Transcriptomic Analysis Provides Novel Insights into Heat Stress Responses in Sheep

Periodic heat waves-induced neuronal etiology in the elderly is mediated by gut-liver-brain axis: a transcriptome profiling approach

Heat stress exposure in intermittent heat waves and subsequent exposure during war theaters pose a clinical challenge that can lead to multi-organ dysfunction and long-term complications in the elderly. Using an aged mouse model and high-throughput sequencing, this study investigated the molecular dynamics of the liver-brain connection during heat stress exposure. Distinctive gene expression patterns induced by periodic heat stress emerged in both brain and liver tissues. An altered transcriptome profile showed heat stress-induced altered acute phase response pathways, causing neural, hepatic, and systemic inflammation and impaired synaptic plasticity. Results also demonstrated that proinflammatory molecules such as S100B, IL-17, IL-33, and neurological disease signaling pathways were upregulated, while protective pathways like aryl hydrocarbon receptor signaling were downregulated. In parallel, Rantes, IRF7, NOD1/2, TREM1, and hepatic injury signaling pathways were upregulated. Furthermore, current research identified Orosomucoid 2 (ORM2) in the liver as one of the mediators of the liver-brain axis due to heat exposure. In conclusion, the transcriptome profiling in elderly heat-stressed mice revealed a coordinated network of liver-brain axis pathways with increased hepatic ORM2 secretion, possibly due to gut inflammation and dysbiosis. The above secretion of ORM2 may impact the brain through a leaky blood-brain barrier, thus emphasizing intricate multi-organ crosstalk.

Exploring candidate genes for heat tolerance in ovine through liver gene expression

Thermotolerance has become an essential factor in the prevention of the adverse effects of heat stress, but it varies among animals. Identifying genes related to heat adaptability traits is important for improving thermotolerance and for selecting more productive animals in hot environments. The primary objective of this research was to find candidate genes in the liver that play a crucial role in the heat stress response of Santa Ines sheep, which exhibit varying levels of heat tolerance. To achieve this goal, 80 sheep were selected based on their thermotolerance and placed in a climate chamber for 10 days, during which the average temperature was maintained at 36 °C from 10 a.m. to 4 p.m. and 28 °C from 4 p.m. to 10 a.m. A subset of 14 extreme animals, with seven thermotolerant and seven non-thermotolerant animals based on heat loss (rectal temperature), were selected for liver sampling. RNA sequencing and differential gene expression analysis were performed. Thermotolerant sheep showed higher expression of genes GPx3, RGS6, GPAT3, VLDLR, LOC101108817, and EVC. These genes were mainly related to the Hedgehog signaling pathway, glutathione metabolism, glycerolipid metabolism, and thyroid hormone synthesis. These enhanced pathways in thermotolerant animals could potentially mitigate the negative effects of heat stress, conferring greater heat resistance.

Impact of carob (Ceratonia siliqua L.) pulp inclusion and warm season on gastrointestinal morphological parameters, immune-redox defences and coccidiosis in concentrate-fed light lambs

This study aimed to evaluate the effects of dietary carob (Ceratonia siliqua L.) pulp and warm season on gastrointestinal morphological parameters, immune-redox defences and coccidiosis in concentrate-fed light lambs. Weaned lambs were assigned to one of three concentrate-based diets: C0 (without carob pulp), C15 (150 g/kg of carob pulp) and C30 (300 g/kg of carob pulp) from 40 to 80 days of age in two consecutive cold and warm batches. Blood samples were collected at Day 80 to determine the metabolic status. Rectal faeces were sampled at Days 50, 65 and 80 to determine consistency and oocyst count per gram. Inclusion of carob pulp in lamb diets did not affect lamb growth but reduced coccidia oocyst excretion, improved faecal consistency and gastrointestinal morphological parameters, enhancing the ruminal thickness of the papilla living strata and reducing the darkness of the epithelium colour. Moreover, carob condensed tannins in the lambs' diet enhanced the expression of antioxidant SOD2 in rumen, while down-regulated NRF2, SOD1, CAT and PPARG in ileum. There was no interaction between the treatments and season in the evaluated variables. Lambs from the warm season exhibited reduced growth performance, altered ruminal epithelium, lower circulating iron levels, increased protein concentrations and higher coccidiosis susceptibility. In addition, regulatory immune and antioxidant mechanisms to counterbalance reactive oxygen species production in gastrointestinal tissues were evident. Dietary inclusion of carob pulp (150 and 300 g/kg) in lamb diets improved gastrointestinal health and homeostasis but did not ameliorate the deleterious effects of warm season.

