Evolution and domestication of Tc1/mariner transposons in the genome of African coelacanth (Latimeria chalumnae).

Here, we comprehensively analysed the abundance, diversity, and activity of Tc1/mariner transposons in African coelacanth (Latimeria chalumnae). Fifteen Tc1/mariner autonomous transposons were identified and grouped into six clades: DD34E/Tc1, DD34D/mariner, DD35D/Fot, DD31D/pogo, DD30-31D/pogo-like, and DD32-36D/Tigger, belonging to three known families: DD34E/Tc1, DD34D/mariner, and DD×D/pogo (DD35D/Fot, DD31D/pogo, DD30-31D/pogo-like, and DD32-36D/Tigger). Thirty-one miniature inverted-repeat transposable element (MITE) transposons of Tc1/mariner were also identified, and 20 of them display similarity to the identified autonomous transposons. The structural organization of these full Tc1/mariner elements includes a transposase gene flanked by terminal inverted repeats (TIRs) with TA dinucleotides. The transposases contain N-terminal DNA binding domain and a C-terminal catalytic domain characterized by the presence of a conservative D(Asp)DE(Glu)/D triad that is essential for transposase activity. The Tc1/mariner superfamily in coelacanth exhibited very low genome coverage (0.3%), but it experienced an extraordinary difference of proliferation dynamics among the six clades identified; moreover, most of them exhibited a very recent and current proliferation, suggesting that some copies of these transposons are putatively active. Additionally, at least four functional genes derived from Tc1/mariner transposons were found. We provide an up-to-date overview of Tc1/mariner in coelacanth, which may be helpful in determining genome and gene evolution in this living fossil.

Unveiling the Genetic Secrets of Chinese Indigenous Pigs from Guizhou Province: Diversity, Evolution and Candidate Genes Affecting Pig Coat Color.

The local pig breeds in Guizhou possess exceptional meat quality, robust adaptability, and resilience to harsh feeding conditions, making them ideal for producing high-quality pork. With over 10 local pig breeds in the region, we focused on 7 specific breeds: Baixi pigs (BX), Congjiang Xiang pigs (CJX), Guanling pigs (GL), Jianhe White Xiang pigs (JHBX), Jiangkou Luobo pigs (JKLB), Kele pigs (KL), and Qiandong Hua pigs (QDH). Unfortunately, these breeds face threats such as introduced species and inbreeding, resulting in a decline in population size and numbers. To better protect and utilize these breeds, we employed genome-wide single-nucleotide polymorphism (SNP) markers to investigate the population structure, genetic diversity, and selection characteristics of 283 pigs across these seven breeds. Our findings revealed distinct ancestral sources between Chinese and Western pig breeds, as demonstrated by principal component analysis, adjacent tree analysis, and ADMIXTURE analysis. Notably, JHBX exhibited a distant genetic relationship from the other six local pig breeds in Guizhou province, showcasing unique genetic characteristics. While the genetic diversity of the six Chinese native pig populations, excluding JHBX, was generally moderate in Guizhou province, the JHBX population displayed low genetic diversity. Therefore, it is imperative to intensify selection efforts to prevent inbreeding decline in JHBX while further enhancing the protection measures for the other six pig populations. Additionally, we identified candidate genes influencing the size disparity among pigs in Guizhou province through signal selection. Our study outcomes serve as a reference for developing effective conservation and utilization plans for pig breeds in Guizhou province and deepen our understanding of the genetic mechanisms underlying pig body size.

Population genetic analysis based on the polymorphisms mediated by transposons in the genomes of pig.

Transposable elements (TEs) mobility is capable of generating a large number of structural variants (SVs), which can have considerable potential as molecular markers for genetic analysis and molecular breeding in livestock. Our results showed that the pig genome contains mainly TE-SVs generated by short interspersed nuclear elements (51,873/76.49%), followed by long interspersed nuclear elements (11,131/16.41%), and more than 84% of the common TE-SVs (Minor allele frequency, MAF > 0.10) were validated to be polymorphic. Subsequently, we utilized the identified TE-SVs to gain insights into the population structure, resulting in clear differentiation among the three pig groups and facilitating the identification of relationships within Chinese local pig breeds. In addition, we investigated the frequencies of TEs in the gene coding regions of different pig groups and annotated the respective TE types, related genes, and functional pathways. Through genome-wide comparisons of Large White pigs and Chinese local pigs utilizing the Beijing Black pigs, we identified TE-mediated SVs associated with quantitative trait loci and observed that they were mainly involved in carcass traits and meat quality traits. Lastly, we present the first documented evidence of TE transduction in the pig genome.

