Pervasive introgression facilitated domestication and adaptation in the Bos species complex

Cardiovascular Plasticity and Adaptation of High-Altitude Birds and Mammals

Exposure to a hypoxic environment at high altitudes imposes severe pressure on animals living there, which utilize substantial cardiovascular and respiratory responses to meet the physiological challenge of oxygen requirement. These responses may result from phenotypic plasticity through short-term exposure (i.e., within a generation) to a new environment or shaped by adaptation (i.e., many generations) through long-term evolution. For example, plasticity triggers a sympathetic-mediated adrenergic response, resulting in an elevation of heart rate and hypoxia-induced pulmonary vasoconstriction that eventually contributes to pulmonary hypertension in some animals. Adaptation to high altitudes can drive an increase in muscular capillarization and adaptive cardiac growth, which promote oxygen diffusion and transportation. Exposure to a high-altitude hypoxic environment stimulates excessive erythropoiesis, which has maladaptive effects and contributes to chronic mountain sickness. Maladaptation caused by plasticity at early stages can be reversed during adaptation. Despite extensive research on high-altitude adaptation, the phenotypic changes and genetic variations in cardiovascular systems responding to high-altitude hypoxia remain insufficiently integrated across taxa. While genomic and transcriptomic studies have advanced our understanding, a cross-taxa comparison of cardiovascular adaptations is still incomplete. We here review recent literature on phenotypic plasticity, adaptations, and genetic and transcriptional basis of cardiovascular systems of mammals and birds living in high altitudes with respect to their duration of exposure at high altitudes. By integrating and comparing data across mammalian and avian species, we aim to provide a framework for understanding the plasticity and adaptation of the cardiovascular system in high-altitude environments.

Transcriptomic Profiling of Hypoxia-Adaptive Responses in Tibetan Goat Fibroblasts

The Tibetan goat (Capra hircus) exhibits remarkable adaptations to high-altitude hypoxia, yet the molecular mechanisms remain unclear. This study integrates RNA-seq, WGCNA, and machine learning to explore gene-environment interactions (G × E) in hypoxia adaptation. Fibroblasts from the Tibetan goat and Yunling goat were cultured under hypoxic (1% O2) and normoxic (21% O2) conditions, respectively. This identified 68 breed-specific (G), 100 oxygen-responsive (E), and 620 interaction-driven (I) Differentially Expressed Genes (DEGs). The notably higher number of interaction-driven DEGs compared to other effects highlights transcriptional plasticity. We defined two gene sets: Environmental Stress Genes (n = 632, E ∪ I) and Genetic Adaptation Genes (n = 659, G ∪ I). The former were significantly enriched in pathways related to oxidative stress defense and metabolic adaptation, while the latter showed prominent enrichment in pathways associated with vascular remodeling and transcriptional regulation. CTNNB1 emerged as a key regulatory factor in both gene sets, interacting with CASP3 and MMP2 to form the core of the protein-protein interaction (PPI) network. Machine learning identified MAP3K5, TGFBR2, RSPO1 and ITGB5 as critical genes. WGCNA identified key modules in hypoxia adaptation, where FOXO3, HEXIM1, and PPARD promote the stabilization of HIF-1α and metabolic adaptation through the HIF-1 signaling pathway and glycolysis. These findings underscore the pivotal role of gene-environment interactions in hypoxic adaptation, offering novel perspectives for both livestock breeding programs and biomedical research initiatives.

Whole Genome Insights into Genetic Diversity, Introgression, and Adaptation of Hunan Cattle

Hunan Province, located in Central-South China, has a hot and humid climate, which has shaped the unique characteristics of its cattle. In this study, we analyzed the genomic diversity of 110 indigenous Hunan cattle using whole-genome sequencing and found that they have a mixed ancestry of indicine and taurine. By grouping the cattle based on their collection regions (western, central, southeastern, and southern Hunan), we used an unsupervised three-component Gaussian model to classify the runs of homozygosity (ROH) and calculated the genomic inbreeding coefficient based on runs of homozygosity (FROH) to assess inbreeding levels. The results showed that western Hunan cattle had the highest level of hybridization, while southern Hunan cattle had the lowest. Through selective sweep analysis, we identified candidate genes and pathways related to environmental adaptation and homeostasis. Notably, the SLC5A2 gene showed strong selection signals across all four regions and exhibited a distinct haplotype compared to other referenced cattle breeds. Additionally, we detected introgression from wild species into Hunan domestic cattle and analyzed their Y-chromosome haplotypes.

Whole-Genome Sequencing Reveals the Role of Cis-Regulatory Elements and eQTL/sQTL in the Adaptive Selection of Hubei Indigenous Cattle

Hubei indigenous cattle have adapted to diverse environmental conditions, exhibiting unique genetic traits associated with both economic and adaptive characteristics. Understanding their adaptive selection offers insight into their evolutionary history and genetic enhancements. In this study, we analyzed whole-genome sequencing (WGS) data from five Hubei indigenous cattle breeds to identify selection signals. Selective sweep analysis revealed the candidate genes (USH2A, TMTC2, ABCC12, and SUGT1) associated with sensory perception, backfat thickness, reproduction, and immune function. The further integration of cis-regulatory elements (CREs) and expression quantitative trait loci (eQTL) highlighted regulatory variants, influencing adaptive traits. Notably, positively selected genes such as RPS6KA2, CRLS1, MGST3, GPCPD1, and LDLRAP1 were associated with lipid metabolism, meat quality, and reproductive traits, influencing aldehyde volatile organic compounds (VOCs) and fat deposition. These findings highlight the understanding of the genetic basis of adaptation and production traits in Hubei indigenous cattle and provide valuable insights for their conservation and potential breeding strategies.

Bos taurus and Bison bison conservative retrotransposon recombination products

Background

Without identifying and studying the genomic characteristics associated with domestication, managing farm animal genetic resources becomes overwhelmingly difficult. Accumulated data confirm that mobile genetic elements participate in the domestication process and, in particular, generate widely abundant microRNAs.

Methods

The recombination products were compared in silico between the long interspersed nuclear element (LINE) and the endogenous retrovirus (ERV), forming the LINE/ERV/LINE sequence, located in a closely linked conserved block of 12 genes, as well as the microRNAs formed by these recombination products in domesticated-wild pairs of mammals. For this comparison, the reference genomes of domesticated cattle (Bos taurus) and its closely related wild species counterpart, bison (Bison bison), were used.

Results

It was found that the above-noted highly conserved recombination products (with more than 81.5% identity) were present in the corresponding block of 12 genes in bison. These recombination products served as sources of 51 microRNAs in bison and 129 microRNAs in cattle, including 50 microRNAs that were similar in both species. A total of 79 microRNAs were found only in cattle trinomial recombination products, with 98% belonging to the mir-30 family, including the cattle-specific bta-miR-30a-5p and bta-miR-30e-5p. The mir-30 family is closely associated with biological processes influencing the quantity and quality of agricultural products.

Conclusion

Trinomial retrotransposon recombination products were fixed in both the cattle genome and the genome of its closely related wild species, the bison. It was found that these products may be involved in the response to intensive artificial selection and the domestication process since interspecific differentiation of microRNAs is associated with regulatory networks that have a significant impact on the formation of economically important traits.

Genomic diversity of Cameroonian Gudali and Gudali-cross cattle

Information on population structure and diversity in cattle breeds is critical for understanding environmental adaptation, as well as optimal utilisation of genetic resources and breed improvement. In this study, we investigated at the genomic level the population structure, genetic diversity and admixture of the local Gudali breed and its crossbred with the Italian Simmental (Simgud) in three agroecological zones of Cameroon. A total of 717 Gudali and 139 Simgud were genotyped using the GeneSeek® Genomic ProfilerTM (GGP) Bovine 100K array and analyzed together with reference breed data from public databases. Principal component (PCA) and admixture analysis separated European Bos taurus from Asian Bos indicus, African Bos taurus and African Bos indicus breeds. These analyses showed that, except for recently admixed cattle, all African indigenous breeds are either pure African Bos taurus (N'dama) or admixtures of African Bos taurus and Bos indicus. Analysis revealed an ancient admixture from Asian origin in Gudali and a more recent and ongoing European introgression. Simgud is an unmanaged crossbreed expected to be primarily a 50% admixture of Gudali and Simmental. We show here that Simgud is, in actuality, composed of two genetic groups representing admixture of between ∼25% to ∼50% Simmental proportion. Diversity analysis revealed high average heterozygosity ([Formula: see text], [Formula: see text]) for the Gudali and ([Formula: see text] , [Formula: see text]) for Simgud respectively. Inbreeding measures based on the mean FIS coefficient were 0.03 for Gudali and 0.07 for Simgud. A general decline in effective population size was observed in Gudali from a large population (Ne=2475), 959 generations (4797 years ago), back to 13 generations (65 years) (Ne=1404) ago. These results were expected, given the breeding efforts that began in 1952 with the introduction of various exotic (imported taurine) breeds and the Gudali selection initiative. This has affected the effective population size of Gudali, despite the general increase in cattle population in the ranches over that period. These results highlight the need for a structured breeding program in Cameroon for improving productivity, while maintaining a large genetic base of the pure Gudali population.