Blood Transcriptomic Analyses Reveal Functional Pathways Associated with Thermotolerance in Pregnant Ewes Exposed to Environmental Heat Stress

Environmental heat stress triggers a series of compensatory mechanisms in sheep that are dependent on their genetic regulation of thermotolerance. Our objective was to identify genes and regulatory pathways associated with thermotolerance in ewes exposed to heat stress. We performed next-generation RNA sequencing on blood collected from 16 pregnant ewes, which were grouped as tolerant and non-tolerant to heat stress according to a physiological indicator. Additional samples were collected to measure complete blood count. A total of 358 differentially expressed genes were identified after applying selection criteria. Gene expression analysis detected 46 GO terms and 52 KEGG functional pathways. The top-three signaling pathways were p53, RIG-I-like receptor and FoxO, which suggested gene participation in biological processes such as apoptosis, cell signaling and immune response to external stressors. Network analysis revealed ATM, ISG15, IRF7, MDM4, DHX58 and TGFβR1 as over-expressed genes with high regulatory potential. A co-expression network involving the immune-related genes ISG15, IRF7 and DXH58 was detected in lymphocytes and monocytes, which was consistent with hematological findings. In conclusion, transcriptomic analysis revealed a non-viral immune mechanism involving apoptosis, which is induced by external stressors and appears to play an important role in the molecular regulation of heat stress tolerance in ewes.

Association between Polymorphism in the Janus Kinase 2 (JAK2) Gene and Selected Performance Traits in Cattle and Sheep

The Janus Kinase 2 (JAK2) tyrosine kinase is an essential component of signal transduction of the class II cytokine receptors, including the growth hormone receptor. Therefore, it may play a crucial role in the signaling pathway of the somatotropic axis, which influences growth, development, and reproductive traits in ruminants. For this purpose, for three breeds of cattle (Hereford, Angus, and Limousin; a total of 781 individuals), two polymorphic sites located in exon 16 (rs210148032; p.Ile704Val, within pseudokinase (JH2)) and exon 23 (silent mutation rs211067160, within JH1 kinase domain) were analyzed. For two breeds of sheep (Pomeranian and Suffolk; 333 individuals in total), two polymorphic sites in exon 6 (rs160146162 and rs160146160; encoding the FERM domain) and one polymorphic site in exon 24 of the JAK2 gene (rs160146116; JH1 kinase domain) were genotyped. In our study, the associations examined for cattle were inconclusive. However, Hereford and Limousin cattle with genotypes AA (e16/RsaI) and AA (e23/HaeIII) tended to have the highest body weight and better daily gains (p ≤ 0.05). No clear tendency was observed in the selected reproductive traits. In the case of sheep, regardless of breed, individuals with the AA (e6/EarI), GG (e6/seq), and AA (e24/Hpy188III) genotypes had the highest body weights and daily gains in the study periods (p ≤ 0.01). The same individuals in the Pomeranian breed also had better fertility and lamb survival (p ≤ 0.01). To the best of our knowledge, these are the first association studies for all these polymorphic sites. Single-nucleotide polymorphisms in the JAK2 gene can serve as genetic markers for growth and selected reproductive traits in ruminants given that they are further investigated in subsequent populations and analyzed using haplotype and/or combined genotype systems.

