Genome-wide selection signatures address trait specific candidate genes in cattle indigenous to arid regions of India

Rethinking River Buffalo Domestication Through the Lens of Population Genetics Tools: Mehsana Buffalo Is a Unique Population

Riverine buffalo domestication likely occurred around 6300 years ago in Northwestern India. Murrah and Surti are important buffalo breeds that originated in this region and the gene flow from these buffaloes to Mehsana buffalo has long been proposed. However, the extent to which Murrah and Surti ancestry diffused across Mehsana has not been investigated thoroughly. Therefore, we investigated the global and local ancestry of Indian Mehsana buffalo using double digest restriction-site associated DNA sequencing data. Principal component analysis, global ancestry analysis, admixture dating, and three population tests revealed with statistical significance that Mehsana is a unique population. Hence, the hypothesis that Mehsana is a crossbreed between Murrah and Surti is not supported by these findings. However, we noticed that some individuals of Mehsana, 6 out 15, were admixed having 41% Murrah-specific ancestry and 11% Surti-specific ancestry. Local ancestry and post-admixture selection signatures (PASS) in admixed Mehsana individuals revealed PASS in the Mehsana genome, that is, on Bubalus bubalis autosomes (BBA), 1-23 linked from Surti and on BBA, 24 linked from Murrah. Interestingly, upon functional enrichment of these signatures, several adaptation-related genes and pathways were ascertained to Surti, while Murrah-derived regions featured genes involved in fatty acid synthesis (Acyl-CoA Synthetase Short-Chain Family Member 2 (ACSS2)) and milk production. Based on local ancestry analysis, we infer that the introgression of the Murrah genome into Mehsana happened in recent times and that of the Surti genome happened in ancient generations. The finding that Mehsana is an independent population highlights the importance of recognizing distinct genetic lineages in domesticated species. This has global implications for reevaluating the origins and uniqueness of other livestock breeds often assumed to be hybrids. Practically, these findings open up new avenues for selective breeding to preserve traits such as disease resistance, adaptability, and production efficiency. Further studies in larger samples are called for.

Potential Genetic Markers Associated with Environmental Adaptability in Herbivorous Livestock

Herbivorous livestock, such as cattle, sheep, goats, horses, and donkeys, play a crucial role in agricultural production and possess remarkable resilience to extreme environmental conditions, driven by complex genetic mechanisms. Recent advancements in high-throughput sequencing, genome assembly, and environmental data integration have enabled a deeper understanding of the genetic basis of their environmental adaptation. This review identifies key genes associated with high-altitude, heat, cold, and drought adaptation, providing insights into the molecular mechanisms underlying these traits. By elucidating these genetic adaptations, our study aims to support conservation efforts, inform selective breeding programs, and enhance agricultural productivity, ultimately contributing to sustainable livestock farming and economic benefits for farmers.

Runs of homozygosity assessment using reduced representation sequencing highlight the evidence of random mating in emu (Dromaius novaehollandiae)

The domestication of emu (Dromaius novaehollandiae) began in the 1970s, but their productive characteristics have not undergone significant genetic enhancement. This study investigated the inbreeding and genetic diversity of 50 emus from various farms in Japan using Double digest restriction-site associated DNA sequencing (ddRAD-seq) markers. Single nucleotide polymorphism (SNP) calling revealed 171 975 high-quality SNPs while runs of homozygosity (ROH) analysis identified 1843 homozygous segments, with an average of 36.86 ROH per individual and a mean genome length of 27 Mb under ROH. The majority (86%) of ROH were short (0.5-1 Mb), indicating ancient or remote inbreeding. The average genomic inbreeding coefficient (FROH) was 0.0228, suggesting nearly no inbreeding. Overlapping ROH regions were identified, with top consensus regions found on chromosomes 8 and Z. Seven candidate genes related to egg production, feather development, and energy metabolism were annotated in these regions. The findings highlight the prevalence of genetic diversity and low inbreeding levels in the studied emu population. This research highlights the potentiality of random mating in genetic management and conservation of emus. Further studies should focus on enhancing productive traits through selective breeding while preserving genetic diversity to ensure the sustainable growth of the emu farming.

Insights from homozygous signatures of cervus nippon revealed genetic architecture for components of fitness

This study investigates the genomic landscape of Sika deer populations, emphasizing the detection and characterization of runs of homozygosity (ROH) and their contribution towards components of fitness. Using 85,001 high-confidence SNPs, the investigation into ROH distribution unveiled nuanced patterns of autozygosity across individuals especially in 2 out of the 8 farms, exhibiting elevated ROH levels and mean genome coverage under ROH segments. The prevalence of shorter ROH segments (0.5-4 Mb) suggests historical relatedness and potential selective pressures within these populations. Intriguingly, despite observed variations in ROH profiles, the overall genomic inbreeding coefficient (FROH) remained relatively low across all farms, indicating a discernible degree of genetic exchange and effective mitigation of inbreeding within the studied Sika deer populations. Consensus ROH (cROH) were found to harbor genes for important functions viz., EGFLAM gene which is involved in the vision function of the eye, SKP2 gene which regulates cell cycle, CAPSL involved in adipogenesis, SPEF2 which is essential for sperm flagellar assembly, DCLK3 involved in the heat stress. This first ever study on ROH in Sika deer, to shed light on the adaptive role of genes in these homozygous regions. The insights garnered from this study have broader implications in the management of genetic diversity in this vulnerable species.