Genetic differentiation and adaptive evolution of buff-tailed bumblebees in Asia

Bumblebees are important pollinating insects, so their declines resulting from environmental change have received intensive attention. Understanding how environmental factors shape the genetic structure of natural populations and identifying the genetic basis of local adaptation will provide insights into how bumblebees cope with environmental change. The buff-tailed bumblebee (Bombus terrestris) has a wide natural distribution range and has been domesticated to produce commercial colonies for greenhouse pollination. Previous population genetics studies on B. terrestris have mainly focused on its European populations; however, its Asian populations, representing the eastern side of its natural distribution, remain largely unsampled. To fill this gap, we collected wild B. terrestris samples from Asia, as well as wild B. terrestris samples from Europe and samples from domesticated colonies. We conducted whole-genome resequencing for 77 collected B. terrestris and performed population genomics analysis. Our results indicate that distinct genetic differentiation (FST = 0.076) exists between B. terrestris in Europe and Asia, with substantial morphological and physiological differences detected between them; B. terrestris in Asia should represent a distinct genetic resource. Demographic analysis suggests that the effective population size of B. terrestris has increased during historic cold periods, indicating their cold-adapted characteristics. Selective sweep analysis identified 331 genes under selection in the genomes of Asian B. terrestris, likely involved in their adaptation to the high ultraviolet radiation, low temperature and low precipitation of their habitats. Our research provides insights into the population genetic structure and genetic basis of local adaptation in the buff-tailed bumblebee, which will be useful for its conservation and management.

Genetic advancements and future directions in ruminant livestock breeding: from reference genomes to multiomics innovations

Ruminant livestock provide a rich source of products, such as meat, milk, and wool, and play a critical role in global food security and nutrition. Over the past few decades, genomic studies of ruminant livestock have provided valuable insights into their domestication and the genetic basis of economically important traits, facilitating the breeding of elite varieties. In this review, we summarize the main advancements for domestic ruminants in reference genome assemblies, population genomics, and the identification of functional genes or variants for phenotypic traits. These traits include meat and carcass quality, reproduction, milk production, feed efficiency, wool and cashmere yield, horn development, tail type, coat color, environmental adaptation, and disease resistance. Functional genomic research is entering a new era with the advancements of graphical pangenomics and telomere-to-telomere (T2T) gap-free genome assembly. These advancements promise to improve our understanding of domestication and the molecular mechanisms underlying economically important traits in ruminant livestock. Finally, we provide new perspectives and future directions for genomic research on ruminant genomes. We suggest how ever-increasing multiomics datasets will facilitate future studies and molecular breeding in livestock, including the potential to uncover novel genetic mechanisms underlying phenotypic traits, to enable more accurate genomic prediction models, and to accelerate genetic improvement programs.

Whole genome insights into genetic diversity, introgression, and adaptation of Yunnan indigenous cattle of Southwestern China

BACKGROUND

Yunnan Province, located in Southwestern China, the intricate geography, variable climate, and abundant vegetation of the region have collectively contributed to shaping the distinctive germplasm characteristics observed in Yunnan indigenous cattle through prolonged domestication. The different breeds of Yunnan cattle exhibit distinct advantageous characteristics and traits, which are an important source of genetic variation because they might carry alleles that enable them to adapt to local environment and tough feeding conditions. However, a comprehensive genomic landscape of genetic resources has yet to be delineated.

RESULTS

Herein, we employed 140 whole-genome sequencing data from Yunnan indigenous cattle across eight breeds to elucidate their genetic diversity and population structure. Utilizing both uniparental and biparental markers, we elucidated the intricate genetic composition of Yunnan indigenous cattle, which is closely correlated with the geographic environment. A predominant East Asian indicine ancestry which gradually diminishes towards the north. The analysis revealed a high genetic diversity among populations and a low-to-moderate inbreeding coefficient, underscoring the rich genetic reservoir of Yunnan cattle breeds. Additionally, gene flow between Yunnan indicine and wild Bos species in and around Yunnan was verified, highlighting localized introgression from Yunnan Gayal as a critical factor in the successful adaptation of Yunnan indicine cattle to the local hot and humid environments.

CONCLUSIONS

Our findings established the SNPs database for facilitating resource conservation and selective breeding. Moreover, these valuable insights into the genomic diversity and adaptive history of Yunnan indigenous cattle breeds contribute significantly to our understanding of their evolutionary dynamics and offer a foundation for future genetic improvement and conservation strategies.

CASTER: Direct species tree inference from whole-genome alignments

Genomes contain mosaics of discordant evolutionary histories, challenging the accurate inference of the tree of life. Although genome-wide data are routinely used for discordance-aware phylogenomic analyses, because of modeling and scalability limitations, the current practice leaves out large chunks of genomes. As more high-quality genomes become available, we urgently need discordance-aware methods to infer the tree directly from a multiple genome alignment. In this study, we introduce Coalescence-Aware Alignment-Based Species Tree Estimator (CASTER), a theoretically justified site-based method that eliminates the need to predefine recombination-free loci. CASTER is scalable to hundreds of mammalian whole genomes. We demonstrate the accuracy and scalability of CASTER in simulations that include recombination and apply CASTER to several biological datasets, showing that its per-site scores can reveal both biological and artifactual patterns of discordance across the genome.

Advancing the Indian cattle pangenome: characterizing non-reference sequences in Bos indicus

BACKGROUND

India harbors the world's largest cattle population, encompassing over 50 distinct Bos indicus breeds. This rich genetic diversity underscores the inadequacy of a single reference genome to fully capture the genomic landscape of Indian cattle. To comprehensively characterize the genomic variation within Bos indicus and, specifically, dairy breeds, we aim to identify non-reference sequences and construct a comprehensive pangenome.

RESULTS

Five representative genomes of prominent dairy breeds, including Gir, Kankrej, Tharparkar, Sahiwal, and Red Sindhi, were sequenced using 10X Genomics 'linked-read' technology. Assemblies generated from these linked-reads ranged from 2.70 Gb to 2.77 Gb, comparable to the Bos indicus Brahman reference genome. A pangenome of Bos indicus cattle was constructed by comparing the newly assembled genomes with the reference using alignment and graph-based methods, revealing 8 Mb and 17.7 Mb of novel sequence respectively. A confident set of 6,844 Non-reference Unique Insertions (NUIs) spanning 7.57 Mb was identified through both methods, representing the pangenome of Indian Bos indicus breeds. Comparative analysis with previously published pangenomes unveiled 2.8 Mb (37%) commonality with the Chinese indicine pangenome and only 1% commonality with the Bos taurus pangenome. Among these, 2,312 NUIs encompassing ~ 2 Mb, were commonly found in 98 samples of the 5 breeds and designated as Bos indicus Common Insertions (BICIs) in the population. Furthermore, 926 BICIs were identified within 682 protein-coding genes, 54 long non-coding RNAs (lncRNA), and 18 pseudogenes. These protein-coding genes were enriched for functions such as chemical synaptic transmission, cell junction organization, cell-cell adhesion, and cell morphogenesis. The protein-coding genes were found in various prominent quantitative trait locus (QTL) regions, suggesting potential roles of BICIs in traits related to milk production, reproduction, exterior, health, meat, and carcass. Notably, 63.21% of the bases within the BICIs call set contained interspersed repeats, predominantly Long Interspersed Nuclear Elements (LINEs). Additionally, 70.28% of BICIs are shared with other domesticated and wild species, highlighting their evolutionary significance.

