Single-copy Orthologs Research Articles

Lacewing‐specific Universal Single Copy Orthologs designed towards resolution of backbone phylogeny of Neuropterida

AbstractUniversal Single Copy Orthologs (USCOs), as a set of markers of nearly universal single‐copy genes, show a superiority in phylogenomic inference. Here, we developed a Benchmarking Universal Single Copy Orthologs (BUSCOs) dataset, neuropterida_odb10, tailored for Neuropterida, based on high‐quality genome assemblies and transcriptome data, comprising 5438 BUSCOs. A range of 1524–5328 complete and single‐copy USCOs could be captured from the genome assemblies and transcriptomes of 104 species of Neuropterida. The reconstruction of a higher‐level phylogeny of Neuropterida based on a comprehensive sampling and refined genomic data in reference to neuropterida_odb10 validates the efficiency of this BUSCO dataset for phylogenomic inference. We recovered Psychopsidae as the sister group to Ithonidae, and corroborated the sister group relationship between Sisyridae and Nevrorthidae within Osmyloidea and the sister group relationship between Chrysopidae and Mantispoidea. Furthermore, our findings highlight that focusing on alignments with a higher presence of parsimony‐informative sites, rather than on the total number of alignments, can diminish errors in gene tree estimation, a process notably vulnerable to error when using multispecies coalescent methods. The neuropterida_odb10 BUSCO reference dataset holds promise for phylogenetic studies at various hierarchical levels, as well as for comparative genomics and the exploration of species diversity within Neuropterida.

Genome sequence resources from three isolates of the apple canker pathogen Neonectria ditissima infecting forest trees

Neonectria ditissima is a generalist ascomycete plant pathogen causing canker diseases on a variety of hardwood tree species and can cross-infect many of them. The fungus enters the plants through wounds throughout the year. N. ditissima is considered a major threat to apple production responsible for the fruit tree canker disease which damages trees and causes rotting of fruits in storage. Nearby forests and shelter belts can serve as source of inoculum for well-managed apple orchards. Thus, knowledge about the N. ditissima isolates infecting different host species is essential for designing integrated pest management strategies. Here, we describe the genomes of three N. ditissima isolates, Nd_iso34, Nd_iso35, and Nd_iso36, infecting European beech, American tulip tree, and American beech, respectively. We obtained genome assemblies of ca. 45 megabases for all isolates, covering 94% of the N. ditissima reference annotation, and 97% of the universal single-copy orthologs (BUSCOs). We conclude that these genome assemblies are a highly relevant resource considering the scarcity of genomic data available for N. ditissima.

Genome report: First whole genome sequence of Triatoma sanguisuga (Le Conte, 1855), vector of Chagas disease.

Triatoma sanguisuga is the most widespread triatomine bug species in the United States (US). The species vectors the human parasite Trypanosoma cruzi , which causes Chagas disease. Vector-borne Chagas disease is rarely diagnosed in the US, but T. sanguisuga has been implicated in a handful of cases. Despite its public health importance, little is known about the genomics or population genetics of T. sanguisuga . Here, we used long-read sequencing to assemble the first whole genome sequence for T. sanguisuga using DNA extracted from one adult specimen from Delaware. The final size of the genome was 1.162 Gbp with 77.7x coverage. The assembly consisted of 183 contigs with an N50 size of 94.97 Kb. The Benchmarking Universal Single-Copy Ortholog (BUSCO) complete score was 99.1%, suggesting a very complete assembly. Genome-wide GC level was 33.56%, and DNA methylation was 18.84%. The genome consists of 61.4% repetitive DNA and 17,799 predicted coding genes. The assembled T. sanguisuga genome was slightly larger than that of Triatominae species Triatoma infestans and Rhodnius prolixus (949 Mbp with 90.4% BUSCO score and 706 Mbp with 96.5% BUSCO score, respectively). The T. sanguisuga genome is the first North American triatomine species genome to be sequenced, and it is the most complete genome yet for any Triatominae species. The T. sangsuiga genome will allow for deeper investigations into epidemiologically relevant aspects of this important vector species, including blood feeding, host seeking, and parasite competence, thus providing potential vector-borne disease management targets and strengthening public health preparedness.