Associations of genome-wide structural variations with phenotypic differences in cross-bred Eurasian pigs.

BACKGROUND: During approximately 10,000 years of domestication and selection, a large number of structural variations (SVs) have emerged in the genome of pig breeds, profoundly influencing their phenotypes and the ability to adapt to the local environment. SVs (≥ 50 bp) are widely distributed in the genome, mainly in the form of insertion (INS), mobile element insertion (MEI), deletion (DEL), duplication (DUP), inversion (INV), and translocation (TRA). While studies have investigated the SVs in pig genomes, genome-wide association studies (GWAS)-based on SVs have been rarely conducted. RESULTS: Here, we obtained a high-quality SV map containing 123,151 SVs from 15 Large White and 15 Min pigs through integrating the power of several SV tools, with 53.95% of the SVs being reported for the first time. These high-quality SVs were used to recover the population genetic structure, confirming the accuracy of genotyping. Potential functional SV loci were then identified based on positional effects and breed stratification. Finally, GWAS were performed for 36 traits by genotyping the screened potential causal loci in the F2 population according to their corresponding genomic positions. We identified a large number of loci involved in 8 carcass traits and 6 skeletal traits on chromosome 7, with FKBP5 containing the most significant SV locus for almost all traits. In addition, we found several significant loci in intramuscular fat, abdominal circumference, heart weight, and liver weight, etc. CONCLUSIONS: We constructed a high-quality SV map using high-coverage sequencing data and then analyzed them by performing GWAS for 25 carcass traits, 7 skeletal traits, and 4 meat quality traits to determine that SVs may affect body size between European and Chinese pig breeds.

Characteristics of Transcriptome and Metabolome Concerning Intramuscular Fat Content in Beijing Black Pigs.

To study the characteristics of genes and metabolites related to intramuscular fat (IMF) content with less influence by breed background and individual differences, the skeletal muscle samples from 40 Beijing black pigs with either high or low IMF content were used to perform transcriptome and metabolome analyses. About 99 genes (twofold-change) were differentially expressed. Up-regulated genes in the high IMF pigs were mainly related to fat metabolism. The key genes in charge of IMF deposition are ADIPOQ, CIDEC, CYP4B1, DGAT2, LEP, OPRL1, PLIN1, SCD, and THRSP. KLHL40, TRAFD1, and HSPA6 were novel candidate genes for the IMF trait due to their high abundances. In the low IMF pigs, the differentially expressed genes involved in virus resistance were up-regulated. About 16 and 18 differential metabolites (1.5 fold-change) were obtained in the positive and negative modes, respectively. Pigs with low IMF had weaker fatty acid oxidation due to the down-regulation of various carnitines. Differentially expressed genes were more important in determining IMF deposition than differential metabolites because relatively few differential metabolites were obtained, and they were merely the products under the physiological status of diverged IMF content. This study provided valuable information for further studies on IMF deposition.

Genetic Evaluation and Population Structure of Jiangsu Native Pigs in China Revealed by SINE Insertion Polymorphisms.