CONCLUSIONS

This is the first report unveiling a robust set of NUIs defining the pangenome of Bos indicus breeds of India. The analyses contribute valuable insights into the genomic landscape of desi cattle breeds.

Identification of candidate genes related to hybrid sterility by genomic structural variation and transcriptome analyses in cattle-yak

Hybrids between closely related but genetically incompatible species are often inviable or sterile. Cattle-yak, an interspecific hybrid of yak and cattle, exhibits male-specific sterility, which limits the fixation of its desired traits and prevents genetic improvement in yak through crossbreeding. Transcriptome profiles of testicular tissues have been generated in cattle, yak, and cattle-yak; however, the genetic variations underlying differential gene expression associated with hybrid sterility have yet to be elucidated. We detected differences in the cellular composition and gene expression of testes from yak and cattle-yak at 3 mo of age, 10 mo of age, and adulthood. Histological analysis revealed that the most advanced germ cells were gonocytes (prospermatogonia) at 3 mo and spermatocytes at 10 mo. Complete spermatogenesis occurred in the seminiferous tubules of adult yak, whereas only spermatogonia and a limited number of spermatocytes were detected in the testis of adult cattle-yak. Transcriptome analysis revealed 180, 6,310, and 6,112 differentially expressed genes (DEG) in yak and cattle-yak at each stage, respectively. Next, we examined the spermatogenic cell types in the backcross generation (BC1) and detected the appearance of round spermatids, indicating the partial recovery of spermatogenesis in these animals. Compared with those in cattle-yak, 272 DEG were identified in the testes of BC1 animals. Notably, we discovered that the expression of X chromosome-linked genes was upregulated in the testis of cattle-yak compared with yak, suggesting a possible abnormality in the process of meiotic sex chromosome inactivation in hybrid animals. We next screened DEG harboring structural variations (SV) and identified a list of SV genes associated with spermatogonial development, meiotic recombination, and double-strand break repair. Furthermore, we found that the SV genes ESCO2 (establishment of sister chromatid cohesion N-acetyltransferase 2) and BRDT (bromodomain testis associated) may be involved in meiotic arrest of cattle-yak spermatocytes. Overall, our research provides a valuable database for identifying structural variant loci that contribute to hybrid sterility.

Genome-wide local ancestry and the functional consequences of admixture in African and European cattle populations

Bos taurus (taurine) and Bos indicus (indicine) cattle diverged at least 150,000 years ago and, since that time, substantial genomic differences have evolved between the two lineages. During the last two millennia, genetic exchange in Africa has resulted in a complex tapestry of taurine-indicine ancestry, with most cattle populations exhibiting varying levels of admixture. Similarly, there are several Southern European cattle populations that also show evidence for historical gene flow from indicine cattle, the highest levels of which are found in the Central Italian White breeds. Here we use two different software tools (MOSAIC and ELAI) for local ancestry inference (LAI) with genome-wide high- and low-density SNP array data sets in hybrid African and residually admixed Southern European cattle populations and obtained broadly similar results despite critical differences in the two LAI methodologies used. Our analyses identified genomic regions with elevated levels of retained or introgressed ancestry from the African taurine, European taurine, and Asian indicine lineages. Functional enrichment of genes underlying these ancestry peaks highlighted biological processes relating to immunobiology and olfaction, some of which may relate to differing susceptibilities to infectious diseases, including bovine tuberculosis, East Coast fever, and tropical theileriosis. Notably, for retained African taurine ancestry in admixed trypanotolerant cattle we observed enrichment of genes associated with haemoglobin and oxygen transport. This may reflect positive selection of genomic variants that enhance control of severe anaemia, a debilitating feature of trypanosomiasis disease, which severely constrains cattle agriculture across much of sub-Saharan Africa.

Complete Genomic Landscape Reveals Hidden Evolutionary History and Selection Signature in Asian Water Buffaloes (Bubalus bubalis)

To identify the genetic determinants of domestication and productivity of Asian water buffaloes (Bubalus bubalis), 470 genomes of domesticated river and swamp buffaloes along with their putative ancestors, the wild water buffaloes (Bubalus arnee) are sequenced and integrated. The swamp buffaloes inherit the morphology of the wild buffaloes. In contrast, most river buffaloes are unique in their morphology, but their genomes cluster with the wild buffaloes. The levels of genomic diversity in Italian river and Indonesian swamp buffaloes decrease at opposite extremes of their distribution range. Purifying selection prevented the accumulation of harmful loss-of-function variants in the Indonesian buffaloes. Genes that evolved rapidly (e.g., GKAP1) following differential selections in the river and swamp buffaloes are involved in their reproduction. Genes related to milk production (e.g., CSN2) and coat color (e.g., MC1R) underwent strong selections in the dairy river buffaloes via soft and hard selective sweeps, respectively. The selective sweeps and single-cell RNA-seq data revealed the luminal cells as the key cell type in response to artificial selection for milk production of the dairy buffaloes. These findings show how artificial selection has been driving the evolutionary divergence and genetic differentiation in morphology and productivity of Asian water buffaloes.

Genome assembly of wisent (Bison bonasus) uncovers a deletion that likely inactivates the THRSP gene

The wisent (Bison bonasus) is Europe's largest land mammal. We produced a HiFi read-based wisent assembly with a contig N50 value of 91 Mb containing 99.7% of the highly conserved single copy mammalian genes which improves contiguity a thousand-fold over an existing assembly. Extended runs of homozygosity in the wisent genome compromised the separation of the HiFi reads into parental-specific read sets, which resulted in inferior haplotype assemblies. A bovine super-pangenome built with assemblies from wisent, bison, gaur, yak, taurine and indicine cattle identified a 1580 bp deletion removing the protein-coding sequence of THRSP encoding thyroid hormone-responsive protein from the wisent and bison genomes. Analysis of 725 sequenced samples across the Bovinae subfamily showed that the deletion is fixed in both Bison species but absent in Bos and Bubalus. The THRSP transcript is abundant in adipose, fat, liver, muscle, and mammary gland tissue of Bos and Bubalus, but absent in bison. This indicates that the deletion likely inactivates THRSP in bison. We show that super-pangenomes can reveal potentially trait-associated variation across phylogenies, but also demonstrate that haplotype assemblies from species that went through population bottlenecks warrant scrutiny, as they may have accumulated long runs of homozygosity that complicate phasing.

Exploring the potential of dental calculus to shed light on past human migrations in Oceania

The Pacific islands and Island Southeast Asia have experienced multiple waves of human migrations, providing a case study for exploring the potential of ancient microbiomes to study human migration. We perform a metagenomic study of archaeological dental calculus from 102 individuals, originating from 10 Pacific islands and 1 island in Island Southeast Asia spanning ~3000 years. Oral microbiome DNA preservation in calculus is far higher than that of human DNA in archaeological bone, and comparable to that of calculus from temperate regions. Oral microbial community composition is minimally driven by time period and geography in Pacific and Island Southeast Asia calculus, but is found to be distinctive compared to calculus from Europe, Africa, and Asia. Phylogenies of individual bacterial species in Pacific and Island Southeast Asia calculus reflect geography. Archaeological dental calculus shows good preservation in tropical regions and the potential to yield information about past human migrations, complementing studies of the human genome.

Recent selection and introgression facilitated high-altitude adaptation in cattle

During the past 3000 years, cattle on the Qinghai-Xizang Plateau have developed adaptive phenotypes under the selective pressure of hypoxia, ultraviolet (UV) radiation, and extreme cold. The genetic mechanism underlying this rapid adaptation is not yet well understood. Here, we present whole-genome resequencing data for 258 cattle from 32 cattle breeds/populations, including 89 Tibetan cattle representing eight populations distributed at altitudes ranging from 3400 m to 4300 m. Our genomic analysis revealed that Tibetan cattle exhibited a continuous phylogeographic cline from the East Asian taurine to the South Asian indicine ancestries. We found that recently selected genes in Tibetan cattle were related to body size (HMGA2 and NCAPG) and energy expenditure (DUOXA2). We identified signals of sympatric introgression from yak into Tibetan cattle at different altitudes, covering 0.64%-3.26% of their genomes, which included introgressed genes responsible for hypoxia response (EGLN1), cold adaptation (LRP11), DNA damage repair (LATS1), and UV radiation resistance (GNPAT). We observed that introgressed yak alleles were associated with noncoding variants, including those in present EGLN1. In Tibetan cattle, three yak introgressed SNPs in the EGLN1 promoter region reduced the expression of EGLN1, suggesting that these genomic variants enhance hypoxia tolerance. Taken together, our results indicated complex adaptation processes in Tibetan cattle, where recently selected genes and introgressed yak alleles jointly facilitated rapid adaptation to high-altitude environments.