Molecular Mechanism of m6A Methylation Modification Genes METTL3 and FTO in Regulating Heat Stress in Sheep

Heat stress is an important environmental factor affecting livestock production worldwide. Primary hepatocytes and preadipocytes derived from Hu sheep were used to establish a heat stress model. Quantitative reverse transcriptase-PCR (qRT-PCR) analysis showed that heat induction significantly increased the expression levels of heat stress protein (HSP) genes and the N6-methyladenosine (m6A) methylation modification genes: methyltransferase-like protein 3 (METTL3), methyltransferase-like protein 14 (METTL14), and fat mass and obesity associated protein (FTO). Heat stress simultaneously promoted cell apoptosis. Transcriptome sequencing identified 3980 upregulated genes and 2420 downregulated genes related to heat stress. A pathway enrichment analysis of these genes revealed significant enrichment in fatty acid biosynthesis, degradation, and the PI3K-Akt and peroxisome proliferator-activated receptor (PPAR) signaling pathways. Overexpression of METTL3 in primary hepatocytes led to significant downregulation of HSP60, HSP70, and HSP110, and significantly increased mRNA m6A methylation; FTO interference generated the opposite results. Primary adipocytes showed similar results. Transcriptome analysis of cells under METTL3 (or FTO) inference and overexpression revealed differentially expressed genes enriched in the mitogen-activated protein kinase (MAPK) signaling pathways, as well as the PI3K-Akt and Ras signaling pathways. We speculate that METTL3 may increase the level of m6A methylation to inhibit fat deposition and/or inhibit the expression of HSP genes to enhance the body's resistance to heat stress, while the FTO gene generated the opposite molecular mechanism. This study provides a scientific basis and theoretical support for sheep feeding and management practices during heat stress.

Differential gene expression analysis using RNA-seq in the blood of goats exposed to transportation stress

Transportation stress causes significant changes in physiological responses in goats; however, studies exploring the transcriptome of stress are very limited. The objective of this study was to determine the differential gene expressions and related pathways in the blood samples using RNA-seq procedure in Spanish goats subjected to different durations of transportation stress. Fifty-four male Spanish goats (8-mo old; BW = 29.7 ± 2.03 kg) were randomly subjected to one of three treatments (TRT; n = 18 goats/treatment): (1) transported for 180 min, (2) transported for 30 min, or (3) held in pens (control). Blood samples were collected before and after treatment for stress hormone, metabolite, and transcriptomic analysis. RNA-seq technology was used to obtain the transcriptome profiles of blood. Analysis of physiological data using SAS showed that plasma cortisol concentrations were higher (P < 0.01) in 180 min and 30 min groups compared to the control group. Enrichment analysis of DEGs related to transportation stress through Gene Ontology and KEGG databases revealed that the differentially expressed genes related to inflammatory pathways, caspases, and apoptosis such as IL1R2, CASP14, CD14, TLR4, and MAPK14 were highly enriched in the transported group of goats compared to non-transported goats. Stress in goats leads to a sequence of events at cellular and molecular levels that causes inflammation and apoptosis.

Molecular markers for thermo-tolerance are associated with reproductive and physiological traits in Pelibuey ewes raised in a semiarid environment

Pelibuey sheep exhibit reproductive activity through the year, but warm weather lowers their fertility and demonstrates physiological limitations of environmental heat stress. Single nucleotide polymorphisms (SNPs) associated with heat stress tolerance in sheep have been reported previously. The objective was to validate the association of seven thermo-tolerance SNP markers with reproductive and physiological traits in Pelibuey ewes raised in a semiarid region. Pelibuey ewes were assigned to a cool (January 1st^.- March 31st^.; n = 101) or warm (April 1st^.- August 31st^.; n = 104) experimental group. All ewes were exposed to fertile rams and assessed for pregnancy diagnosis 90 days later; lambing day was reported at birth. These data served to calculate the reproductive traits of services per conception, prolificacy, days to estrus, days to conception, conception rate and lambing rate. Rectal temperature, rump/leg skin temperature and respiratory rate were measured and reported as physiological traits. Blood samples were collected and processed to extract DNA, which was genotyped using the TaqMan allelic discrimination method and qPCR. A mixed effects statistical model was used to validate associations between SNP genotypes and phenotypic traits. The SNPs rs421873172, rs417581105 and rs407804467 were confirmed as markers associated with reproductive and physiological traits (P < 0.05), and these SNPs were in the genes PAM, STAT1 and FBXO11, respectively. Interestingly, these SNP markers resulted as predictors for the evaluated traits but only in ewes from the warm group, which indicated their association with heat-stress tolerance. An additive SNP effect was confirmed with the highest contribution (P < 0.01) of the SNP rs417581105 for the evaluated traits. Reproductive performance improved (P < 0.05) and physiological parameters decreased in ewes carrying favorable SNP genotypes. In conclusion, three thermo-tolerance SNP markers were associated with improved reproductive and physiological traits in a prospective population of heat-stressed ewes raised in a semiarid environment.