Short interspersed nuclear elements (SINEs), one type of retrotransposon, are considered to be ideal molecular markers due to their wide distribution in the genome, high copy number, and high polymorphism. Preliminary studies have identified more than 35,000 SINE-retrotransposon insertion polymorphisms (RIPs) in the pig genome. In this study, 18 SINE-RIPs were used to evaluate the genetic variation and population structure of seven native pig populations and two crossbreeds in the Jiangsu Province of China. Two commercial pig breeds (Duroc and Large White) and one Italian native breed (Sicilian Black pig) were selected as the control. The results showed that all 18 SINE-RIPs were polymorphic among these pigs. The Jiangsu native pig populations (Erhualian, Fengjing, Middle Meishan, Mi, Shawutou, Small Meishan, and Huai) were shown to be more polymorphic than the crossbreeds (Sushan and Sujiang) and external breeds (Sicilian Black pig, Large White, and Duroc) based on the expected heterozygosity and polymorphic information content values. Some native pigs, including Small Meishan, Mi, Middle Meishan, and Erhualian, had a higher degree of inbreeding according to the FIS values. Based on the neighbor-joining tree, all of the Jiangsu native pig populations formed one branch, while the three external pig breeds formed the other branches, with the two crossbreeds containing more than 50% external pig ancestry. The Huai pigs were independent of the other Jiangsu native pigs but shared a common ancestor with Sujiang and Mi. The results provide a new perspective on the population structure of these native pig breeds and will assist with the conservation and utilization of Chinese native pigs.

Dose-Dependent Effects of Royal Jelly on Estrogen- and Progesterone-Induced Mammary Gland Hyperplasia in Rats.

SCOPE: Royal jelly (RJ) has a wide range of biological functions, its effect on hyperplasia of the mammary gland (HMG) in mammals is unclear. This study aims to investigate the effect of RJ on HMG and the dose-response relationship of RJ in the treatment of HMG. METHODS AND RESULTS: HMG rats are induced by intramuscular injection of estrogen (E2) and progesterone, and are treated with different doses of RJ (100, 200, 400, and 800 mg kg-1 d-1 ). As a result, RJ improves the expansion of acinar and breast tissue ducts, particularly at 100 and 800 mg kg-1 d-1 . These two doses also inhibit serum E2 and prolactin (PRL) secretion and increase serum progesterone secretion and the expression of estrogen receptor (ER)-ß in the breast tissue. In addition, 800 mg kg-1 d-1 decrease and increase the mRNA expression of, respectively, hypothalamic gonadotropin-releasing hormone (GnRH) and pituitary GnRH receptors (GnRH-R). The lowest dosage (100 mg kg-1 d-1 ) increases GnRH-R mRNA expression as well. However, the effects of 200 and 400 mg kg-1 d-1 RJ on the reproductive parameters of HMG are not significant, implying a dose-dependent effect. CONCLUSION: RJ regulates endocrine dyscrasia in HMG rats and improves the breast tissue structure, indicating its potential in the prevention and treatment on HMG.

Revisiting the Tigger Transposon Evolution Revealing Extensive Involvement in the Shaping of Mammal Genomes.

The data of this study revealed that Tigger was found in a wide variety of animal genomes, including 180 species from 36 orders of invertebrates and 145 species from 29 orders of vertebrates. An extensive invasion of Tigger was observed in mammals, with a high copy number. Almost 61% of those species contain more than 50 copies of Tigger; however, 46% harbor intact Tigger elements, although the number of these intact elements is very low. Common HT events of Tigger elements were discovered across different lineages of animals, including mammals, that may have led to their widespread distribution, whereas Helogale parvula and arthropods may have aided Tigger HT incidences. The activity of Tigger seems to be low in the kingdom of animals, most copies were truncated in the mammal genomes and lost their transposition activity, and Tigger transposons only display signs of recent and current activities in a few species of animals. The findings suggest that the Tigger family is important in structuring mammal genomes.

Genetic Diversity and Population Structures in Chinese Miniature Pigs Revealed by SINE Retrotransposon Insertion Polymorphisms, a New Type of Genetic Markers.