Selection signatures for high altitude adaptation in livestock: A review

High altitude adapted livestock species (cattle, yak, goat, sheep, and horse) has critical role in the human socioeconomic sphere and acts as good source of animal source products including milk, meat, and leather, among other things. These species sustain production and reproduction even in harsh environments on account of adaptation resulting from continued evolution of beneficial traits. Selection pressure leads to various adaptive strategies in livestock whose footprints are evident at the different genomic sites as the "Selection Signature". Scrutiny of these signatures provides us crucial insight into the evolutionary process and domestication of livestock adapted to diverse climatic conditions. These signatures have the potential to change the sphere of animal breeding and further usher the selection programmes in right direction. Technological revolution and recent strides made in genomic studies has opened the routes for the identification of selection signatures. Numerous statistical approaches and bioinformatics tools have been developed to detect the selection signature. Consequently, studies across years have identified candidate genes under selection region found associated with numerous traits which have a say in adaptation to high-altitude environment. This makes it pertinent to have a better understanding about the selection signature, the ways to identify and how to utilize them for betterment of livestock populations as well as farmers. This review takes a closer look into the general concept, various methodologies, and bioinformatics tools commonly employed in selection signature studies and summarize the results of recent selection signature studies related to high-altitude adaptation in various livestock species. This review will serve as an informative and useful insight for researchers and students in the field of animal breeding and evolutionary biology.

Insights into Adaption and Growth Evolution: Genome-Wide Copy Number Variation Analysis in Chinese Hainan Yellow Cattle Using Whole-Genome Re-Sequencing Data

Copy number variation (CNV) serves as a crucial source of genomic variation and significantly aids in the mining of genomic information in cattle. This study aims to analyze re-sequencing data from Chinese Hainan yellow cattle, to uncover breed CNV information, and to elucidate the resources of population genetic variation. We conducted whole-genome sequencing on 30 Chinese Hainan yellow cattle, thus generating 814.50 Gb of raw data. CNVs were called using CNVnator software, and subsequent filtering with Plink and HandyCNV yielded 197,434 high-quality CNVs and 5852 CNV regions (CNVRs). Notably, the proportion of deleted sequences (81.98%) exceeded that of duplicated sequences (18.02%), with the lengths of CNVs predominantly ranging between 20 and 500 Kb This distribution demonstrated a decrease in CNVR count with increasing fragment length. Furthermore, an analysis of the population genetic structure using CNVR databases from Chinese, Indian, and European commercial cattle breeds revealed differences between Chinese Bos indicus and Indian Bos indicus. Significant differences were also observed between Hainan yellow cattle and European commercial breeds. We conducted gene annotation for both Hainan yellow cattle and European commercial cattle, as well as for Chinese Bos indicus and Indian Bos indicus, identifying 206 genes that are expressed in both Chinese and Indian Bos indicus. These findings may provide valuable references for future research on Bos indicus. Additionally, selection signatures analysis based on Hainan yellow cattle and three European commercial cattle breeds identified putative pathways related to heat tolerance, disease resistance, fat metabolism, environmental adaptation, candidate genes associated with reproduction and the development of sperm and oocytes (CABS1, DLD, FSHR, HSD17B2, KDM2A), environmental adaptation (CNGB3, FAM161A, DIAPH3, EYA4, AAK1, ERBB4, ERC2), oxidative stress anti-inflammatory response (COMMD1, OXR1), disease resistance (CNTN5, HRH4, NAALADL2), and meat quality (EHHADH, RHOD, GFPT1, SULT1B1). This study provides a comprehensive exploration of CNVs at the molecular level in Chinese Hainan yellow cattle, offering theoretical support for future breeding and selection programs aimed at enhancing qualities of this breed.

Whole genome resequencing-based analysis of plateau adaptation in Meiren yak (Bos grunniens)

The Meiren yak is an important genetic resource in Gansu Province, China. In this study, we aimed to explore the evolutionary history and population structure of the genetic resource of Meiren yak and to mine the characteristic genes of Meiren yak. We analysed a total of 93 yaks of eight yak breeds based on whole genome resequencing combined with population genomics and used θπ ratio and Fst method to screen the selected sites in the genome region. The results proved that Meiren yak can be used as a potential genetic resource in Gansu Province. The genes in Meiren yak with positive selection in selection signal analysis were subjected to the Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) functional enrichment analyses, which indicated that the genes were related to the adaptability to high altitude and hypoxic environment. By analysing the genetic variation of Meiren yak at the genome-wide level, this study provided a theoretical basis for genetic improvement of Meiren yak and for the development of high-quality yak resources.

Deep Ancestral Introgressions between Ovine Species Shape Sheep Genomes via Argali-Mediated Gene Flow

Previous studies revealed extensive genetic introgression between Ovis species, which affects genetic adaptation and morphological traits. However, the exact evolutionary scenarios underlying the hybridization between sheep and allopatric wild relatives remain unknown. To address this problem, we here integrate the reference genomes of several ovine and caprine species: domestic sheep, argali, bighorn sheep, snow sheep, and domestic goats. Additionally, we use 856 whole genomes representing 169 domestic sheep populations and their six wild relatives: Asiatic mouflon, urial, argali, snow sheep, thinhorn sheep, and bighorn sheep. We implement a comprehensive set of analyses to test introgression among these species. We infer that the argali lineage originated ∼3.08 to 3.35 Mya and hybridized with the ancestor of Pachyceriforms (e.g. bighorn sheep and snow sheep) at ∼1.56 Mya. Previous studies showed apparent introgression from North American Pachyceriforms into the Bashibai sheep, a Chinese native sheep breed, despite of their wide geographic separation. We show here that, in fact, the apparent introgression from the Pachyceriforms into Bashibai can be explained by the old introgression from Pachyceriforms into argali and subsequent recent introgression from argali into Bashibai. Our results illustrate the challenges of estimating complex introgression histories and provide an example of how indirect and direct introgression can be distinguished.

Screening of functional genes for hypoxia adaptation in Tibetan pigs by combined genome resequencing and transcriptome analysis

The high-altitude, low-oxygen environment of the Qinghai-Tibet Plateau poses significant challenges for the introduction of superior livestock breeds. However, local plateau species have adapted to thrive and reproduce under these harsh conditions. Understanding the molecular mechanisms behind plateau animals' adaptation to low-oxygen environments is essential for breeding livestock suited to high-altitude regions. Tibetan pigs, which have undergone long-term natural selection and artificial breeding, have developed the ability to survive and reproduce in hypoxic environments. In this study, we conducted whole-genome resequencing of 30 Tibetan pigs from high-altitude regions and 30 Diannan small-ear pigs from low-altitude areas, to identify candidate genes that support Tibetan pigs' adaptation to hypoxic conditions through selection signal analysis. Additionally, we performed transcriptome sequencing on five tissues (heart, liver, spleen, lung, and bone marrow) from both Tibetan pigs and Diannan small-ear pigs to identify genes with significant differential expression between the two breeds. We then integrated the genomic and transcriptomic data by examining the expression of candidate genes identified in selection signal analysis across different tissues. The selection signal analysis identified 10 genes-HES4, ANGPT1, HIF3A, SPHK2, PCK2, RCN3, HIGD2A, DNM2, IRF9, and SRF-that were under positive selection in the Tibetan pig population and are associated with hypoxia adaptation. When combined with transcriptome data, we found that five of these genes-HIF3A, RCN3, HIGD2A, PCK2, and IRF9-exhibited differential expression. Through an integrated approach of selection signal and transcriptome analysis, we identified five key functional genes that contribute to the adaptation of Tibetan pigs to hypoxic environments. These findings offer new insights into the adaptability of plateau animals.

