this research contribute to the growing body of knowledge surrounding interactions and dynamics of host-phage and pave the way for further exploration and potential applications in the field of microbial ecology.7mTZubWt51_LqpKWPutADaVideo

The gapless genome assembly and multi-omics analyses unveil a pivotal regulatory mechanism of oil biosynthesis in the olive tree.

Olive is a valuable oil-bearing tree with fruits containing high levels of fatty acids. Oil production is a multifaceted process involving intricate interactions between fatty acid biosynthesis and other metabolic pathways that are affected by genetics and the developmental stages of the fruit. However, a comprehensive understanding of the underlying regulatory mechanisms is still lacking. Here, we generated a gap-free telomere-to-telomere assembly for Olea europaea cv. 'Leccino', representing an olive genome with the highest contiguity and completeness to date. The combination of time-course metabolomics and transcriptomics datasets revealed a negative correlation between fatty acid and flavonoid biosynthesis in the initial phase of olive fruit development, which was subject to an opposing regulatory mechanism mediated by the hub transcription factor MYC2. Multifaceted molecular assays demonstrated that MYC2 is a repressor of fatty acid biosynthesis by downregulating the expression of BCCP2 (biotin carboxylase carrier protein 2), while it acts as an activator of FLS (flavonol synthase), leading to an increase in flavonoid synthesis. Furthermore, the expression of MYC2 is regulated by fluctuations of methyl jasmonate content during olive fruit development. Our study completes a high-quality gapless genome of an olive cultivar, and provides new insight into the regulatory mechanisms underlying the biosynthesis of fatty acids and flavonoids in its fruit.

Haplotype-resolved genome assembly and implementation of VitExpress, an open interactive transcriptomic platform for grapevine

Haplotype-resolved genome assemblies were produced for Chasselas and Ugni Blanc, two heterozygous Vitis vinifera cultivars by combining high-fidelity long-read sequencing and high-throughput chromosome conformation capture (Hi-C). The telomere-to-telomere full coverage of the chromosomes allowed us to assemble separately the two haplo-genomes of both cultivars and revealed structural variations between the two haplotypes of a given cultivar. The deletions/insertions, inversions, translocations, and duplications provide insight into the evolutionary history and parental relationship among grape varieties. Integration of de novo single long-read sequencing of full-length transcript isoforms (Iso-Seq) yielded a highly improved genome annotation. Given its higher contiguity, and the robustness of the IsoSeq-based annotation, the Chasselas assembly meets the standard to become the annotated reference genome for V. vinifera. Building on these resources, we developed VitExpress, an open interactive transcriptomic platform, that provides a genome browser and integrated web tools for expression profiling, and a set of statistical tools (StatTools) for the identification of highly correlated genes. Implementation of the correlation finder tool for MybA1, a major regulator of the anthocyanin pathway, identified candidate genes associated with anthocyanin metabolism, whose expression patterns were experimentally validated as discriminating between black and white grapes. These resources and innovative tools for mining genome-related data are anticipated to foster advances in several areas of grapevine research.

Genome assembly of the rare and endangered Grantham's camellia, Camellia granthamiana.

Grantham's camellia (Camellia granthamiana Sealy) is a rare and endangered tea species discovered in Hong Kong in 1955 and endemic to southern China. Despite its high conservation value, the genomic resources of C. granthamiana are limited. Here, we present a chromosome-scale draft genome of the tetraploid C. granthamiana (2n = 4x =60), combining PacBio long-read sequencing and Omni-C data. The assembled genome size is ∼2.4Gb, with most sequences anchored to 15 pseudochromosomes resembling a monoploid genome. The genome has high contiguity, with a scaffold N50 of 139.7 Mb, and high completeness (97.8% BUSCO score). Our gene model prediction resulted in 68,032 protein-coding genes (BUSCO score of 90.9%). We annotated 1.65Gb of repeat content (68.48% of the genome). Our Grantham's camellia genome assembly is a valuable resource for investigating Grantham's camellia's biology, ecology, and phylogenomic relationships with other Camellia species, and provides a foundation for further conservation measures.