Chromosome-level genome assembly of Huai pig (Sus scrofa)

Although advances in long-read sequencing technology and genome assembly techniques have facilitated the study of genomes, little is known about the genomes of unique Chinese indigenous breeds, including the Huai pig. Huai pig is an ancient domestic pig breed and is well-documented for its redder meat color and high forage tolerance compared to European domestic pigs. In the present study, we sequenced and assembled the Huai pig genome using PacBio, Hi-C, and Illumina sequencing technologies. The final highly contiguous chromosome-level Huai pig genome spans 2.53 Gb with a scaffold N50 of 138.92 Mb. The Benchmarking Universal Single-Copy Orthologs (BUSCO) completeness score for the assembled genome was 95.33%. Remarkably, 23,389 protein-coding genes were annotated in the Huai-pig genome, along with 45.87% repetitive sequences. Overall, this study provided new foundational resources for future genetic research on Chinese domestic pigs.

Museomics reveal origins of East African Pleophylla forest chafers and Miocene forest connectivity

Here we present a nearly complete species-level phylogeny including 23 of the 25 known species of the forest-dwelling herbivorous scarab chafer beetle genus Pleophylla (Coleoptera: Scarabaeidae: Sericinae), based on the analysis of 950 nuclear genes (metazoan-level universal single-copy orthologs; mzl-USCOs). DNA sequences were obtained from freshly collected, ethanol-preserved samples and from dried museum specimens by target enrichment or genome shotgun sequencing. Alignment completeness of mzl-USCOs newly obtained here by target DNA enrichment of ethanol samples were very heterogenous and lower (29–62 %) than in Dietz et al. (2023a), while that of sequences recovered from dried samples was even lower (∼19 %). Alignment completeness of the sequences obtained from low coverage shotgun sequencing was highest (∼92 %), although the average coverage was much lower than for the target enrichment samples. We used the resulting phylogeny to reconstruct the historical biogeography of the group. To estimate a time-calibrated tree, we combined the mzl-USCO data of Pleophylla with a nucleotide alignment from an available transcriptomic dataset of Scarabaeoidea and used two different sets of secondary calibration points. Despite the problems associated with the capture rate of mzl-USCO sequences from museum specimens, we were able to infer a well-resolved phylogeny of the genus Pleophylla that also provided reliable estimates of the phylogenetic position of species for which we had little sequence data. Our study clearly identified South Africa as the geographic origin of Pleophylla. Timing and biogeographic history confirm a persistent fragmentation of forests since the Eocene. The occurrence of only one long-distance dispersal event from southern Africa to the Eastern African Arc even during the Miocene highlights the limited dispersal possibilities for these forest-adapted chafers, which do not seem to have had important northerly range expansions along hypothetical forest corridors during the Pleistocene.

Phylogenomics supports a single origin of terrestriality in isopods.

Terrestriality, the adaptation to life on land, is one of the key evolutionary transitions, occurring numerous times across the tree of life. Within Arthropoda, there have been several independent transitions: in hexapods, myriapods, arachnids and isopods. Isopoda is a morphologically diverse order within Crustacea, with species adapted to almost every environment on Earth. The order is divided into 11 suborders with the most speciose, Oniscidea, including terrestrial isopods such as woodlice and sea-slaters. Recent molecular phylogenetic studies have challenged traditional isopod morphological taxonomy, suggesting that several well-accepted suborders, including Oniscidea, may be non-monophyletic. This implies that terrestriality may have evolved multiple times. Current molecular hypotheses, however, are based on limited sequence data. Here, I collate available genome and transcriptome datasets for 36 isopods and four peracarid crustaceans from public sources, generate assemblies and use 970 single-copy orthologues to estimate isopod relationships and divergence times with molecular dating. The resulting phylogenetic analyses support monophyly of terrestrial isopods and suggest conflicting relationships based on nuclear ribosomal RNA sequences may be caused by long-branch attraction. Dating analyses suggest a Permo-Carboniferous origin of isopod terrestriality, much more recently than other terrestrial arthropods.

Chromosome-level genome assembly and annotation of Clanis bilineata tsingtauica Mell (Lepidoptera: Sphingidae).