Physiological and Genetic Basis of High-Altitude Indigenous Animals' Adaptation to Hypoxic Environments

Adaptation is one of the fundamental characteristics of life activities; humans and animals inhabiting high altitudes are well adapted to hypobaric hypoxic environments, and studies on the mechanisms of this adaptation emerged a hundred years ago. Based on these studies, this paper reviews the adaptive changes in hypoxia-sensitive tissues and organs, as well as at the molecular genetic level, such as pulmonary, cardiovascular, O2-consuming tissues, and the hemoglobin and HIF pathway, that occur in animals in response to the challenge of hypobaric hypoxia. High-altitude hypoxia adaptation may be due to the coordinated action of genetic variants in multiple genes and, as a result, adaptive changes in multiple tissues and organs at the physiological and biochemical levels. Unraveling their mechanisms of action can provide a reference for the prevention and treatment of multiple diseases caused by chronic hypoxia.

Phylogenetic Relations and High-Altitude Adaptation in Wild Boar (Sus scrofa), Identified Using Genome-Wide Data

The Qinghai-Tibet Plateau (QTP) wild boar is an excellent model for investigating high-altitude adaptation. In this study, we analyzed genome-wide data from 93 wild boars compiled from various studies worldwide, including the QTP, southern and northern regions of China, Europe, Northeast Asia, and Southeast Asia, to explore their phylogenetic patterns and high-altitude adaptation based on genome-wide selection signal analysis and run of homozygosity (ROH) estimation. The findings demonstrate the alignment between the phylogenetic associations among wild boars and their geographical location. An ADMIXTURE analysis indicated a relatively close genetic relationship between QTP and southern Chinese wild boars. Analyses of the fixation index and cross-population extended haplotype homozygosity between populations revealed 295 candidate genes (CDGs) associated with high-altitude adaptation, such as TSC2, TELO2, SLC5A1, and SLC5A4. These CDGs were significantly overrepresented in pathways such as the mammalian target of rapamycin signaling and Fanconi anemia pathways. In addition, 39 ROH islands and numerous selective CDGs (e.g., SLC5A1, SLC5A4, and VCP), which are implicated in glucose metabolism and mitochondrial function, were discovered in QTP wild boars. This study not only assessed the phylogenetic history of QTP wild boars but also advanced our comprehension of the genetic mechanisms underlying the adaptation of wild boars to high altitudes.

Gelatinase MMP Expression Is Correlated with Muscle Fiber Growth in Maiwa Yak Gluteus Maximus

Yak (Bos grunniens) is the only large mammal species in the Qinghai-Tibet Plateau. The most of the studies in yak remain confined for the main contributor of meat, which requires a good understanding of muscle growth. Matrix metalloproteinases-2 (MMP-2) and MMP-9 are widely expressed in mammal tissues they mainly degrade collagen in the extracellular matrix for muscle development. However, the influence of MMPs on yak muscle remains unclear. Hence, we assessed the expression of MMP-2, MMP-9, and related factors with ages in Maiwa yak for study the correlation between MMPs expression and yak muscle growth. The mRNA expression of MMP-2, MMP-9, MMP-14, and collagen III increased with age, except collagen I by quantitative real-time PCR. Moreover, muscle fiber diameter increased with age, whereas the density decreased, which showed that fiber grew thicker with age using hematoxylin-eosin staining. Interestingly, MMP and collagen expression significantly decreased with age using western blotting. Pearson correlation method showed that both mRNA and protein expression of MMP-14 and collagen were strongly correlated with muscle fiber growth, but MMP-2 protein and MMP-9 mRNA expression were moderately correlated with muscle fiber growth. Overall, the expression of MMPs and collagen significantly changed with age, which means that MMPs and their function related genes could correlate with Maiwa yak muscle fiber growth.

Museum Genomics Reveals the Hybrid Origin of an Extinct Crater Lake Endemic

Crater lake fishes are common evolutionary model systems, with recent studies suggesting a key role for gene flow in promoting rapid adaptation and speciation. However, the study of these young lakes can be complicated by human-mediated extinctions. Museum genomics approaches integrating genetic data from recently extinct species are, therefore, critical to understanding the complex evolutionary histories of these fragile systems. Here, we examine the evolutionary history of an extinct Southern Hemisphere crater lake endemic, the rainbowfish Melanotaenia eachamensis. We undertook a comprehensive sampling of extant rainbowfish populations of the Atherton Tablelands of Australia alongside historical museum material to understand the evolutionary origins of the extinct crater lake population and the dynamics of gene flow across the ecoregion. The extinct crater lake species is genetically distinct from all other nearby populations due to historic introgression between 2 proximate riverine lineages, similar to other prominent crater lake speciation systems, but this historic gene flow has not been sufficient to induce a species flock. Our results suggest that museum genomics approaches can be successfully combined with extant sampling to unravel complex speciation dynamics involving recently extinct species.

Introgression drives adaptation to the plateau environment in a subterranean rodent

BACKGROUND

Introgression has repeatedly been shown to play an important role in the adaptation of species to extreme environments, yet how introgression enables rodents with specialized subterranean lifestyle to acclimatize to high altitudes is still unclear. Myospalacinae is a group of subterranean rodents, among which the high-altitude plateau zokors (Eospalax baileyi) and the low-altitude Gansu zokors (E. cansus) are sympatrically distributed in the grassland ecosystems of the Qinghai-Tibet Plateau (QTP). Together, they provide a model for the study of the role of introgression in the adaptation of low-altitude subterranean rodents to high altitudes.

RESULTS

Applying low-coverage whole-genome resequencing and population genetics analyses, we identified evidence of adaptive introgression from plateau zokors into Gansu zokors, which likely facilitated the adaptation of the latter to the high-altitude environment of the QTP. We identified positively selected genes with functions related to energy metabolism, cardiovascular system development, calcium ion transport, and response to hypoxia which likely made critical contributions to adaptation to the plateau environment in both plateau zokors and high-altitude populations of Gansu zokors.

CONCLUSIONS

Introgression of genes associated with hypoxia adaptation from plateau zokors may have played a role in the adaptation of Gansu zokors to the plateau environment. Our study provides new insights into the understanding of adaptive evolution of species on the QTP and the importance of introgression in the adaptation of species to high-altitude environments.

Complex patterns of gene flow and convergence in the evolutionary history of the spiral-horned antelopes (Tragelaphini)

The Tragelaphini, also known as spiral-horned antelope, is a phenotypically diverse mammalian tribe comprising a single genus, Tragelaphus. The evolutionary history of this tribe has attracted the attention of taxonomists and molecular geneticists for decades because its diversity is characterised by conflicts between morphological and molecular data as well as between mitochondrial, nuclear and chromosomal DNA. These inconsistencies point to a complex history of ecological diversification, coupled by either phenotypic convergence or introgression. Therefore, to unravel the phylogenetic relationships among spiral-horned antelopes, and to further investigate the role of divergence and gene flow in trait evolution, we sequenced genomes for all nine accepted species of the genus Tragelaphus, including a genome each for the highly divergent bushbuck lineages (T. s. scriptus and T. s. sylvaticus). We successfully reconstructed the Tragelaphus species tree, providing genome-level support for the early Pliocene divergence and monophyly of the nyala (T. angasii) and lesser kudu (T. imberbis), the monophyly of the two eland species (T. oryx and T. derbianus) and, importantly, the monophyly of kéwel (T. s. scriptus) and imbabala (T. s. sylvaticus) bushbuck. We found strong evidence for gene flow in at least four of eight nodes on the species tree. Among the six phenotypic traits assessed here, only habitat type mapped onto the species tree without homoplasy, showing that trait evolution was the result of complex patterns of divergence, introgression and convergent evolution.