Whole-genome sequencing of Ganoderma boninense, the causal agent of basal stem rot disease in oil palm, via combined short- and long-read sequencing

The hemibiotrophic Basidiomycete pathogen Ganoderma boninense (Gb) is the dominant causal agent of oil palm basal stem rot disease. Here, we report a complete chromosomal genome map of Gb using a combination of short-read Illumina and long-read Pacific Biosciences (PacBio) sequencing platforms combined with chromatin conformation capture data from the Chicago and Hi-C platforms. The genome was 55.87 Mb in length and assembled to a high contiguity (N50: 304.34 kb) of 12 chromosomes built from 112 scaffolds, with a total of only 4.34 Mb (~ 7.77%) remaining unplaced. The final assemblies were evaluated for completeness of the genome by using Benchmarking Universal Single Copy Orthologs (BUSCO) v4.1.4, and based on 4464 total BUSCO polyporales group searches, the assemblies yielded 4264 (95.52%) of the conserved orthologs as complete and only a few fragmented BUSCO of 42 (0.94%) as well as a missing BUSCO of 158 (3.53%). Genome annotation predicted a total of 21,074 coding genes, with a GC content ratio of 59.2%. The genome features were analyzed with different databases, which revealed 2471 Gene Ontology/GO (11.72%), 5418 KEGG (Kyoto Encyclopedia of Genes and Genomes) Orthologous/KO (25.71%), 13,913 Cluster of Orthologous Groups of proteins/COG (66.02%), 60 ABC transporter (0.28%), 1049 Carbohydrate-Active Enzymes/CAZy (4.98%), 4005 pathogen–host interactions/PHI (19%), and 515 fungal transcription factor/FTFD (2.44%) genes. The results obtained in this study provide deep insight for further studies in the future.

Chromosome-level genome assembly of the yeast Lodderomyces beijingensis reveals the genetic nature of metabolic adaptations and identifies subtelomeres as hotspots for amplification of mating type loci.

Lodderomyces beijingensis is an ascosporic ascomycetous yeast. In contrast to related species Lodderomyces elongisporus, which is a recently emerging human pathogen, L. beijingensis is associated with insects. To provide an insight into its genetic makeup, we investigated the genome of its type strain, CBS 14171. We demonstrate that this yeast is diploid and describe the high contiguity nuclear genome assembly consisting of eight chromosome-sized contigs with a total size of about 15.1 Mbp. We find that the genome sequence contains multiple copies of the mating type loci and codes for essential components of the mating pheromone response pathway, however, the missing orthologs of several genes involved in the meiotic program raise questions about the mode of sexual reproduction. We also show that L. beijingensis genome codes for the 3-oxoadipate pathway enzymes, which allow the assimilation of protocatechuate. In contrast, the GAL gene cluster underwent a decay resulting in an inability of L. beijingensis to utilize galactose. Moreover, we find that the 56.5 kbp long mitochondrial DNA is structurally similar to known linear mitochondrial genomes terminating on both sides with covalently closed single-stranded hairpins. Finally, we discovered a new double-stranded RNA mycovirus from the Totiviridae family and characterized its genome sequence.

Genome assembly of the milky mangrove Excoecaria agallocha.

The milky mangrove Excoecaria agallocha is a latex-secreting mangrove that are distributed in tropical and subtropical regions. While its poisonous latex is regarded as a potential source of phytochemicals for biomedical applications, the genomic resources of E.agallocha remains limited. Here, we present a chromosomal level genome of E.agallocha, assembled from the combination of PacBio long-read sequencing and Omni-C data. The resulting assembly size is 1,332.45Mb and has high contiguity and completeness with a scaffold N50 of 58.9Mb and a BUSCO score of 98.4%, with 86.08% of sequences anchored to 18 pseudomolecules. 73,740 protein-coding genes were also predicted. The milky mangrove genome provides a useful resource for further understanding the biosynthesis of phytochemical compounds in E.agallocha.