The soybean hawkmoth Clanis bilineata tsingtauica Mell (Lepidoptera, Sphingidae; CBT), as one of the main leaf-chewing pests of soybeans, has gained popularity as an edible insect in China recently due to its high nutritional value. However, high-quality genome of CBT remains unclear, which greatly limits further research. In the present study, we assembled a high-quality chromosome-level genome of CBT using PacBio HiFi reads and Hi-C technologies for the first time. The size of the assembled genome is 477.45 Mb with a contig N50 length of 17.43 Mb. After Hi-C scaffolding, the contigs were anchored to 29 chromosomes with a mapping rate of 99.61%. Benchmarking Universal Single-Copy Orthologues (BUSCO) completeness value is 99.49%. The genome contains 252.16 Mb of repeat elements and 14,214 protein-coding genes. In addition, chromosomal synteny analysis showed that the genome of CBT has a strong synteny with that of Manduca sexta. In conclusion, this high-quality genome provides an important resource for future studies of CBT and contributes to the development of integrated pest management strategies.

A new high-quality genome assembly and annotation for the threatened Florida Scrub-Jay (Aphelocoma coerulescens).

The Florida Scrub-Jay (Aphelocoma coerulescens), a Federally Threatened, cooperatively-breeding bird, is an emerging model system in evolutionary biology and ecology. Extensive individual-based monitoring and genetic sampling for decades has yielded a wealth of data, allowing for the detailed study of social behavior, demography, and population genetics of this natural population. Here, we report a linkage map and a chromosome-level genome assembly and annotation for a female Florida Scrub-Jay made with long-read sequencing technology, chromatin conformation data, and the linkage map. We constructed a linkage map comprising 4,468 SNPs that had 34 linkage groups and a total sex-averaged autosomal genetic map length of 2446.78 cM. The new genome assembly is 1.33 Gb in length, consisting of 33 complete or near-complete autosomes and the sex chromosomes (ZW). This highly contiguous assembly has an NG50 of 68 Mb and a Benchmarking Universal Single-Copy Orthologs (BUSCO) completeness score of 97.1% with respect to the Aves database. The annotated gene set has a BUSCO transcriptome completeness score of 95.5% and 17,964 identified protein-coding genes, 92.5% of which have associated functional annotations. This new, high-quality genome assembly and linkage map of the Florida Scrub-Jay provides valuable tools for future research into the evolutionary dynamics of small, natural populations of conservation concern.

Genome sequence of the sugarcane aphid, Melanaphis sacchari (Hemiptera: Aphididae).

The sugarcane aphid, Melanaphis sacchari (Zehntner, 1897), is an agricultural pest that causes damage to plants in the Poaceae (the grasses) family, such as sorghum and sugarcane. Here, we used Nanopore long reads and Hi-C interaction map to generate a chromosome-level assembly with a total length of 356.1 Mb, of which 85.5% (304.6 Mb) is contained within the three autosomes and the X chromosome. Repetitive sequences accounted for 16.29% of the chromosomes and a total of 12,530 protein-coding genes were annotated, achieving 95.8% benchmarking universal single-copy orthologs (BUSCO) gene completeness. This offers a substantial improvement compared to previous low-quality genomic resources. Phylogenomic analysis by comparing M. sacchari with twenty-four published aphid genomes representing three aphid tribes reveals that M. sacchari belongs to the tribe Aphidini and maintained a conserved chromosome structure with other Aphidini species. The high-quality genomic resources reported in this study will be useful for understanding the evolution of aphid genomes and studying pest management of M. sacchari.

Comparative Genomics of Fungi in Nectriaceae Reveals Their Environmental Adaptation and Conservation Strategies.

This study presents the first genome assembly of the freshwater saprobe fungus Neonectria lugdunensis and a comprehensive phylogenomics analysis of the Nectriaceae family, examining genomic traits according to fungal lifestyles. The Nectriaceae family, one of the largest in Hypocreales, includes fungi with significant ecological roles and economic importance as plant pathogens, endophytes, and saprobes. The phylogenomics analysis identified 2684 single-copy orthologs, providing a robust evolutionary framework for the Nectriaceae family. We analyzed the genomic characteristics of 17 Nectriaceae genomes, focusing on their carbohydrate-active enzymes (CAZymes), biosynthetic gene clusters (BGCs), and adaptations to environmental temperatures. Our results highlight the adaptation mechanisms of N. lugdunensis, emphasizing its capabilities for plant litter degradation and enzyme activity in varying temperatures. The comparative genomics of different Nectriaceae lifestyles revealed significant differences in genome size, gene content, repetitive elements, and secondary metabolite production. Endophytes exhibited larger genomes, more effector proteins, and BGCs, while plant pathogens had higher thermo-adapted protein counts, suggesting greater resilience to global warming. In contrast, the freshwater saprobe shows less adaptation to warmer temperatures and is important for conservation goals. This study underscores the importance of understanding fungal genomic adaptations to predict ecosystem impacts and conservation targets in the face of climate change.