Multi-omic Analyses Shed Light on The Genetic Control of High-altitude Adaptation in Sheep

Sheep were domesticated in the Fertile Crescent and then spread globally, where they have been encountering various environmental conditions. The Tibetan sheep has adapted to high altitudes on the Qinghai-Tibet Plateau over the past 3000 years. To explore genomic variants associated with high-altitude adaptation in Tibetan sheep, we analyzed Illumina short-reads of 994 whole genomes representing ∼ 60 sheep breeds/populations at varied altitudes, PacBio High fidelity (HiFi) reads of 13 breeds, and 96 transcriptomes from 12 sheep organs. Association testing between the inhabited altitudes and 34,298,967 variants was conducted to investigate the genetic architecture of altitude adaptation. Highly accurate HiFi reads were used to complement the current ovine reference assembly at the most significantly associated β-globin locus and to validate the presence of two haplotypes A and B among 13 sheep breeds. The haplotype A carried two homologous gene clusters: (1) HBE1, HBE2, HBB-like, and HBBC, and (2) HBE1-like, HBE2-like, HBB-like, and HBB; while the haplotype B lacked the first cluster. The high-altitude sheep showed highly frequent or nearly fixed haplotype A, while the low-altitude sheep dominated by haplotype B. We further demonstrated that sheep with haplotype A had an increased hemoglobin-O2 affinity compared with those carrying haplotype B. Another highly associated genomic region contained the EGLN1 gene which showed varied expression between high-altitude and low-altitude sheep. Our results provide evidence that the rapid adaptive evolution of advantageous alleles play an important role in facilitating the environmental adaptation of Tibetan sheep.

Genomic structural variation contributes to evolved changes in gene expression in high-altitude Tibetan sheep

Tibetan sheep were introduced to the Qinghai Tibet plateau roughly 3,000 B.P., making this species a good model for investigating genetic mechanisms of high-altitude adaptation over a relatively short timescale. Here, we characterize genomic structural variants (SVs) that distinguish Tibetan sheep from closely related, low-altitude Hu sheep, and we examine associated changes in tissue-specific gene expression. We document differentiation between the two sheep breeds in frequencies of SVs associated with genes involved in cardiac function and circulation. In Tibetan sheep, we identified high-frequency SVs in a total of 462 genes, including EPAS1, PAPSS2, and PTPRD. Single-cell RNA-Seq data and luciferase reporter assays revealed that the SVs had cis-acting effects on the expression levels of these three genes in specific tissues and cell types. In Tibetan sheep, we identified a high-frequency chromosomal inversion that exhibited modified chromatin architectures relative to the noninverted allele that predominates in Hu sheep. The inversion harbors several genes with altered expression patterns related to heart protection, brown adipocyte proliferation, angiogenesis, and DNA repair. These findings indicate that SVs represent an important source of genetic variation in gene expression and may have contributed to high-altitude adaptation in Tibetan sheep.

Structural variant landscapes reveal convergent signatures of evolution in sheep and goats

BACKGROUND

Sheep and goats have undergone domestication and improvement to produce similar phenotypes, which have been greatly impacted by structural variants (SVs). Here, we report a high-quality chromosome-level reference genome of Asiatic mouflon, and implement a comprehensive analysis of SVs in 897 genomes of worldwide wild and domestic populations of sheep and goats to reveal genetic signatures underlying convergent evolution.

RESULTS

We characterize the SV landscapes in terms of genetic diversity, chromosomal distribution and their links with genes, QTLs and transposable elements, and examine their impacts on regulatory elements. We identify several novel SVs and annotate corresponding genes (e.g., BMPR1B, BMPR2, RALYL, COL21A1, and LRP1B) associated with important production traits such as fertility, meat and milk production, and wool/hair fineness. We detect signatures of selection involving the parallel evolution of orthologous SV-associated genes during domestication, local environmental adaptation, and improvement. In particular, we find that fecundity traits experienced convergent selection targeting the gene BMPR1B, with the DEL00067921 deletion explaining ~10.4% of the phenotypic variation observed in goats.

CONCLUSIONS

Our results provide new insights into the convergent evolution of SVs and serve as a rich resource for the future improvement of sheep, goats, and related livestock.

Detection of Ghost Introgression Requires Exploiting Topological and Branch Length Information

In recent years, the study of hybridization and introgression has made significant progress, with ghost introgression-the transfer of genetic material from extinct or unsampled lineages to extant species-emerging as a key area for research. Accurately identifying ghost introgression, however, presents a challenge. To address this issue, we focused on simple cases involving 3 species with a known phylogenetic tree. Using mathematical analyses and simulations, we evaluated the performance of popular phylogenetic methods, including HyDe and PhyloNet/MPL, and the full-likelihood method, Bayesian Phylogenetics and Phylogeography (BPP), in detecting ghost introgression. Our findings suggest that heuristic approaches relying on site-pattern counts or gene-tree topologies struggle to differentiate ghost introgression from introgression between sampled non-sister species, frequently leading to incorrect identification of donor and recipient species. The full-likelihood method BPP uses multilocus sequence alignments directly-hence taking into account both gene-tree topologies and branch lengths, by contrast, is capable of detecting ghost introgression in phylogenomic datasets. We analyzed a real-world phylogenomic dataset of 14 species of Jaltomata (Solanaceae) to showcase the potential of full-likelihood methods for accurate inference of introgression.

Nuclear sequences of mitochondrial origin in domestic yak

Mitochondrial DNA sequences are frequently transferred into the nuclear genome, generating nuclear mitochondrial DNA sequences (NUMTs). Here, we analysed, for the first time, NUMTs in the domestic yak genome. We obtained 499 alignment matches covering 340.2 kbp of the yak nuclear genome. After a merging step, we identified 167 NUMT regions with a total length of ~ 503 kbp, representing 0.02% of the nuclear genome. We discovered copies of all mitochondrial regions and found that most NUMT regions are intergenic or intronic and mostly untranscribed. 98 different NUMT regions from domestic yak showed high homology with cow and/or wild yak genomes, suggesting selection or hybridization between domestic/wild yak and cow. To rule out the possibility that the identified NUMTs could be artifacts of the domestic yak genome assembly, we validated experimentally five NUMT regions by PCR amplification. As NUMT regions show high similarity to the mitochondrial genome can potentially pose a risk to domestic yak DNA mitochondrial studies, special care is therefore needed to select primers for PCR amplification of mitochondrial DNA sequences.

Genomic insights into the population history and adaptive traits of Latin American Criollo cattle

Criollo cattle, the descendants of animals brought by Iberian colonists to the Americas, have been the subject of natural and human-mediated selection in novel tropical agroecological zones for centuries. Consequently, these breeds have evolved distinct characteristics such as resistance to diseases and exceptional heat tolerance. In addition to European taurine (Bos taurus) ancestry, it has been proposed that gene flow from African taurine and Asian indicine (Bos indicus) cattle has shaped the ancestry of Criollo cattle. In this study, we analysed Criollo breeds from Colombia and Venezuela using whole-genome sequencing (WGS) and single-nucleotide polymorphism (SNP) array data to examine population structure and admixture at high resolution. Analysis of genetic structure and ancestry components provided evidence for African taurine and Asian indicine admixture in Criollo cattle. In addition, using WGS data, we detected selection signatures associated with a myriad of adaptive traits, revealing genes linked to thermotolerance, reproduction, fertility, immunity and distinct coat and skin coloration traits. This study underscores the remarkable adaptability of Criollo cattle and highlights the genetic richness and potential of these breeds in the face of climate change, habitat flux and disease challenges. Further research is warranted to leverage these findings for more effective and sustainable cattle breeding programmes.

Whole-genome resequencing reveals the uniqueness of Subei yak

Subei yak is an essential local yak in the Gansu Province, which genetic resource has recently been discovered. It is a meat-milk dual-purpose variety with high fecundity and relatively stable population genetic structure. However, its population genetic structure and genetic diversity are yet to be reported. Therefore, this study aimed to identify molecular markers of Subei yak genome by whole-genome resequencing, and to analyze the population structure and genetic diversity of Subei yak. This study screened 12,079,496 single nucleotide polymorphism (SNP) molecular markers in the 20 Subei yaks genome using whole-genome resequencing technology. Of these SNPs, 32.09% were located in the intronic region of the genome. Principal component analysis, phylogenetic analysis, and population structure analysis revealed that the Subei yak belonged to an independent group in the domestic yak population. A selective clearance analysis was carried out on Subei yak and other domestic yaks, and the genes under positive selection were annotated. The functional enrichment analysis showed that Subei yak possessed prominent selection characteristics in terms of external environment perception, hypoxia adaptation, and muscle development. Furthermore, Subei yak showed excellent muscle fat deposition and meat quality traits. Thus, this study will serve as a reference for discovering population structure, genetic evolution, and other unique traits of Subei yak and for expanding the genetic variation catalog of yaks.

