Fish Genomes Research Articles

Mitochondrial dysfunction matures Ras-induced early senescence to full senescence with a proinflammatory senescence-associated secretory phenotype in the fish cell line, EPC

Fish cell lines differ from most mammalian diploid cell lines by the fact that cellular senescence is not readily induced. Previously, we demonstrated that the absence of the p16 gene in the fish genome prevents cells from reaching full senescence even when Ras is activated. Drosophila also lacks p16; however, early senescence triggered by Ras activation progresses to full senescence and is accompanied by a proinflammatory senescence-associated secretory phenotype (SASP), due to mitochondrial deficiency. It is unclear whether mitochondrial deficiency can also induce the maturation of Ras-induced early senescence (RIS) to full senescence along with a proinflammatory SASP in fish cell lines. Here, we investigated whether mitochondrial dysfunction induced by carbonyl cyanide 3-chlorophenylhydrazone (CCCP) in concert with activated Ras results in full senescence and whether this is accompanied by a proinflammatory SASPs in the EPC fish cell line. We found that although EPC cells with mitochondrial dysfunction exhibited a proinflammatory SASP, this did not result in permanent cell proliferation arrest or the upregulation of endogenous Ras expression. These findings suggest that other factors must act in concert with mitochondrial dysfunction to induce full senescence. The proliferation of EPC cells overexpressing a constitutively active mutant of H-Ras (H-RasV12) was markedly reduced, irrespective of CCCP treatment. These findings suggest that there are similarities between the cellular senescence observed in fish and Drosophila cells lacking the p16 gene. However, it should be noted that fish cells differ from Drosophila cells in that mitochondrial dysfunction alone can induce proinflammatory SASP factors.

Binding site redundancy is critical for the regulation of fas by miR-30c in blunt snout bream (Megalobrama amblycephala)

MiR-30c and fatty acid synthase (fas) both play important roles in physiological processes such as lipid synthesis and fat metabolism. Predictive analysis revealed that fas is a target gene of miR-30c with multiple seed sites. Seed sites are useful to predict miRNA targeting relationships; however, detailed analyses of seed sites in fish genomes remain poorly studied. In this study, the regulatory relationship between miR-30c and fas, number and effect of seed regions, and mechanism by which miR-30c regulates lipid metabolism were evaluated in blunt snout bream (Megalobrama amblycephala). Four miR-30c target sites for fas were identified using various prediction tools. miR-30c mimics were transfected into 293 T cells, and dual-luciferase reporter assays were used to evaluate the roles of different fas target sites. When a single target site was mutated, relative luciferase activity was higher than that in the control group, with different activity levels depending on the mutation site. When multiple target sites were mutated, relative luciferase activity increased significantly as the number of mutation sites increased and was the highest when the four sites were mutated simultaneously. The miR-30c agomir was injected into the abdominal cavity of M. amblycephala at various concentrations for analyses of physiological and biochemical parameters in the liver and blood and the expression of genes related to lipid metabolism in the liver. Total cholesterol, free fatty acid, triglyceride, and low density lipoprotein levels were significantly lower after miR-30c agomir injection comparing to the control (P < 0.05). Additionally, the expression levels of genes related to lipid metabolism were significantly lower after miR-30c agomir injection than in the control (P < 0.05). In summary, this study identified four specific miR-30c target sites in the 3′ UTR of fas mRNA; the effects of these sites are cumulative, and the redundancy ensures the accurate regulation of fas during evolution. In addition, miR-30c has a negative regulatory effect on fas and regulates lipid metabolism via various genes related to this process. Therefore, the regulation of miR-30c can effectively ameliorate the side effects of a high-fat diet on liver function in M. amblycephala.

Characterization of hAT DNA transposon superfamily in the genome of Neotropical fish Apareiodon sp.

