Departamento de Ciencias Agronómicas y Veterinarias, Instituto Tecnológico de Sonora, Ciudad Obregón, Sonora, 85000, México.
School of Animal and Comparative Biomedical Sciences, The University of Arizona, Tucson, Arizona, 85721, USA.
J Therm Biol. 2021 Oct;101:103095. doi: 10.1016/j.jtherbio.2021.103095. Epub 2021 Sep 16.
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.
环境热应激会对温暖半干旱地区的绵羊生产产生负面影响。由于环境变异性和动物之间的遗传变异，动物对温暖天气的耐受能力很难自然测量。在这项研究中，我们开发了一种耐热性指标 (TTI)，以在受控环境中定义怀孕绵羊的耐热性。接下来，我们进行了全基因组关联研究 (GWAS)，以鉴定与绵羊耐热性相关的基因组区域和靶基因。127 只怀孕的哥伦比亚-兰布赖特杂交母羊在气候控制室内受到 57 天的热应激，通过将温度-湿度指数提高到≥30 来实现。每天收集直肠温度 (RT) 和采食量 (FI) 数据，并用于预测 TTI 分析。在热应激的第十天，回归分析表明 FI 稳定；然而，当母羊的 RT 超过 39.8°C 时，它们的 FI 就会低于耐热性母羊。这个平均预测温度用于将每只母羊分类为耐热 (≤39.8°C) 和不耐热 (>39.8°C)。进行了全基因组关联分析，并比较了耐热和不耐热母羊之间的基因组区域。单标记基因组分析检测到 16 个与耐热性相关的单核苷酸多态性 (SNP) (P<0.0001)，而多标记贝叶斯分析鉴定出 8 个重叠的 1-Mb 染色体区域，占与耐热性相关的遗传变异的 11.39%。4 个内含子 SNP 对耐热性有显著贡献，这些标记位于 FBXO11(rs407804467)、PHC3(rs414179061)、TSHR(rs418575898) 和 STAT1(rs417581105) 基因内。总之，含有四个内含子 SNP 的基因组区域与耐热性相关，这些候选基因被提议影响人工诱导温暖气候下怀孕母羊的耐热性。此外，这些遗传标记可用于在半干旱地区管理的绵羊进一步的遗传选择计划中。