Hypoxia Inducible Factor pathway proteins in high-altitude mammals

Humans and other mammals inhabit hypoxic high-altitude locales. In many of these species, genes under positive selection include ones in the Hypoxia Inducible Factor (HIF) pathway. One is PHD2 (EGLN1), which encodes for a key oxygen sensor. Another is HIF2A (EPAS1), which encodes for a PHD2-regulated transcription factor. Recent studies have provided insights into mechanisms for these high-altitude alleles. These studies have (i) shown that selection can occur on nonconserved, unstructured regions of proteins, (ii) revealed that high altitude-associated amino acid substitutions can have differential effects on protein-protein interactions, (iii) provided evidence for convergent evolution by different molecular mechanisms, and (iv) suggested that mutations in different genes can complement one another to produce a set of adaptive phenotypes.

Integration of ATAC-Seq and RNA-Seq Analysis to Identify Key Genes in the Longissimus Dorsi Muscle Development of the Tianzhu White Yak

During the postnatal stages, skeletal muscle development undergoes a series of meticulously regulated alterations in gene expression. However, limited studies have employed chromatin accessibility to unravel the underlying molecular mechanisms governing muscle development in yak species. Therefore, we conducted an analysis of both gene expression levels and chromatin accessibility to comprehensively characterize the dynamic genome-wide chromatin accessibility during muscle growth and development in the Tianzhu white yak, thereby elucidating the features of accessible chromatin regions throughout this process. Initially, we compared the differences in chromatin accessibility between two groups and observed that calves exhibited higher levels of chromatin accessibility compared to adult cattle, particularly within ±2 kb of the transcription start site (TSS). In order to investigate the correlation between alterations in chromatin accessible regions and variations in gene expression levels, we employed a combination of ATAC-seq and RNA-seq techniques, leading to the identification of 18 central transcriptional factors (TFs) and 110 key genes with significant effects. Through further analysis, we successfully identified several TFs, including Sp1, YY1, MyoG, MEF2A and MEF2C, as well as a number of candidate genes (ANKRD2, ANKRD1, BTG2 and LMOD3) which may be closely associated with muscle growth and development. Moreover, we constructed an interactive network program encompassing hub TFs and key genes related to muscle growth and development. This innovative approach provided valuable insights into the molecular mechanism underlying skeletal muscle development in the postnatal stages of Tianzhu white yaks while also establishing a solid theoretical foundation for future research on yak muscle development.

Evidence for early domestic yak, taurine cattle, and their hybrids on the Tibetan Plateau

Domestic yak, cattle, and their hybrids are fundamental to herder survival at high altitudes on the Tibetan Plateau. However, little is known about their history. Bos remains are uncommon in this region, and ancient domestic yak have not been securely identified. To identify Bos taxa and investigate their initial management, we conducted zooarchaeological analyses of 193 Bos specimens and sequenced five nuclear genomes from recently excavated assemblages at Bangga. Morphological data indicated that more cattle than yak were present. Ancient mitochondrial DNA and nuclear genome sequences identified taurine cattle and provided evidence for domestic yak and yak-cattle hybridization ~2500 years ago. Reliance on diverse Bos species and their hybrid has increased cattle adaptation and herder resilience to plateau conditions. Ancient cattle and yak at Bangga were closely related to contemporary livestock, indicating early herder legacies and the continuity of cattle and yak husbandry on the Tibetan Plateau.

Inference of Admixture Origins in Indigenous African Cattle

Present-day African cattle retain a unique genetic profile composed of a mixture of the Bos taurus and Bos indicus populations introduced into the continent at different time periods. However, details of the admixture history and the exact origins of the source populations remain obscure. Here, we infer the source of admixture in the earliest domestic cattle in Africa, African taurine. We detect a significant contribution (up to ∼20%) from a basal taurine lineage, which might represent the now-extinct African aurochs. In addition, we show that the indicine ancestry of African cattle, although most closely related to so-far sampled North Indian indicine breeds, has a small amount of additional genetic affinity to Southeast Asian indicine breeds. Our findings support the hypothesis of aurochs introgression into African taurine and generate a novel hypothesis that the origin of indicine ancestry in Africa might be different indicine populations than the ones found in North India today.

Global genetic diversity, introgression, and evolutionary adaptation of indicine cattle revealed by whole genome sequencing

Indicine cattle, also referred to as zebu (Bos taurus indicus), play a central role in pastoral communities across a wide range of agro-ecosystems, from extremely hot semiarid regions to hot humid tropical regions. However, their adaptive genetic changes following their dispersal into East Asia from the Indian subcontinent have remained poorly documented. Here, we characterize their global genetic diversity using high-quality whole-genome sequencing data from 354 indicine cattle of 57 breeds/populations, including major indicine phylogeographic groups worldwide. We reveal their probable migration into East Asia was along a coastal route rather than inland routes and we detected introgression from other bovine species. Genomic regions carrying morphology-, immune-, and heat-tolerance-related genes underwent divergent selection according to Asian agro-ecologies. We identify distinct sets of loci that contain promising candidate variants for adaptation to hot semi-arid and hot humid tropical ecosystems. Our results indicate that the rapid and successful adaptation of East Asian indicine cattle to hot humid environments was promoted by localized introgression from banteng and/or gaur. Our findings provide insights into the history and environmental adaptation of indicine cattle.

Evolutionary origin of genomic structural variations in domestic yaks

Yak has been subject to natural selection, human domestication and interspecific introgression during its evolution. However, genetic variants favored by each of these processes have not been distinguished previously. We constructed a graph-genome for 47 genomes of 7 cross-fertile bovine species. This allowed detection of 57,432 high-resolution structural variants (SVs) within and across the species, which were genotyped in 386 individuals. We distinguished the evolutionary origins of diverse SVs in domestic yaks by phylogenetic analyses. We further identified 334 genes overlapping with SVs in domestic yaks that bore potential signals of selection from wild yaks, plus an additional 686 genes introgressed from cattle. Nearly 90% of the domestic yaks were introgressed by cattle. Introgression of an SV spanning the KIT gene triggered the breeding of white domestic yaks. We validated a significant association of the selected stratified SVs with gene expression, which contributes to phenotypic variations. Our results highlight that SVs of different origins contribute to the phenotypic diversity of domestic yaks.

Structural variation and introgression from wild populations in East Asian cattle genomes confer adaptation to local environment

BACKGROUND

Structural variations (SVs) in individual genomes are major determinants of complex traits, including adaptability to environmental variables. The Mongolian and Hainan cattle breeds in East Asia are of taurine and indicine origins that have evolved to adapt to cold and hot environments, respectively. However, few studies have investigated SVs in East Asian cattle genomes and their roles in environmental adaptation, and little is known about adaptively introgressed SVs in East Asian cattle.

RESULTS

In this study, we examine the roles of SVs in the climate adaptation of these two cattle lineages by generating highly contiguous chromosome-scale genome assemblies. Comparison of the two assemblies along with 18 Mongolian and Hainan cattle genomes obtained by long-read sequencing data provides a catalog of 123,898 nonredundant SVs. Several SVs detected from long reads are in exons of genes associated with epidermal differentiation, skin barrier, and bovine tuberculosis resistance. Functional investigations show that a 108-bp exonic insertion in SPN may affect the uptake of Mycobacterium tuberculosis by macrophages, which might contribute to the low susceptibility of Hainan cattle to bovine tuberculosis. Genotyping of 373 whole genomes from 39 breeds identifies 2610 SVs that are differentiated along a "north-south" gradient in China and overlap with 862 related genes that are enriched in pathways related to environmental adaptation. We identify 1457 Chinese indicine-stratified SVs that possibly originate from banteng and are frequent in Chinese indicine cattle.

CONCLUSIONS

Our findings highlight the unique contribution of SVs in East Asian cattle to environmental adaptation and disease resistance.