Characterization of gut symbionts from wild-caught Drosophila and other Diptera: description of Utexia brackfieldae gen. nov., sp. nov., Orbus sturtevantii sp. nov., Orbus wheelerorum sp. nov, and Orbus mooreae sp. nov.

Non-culture based surveys show that the bacterial family Orbaceae is widespread in guts of insects, including wild Drosophila. Relatively few isolates have been described, and none has been described from Drosophila. We present the isolation and characterization of five strains of Orbaceae from wild-caught flies of the genera Drosophila (Diptera: Drosophilidae) and Neogriphoneura (Diptera: Lauxaniidae). Cells are generally rod-shaped, mesophilic, and measure 0.8-2.0 µm long by 0.3-0.5 µm wide. Optimal growth was observed under ambient atmosphere. Reconstruction of phylogenies from the 16S rRNA gene and from single-copy orthologs verify placement of these strains within Orbaceae. Cells exhibited similar fatty acid profiles to those of other Orbaceae. Strain lpD01T shared 74% average nucleotide identity (ANI) with its closest relatives Ca. Schmidhempelia bombi Bimp and Zophobihabitans entericus IPMB12T. Results from multiple genome-wide similarity comparisons indicate lpD01T should be classified as a novel species within a novel genus. The major respiratory quinone for lpD01T is ubiquinone Q-8. lpD02T, lpD03, lpD04T, and BiBT are more closely related to Orbus hercynius CN3T (76, 77, 76, and 77% ANI, respectively) than to other described Orbaceae. Genomic and phylogenetic analyses suggest that lpD03 and lpD04T belong to the same species and that lpD02T, lpD03/lpD04T, and BiBT are each novel species of the genus Orbus. The proposed names of these strains are Utexia brackfieldae gen. nov., sp. nov. (type strain lpD01T =NCIMB 15517T =ATCC TSD-399T), Orbus sturtevantii sp. nov (type strain lpD02T =NCIMB 15518T =ATCC TSD-400T), Orbus wheelerorum sp. nov. (type strain lpD04T =NCIMB 15520T =ATCC TSD-401T), and Orbus mooreae sp. nov (type strain BiBT=NCIMB 15516T =ATCC TSD-402T). The isolation and characterization of these strains expands the repertoire of culturable bacteria naturally associated with insects, including the model organism D. melanogaster.

Functional and evolutionary insights into chemosensation and specialized herbivory from the genome of the red milkweed beetle, Tetraopes tetrophthalmus (Cerambycidae: Lamiinae).

Tetraopes are aposematic longhorn beetles (Cerambycidae) that feed primarily on toxic plants in the genus Asclepias (milkweeds). Studies of Tetraopes and their host plants have revealed compelling evidence for insect-plant coevolution and cospeciation. We sequenced, assembled and annotated the genome of the common red milkweed beetle, Tetraopes tetrophthalmus, and explored gene content and evolution, focusing on annotated genes putatively involved in chemosensation, allelochemical detoxification, and phytophagy. Comparisons were made to the Asian longhorned beetle (Anoplophora glabripennis) genome. The genome assembly comprised 779Mb distributed across 1057 contigs, with an N50 of 2.21Mb and 13,089 putative genes, including 97.3% of expected single-copy orthologs. Manual curation identified 122 putative odorant receptors (OR) and 162 gustatory receptors (GR), the former number similar to A. glabripennis but the latter only 69% of the A. glabripennis suite. We also documented a greater percentage of pseudogenic GRs and ORs compared to A. glabripennis, suggesting an ongoing reduction in chemosensory function, perhaps related to host specialization. We found lower diversity within certain well-studied gene families predicted to encode putative plant cell wall degrading enzymes in the T. tetrophthalmus genome, perhaps also due to host specialization. Exploring genes relevant to stress and allelochemical detoxification revealed evidence of an abundance of ABC-family genes in the T. tetrophthalmus genome, which may be related to sequestering toxic cardiac glycosides. Our studies further illuminate the genomic basis and evolution of chemosensation in longhorn beetles and provide a new vantage point from which to explore the ecology and evolution of specialized plant-feeding in Tetraopes and other phytophagous beetles.