DNA transposons are diverse in fish genomes and have been described to generate genomic evolutionary novelties. hAT transposable element data are scarce in Teleostei genomes, making it challenging to conduct comparative genomic studies to understand their neutrality or function. This study aimed to perform a genomic and molecular characterization of hAT copies to assess the diversity of these elements and associate changes in these sequences to genomic and karyotypic novelties in Apareiodon sp. The data revealed that hAT TEs are highly abundant in the Apareiodon sp. genome, with few possibly autonomous copies. Highly conserved sequences with likely functional transposases were observed in nine hAT elements. A great diversity of hAT subgroups was observed, especially from Ac, Charlie, Blackjack, Tip100, hAT6, and hAT5, and a similar wave of hAT genomic invasion was identified in the genome for these six groups of hAT sequences. The data also revealed a distinct number of microsatellites within degenerated hAT copies. hAT sites were demonstrated to be dispersed in the Apareiodon sp. chromosomes and not involved in W chromosome-specific region differentiation. In conclusion, the genomic analysis revealed a great diversity of hAT elements, possible autonomous copies, and differentiation of degenerated transposable elements into tandem sequences.

Two high quality chromosome-scale genome assemblies of female and male silver pomfret (Pampus argenteus)

Pampus argenteus is a highly commercial marine fish whose population is declining sharply. Here, we generated a female P. argenteus genome, spanning 536.33 Mb with contig N50 of 1.79 Mb; 24070 genes (99.50% of 24,182) were functionally annotated. To improve quality of it, we assembled a 553.79 Mb genome of male fish with contig N50 of 24.75 Mb through HiFi and ultra-long ONT sequence technologies; 550.82 Mb were anchored onto 24 gap-free chromosomes; 22,892 genes (98.1% of 23,346) were functionally annotated; the QV value was 51.55 with 98.9% of BUSCO and 99.39% coverage of Illumina reads. Finally, we compared this genome with previous published one, revealing 37,301 SVs. 52.82 Mb and 18.05 Mb SDs were characterized in our and published assemblies, respectively, and 48.96 Mb PURs were constructed. Thus, this genome assembly exhibits excellent completeness, continuity and accuracy comparing to the published one, which can be current preferred reference genome. Overall, these works help aquaculture and wild resources recovery of P. argenteus and provide a valuable genetic resource for study.

The evolution of tenascins

BackgroundThe evolution of extracellular matrix is tightly linked to the evolution of organogenesis in metazoans. Tenascins are extracellular matrix glycoproteins of chordates that participate in integrin-signaling and morphogenetic events. Single tenascins are encoded by invertebrate chordates, and multiple tenascin paralogs are found in vertebrates (designated tenascin-C, tenascin-R, tenascin-W and tenascin-X) yet, overall, the evolution of this family has remained unclear.ResultsThis study examines the genomes of hemichordates, cephalochordates, tunicates, agnathans, cartilaginous fishes, lobe-finned fishes, ray-finned fishes and representative tetrapods to identify predicted tenascin proteins. We comprehensively assess their evolutionary relationships by sequence conservation, molecular phylogeny and examination of conservation of synteny of the encoding genes. The resulting new evolutionary model posits the origin of tenascin in an ancestral chordate, with tenascin-C-like and tenascin-R-like paralogs emerging after a whole genome duplication event in an ancestral vertebrate. Tenascin-X appeared following a second round of whole genome duplication in an ancestral gnathostome, most likely from duplication of the gene encoding the tenascin-R homolog. The fourth gene, encoding tenascin-W (also known as tenascin-N), apparently arose from a local duplication of tenascin-R.ConclusionsThe diversity of tenascin paralogs observed in agnathans and gnathostomes has evolved through selective retention of novel genes that arose from a combination of whole genome and local duplication events. The evolutionary appearance of specific tenascin paralogs coincides with the appearance of vertebrate-specific cell and tissue types where the paralogs are abundantly expressed, such as the endocranium and facial skeleton (tenascin-C), an expanded central nervous system (tenascin-R), and bone (tenascin-W).

Triple-color FISH chromosome constitution and genome size analyses confirmed the ploidy of newly developed ten Hibiscus sp. cultivars with different breeding history

Triple-color FISH chromosome constitution and genome size analyses confirmed the ploidy of newly developed ten Hibiscus sp. cultivars with different breeding history

Fish Genomics and Its Application in Disease‐Resistance Breeding

ABSTRACTGlobal aquaculture production has been rising for several decades, with up to 76% of the total production from fish. However, the problem of fish diseases is becoming more and more prominent in today's context of pursuing sustainable aquaculture. Since the first fish genome assembly reported in 2002, genomic approaches have been successfully implemented in fish breeding to enhance disease resistance and reduce economic losses caused by diverse fish diseases. Here, we present a review of the current progress in fish genomics and its application in disease‐resistance breeding. First, assembly data for all publicly available fish genomes were curated and statistical analysis of these data were performed. Subsequently, genomics‐assisted breeding approaches (including quantitative trait loci mapping, genome‐wide association study, marker‐assisted selection, genomic selection, gene transfer, and genome editing) that have been applied in practical disease–resistance breeding programs are outlined. In addition, candidate genetic markers that could possibly be utilized in breeding were summarized. Finally, remaining challenges and further directions were discussed. In summary, this review provides insight into fish genomics and genomics‐assisted breeding of disease‐resistant fish varieties.