Genome assembly of the edible jelly fungus Dacryopinax spathularia (Dacrymycetaceae).

The edible jelly fungus Dacryopinax spathularia (Dacrymycetaceae) is wood-decaying and can be commonly found worldwide. It has found application in food additives, given its ability to synthesize long-chain glycolipids, among other uses. In this study, we present the genome assembly of D. spathularia using a combination of PacBio HiFi reads and Omni-C data. The genome size is 29.2Mb. It has high sequence contiguity and completeness, with a scaffold N50 of 1.925Mb and a 92.0% BUSCO score. A total of 11,510 protein-coding genes and 474.7 kb repeats (accounting for 1.62% of the genome) were predicted. The D. spathularia genome assembly generated in this study provides a valuable resource for understanding their ecology, such as their wood-decaying capability, their evolutionary relationships with other fungi, and their unique biology and applications in the food industry.

Long-read sequencing and optical mapping generates near T2T assemblies that resolves a centromeric translocation

Long-read genome sequencing (lrGS) is a promising method in genetic diagnostics. Here we investigate the potential of lrGS to detect a disease-associated chromosomal translocation between 17p13 and the 19 centromere. We constructed two sets of phased and non-phased de novo assemblies; (i) based on lrGS only and (ii) hybrid assemblies combining lrGS with optical mapping using lrGS reads with a median coverage of 34X. Variant calling detected both structural variants (SVs) and small variants and the accuracy of the small variant calling was compared with those called with short-read genome sequencing (srGS). The de novo and hybrid assemblies had high quality and contiguity with N50 of 62.85 Mb, enabling a near telomere to telomere assembly with less than a 100 contigs per haplotype. Notably, we successfully identified the centromeric breakpoint of the translocation. A concordance of 92% was observed when comparing small variant calling between srGS and lrGS. In summary, our findings underscore the remarkable potential of lrGS as a comprehensive and accurate solution for the analysis of SVs and small variants. Thus, lrGS could replace a large battery of genetic tests that were used for the diagnosis of a single symptomatic translocation carrier, highlighting the potential of lrGS in the realm of digital karyotyping.

Comparing landscape characteristics to understand Malayan tapir (Tapirus indicus) conflicts: A case study in Negeri Sembilan

The IUCN Red List has listed the Malayan tapir (Tapirus indicus) as an endangered species in 2016, owing to its declining population trend. Human-caused forest degradation and encroachment on wildlife habitats drive this species to roam out of its natural range, resulting in human-tapir conflict (HTC). This study executes kernel density analysis on 78 HTC points recorded in Negeri Sembilan from 2013 to 2018 to determine the high and low HTC zones, and investigates the influence of five landscape variables on the occurrence of HTC. Values of five landscape variables in high and low HTC zones were extracted, and the significance of occurrence between these two zones was tested using an independent sample t-test. In terms of spatial distribution, Kuala Pilah and Jelebu covered high-conflict zones, while the lowest conflict zone was in Rembau. The t-test indicated that elevation (t = –3.551, p < 0.05) and slope (t = –2.012, p < 0.05) were significant between high and low conflict zones. Distance to the forest (t = 1.424, p > 0.05), distance to water (t = –0.106, p > 0.05), and distance to urban areas (t = –1.536, p > 0.05) were not significant for HTC. HTC tends to occur in low topographic areas, while tapirs outside of their natural habitat forage in close proximity to the forest and water bodies, but restrict their movement near human settlements. Hot Spot Analysis (Getis-Ord Gi*) on forest patches revealed an overlaping region between high HTC zones and low forest-patch contiguity, indicating that forest fragmentation may promote tapir conflicts. Hence, by systematically recording the conflict distribution in Negeri Sembilan, many actions could be taken into consideration to mitigate HTC in this state.