A chromosome-level genome assembly of the gall maker pest inquiline, Diomorus aiolomorphi Kamijo (Hymenoptera: Torymidae)

Diomorus aiolomorphi Kamijo (Hymenoptera: Torymidae) is an inquiline of gall maker Aiolomorphus rhopaloides Walker (Hymenoptera: Eurytomidae). They are of significant economic significance and predominantly inhabit bamboo forest. So far, only four scaffold-level genomes have been published for the family Torymidae. In this study, we present a high-quality genome assembly of D. aiolomorphi at the chromosome level, achieved through the integration of Nanopore (ONT) long-read, Illumina pair-end DNA short-read, and High-through Chromosome Conformation Capture (Hi-C) sequencing methods. The final assembly was 1,084.56 Mb in genome size, with 1,083.41 Mb (99.89%) assigned to five pseudochromosomes. The scaffold N50 length reached 224.87 Mb, and the complete Benchmarking Universal Single-Copy Orthologs (BUSCO) score was 97.3%. The genome contained 762.12 Mb of repetitive elements, accounting for 70.27% of the total genome size. A total of 18,011 protein-coding genes were predicted, with 17,829 genes being functionally annotated. The high-quality genome assembly of D. aiolomorphi presented in this study will serve as a valuable genomic resource for future research on parasitoid wasps. The results of this study may also contribute to the development of biological control strategies for pest management in bamboo forests, enhancing ecological balance and economic sustainability.

A Chromosome-level genome assembly of giant river prawn (Macrobrachium rosenbergii)

The giant river prawn (Macrobrachium rosenbergii) is one of the most widely cultured crustacean species. In recent years, its aquaculture has faced challenges, including the degradation of germplasm resources and the emergence of viral diseases. Genomic information can be a valuable resource for developing molecular breeding programs for this important aquaculture species. Here we constructed a high-quality reference genome for M. rosenbergii by integrating Nanopore, Illumina, and high-throughput chromosome conformation capture (Hi-C) technologies. The final genome assembly is 3.18 Gb in size, with scaffold N50 and contig N50 of 62.73 Mb and 8.92 Mb, respectively. Approximately 98.6% of the assembled sequences were anchored into 59 pseudo-chromosomes. Benchmarking Universal Single-Copy Orthologs (BUSCO) benchmark of the genome assembly reached 94.5%. Repetitive sequences comprise 43.77% of the assembled genome, and 17,436 protein-coding genes were annotated. The high-quality genome of M. rosenbergii will empower molecular breeding efforts and provide invaluable resources for comparative genomic analysis of decapod species.

Refinement of the Antarctic fur seal (Arctocephalus gazella) reference genome increases continuity and completeness.

The Antarctic fur seal (Arctocephalus gazella) is an important top predator and indicator of the health of the Southern Ocean ecosystem. Although abundant, this species narrowly escaped extinction due to historical sealing and is currently declining as a consequence of climate change. Genomic tools are essential for understanding these anthropogenic impacts and for predicting long-term viability. However, the current reference genome ("arcGaz3") shows considerable room for improvement in terms of both completeness and contiguity. We therefore combined PacBio sequencing, haplotype-aware HiRise assembly and scaffolding based on Hi-C information to generate a refined assembly of the Antarctic fur seal reference genome ("arcGaz4_h1"). The new assembly is 2.53Gb long, has a scaffold N50 of 55.6Mb and includes 18 chromosome-sized scaffolds, which correspond to the 18 chromosomes expected in otariids. Genome completeness is greatly improved, with 23,408 annotated genes and a Benchmarking Universal Single-Copy Orthologs (BUSCO) score raised from 84.7% to 95.2%. We furthermore included the new genome in a reference-free alignment of the genomes of eleven pinniped species to characterize evolutionary conservation across the Pinnipedia using genome-wide Genomic Evolutionary Rate Profiling (GERP). We then implemented Gene Ontology (GO) enrichment analyses to identify biological processes associated with those genes showing the highest levels of either conservation or differentiation between the two major pinniped families, the Otariidae and Phocidae. We show that processes linked to neuronal development, the circulatory system and osmoregulation are overrepresented both in conserved as well as in differentiated regions of the genome.