Evolution of Key Oxygen-Sensing Genes Is Associated with Hypoxia Tolerance in Fishes.

Low dissolved oxygen (hypoxia) is recognized as a major threat to aquatic ecosystems worldwide. Because oxygen is paramount for the energy metabolism of animals, understanding the functional and genetic drivers of whole-animal hypoxia tolerance is critical to predicting the impacts of aquatic hypoxia. In this study, we investigate the molecular evolution of key genes involved in the detection of and response to hypoxia in ray-finned fishes: the prolyl hydroxylase domain (PHD)-hypoxia-inducible factor (HIF) oxygen-sensing system, also known as the EGLN (egg-laying nine)-HIF oxygen-sensing system. We searched fish genomes for HIFA and EGLN genes, discovered new paralogs from both gene families, and analyzed protein-coding sites under positive selection. The physicochemical properties of these positively selected amino acid sites were summarized using linear discriminants for each gene. We employed phylogenetic generalized least squares to assess the relationship between these linear discriminants for each HIFA and EGLN and hypoxia tolerance as reflected by the critical oxygen tension (Pcrit) of the corresponding species. Our results demonstrate that Pcrit in ray-finned fishes correlates with the physicochemical variation of positively selected sites in specific HIFA and EGLN genes. For HIF2A, two linear discriminants captured more than 90% of the physicochemical variation of these sites and explained between 20% and 39% of the variation in Pcrit. Thus, variation in HIF2A among fishes may contribute to their capacity to cope with aquatic hypoxia, similar to its proposed role in conferring tolerance to high-altitude hypoxia in certain lineages of terrestrial vertebrates.

Decoding the fish genome opens a new era in important trait research and molecular breeding in China.

Aquaculture represents the fastest-growing global food production sector, as it has become an essential component of the global food supply. China has the world's largest aquaculture industry in terms of production volume. However, the sustainable development of fish culture is hindered by several concerns, including germplasm degradation and disease outbreaks. The practice of genomic breeding, which relies heavily on genome information and genotypephenotype relationships, has significant potential for increasing the efficiency of aquaculture production. In 2014, the completion of the genome sequencing and annotation of the Chinese tongue sole signified the beginning of the fish genomics era in China. Since then, domestic researchers have made dramatic progress in functional genomic studies. To date, the genomes of more than 60 species of fish in China have been assembled and annotated. Based on these reference genomes, evolutionary, comparative, and functional genomic studies have revolutionized our understanding of a wide range of biologically and economically important traits of fishes, including growth and development, sex determination, disease resistance, metamorphosis, and pigmentation. Furthermore, genomic tools and breeding techniques such as SNP arrays, genomic selection, and genome editing have greatly accelerated genetic improvement through the incorporation of functional genomic information into breeding activities. This review aims to summarize the current status, advances, and perspectives of the genome resources, genomic study of important traits, and genomic breeding techniques of fish in China. The review will provide aquaculture researchers, fish breeders, and farmers with updated information concerning fish genomic research and breeding technology. The summary will help to promote the genetic improvement of production traits and thus will support the sustainable development of fish aquaculture.