RIPs have been developed as effective genetic markers and popularly applied for genetic analysis in plants, but few reports are available for domestic animals. Here, we established 30 new molecular markers based on the SINE RIPs, and applied them for population genetic analysis in seven Chinese miniature pigs. The data revealed that the closed herd (BM-clo), inbreeding herd (BM-inb) of Bama miniature pigs were distinctly different from the BM-cov herds in the conservation farm, and other miniature pigs (Wuzhishan, Congjiang Xiang, Tibetan, and Mingguang small ear). These later five miniature pig breeds can further be classified into two clades based on a phylogenetic tree: one included BM-cov and Wuzhishan, the other included Congjiang Xiang, Tibetan, and Mingguang small ear, which was well-supported by structure analysis. The polymorphic information contents estimated by using SINE RIPs are lower than the predictions based on microsatellites. Overall, the genetic distances and breed-relationships between these populations revealed by 30 SINE RIPs generally agree with their evolutions and geographic distributions. We demonstrated the potential of SINE RIPs as new genetic markers for genetic monitoring and population structure analysis in pigs, which can even be extended to other livestock animals.

Diversity and Evolution of pogo and Tc1/mariner Transposons in the Apoidea Genomes.

Bees (Apoidea), the largest and most crucial radiation of pollinators, play a vital role in the ecosystem balance. Transposons are widely distributed in nature and are important drivers of species diversity. However, transposons are rarely reported in important pollinators such as bees. Here, we surveyed 37 bee genomesin Apoidea, annotated the pogo and Tc1/mariner transposons in the genome of each species, and performed a phylogenetic analysis and determined their overall distribution. The pogo and Tc1/mariner families showed high diversity and low abundance in the 37 species, and their proportion was significantly higher in solitary bees than in social bees. DD34D/mariner was found to be distributed in almost all species and was found in Apis mellifera, Apis mellifera carnica, Apis mellifera caucasia, and Apis mellifera mellifera, and Euglossa dilemma may still be active. Using horizontal transfer analysis, we found that DD29-30D/Tigger may have experienced horizontal transfer (HT) events. The current study displayed the evolution profiles (including diversity, activity, and abundance) of the pogo and Tc1/mariner transposons across 37 species of Apoidea. Our data revealed their contributions to the genomic variations across these species and facilitated in understanding of the genome evolution of this lineage.

Intruder (DD38E), a recently evolved sibling family of DD34E/Tc1 transposons in animals.

BACKGROUND: A family of Tc1/mariner transposons with a characteristic DD38E triad of catalytic amino acid residues, named Intruder (IT), was previously discovered in sturgeon genomes, but their evolutionary landscapes remain largely unknown. RESULTS: Here, we comprehensively investigated the evolutionary profiles of ITs, and evaluated their cut-and-paste activities in cells. ITs exhibited a narrow taxonomic distribution pattern in the animal kingdom, with invasions into two invertebrate phyla (Arthropoda and Cnidaria) and three vertebrate lineages (Actinopterygii, Agnatha, and Anura): very similar to that of the DD36E/IC family. Some animal orders and species seem to be more hospitable to Tc1/mariner transposons, one order of Amphibia and seven Actinopterygian orders are the most common orders with horizontal transfer events and have been invaded by all four families (DD38E/IT, DD35E/TR, DD36E/IC and DD37E/TRT) of Tc1/mariner transposons, and eight Actinopterygii species were identified as the major hosts of these families. Intact ITs have a total length of 1.5-1.7 kb containing a transposase gene flanked by terminal inverted repeats (TIRs). The phylogenetic tree and sequence identity showed that IT transposases were most closely related to DD34E/Tc1. ITs have been involved in multiple events of horizontal transfer in vertebrates and have invaded most lineages recently (< 5 million years ago) based on insertion age analysis. Accordingly, ITs presented high average sequence identity (86-95%) across most vertebrate species, suggesting that some are putatively active. ITs can transpose in human HeLa cells, and the transposition efficiency of consensus TIRs was higher than that of the TIRs of natural isolates. CONCLUSIONS: We conclude that DD38E/IT originated from DD34E/Tc1 and can be detected in two invertebrate phyla (Arthropoda and Cnidaria), and in three vertebrate lineages (Actinopterygii, Agnatha and Anura). IT has experienced multiple HT events in animals, dominated by recent amplifications in most species and has high identity among vertebrate taxa. Our reconstructed IT transposon vector designed according to the sequence from the "cat" genome showed high cut-and-paste activity. The data suggest that IT has been acquired recently and is active in many species. This study is meaningful for understanding the evolution of the Tc1/mariner superfamily members and their hosts.