The genome of Citrus australasica reveals disease resistance and other species specific genes

BackgroundThe finger lime (Citrus australasica), one of six Australian endemic citrus species shows a high natural phenotypic diversity and novel characteristics. The wide variation and unique horticultural features have made this lime an attractive candidate for domestication. Currently no haplotype resolved genome is available for this species. Here we present a high quality, haplotype-resolved reference genome for this species using PacBio HiFi and Hi-C sequencing.ResultsHifiasm assembly and SALSA scaffolding resulted in a collapsed genome size of 344.2 Mb and 321.1 Mb and 323.2 Mb size for the two haplotypes. The nine pseudochromosomes of the collapsed genome had an N50 of 35.2 Mb, 99.1% genome assembly completeness and 98.9% gene annotation completeness (BUSCO). A total of 41,304 genes were predicted in the nuclear genome. Comparison with C. australis revealed that 13,661 genes in pseudochromosomes were unique in C. australasica. These were mainly involved in plant-pathogen interactions, stress response, cellular metabolic and developmental processes, and signal transduction. The two genomes showed a syntenic arrangement at the chromosome level with large structural rearrangements in some chromosomes. Genetic variation among five C. australasica cultivars was analysed. Genes related to defense, synthesis of volatile compounds and red/yellow coloration were identified in the genome. A major expansion of genes encoding thylakoid curvature proteins was found in the C. australasica genome.ConclusionsThe genome of C. australasica present in this study is of high quality and contiguity. This genome helps deepen our understanding of citrus evolution and reveals disease resistance and quality related genes with potential to accelerate the genetic improvement of citrus.

An improved chromosome-level genome assembly of perennial ryegrass (Lolium perenne L.).

This work is an update and extension of the previously published article "Ultralong Oxford Nanopore Reads Enable the Development of a Reference-Grade Perennial Ryegrass Genome Assembly" by Frei etal.The published genome assembly of the doubled haploid perennial ryegrass (Lolium perenne L.) genotype Kyuss (Kyuss v1.0) marked a milestone for forage grass research and breeding. However, order and orientation errors may exist in the pseudo-chromosomes of Kyuss, since barley (Hordeum vulgare L.), which diverged 30million years ago from perennial ryegrass, was used as the reference to scaffold Kyuss. To correct for structural errors possibly present in the published Kyuss assembly, we de novo assembled the genome again and generated 50-fold coverage high-throughput chromosome conformation capture (Hi-C) data to assist pseudo-chromosome construction. The resulting new chromosome-level assembly Kyuss v2.0 showed improved quality with high contiguity (contig N50 = 120Mb), high completeness (total BUSCO score = 99%), high base-level accuracy (QV = 50), and correct pseudo-chromosome structure (validated by Hi-C contact map). This new assembly will serve as a better reference genome for Lolium spp. and greatly benefit the forage and turf grass research community.

A new chromosome-scale duck genome shows a major histocompatibility complex with several expanded multigene families

BackgroundThe duck (Anas platyrhynchos) is one of the principal natural hosts of influenza A virus (IAV), harbors almost all subtypes of IAVs and resists to many IAVs which cause extreme virulence in chicken and human. However, the response of duck’s adaptive immune system to IAV infection is poorly characterized due to lack of a detailed gene map of the major histocompatibility complex (MHC).ResultsWe herein reported a chromosome-scale Beijing duck assembly by integrating Nanopore, Bionano, and Hi-C data. This new reference genome SKLA1.0 covers 40 chromosomes, improves the contig N50 of the previous duck assembly with highest contiguity (ZJU1.0) of more than a 5.79-fold, surpasses the chicken and zebra finch references in sequence contiguity and contains a complete genomic map of the MHC. Our 3D MHC genomic map demonstrated that gene family arrangement in this region was primordial; however, families such as AnplMHCI, AnplMHCIIβ, AnplDMB, NKRL (NK cell receptor-like genes) and BTN underwent gene expansion events making this area complex. These gene families are distributed in two TADs and genes sharing the same TAD may work in a co-regulated model.ConclusionsThese observations supported the hypothesis that duck’s adaptive immunity had been optimized with expanded and diversified key immune genes which might help duck to combat influenza virus. This work provided a high-quality Beijing duck genome for biological research and shed light on new strategies for AIV control.