Chromosome-scale reference genome of an ancient landrace: unveiling the genetic basis of seed weight in the food legume crop pigeonpea (Cajanus cajan).

Pigeonpea (Cajanus cajan) is a nutrient-rich and versatile food legume crop of tropical and subtropical regions. In this study, we describe the de novo assembly of a high-quality genome for the ancient pigeonpea landrace 'D30', achieved through a combination of Pacific Biosciences high-fidelity (PacBio HiFi) and high-throughput chromatin conformation capture (Hi-C) sequencing technologies. The assembled 'D30' genome has a size of 813.54Mb, with a contig N50 of 10.74Mb, a scaffold N50 of 73.07Mb, and a GC content of 35.67%. Genomic evaluation revealed that the 'D30' genome contains 99.2% of Benchmarking Universal Single-Copy Orthologs (BUSCO) and achieves a 29.06 long terminal repeat (LTR) assembly index (LAI). Genome annotation indicated that 'D30' encompasses 431.37Mb of repeat elements (53.02% of the genome) and 37 977 protein-coding genes. Identification of single-nucleotide polymorphisms (SNPs), insertions/deletions (indels), and structural variations between 'D30' and the published genome of pigeonpea cultivar 'Asha' suggests that genes affected by these variations may play important roles in biotic and abiotic stress responses. Further investigation of genomic regions under selection highlights genes enriched in starch and sucrose metabolism, with 42.11% of these genes highly expressed in seeds. Finally, we conducted genome-wide association studies (GWAS) to facilitate the identification of 28 marker-trait associations for six agronomic traits of pigeonpea. Notably, we discovered a calmodulin-like protein (CcCML) that harbors a dominant haplotype associated with the 100-seed weight of pigeonpea. Our study provides a foundational resource for developing genomics-assisted breeding programs in pigeonpea.

ZDB: bacterial comparative genomics made easy.

The analysis and comparison of genomes rely on different tools for tasks such as annotation, orthology prediction, and phylogenetic inference. Most tools are specialized for a single task, and additional efforts are necessary to integrate and visualize the results. To fill this gap, we developed zDB, an application integrating a Nextflow analysis pipeline and a Python visualization platform built on the Django framework. The application is available on GitHub (https://github.com/metagenlab/zDB) and from the bioconda channel. Starting from annotated Genbank files, zDB identifies orthologs and infers a phylogeny for each orthogroup. A species phylogeny is also constructed from shared single-copy orthologs. The results can be enriched with Pfam protein domain prediction, Cluster of Orthologs Genes and Kyoto Encyclopedia of Genes and Genomes annotations, and Swissprot homologs. The web application allows searching for specific genes or annotations, running Blast queries, and comparing genomic regions and whole genomes. The metabolic capacities of organisms can be compared at either the module or pathway levels. Finally, users can run queries to examine the conservation of specific genes or annotations across a chosen subset of genomes and display the results as a list of genes, Venn diagram, or heatmaps. Those features make zDB useful for both bioinformaticians and researchers more accustomed to laboratory research.IMPORTANCEGenome comparison and analysis rely on many independent tools, leaving to scientists the burden to integrate and visualize their results for interpretation. To alleviate this burden, we have built zDB, a comparative genomics tool that includes both an analysis pipeline and a visualization platform. The analysis pipeline automates gene annotation, orthology prediction, and phylogenetic inference, while the visualization platform allows scientists to easily explore the results in a web browser. Among other features, the interface allows users to visually compare whole genomes and targeted regions, assess the conservation of genes or metabolic pathways, perform Blast searches, or look for specific annotations. Altogether, this tool will be useful for a broad range of applications in comparative studies between two and hundred genomes. Furthermore, it is designed to allow sharing of data sets easily at a local or international scale, thereby supporting exploratory analyses for non-bioinformaticians on the genome of their favorite organisms.