Evolution of pogo, a separate superfamily of IS630-Tc1-mariner transposons, revealing recurrent domestication events in vertebrates.

BACKGROUND: Tc1/mariner and Zator, as two superfamilies of IS630-Tc1-mariner (ITm) group, have been well-defined. However, the molecular evolution and domestication of pogo transposons, once designated as an important family of the Tc1/mariner superfamily, are still poorly understood. RESULTS: Here, phylogenetic analysis show that pogo transposases, together with Tc1/mariner, DD34E/Gambol, and Zator transposases form four distinct monophyletic clades with high bootstrap supports (> = 74%), suggesting that they are separate superfamilies of ITm group. The pogo superfamily represents high diversity with six distinct families (Passer, Tigger, pogoR, Lemi, Mover, and Fot/Fot-like) and wide distribution with an expansion spanning across all the kingdoms of eukaryotes. It shows widespread occurrences in animals and fungi, but restricted taxonomic distribution in land plants. It has invaded almost all lineages of animals-even mammals-and has been domesticated repeatedly in vertebrates, with 12 genes, including centromere-associated protein B (CENPB), CENPB DNA-binding domain containing 1 (CENPBD1), Jrk helix-turn-helix protein (JRK), JRK like (JRKL), pogo transposable element derived with KRAB domain (POGK), and with ZNF domain (POGZ), and Tigger transposable element-derived 2 to 7 (TIGD2-7), deduced as originating from this superfamily. Two of them (JRKL and TIGD2) seem to have been co-domesticated, and the others represent independent domestication events. Four genes (TIGD3, TIGD4, TIGD5, and POGZ) tend to represent ancient domestications in vertebrates, while the others only emerge in mammals and seem to be domesticated recently. Significant structural variations including target site duplication (TSD) types and the DDE triad signatures (DD29-56D) were observed for pogo transposons. Most domesticated genes are derived from the complete transposase genes; but CENPB, POGK, and POGZ are chimeric genes fused with additional functional domains. CONCLUSIONS: This is the first report to systematically reveal the evolutionary profiles of the pogo transposons, suggesting that pogo and Tc1/Mariner are two separate superfamilies of ITm group, and demonstrating the repeated domestications of pogo in vertebrates. These data indicate that pogo transposons have played important roles in shaping the genome and gene evolution of fungi and animals. This study expands our understanding of the diversity of pogo transposons and updates the classification of ITm group.

Traveler, a New DD35E Family of Tc1/Mariner Transposons, Invaded Vertebrates Very Recently.

The discovery of new members of the Tc1/mariner superfamily of transposons is expected based on the increasing availability of genome sequencing data. Here, we identified a new DD35E family termed Traveler (TR). Phylogenetic analyses of its DDE domain and full-length transposase showed that, although TR formed a monophyletic clade, it exhibited the highest sequence identity and closest phylogenetic relationship with DD34E/Tc1. This family displayed a very restricted taxonomic distribution in the animal kingdom and was only detected in ray-finned fish, anura, and squamata, including 91 vertebrate species. The structural organization of TRs was highly conserved across different classes of animals. Most intact TR transposons had a length of ∼1.5 kb (range 1,072-2,191 bp) and harbored a single open reading frame encoding a transposase of ∼340 aa (range 304-350 aa) flanked by two short-terminal inverted repeats (13-68 bp). Several conserved motifs, including two helix-turn-helix motifs, a GRPR motif, a nuclear localization sequence, and a DDE domain, were also identified in TR transposases. This study also demonstrated the presence of horizontal transfer events of TRs in vertebrates, whereas the average sequence identities and the evolutionary dynamics of TR elements across species and clusters strongly indicated that the TR family invaded the vertebrate lineage very recently and that some of these elements may be currently active, combining the intact TR copies in multiple lineages of vertebrates. These data will contribute to the understanding of the evolutionary history of Tc1/mariner transposons and that of their hosts.

Multiple Invasions of Visitor, a DD41D Family of Tc1/mariner Transposons, throughout the Evolution of Vertebrates.