Molecular regulation, breed differences and genes involved in stress control in farm animals

Stress is a state of disturbed homeostasis evoking a multiplicity of somatic and mental adaptive reactions resulting from any of the 5 freedoms of animals being violated. Many environmental forces disrupt homeostasis in farm animals, such as extreme temperatures, poor nutrition, noise, hunger, and thirst. During stressful situations, neuronal circuits in the limbic system and prefrontal cortex are activated, which lead to the release of adrenalin and noradrenalin. The hormones released during stress are needed for adaptation to acute stress and are regulated by many genes. This review examined molecular regulation, breed differences, and genes involved in stress control in farm animals. Major molecular regulation of stress, such as oxidative, cytosolic heat shock, unfolded protein, and hypoxic responses, were discussed. The responses of various poultry, ruminant, and pig breeds to different stress types were also discussed. Gene expressions and polymorphisms in the neuroendocrine and neurotransmitter pathways were also elucidated. The information obtained from this review will help farmers mitigate stress in farm animals through appropriate breed and gene-assisted selection. Also, information obtained from this review will add to the field of stress genetics since stress is a serious welfare issue in farm animals.

Transcriptomic Analysis of the Porcine Gut in Response to Heat Stress and Dietary Soluble Fiber from Beet Pulp

This study aimed to investigate the impact of heat stress (HS) and the effects of dietary soluble fiber from beet pulp (BP) on gene expression (differentially expressed genes, DEGs) of the porcine jejunum. Out of the 82 DEGs, 47 genes were up-regulated, and 35 genes were downregulated between treatments. The gene ontology (GO) enrichment analysis showed that the DEGs were related mainly to the actin cytoskeleton organization and muscle structure development in biological processes, cytoplasm, stress fibers, Z disc, cytoskeleton, and the extracellular regions in cellular composition, and actin binding, calcium ion binding, actin filament binding, and pyridoxal phosphate binding in the molecular function. The KEGG pathway analysis showed that the DEGs were involved in hypertrophic cardiomyopathy, dilated cardiomyopathy, vascular smooth muscle contraction, regulation of actin cytoskeleton, mucin type O-glycan biosynthesis, and African trypanosomiasis. Several of the genes (HSPB6, HSP70, TPM1, TAGLN, CCL4) in the HS group were involved in cellular oxidative stress, immune responses, and cellular differentiation. In contrast, the DEGs in the dietary BP group were related to intestinal epithelium integrity and immune response to pathogens, including S100A2, GCNT3, LYZ, SCGB1A1, SAA3, and ST3GAL1. These findings might help understand the HS response and the effect of dietary fiber (DF) regarding HS and be a valuable reference for future studies.

Genome-wide association study of a thermo-tolerance indicator in pregnant ewes exposed to an artificial heat-stressed environment