MIPs: multi-locus intron polymorphisms in species identification and population genomics

The study of species groups in which the presence of interspecific hybridization or introgression phenomena is known or suspected involves analysing shared bi-parentally inherited molecular markers. Current methods are based on different categories of markers among which the classical microsatellites or the more recent genome wide approaches for the analyses of thousands of SNPs or hundreds of microhaplotypes through high throughput sequencing. Our approach utilizes intron-targeted amplicon sequencing to characterise multi-locus intron polymorphisms (MIPs) and assess genetic diversity. These highly variable intron regions, combined with inter-specific transferable loci, serve as powerful multiple-SNP markers potentially suitable for various applications, from species and hybrid identification to population comparisons, without prior species knowledge. We developed the first panel of MIPs highly transferable across fish genomes, effectively distinguishing between species, even those closely related, and populations with different structures. MIPs offer versatile, hypervariable nuclear markers and promise to be especially useful when multiple nuclear loci must be genotyped across different species, such as for the monitoring of interspecific hybridization. Moreover, the relatively long sequences obtained ease the development of single-locus PCR-based diagnostic markers. This method, here demonstrated in teleost fishes, can be readily applied to other taxa, unlocking a new source of genetic variation.

Quantitative trait loci concentrate in specific regions of the Mexican cavefish genome and reveal key candidate genes for cave-associated evolution.

A major goal of modern biology is connecting phenotype with its underlying genetic basis. The Mexican cavefish (Astyanax mexicanus), a characin fish species comprised of a surface ecotype and a cave-derived ecotype, is well suited as a model to study the genetic mechanisms underlying adaptation to extreme environments. Here we map 206 previously published quantitative trait loci (QTL) for cave-derived traits in A. mexicanus to the newest version of the surface fish genome assembly, AstMex3. These analyses revealed that QTL cluster in the genome more than expected by chance, and this clustering is not explained by the distribution of genes in the genome. To investigate whether certain characteristics of the genome facilitate phenotypic evolution, we tested whether genomic characteristics associated with increased opportunities for mutation, such as highly mutagenic CpG sites, are reliable predictors of the sites of trait evolution but did not find any significant trends. Finally, we combined the QTL map with previously collected expression and selection data to identify 36 candidate genes that may underlie the repeated evolution of cave phenotypes, including rgrb, which is predicted to be involved in phototransduction. We found this gene has disrupted exons in all non-hybrid cave populations but intact reading frames in surface fish. Overall, our results suggest specific regions of the genome may play significant roles in driving adaptation to the cave environment in Astyanax mexicanus and demonstrate how this compiled dataset can facilitate our understanding of the genetic basis of repeated evolution in the Mexican cavefish.

The Chinese longsnout catfish genome provides novel insights into the feeding preference and corresponding metabolic strategy of carnivores.

Fish show variation in feeding habits to adapt to complex environments. However, the genetic basis of feeding preference and the corresponding metabolic strategies that differentiate feeding habits remain elusive. Here, by comparing the whole genome of a typical carnivorous fish (Leiocassis longirostris Günther) with that of herbivorous fish, we identify 250 genes through both positive selection and rapid evolution, including taste receptor taste receptor type 1 member 3 (tas1r3) and trypsin We demonstrate that tas1r3 is required for carnivore preference in tas1r3-deficient zebrafish and in a diet-shifted grass carp model. We confirm that trypsin correlates with the metabolic strategies of fish with distinct feeding habits. Furthermore, marked alterations in trypsin activity and metabolic profiles are accompanied by a transition of feeding preference in tas1r3-deficient zebrafish and diet-shifted grass carp. Our results reveal a conserved adaptation between feeding preference and corresponding metabolic strategies in fish, and provide novel insights into the adaptation of feeding habits over the evolution course.

FishTEDB 2.0: an update fish transposable element (TE) database with new functions to facilitate TE research.

We launched the initial version of FishTEDB in 2018, which aimed to establish an open-source, user-friendly, data-rich transposable element (TE) database. Over the past 5 years, FishTEDB 1.0 has gained approximately 10 000 users, accumulating more than 450 000 interactions. With the unveiling of extensive fish genome data and the increasing emphasis on TE research, FishTEDB needs to extend the richness of data and functions. To achieve the above goals, we introduced 33 new fish species to FishTEDB 2.0, encompassing a wide array of fish belonging to 48 orders. To make the updated database more functional, we added a genome browser to visualize the positional relationship between TEs and genes and the estimated TE insertion time in different species. In conclusion, we released a new version of the fish TE database, FishTEDB 2.0, designed to assist researchers in the future study of TE functions and promote the progress of biological theories related to TEs. Database URL: https://www.fishtedb.com/.

Astyanax mexicanus surface and cavefish chromosome-scale assemblies for trait variation discovery.