Ancient Mongolian aurochs genomes reveal sustained introgression and management in East Asia

Societies in East Asia have utilized domesticated cattle for over 5000 years, but the genetic history of cattle in East Asia remains understudied. Genome-wide analyses of 23 ancient Mongolian cattle reveal that East Asian aurochs and ancient East Asian taurine cattle are closely related, but neither are closely related to any modern East Asian breeds. We observe binary variation in aurochs diet throughout the early Neolithic, and genomic evidence shows millennia of sustained male-dominated introgression. We identify a unique connection between ancient Mongolian aurochs and the European Hereford breed. These results point to the likelihood of human management of aurochs in Northeast Asia prior to and during the initial adoption of taurine cattle pastoralism.

Mid-Pleistocene Transitions Forced Himalayan ibex to Evolve Independently after Split into an Allopatric Refugium

Pleistocene glaciations had profound impact on the spatial distribution and genetic makeup of species in temperate ecosystems. While the glacial period trapped several species into glacial refugia and caused abrupt decline in large populations, the interglacial period facilitated population growth and range expansion leading to allopatric speciation. Here, we analyzed 40 genomes of four species of ibex and found that Himalayan ibex in the Pamir Mountains evolved independently after splitting from its main range about 0.1 mya following the Pleistocene species pump concept. Demographic trajectories showed Himalayan ibex experienced two historic bottlenecks, one each c. 0.8-0.5 mya and c. 50-30 kya, with an intermediate large population expansion c. 0.2-0.16 mya coinciding with Mid-Pleistocene Transitions. We substantiate with multi-dimensional evidence that Himalayan ibex is an evolutionary distinct phylogenetic species of Siberian ibex which need to be prioritized as Capra himalayensis for taxonomic revision and conservation planning at a regional and global scale.

A Chinese indicine pangenome reveals a wealth of novel structural variants introgressed from other Bos species

Chinese indicine cattle harbor a much higher genetic diversity compared with other domestic cattle, but their genome architecture remains uninvestigated. Using PacBio HiFi sequencing data from 10 Chinese indicine cattle across southern China, we assembled 20 high-quality partially phased genomes and integrated them into a multiassembly graph containing 148.5 Mb (5.6%) of novel sequence. We identified 156,009 high-confidence nonredundant structural variants (SVs) and 206 SV hotspots spanning ∼195 Mb of gene-rich sequence. We detected 34,249 archaic introgressed fragments in Chinese indicine cattle covering 1.93 Gb (73.3%) of the genome. We inferred an average of 3.8%, 3.2%, 1.4%, and 0.5% of introgressed sequence originating, respectively, from banteng-like, kouprey-like, gayal-like, and gaur-like Bos species, as well as 0.6% of unknown origin. Introgression from multiple donors might have contributed to the genetic diversity of Chinese indicine cattle. Altogether, this study highlights the contribution of interspecies introgression to the genomic architecture of an important livestock population and shows how exotic genomic elements can contribute to the genetic variation available for selection.

Global dispersal and adaptive evolution of domestic cattle: a genomic perspective

Domestic cattle have spread across the globe and inhabit variable and unpredictable environments. They have been exposed to a plethora of selective pressures and have adapted to a variety of local ecological and management conditions, including UV exposure, diseases, and stall-feeding systems. These selective pressures have resulted in unique and important phenotypic and genetic differences among modern cattle breeds/populations. Ongoing efforts to sequence the genomes of local and commercial cattle breeds/populations, along with the growing availability of ancient bovid DNA data, have significantly advanced our understanding of the genomic architecture, recent evolution of complex traits, common diseases, and local adaptation in cattle. Here, we review the origin and spread of domestic cattle and illustrate the environmental adaptations of local cattle breeds/populations.

Insight into the evolutionary and domesticated history of the most widely cultivated mushroom Agaricus bisporus via mitogenome sequences of 361 global strains

Agaricus bisporus is the most widely cultivated edible mushroom in the world with a only around three hundred years known history of cultivation. Therefore, it represents an ideal organism not only to investigate the natural evolutionary history but also the understanding on the evolution going back to the early era of domestication. In this study, we generated the mitochondrial genome sequences of 352 A. bisporus strains and 9 strains from 4 closely related species around the world. The population mitogenomic study revealed all A. bisporus strains can be divided into seven clades, and all domesticated cultivars present only in two of those clades. The molecular dating analysis showed this species origin in Europe on 4.6 Ma and we proposed the main dispersal routes. The detailed mitogenome structure studies showed that the insertion of the plasmid-derived dpo gene caused a long fragment (MIR) inversion, and the distributions of the fragments of dpo gene were strictly in correspondence with these seven clades. Our studies also showed A. bisporus population contains 30 intron distribution patterns (IDPs), while all cultivars contain only two IDPs, which clearly exhibit intron loss compared to the others. Either the loss occurred before or after domestication, that could suggest that the change facilitates their adaptation to the cultivated environment.

Analysis of genomic copy number variations through whole-genome scan in Chinese Qaidam cattle

Qaidam cattle (CDM) are indigenous breed inhabiting Northwest China. In the present study, we newly sequenced 20 Qaidam cattle to investigate the copy number variants (CNVs) based on the ARS-UMD1.2 reference genome. We generated the CNV region (CNVR) datasets to explore the genomic CNV diversity and population stratification. The other four cattle breeds (Xizang cattle, XZ; Kazakh cattle, HSK; Mongolian cattle, MG; and Yanbian cattle, YB) from the regions of North China embracing 43 genomic sequences were collected and are distinguished from each of the other diverse populations by deletions and duplications. We also observed that the number of duplications was significantly more than deletions in the genome, which may be less harmful to gene formation and function. At the same time, only 1.15% of CNVRs overlapped with the exon region. Population differential CNVRs and functional annotations between the Qaidam cattle population and other cattle breeds revealed the functional genes related to immunity (MUC6), growth (ADAMTSL3), and adaptability (EBF2). Our analysis has provided numerous genomic characteristics of some Chinese cattle breeds, which are valuable as customized biological molecular markers in cattle breeding and production.

Genome-wide analysis emancipates genomic diversity and signature of selection in Altay white-headed cattle of Xinjiang, China

Altay white-headed cattle have not received enough attention for several reasons. Due to irrational breeding and selection practices, the number of pure Altay white-headed cattle has decreased significantly and the breed is now on the eve of extinction. The genomic characterization will be a crucial step towards understanding the genetic basis of productivity and adaptability to survival under native Chinese agropastoral systems; nevertheless, no attempt has been made in Altay white-headed cattle. In the current study, we compared the genomes of 20 Altay white-headed cattle to the genomes of 144 individuals in representative breeds. Population genetic diversity revealed that the nucleotide diversity of Altay white-headed cattle was less than that of indicine breeds and comparable to that of Chinese taurus cattle. Using population structure analysis, we also found that Altay white-headed cattle carried the ancestry of the European and East Asian cattle lineage. In addition, we used three different methods (FST, θπ ratio and XP-EHH) to investigate the adaptability and white-headed phenotype of Altay white-headed cattle and compared it with Bohai black cattle. We found EPB41L5, SCG5 and KIT genes on the list of the top one percent genes, these genes might have an association with environmental adaptability and the white-headed phenotype for this breed. Our research reveals the distinctive genomic features of Altay white-headed cattle at the genome-wide level.

Genetic Structure Analysis of 155 Transboundary and Local Populations of Cattle (Bos taurus, Bos indicus and Bos grunniens) Based on STR Markers

Every week, 1-2 breeds of farm animals, including local cattle, disappear in the world. As the keepers of rare allelic variants, native breeds potentially expand the range of genetic solutions to possible problems of the future, which means that the study of the genetic structure of these breeds is an urgent task. Providing nomadic herders with valuable resources necessary for life, domestic yaks have also become an important object of study. In order to determine the population genetic characteristics, and clarify the phylogenetic relationships of modern representatives of 155 cattle populations from different regions of the world, we collected a large set of STR data (10,250 individuals), including unique native cattle, 12 yak populations from Russia, Mongolia and Kyrgyzstan, as well as zebu breeds. Estimation of main population genetic parameters, phylogenetic analysis, principal component analysis and Bayesian cluster analysis allowed us to refine genetic structure and provided insights in relationships of native populations, transboundary breeds and populations of domestic yak. Our results can find practical application in conservation programs of endangered breeds, as well as become the basis for future fundamental research.