Environmental heat stress negatively influences sheep production in warm semi-arid regions. An animal's ability to tolerate warm weather is difficult to measure naturally due to environmental variability and genetic variation between animals. In this study we developed a thermo-tolerance indicator (TTI) to define heat stress tolerance in pregnant sheep in a controlled environment. Next, we performed a genome-wide association study (GWAS) to identify genomic regions and target genes associated with thermo-tolerance in sheep. Pregnant Columbia-Rambouillet crossbred ewes (n = 127) were heat-stressed inside a climate-controlled chamber for 57 days by increasing the temperature-humidity index to ≥30. Rectal temperature (RT) and feed intake (FI) data were collected daily and used for the predictive TTI analysis. After the tenth day of heat stress, the regression analyses revealed that FI was stable; however, when the ewe's RT exceeded 39.8 °C their FI was less than thermo-tolerant ewes. This average predicted temperature was used to classify each ewe as heat stress tolerant (≤39.8 °C) and non-heat stress tolerant (>39.8 °C). A GWAS analysis was performed and genomic regions were compared between heat stress tolerant and non-tolerant ewes. The single-marker genomic analysis detected 16 single nucleotide polymorphisms (SNP) associated with heat stress tolerance (P < 0.0001), whereas the multi-marker Bayesian analysis identified 8 overlapped 1-Mb chromosomal regions accounting for 11.39% of the genetic variation associated with tolerance to heat stress. Four intragenic SNP showed a remarkable contribution to thermo-tolerance, and these markers were within the genes FBXO11 (rs407804467), PHC3 (rs414179061), TSHR (rs418575898) and STAT1 (rs417581105). In conclusion, genomic regions harboring four intragenic SNP were associated with heat stress tolerance, and these candidate genes are proposed to influence heat tolerance in pregnant ewes subjected to an artificially induced warm climate. Moreover, these genetic markers could be suitable for use in further genetic selection programs in sheep managed in semi-arid regions.

Identifying the heat resistant genes by multi-tissue transcriptome sequencing analysis in Turpan Black sheep

Heat stress not only affects the physical condition but also affects reproductive performance in sheep. A thorough understanding of the molecular and physiological mechanisms underlying heat stress would certainly improve livestock productivity and provide genetic evaluation ways for heat resistant breeds selection. In this study, 85 Turpan Black sheep, a breed exhibited excellent heat resistance from long-term artificial selection, and 85 heat sensitive Kazakh sheep in Turpan basin were tested for physiological and reproductive performance from July to August in summer. The results showed that the estrus rate was significantly higher in Turpan Black sheep (P < 0.05), while the heart rate and respiratory rate of Turpan Black sheep are significantly lower than that of Kazakh sheep (P < 0.05). Furthermore, to clarify genes participated in heat stress response, the pituitary, ovarian and hepatic tissues from three Turpan Black sheep and three Kazakh sheep were subjected to RNA-seq. The results indicated that 32, 49 and 69 genes were up-regulated, and 39, 60 and 145 genes were down-regulated in pituitary, ovarian and hepatic tissues in Turpan Black sheep compared with that of the Kazakh sheep, respectively. KEGG and gene set enrichment analysis showed that the differentially expressed genes were mainly involved in signal transduction pathways. In particular, the differentially expressed genes in hepar were enriched in the energy metabolism pathway, while the differentially expressed genes in ovarian tissue were enriched in the ovarium steroidogenesis pathway. In conclusion, our results implied that the pituitary-ovary axis might include hepar as downstream targeted organism in heat resistant regulation. Under heat stress, the signals released from pituitary would impact steroidogenesis in ovary, and further alter energy metabolism in hepar. As we know, this is the first comparative study to investigate the gene expression in multi-tissue in sheep under heat stress.

Impacts of heat stress on immune responses and oxidative stress in farm animals and nutritional strategies for amelioration

Heat stress is one of the greatest challenges for the global livestock industries as increased environmental temperature and humidity compromises animal production during summer leading to devastating economic consequences. Over the last 30 years, significant developments have been achieved in cooling and provision of shade and shelter to mitigate heat stress reducing some of the losses associated with heat stress in farm animals. However, the recent increase in the incidence of heat waves which are also becoming more severe and lasting longer, due to climate change, further accentuates the problem of heat stress. Economic losses associated with heat stress are both direct due to loss in production and animal life, and indirect due to poorer quality products as a result of poor animal health and welfare. Animal health is affected due to impaired immune responses and increased reactive oxygen species production and/or deficiency of antioxidants during heat stress leading to an imbalance between oxidant and antioxidants and resultant oxidative stress. Research over the last 20 years has achieved partial success in understanding the intricacies of heat stress impacts on oxidative stress and immune responses and developing interventions to ameliorate impacts of heat stress, improving immune responses and farm animal health. This paper reviews the body of knowledge on heat stress impacts on immune response in farm animals. The impacts of heat stress on both cell-mediated and humoral immune responses have been discussed identifying the shift in immune response from cell-mediated towards humoral response, thereby weakening the immune status of the animal. Both species and breed differences have been identified as influencing how heat stress impacts the immune status of farm animals. In addition, crosstalk signaling between the immune system and oxidative stress has been considered and the role of antioxidants as potential nutritional strategies to mitigate heat stress has been discussed.