The ability of organisms to adapt to sudden extreme environmental changes produces some of the most drastic examples of rapid phenotypic evolution. The Mexican Tetra, Astyanax mexicanus, is abundant in the surface waters of northeastern Mexico, but repeated colonizations of cave environments have resulted in the independent evolution of troglomorphic phenotypes in several populations. Here, we present three chromosome-scale assemblies of this species, for one surface and two cave populations, enabling the first whole-genome comparisons between independently evolved cave populations to evaluate the genetic basis for the evolution of adaptation to the cave environment. Our assemblies represent the highest quality of sequence completeness with predicted protein-coding and noncoding gene metrics far surpassing prior resources and, to our knowledge, all long-read assembled teleost genomes, including zebrafish. Whole-genome synteny alignments show highly conserved gene order among cave forms in contrast to a higher number of chromosomal rearrangements when compared with other phylogenetically close or distant teleost species. By phylogenetically assessing gene orthology across distant branches of amniotes, we discover gene orthogroups unique to A. mexicanus. When compared with a representative surface fish genome, we find a rich amount of structural sequence diversity, defined here as the number and size of insertions and deletions as well as expanding and contracting repeats across cave forms. These new more complete genomic resources ensure higher trait resolution for comparative, functional, developmental, and genetic studies of drastic trait differences within a species.

The chromosome-scale reference genome for the pinfish (Lagodon rhomboides) provides insights into their evolutionary and demographic history.

The pinfish (Lagodon rhomboides) is an ecologically, economically, and culturally relevant member of the family Sparidae, playing crucial roles in the marine food webs of the western Atlantic Ocean and Gulf of Mexico. Despite their high abundance and ecological importance, there is a scarcity of genomic resources for this species. We assembled and annotated a chromosome-scale genome for the pinfish, resulting in a highly contiguous 785 Mb assembly of 24 scaffolded chromosomes. The high-quality assembly contains 98.9% complete BUSCOs and shows strong synteny to other chromosome-scale genomes of fish in the family Sparidae, with a limited number of large-scale genomic rearrangements. Leveraging this new genomic resource, we found evidence of significant expansions of dietary gene families over the evolutionary history of the pinfish, which may be associated with an ontogenetic shift from carnivory to herbivory seen in this species. Estimates of historical patterns of population demography using this new reference genome identified several periods of population growth and contraction which were associated with ancient climatic shifts and sea level changes. This genome serves as a valuable reference for future studies of population genomics and differentiation and provides a much-needed genomic resource for this western Atlantic sparid.

FEVER: an interactive web-based resource for evolutionary transcriptomics across fishes.

Teleost fish represent one of the largest and most diverse clades of vertebrates, which makes them great models in various research areas such as ecology and evolution. Recent sequencing endeavors provided high-quality genomes for species covering the main fish evolutionary lineages, opening up large-scale comparative genomics studies. However, transcriptomic data across fish species and organs are heterogenous and have not been integrated with newly sequenced genomes making gene expression quantification and comparative analyses particularly challenging. Thus, resources integrating genomic and transcriptomic data across fish species and organs are still lacking. Here, we present FEVER, a web-based resource allowing evolutionary transcriptomics across species and tissues. First, based on query genes FEVER reconstructs gene trees providing orthologous and paralogous relationships as well as their evolutionary dynamics across 13 species covering the major fish lineages, and 4 model species as evolutionary outgroups. Second, it provides unbiased gene expression across 11 tissues using up-to-date fish genomes. Finally, genomic and transcriptomic data are combined together allowing the exploration of gene expression evolution following speciation and duplication events. FEVER is freely accessible at https://fever.sk8.inrae.fr/.

Revolutionizing Fish Biotechnology: A Current Status and Future Prospects

Fish biotechnology has witnessed significant advancements in recent years, driven by a convergence of interdisciplinary research efforts spanning genetics, genomics, aquaculture, and molecular biology. This synthesis study examines the significant advancements in fish biotechnology and presents potential opportunities for transforming the sector in the future. The emergence of genome editing technologies, such as CRISPR-Cas9, has fundamentally transformed the accurate manipulation of fish genomes, allowing for specific alterations in features that span from disease resistance to growth improvement. These methods show great potential for promoting sustainable aquaculture operations and protecting endangered species. In addition, the incorporation of omics technologies, like as genomics, transcriptomics, and proteomics, has yielded unparalleled understanding of the molecular pathways that underlie complex features in fish. This comprehensive approach has enabled the identification of crucial genes and regulatory circuits that control different physiological processes, therefore aiding the creation of new therapies for disease management and selective breeding. The recent advancements in fish biotechnology have had a significant and positive effect on the industry. These achievements highlight the potential for transforming the sector through collaboration across many disciplines, technical innovation, and the adoption of sustainable methods.