De Novo Genome Assembly of the Sea Star Patiria pectinifera (Muller & Troschel, 1842) Using Oxford Nanopore Technology and Illumina Platforms

The sea star Patiria pectinifera (Asteroidea; Asterinidae; homotypic synonym: Asterina pectinifera; Muller & Troschel, 1842) is widely distributed in the coastal regions of the Seas of East Asia and the northern Pacific Ocean. Here, a de novo genome sequence of P. pectinifera as a reference for fundamental and applied research was constructed by employing a combination of long-read Oxford Nanopore Technology (ONT) PromethION, short-read Illumina platforms, and 10 × Genomics. The draft genome of P. pectinifera, containing 13,848,344 and 156,878,348 contigs from ONT and Illumina platforms, respectively, was obtained. Assembly with CANU resulted in 2262 contigs with an N50 length of 367 kb. Finally, ARCS + LINKS assembly combined these contigs into 328 scaffolds, totaling 499 Mb with an N50 length of 2 Mbp. The estimated genome size by GenomeScope analysis was 461 Mb. BUSCO analysis indicated that 930 (97.5%) of the expected genes were found in the assembly, with 889 (93.2%) being single-copy and 41 (4.3%) duplicated after searching against the metazoan database. Annotation, utilizing sequences obtained from Illumina RNA-Seq and Pacific Biosciences Iso-Seq, led to the identification of 22,367 protein-coding genes. When examining the orthologous relationship of P. pectinifera against the scaffolds of the common sea star Patiria miniata, high contiguity was observed. Annotation of repeat elements highlighted an enrichment of 1,121,079 transposable elements, constituting 47% of the genome, suggesting their potential role in shaping the genome structure of P. pectinifera. This de novo genome assembly is expected to be a valuable resource for future studies, providing insight into the developmental, environmental, and ecological aspects of P. pectinifera biology.

Genomic exploration of the endangered oriental stork, Ciconia boyciana, sheds light on migration adaptation and future conservation.

The oriental stork, Ciconia boyciana, is an endangered migratory bird listed on the International Union for Conservation of Nature's Red List. The bird population has experienced a rapid decline in the past decades, with nest locations and stop-over sites largely degraded due to human-bird conflicts. Multipronged conservation efforts are required to secure the future of oriental storks. We propose that a thorough understanding of the genome-wide genetic background of this threatened bird species is critical to make future conservation strategies. In this study, the first chromosome-scale reference genome was presented for the oriental stork with high quality, contiguity, and accuracy. The assembled genome size was 1.24 Gb with a scaffold N50 of 103 Mb, and 1.23 Gb contigs (99.32%) were anchored to 35 chromosomes. Population genomic analysis did not show a genetic structure in the wild population. Genome-wide genetic diversity (π = 0.0012) of the oriental stork was at a moderate to high level among threatened bird species, and the inbreeding risk was also not significant (FROH = 5.56% ± 5.30%). Reconstruction of demographic history indicated a rapid recent population decline likely driven by human activities. Genes that were under positive selection associated with the migratory trait were identified in relation to the long-term potentiation, photoreceptor cell organization, circadian rhythm, muscle development, and energy metabolism, indicating the essential interplay between genetic and ecological adaptation. Our study presents the first chromosome-scale genome assembly of the oriental stork and provides a genomic basis for understanding a genetic background of the oriental stork, the population's extinction risks, and the migratory characteristics, which will facilitate the decision of future conservation plans for this species.