m6A mRNA methylation analysis provides novel insights into heat stress responses in the liver tissue of sheep

N⁶-methyladenosine (m⁶A) mRNA methylation varies in response to stress. However, no map of m⁶A mRNA methylation has been obtained for sheep, nor is it known what effect this has on regulating heat stress in sheep. Here, we obtained m⁶A methylation maps of sheep liver tissues with and without heat stress by MeRIP-seq. In total, 8306 m⁶A peaks associated with 2697 genes were detected in the heat stress group, and 12,958 m⁶A peaks associated with 5494 genes were detected in the control group. Peaks were mainly enriched in coding regions and near stop codons with classical RRACH motifs. Methylation levels of heat stress and control sheep were higher near stop codons, although methylation was significantly lower in heat stress sheep. GO and KEGG revealed that differential m⁶A-containing genes were significantly enriched in the stress response and fat metabolism. Our results showed that m⁶A mRNA methylation modifications regulate heat stress in sheep.

Heat stress effects on sheep: Are hair sheep more heat resistant?

Climatic variables can trigger physiological, biochemical, haematological and hormonal alterations that influence the maintenance of homeothermy and can affect production and productivity in sheep. Different mechanisms are responsible for tolerance to heat stress (HS) including coat and skin colour, body size, fat distribution, physiological reactions and not just coat type (hair/wool). This review looks at physical, physiological, molecular and genetic aspects of heat tolerance in sheep and how they affect hair and wool sheep. We propose that it is the adaptation to hot environments and not the type of coat (wool/hair) itself that determines the capacity of the resistance of the animal to HS, due to modifications in essential pathways such as energy metabolism, physiological responses and body size. When studied in similar environments, commercial wool breeds tend to show higher heat stress, but hair breeds tend not to differ from wool breeds that are adapted to hot environments.

Resilience of Small Ruminants to Climate Change and Increased Environmental Temperature: A Review

Simple Summary

Small ruminants are critical for food security and livelihood, especially under extreme stressful and diverse climatic environments. Generally, sheep and goats are farmed on grazing land in relatively large groups relying on low inputs in terms of feed, water and labor, and possess high thermotolerance compared to large ruminants such as cattle. Climate change has been recognized as a harmful factor influencing sheep and goat production. Small ruminants are vulnerable to direct and indirect effects of climate change, including heat stress, limited and low-quality pasture availability and emerging infectious diseases. In this context, selection of animals for thermotolerance is one viable strategy that exploits natural variation within and between breeds for desirable traits. The various biological markers used to improve thermotolerance in small ruminants include behavioral (feed intake, water intake), physiological (respiration rate, rectal temperature, sweating rate), hormonal (T3, T4 and growth hormone) responses and the response of molecular regulators.

Abstract

Climate change is a major global threat to the sustainability of livestock systems. Climatic factors such as ambient temperature, relative humidity, direct and indirect solar radiation and wind speed influence feed and water availability, fodder quality and disease occurrence, with production being most efficient in optimal environmental conditions. Among these climatic variables, ambient temperature fluctuations have the most impact on livestock production and animal welfare. Continuous exposure of the animals to heat stress compromises growth, milk and meat production and reproduction. The capacity of an animal to mitigate effects of increased environmental temperature, without progressing into stress response, differs within and between species. Comparatively, small ruminants are better adapted to hot environments than large ruminants and have better ability to survive, produce and reproduce in harsh climatic regions. Nevertheless, the physiological and behavioral changes in response to hot environments affect small ruminant production. It has been found that tropical breeds are more adaptive to hot climates than high-producing temperate breeds. The growing body of knowledge on the negative impact of heat stress on small ruminant production and welfare will assist in the development of suitable strategies to mitigate heat stress. Selection of thermotolerant breeds, through identification of genetic traits for adaption to extreme environmental conditions (high temperature, feed scarcity, water scarcity), is a viable strategy to combat climate change and minimize the impact on small ruminant production and welfare. This review highlights such adaption within and among different breeds of small ruminants challenged by heat stress.