Whole-Genome Survey Analyses of Five Goby Species Provide Insights into Their Genetic Evolution and Invasion-Related Genes.

As one of the most abundant groups in marine fish families, Gobiidae fish are important fishery resources in China, and some are also invasive species in certain regions worldwide. However, the phylogenetic relationships of Gobiidae fish remain ambiguous, and the study of their invasion-related genes is still scarce. This study used high-throughput sequencing technology to conduct a whole-genome survey of five Gobiidae fish species: Acanthogobius flavimanus, Acanthogobius stigmothonus, Favonigobius gymnauchen, Ctenotrypauchen microcephalus, and Tridentiger barbatus. De novo assembly of five fish genomes was performed, and genomic traits were compared through K-mer analysis. Among the five Gobiidae fish genomes, F. gymnauchen had the largest genome size (1601.98 Mb) and the highest heterozygosity (1.56%) and repeat rates (59.83%). Phylogenetic studies showed that A. flavimanus was most closely linked to A. stigmothonus, while Apogonidae and Gobiidae were closely related families. PSMC analysis revealed that C. microcephalus experienced a notable population expansion than the other four fish species in the Early Holocene. By using the KOG, GO, and KEGG databases to annotate single-copy genes, the annotated genes of the five fish were mainly classified as "signal transduction mechanisms", "cellular process", "cellular anatomical entity", and "translation". Acanthogobius flavimanus, A. stigmothonus, and T. barbatus had more genes classified as "response to stimulus" and "localization", which may have played an important role in their invasive processes. Our study also provides valuable material about Gobiidae fish genomics and genetic evolution.

Genome editing of FTR42 improves zebrafish survival against virus infection by enhancing IFN immunity

Genome editing of FTR42 improves zebrafish survival against virus infection by enhancing IFN immunity

Genome-Wide Identification, Sequence Alignment, and Transcription of Five Sex-Related Genes in Largemouth Bass (Micropterus Salmoides).

Largemouth bass (Micropterus Salmoides) is an economically important fish species in China. Most research has focused on its growth, disease resistance, and nutrition improvement. However, the sex-determining genes in largemouth bass are still unclear. The transforming growth factor-beta (TGF-β) gene family, including amh, amhr2 and gsdf, plays an important role in the sex determination and differentiation of various fishes. These genes are potentially involved in sex determination in largemouth bass. We performed a systematic analysis of 5 sex-related genes (amh, amhr2, gsdf, cyp19a1, foxl2) in largemouth bass using sequence alignment, collinearity analysis, transcriptome, and quantitative real-time polymerase chain reaction (qRT-PCR). This included a detailed assessment of their sequences, gene structures, evolutionary traits, and gene transcription patterns in various tissues including gonads, and at different developmental stages. Comparative genomics revealed that the 5 sex-related genes were highly conserved in various fish genomes. These genes did not replicate, mutate or lose in largemouth bass. However, some were duplicated (amh, amhr2 and gsdf), mutated (gsdf) or lost (amhr2) in other fishes. Some genes (e.g., gsdf) showed significant differences in genomic sequence between males and females, which may contribute to sex determination and sex differentiation in these fishes. qRT-PCR was applied to quantify transcription profiling of the 5 genes during gonadal development and in the adult largemouth bass. Interestingly, amh, amhr2 and gsdf were predominantly expressed in the testis, while cyp19a1 and foxl2 were mainly transcribed in the ovary. All 5 sex-related genes were differentially expressed in the testes and ovaries from the 56th day post-fertilization (dpf). We therefore speculate that male/female differentiation in the largemouth bass may begin at this critical time-point. Examination of the transcriptome data also allowed us to screen out several more sex-related candidate genes. Our results provide a valuable genetic resource for investigating the physiological functions of these 5 sex-related genes in sex determination and gonadal differentiation, as well as in the control of gonad stability in adult largemouth bass.