Although the DD41D (named as Visitor, VS) family of Tc1/mariner transposons was discovered in Arthropods and Mollusca, the evolution profile of this family is still largely unknown. We found that VS is widespread in the animal kingdom, including 140 species of 18 orders in invertebrates and 30 species of 12 orders in vertebrates, and one land plant species. Our data revealed multiple horizontal transfer events in both invertebrates and vertebrates and invasion into multiple lineages of mammals, including Chiroptera (seven species), Dasyuromorphia/Marsupialia (one species), Didelphimorphia/Marsupialia (one species), Diprotodontia/Marsupialia (two species), and Primates (one species). Phylogenetic analysis revealed a close relationship of VSs to DD37D/maT and DD34D/mariner and confirmed that VSs with the DD40D signature identified previously are not a distinct family but originated from DD41D/VS. Age analysis revealed that the most recent invasion of VSs was found in ray-finned fishes and a toad, followed by relatively young invasions in bats and marsupials, whereas VSs in mammals, jawless fishes, and lizards were mainly represented by ancient copies, suggesting old age. Phylogenetic analyses and comparison of pairwise distances between VSs and recombination-activating gene 1 (RAG1) support horizontal transfer events of VSs in vertebrates. The intact VSs from bats were nonfunctional as determined by the transposition activity assay. Some vertebrate lineages and species were identified as the hot hosts of Tc1/mariner transposons. Overall, our study presents the evolution profile of VSs and suggests that VSs play roles in diversifying and shaping the genomes of diverse animal lineages.

Incomer, a DD36E family of Tc1/mariner transposons newly discovered in animals.

BACKGROUND: The Tc1/mariner superfamily might represent the most diverse and widely distributed group of DNA transposons. Several families have been identified; however, exploring the diversity of this superfamily and updating its classification is still ongoing in the life sciences. RESULTS: Here we identified a new family of Tc1/mariner transposons, named Incomer (IC), which is close to, but distinct from the known family DD34E/Tc1. ICs have a total length of about 1.2 kb, and harbor a single open reading frame encoding a ~ 346 amino acid transposase with a DD36E motif and flanked by short terminal inverted repeats (TIRs) (22-32 base pairs, bp). This family is absent from prokaryotes, and is mainly distributed among vertebrates (141 species of four classes), including Agnatha (one species of jawless fish), Actinopterygii (132 species of ray-finned fish), Amphibia (four species of frogs), and Mammalia (four species of bats), but have a restricted distribution in invertebrates (four species in Insecta and nine in Arachnida). All ICs in bats (Myotis lucifugus, Eptesicus fuscus, Myotis davidii, and Myotis brandtii) are present as truncated copies in these genomes, and most of them are flanked by relatively long TIRs (51-126 bp). High copy numbers of miniature inverted-repeat transposable elements (MITEs) derived from ICs were also identified in bat genomes. Phylogenetic analysis revealed that ICs are more closely related to DD34E/Tc1 than to other families of Tc1/mariner (e.g., DD34D/mariner and DD × D/pogo), and can be classified into four distinct clusters. The host and IC phylogenies and pairwise distance comparisons between RAG1 genes and all consensus sequences of ICs support the idea that multiple episodes of horizontal transfer (HT) of ICs have occurred in vertebrates. In addition, the discovery of intact transposases, perfect TIRs and target site duplications of ICs suggests that this family may still be active in Insecta, Arachnida, frogs, and fish. CONCLUSIONS: Exploring the diversity of Tc1/mariner transposons and revealing their evolutionary profiles will help provide a better understanding of the evolution of DNA transposons and their impact on genomic evolution. Here, a newly discovered family (DD36E/Incomer) of Tc1/mariner transposons is described in animals. It displays a similar structural organization and close relationship with the known DD34E/Tc1 elements, but has a relatively narrow distribution, indicating that DD36E/IC might have originated from the DD34E/Tc1 family. Our data also support the hypothesis of horizontal transfer of IC in vertebrates, even invading one lineage of mammals (bats). This study expands our understanding of the diversity of Tc1/mariner transposons and updates the classification of this superfamily.