Floods, Hurricanes, and Other Catastrophes: A Challenge for the Immune System of Livestock and Other Animals

Climate change involves different dramatic phenomena including desertification and wildfires, severe storms such as hurricanes and blizzards, increased sea levels resulting in flooding coastal cities and rise of atmospheric CO₂ concentration. The alteration of the climate in a specific region affects the life of indigenous animals and humans. The climate changes influence living beings both directly and indirectly. The immune system of animals dramatically suffers the climate instability, making animals more susceptible to infectious and not infectious diseases. Different species of livestock animals respond with similar mechanisms to global warming, but some of them are more susceptible depending on their age, metabolism, and genetic conditions. The selection and study of autochthonous species and breeds, more easily adapted to specific environmental conditions could be an interesting strategy to face livestock rearing in the future.

Genome-Wide Association Study of Body Weight Traits in Chinese Fine-Wool Sheep

Body weight is an important economic trait for sheep and it is vital for their successful production and breeding. Therefore, identifying the genomic regions and biological pathways that contribute to understanding variability in body weight traits is significant for selection purposes. In this study, the genome-wide associations of birth, weaning, yearling, and adult weights of 460 fine-wool sheep were determined using resequencing technology. The results showed that 113 single nucleotide polymorphisms (SNPs) reached the genome-wide significance levels for the four body weight traits and 30 genes were annotated effectively, including AADACL3, VGF, NPC1, and SERPINA12. The genes annotated by these SNPs significantly enriched 78 gene ontology terms and 25 signaling pathways, and were found to mainly participate in skeletal muscle development and lipid metabolism. These genes can be used as candidate genes for body weight in sheep, and provide useful information for the production and genomic selection of Chinese fine-wool sheep.

Liver Transcriptome Changes of Hyla Rabbit in Response to Chronic Heat Stress

Simple Summary

It has been widely acknowledged in farm animals that environmental heat stress would have comprehensive influences on many kinds of physiological aspects, including the metabolic characteristics, production performances, welfare concerns, etc. The rabbit is a small herbivore and needs to regulate the body temperature in a fine mechanism. Little is known, however, about the genes and pathways that are involved in the regulatory responses under chronic heat stress conditions. In the present study, we investigated the liver transcriptome changes in response to chronic heat stress for Hyla rabbit, that is a commercial meat breed recently introduced into China. We successfully revealed the differentially expressed genes that were significantly enriched in heat stress related biological processes. The results would help us for better understanding the molecular mechanisms underlying physiological responses against heat stress in rabbits.

Abstract

Rabbit is an economically important farm animal in China and also is a widely used animal model in biological researches. Rabbits are very sensitive to the environmental conditions, therefore we investigated the liver transcriptome changes in response to chronic heat stress in the present study. Six Hyla rabbits were randomly divided into two groups: chronic heat stress (HS) and controls without heat stress (CN). Six RNA-Seq libraries totally yielded 380 million clean reads after the quality filtering. Approximately 85.07% of reads were mapped to the reference genome. After assembling transcripts and quantifying gene expression levels, we detected 51 differentially expressed genes (DEGs) between HS and CN groups with thresholds of the adjusted p-value < 0.05 and |log2(FoldChange)| > 1. Among them, 33 and 18 genes were upregulated and downregulated, respectively. Gene ontology analyses further revealed that these DEGs were mainly associated with metabolism of lipids, thyroid hormone metabolic process, and cellular modified amino acid catabolic process. The upregulated ACACB, ACLY, LSS, and CYP7A1 genes were found to be inter-related through biological processes of thioester biosynthetic process, acyl-CoA biosynthetic process, acetyl-CoA metabolic process, and others. Six DEGs were further validated by quantitative real-time PCR analysis. The results revealed the candidate genes and biological processes that will potentially be considered as important regulatory factors involved in the heat stress response in rabbits.