[Runs of Homozygosity Decipher Genetic Diversity in Cattle Breed Dwelling in the Colder Regions of the World]

BACKGROUND

Our study focuses on Yakutian cattle, a Siberian native breed, examining its inbreeding and diversity through genome-wide analysis of runs of homozygosity (ROHs). Yakutian cattle are adapted to Siberia's harsh sub-arctic conditions, enduring temperatures below -70°C. However, the population genetics studies on this breed are scanty, to document the genetic uniqueness in these cattle.

RESULTS

We analyzed 40 Yakutian cattle with strict quality control for ROH detection yielding 683 homozygous segments, averaging 17 per individual with an average length of 9 Mb. ROH regions were found to be involved in important pathways pertaining to cold adaptation. Autozygosity ranged from 1% to 12% of the genome, with a relatively low average inbreeding coefficient (FROH) of 0.057, as compared to other breeds. Also, the different diversity indicators, namely, principal component analysis, heterozygosity, and effective population size analysis, revealed the prevalence of genetic diversity within the breed.

CONCLUSION

Our findings on ROH are the first of its kind in Yakutian cattle that support their adaptability to colder environments, as evidenced by low inbreeding and high genetic diversity.

Puberty classifications in beef heifers are moderately to highly heritable and associated with candidate genes related to cyclicity and timing of puberty

Introduction: Pubertal attainment is critical to reproductive longevity in heifers. Previously, four heifer pubertal classifications were identified according to attainment of blood plasma progesterone concentrations > 1 ng/ml: 1) Early; 2) Typical; 3) Start-Stop; and 4) Non-Cycling. Early and Typical heifers initiated and maintained cyclicity, Start-Stop started and then stopped cyclicity and Non-Cycling never initiated cyclicity. Start-Stop heifers segregated into Start-Stop-Discontinuous (SSD) or Start-Stop-Start (SSS), with SSD having similar phenotypes to Non-Cycling and SSS to Typical heifers. We hypothesized that these pubertal classifications are heritable, and loci associated with pubertal classifications could be identified by genome wide association studies (GWAS). Methods: Heifers (n = 532; 2017 - 2022) genotyped on the Illumina Bovine SNP50 v2 or GGP Bovine 100K SNP panels were used for variant component estimation and GWAS. Heritability was estimated using a univariate Bayesian animal model. Results: When considering pubertal classifications: Early, Typical, SSS, SSD, and Non-Cycling, pubertal class was moderately heritable (0.38 ± 0.08). However, when heifers who initiated and maintained cyclicity were compared to those that did not cycle (Early+Typical vs. SSD+Non-Cycling) heritability was greater (0.59 ± 0.19). A GWAS did not identify single nucleotide polymorphisms (SNPs) significantly associated with pubertal classifications, indicating puberty is a polygenic trait. A candidate gene approach was used, which fitted SNPs within or nearby a set of 71 candidate genes previously associated with puberty, PCOS, cyclicity, regulation of hormone secretion, signal transduction, and methylation. Eight genes/regions were associated with pubertal classifications, and twenty-two genes/regions were associated with whether puberty was attained during the trial. Additionally, whole genome sequencing (WGS) data on 33 heifers were aligned to the reference genome (ARS-UCD1.2) to identify variants in FSHR, a gene critical to pubertal attainment. Fisher's exact test determined if FSHR SNPs segregated by pubertal classification. Two FSHR SNPs that were not on the bovine SNP panel were selected for additional genotyping and analysis, and one was associated with pubertal classifications and whether they cycled during the trial. Discussion: In summary, these pubertal classifications are moderately to highly heritable and polygenic. Consequently, genomic tools to inform selection/management of replacement heifers would be useful if informed by SNPs associated with cyclicity and early pubertal attainment.

Phenotypic and genetic characterization of unexplored, potential cattle population of Madhya Pradesh

Bawri or Garri, a non-descript cattle population managed under an extensive system in Madhya Pradesh state of India, was identified and characterized both genetically and phenotypically to check whether or not it can be recognised as a breed. The cattle have white and gray colour and are medium sized with 122.5 ± 7.5 cm and 109.45 ± 0.39 cm height at withers in male and female, respectively. Double-digest restriction site associated DNA (ddRAD) sequencing was employed to identify ascertainment bias free SNPs representing the entire genome cost effectively; resulting in calling 1,156,650 high quality SNPs. Observed homozygosity was 0.76, indicating Bawri as a quite unique population. However, the inbreeding coefficient was 0.025, indicating lack of selection. SNPs found here can be used in GWAS and genetic evaluation programs. Considering the uniqueness of Bawri cattle, it can be registered as a breed for its better genetic management.