Chromosome-Level Genome Assembly of the Viviparous Eelpout Zoarces viviparus.

The viviparous eelpout Zoarces viviparus is a common fish across the North Atlantic and has successfully colonized habitats across environmental gradients. Due to its wide distribution and predictable phenotypic responses to pollution, Z. viviparus is used as an ideal marine bioindicator organism and has been routinely sampled over decades by several countries to monitor marine environmental health. Additionally, this species is a promising model to study adaptive processes related to environmental change, specifically global warming. Here, we report the chromosome-level genome assembly of Z. viviparus, which has a size of 663 Mb and consists of 607 scaffolds (N50 = 26 Mb). The 24 largest represent the 24 chromosomes of the haploid Z. viviparus genome, which harbors 98% of the complete Benchmarking Universal Single-Copy Orthologues defined for ray-finned fish, indicating that the assembly is highly contiguous and complete. Comparative analyses between the Z. viviparus assembly and the chromosome-level genomes of two other eelpout species revealed a high synteny, but also an accumulation of repetitive elements in the Z. viviparus genome. Our reference genome will be an important resource enabling future in-depth genomic analyses of the effects of environmental change on this important bioindicator species.

Genome assembly of Hibiscus sabdariffa L. provides insights into metabolisms of medicinal natural products.

Hibiscus sabdariffa L. is a widely cultivated herbaceous plant with diverse applications in food, tea, fiber, and medicine. In this study, we present a high-quality genome assembly of H. sabdariffa using more than 33 Gb of high-fidelity (HiFi) long-read sequencing data, corresponding to ∼20× depth of the genome. We obtained 3 genome assemblies of H. sabdariffa: 1 primary and 2 partially haplotype-resolved genome assemblies. These genome assemblies exhibit N50 contig lengths of 26.25, 11.96, and 14.50 Mb, with genome coverage of 141.3, 86.0, and 88.6%, respectively. We also utilized 26 Gb of total RNA sequencing data to predict 154k, 79k, and 87k genes in the respective assemblies. The completeness of the primary genome assembly and its predicted genes was confirmed by the benchmarking universal single-copy ortholog analysis with a completeness rate of 99.3%. Based on our high-quality genomic resources, we constructed genetic networks for phenylpropanoid and flavonoid metabolism and identified candidate biosynthetic genes, which are responsible for producing key intermediates of roselle-specific medicinal natural products. Our comprehensive genomic and functional analysis opens avenues for further exploration and application of valuable natural products in H. sabdariffa.

Long-Read-Based Hybrid Genome Assembly and Annotation of Snow Algal Strain CCCryo 101-99 (cf. Sphaerocystis sp., Chlamydomonadales).

Polar regions harbor a diversity of cold-adapted (cryophilic) algae, which can be categorized into psychrophilic (obligate cryophilic) and cryotrophic (nonobligate cryophilic) snow algae. Both can accumulate significant biomasses on glacier and snow habitats and play major roles in global climate dynamics. Despite their significance, genomic studies on these organisms remain scarce, hindering our understanding of their evolutionary history and adaptive mechanisms in the face of climate change. Here, we present the draft genome assembly and annotation of the psychrophilic snow algal strain CCCryo 101-99 (cf. Sphaerocystis sp.). The draft haploid genome assembly is 122.5 Mb in length and is represented by 664 contigs with an N50 of 0.86 Mb, a Benchmarking Universal Single-Copy Orthologs (BUSCO) completeness of 92.9% (n = 1,519), a maximum contig length of 5.3 Mb, and a guanine-cystosine (GC) content of 53.1%. In total, 28.98% of the genome (35.5 Mb) contains repetitive elements. We identified 417 noncoding RNAs and annotated the chloroplast genome. The predicted proteome comprises 14,805 genes with a BUSCO completeness of 97.8%. Our preliminary analyses reveal a genome with a higher repeat content compared with mesophilic chlorophyte relatives, alongside enrichment in gene families associated with photosynthesis and flagella functions. Our current data will facilitate future comparative studies, improving our understanding of the likely response of polar algae to a warming climate as well as their evolutionary trajectories in permanently cold environments.