BACKGROUND Heat stress adversely affects pig growth and reproduction performance by reducing feed intake, weight gain, farrowing rate, and litter size. Heat tolerance is an important characteristic in pigs, allowing them to mitigate the negative effects of heat stress on their physiological activities. Yet, genetic variation and signaling pathways associated with the biological processes of heat-tolerant pigs are currently not fully understood. This study examined differentially expressed genes and constructed gene co-expression networks on mRNAs of pigs under different heat-stress conditions using whole transcriptomic RNA-seq analyses. Semen parameters, including total sperm number per ejaculate, motility, normal morphology rate, droplets, and rejected ejaculate rate, were measured weekly on 12 boars for two time periods: thermoneutral (January to May), and heat stress (July to October). Boars were classified into heat-tolerant (n = 6) and heat-susceptible (n = 6) groups based on the variation of their ejaculate parameters across the two periods. RNA was isolated from the blood samples collected from the thermoneutral and heat stress periods for gene expression analysis. RESULTS Under heat stress, a total of 66 differentially expressed genes (25 down-regulated, 41 up-regulated) were identified in heat-tolerant pigs compared to themselves during the thermoneutral period. A total of 1041 differentially expressed genes (282 down-regulated, 759 up-regulated) were identified in the comparison between heat-tolerant pigs and heat-susceptible pigs under heat stress. Weighted gene co-expression network analysis detected 4 and 7 modules with genes highly associated (r > 0.50, p < 0.05) with semen quality parameters in heat-tolerant and heat-susceptible pigs under the effects of heat stress, respectively. CONCLUSION This study utilized the sensitivity of semen to heat stress to discriminate the heat-tolerance ability of pigs. The gene expression profiles under the thermoneutral and heat stress conditions were documented in heat-tolerant and heat-susceptible boars. Findings contribute to the understanding of genes and biological mechanisms related to heat stress response in pigs and provide potential biomarkers for future investigations on the reproductive performance of pigs.

中文翻译：

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转录组分析鉴定了猪耐热性的基因和共表达网络。


背景技术热应激通过降低采食量、体重增加、产仔率和产仔数对猪的生长和繁殖性能产生不利影响。耐热性是猪的一个重要特征，使它们能够减轻热应激对其生理活动的负面影响。然而，与耐热猪的生物过程相关的遗传变异和信号通路目前尚未完全了解。本研究利用全转录组 RNA-seq 分析检查了不同热应激条件下猪 mRNA 的差异表达基因并构建了基因共表达网络。每周对 12 头公猪进行两个时间段的精液参数测量，包括每次射精的精子总数、活力、正常形态率、液滴和拒绝射精率：热中性（1 月至 5 月）和热应激（7 月至 10 月）。根据两个时期的射精参数变化，将公猪分为耐热组 (n = 6) 和耐热组 (n = 6)。从热中性和热应激时期收集的血液样本中分离出 RNA，用于基因表达分析。结果 在热应激下，与热中性时期的耐热猪相比，共鉴定出 66 个差异表达基因（25 个下调，41 个上调）。通过热应激下耐热猪和热敏感猪的比较，共鉴定出1041个差异表达基因（282个下调，759个上调）。加权基因共表达网络分析检测到 4 和 7 个模块与基因高度相关（r > 0.50，p < 0。05）分别在热应激影响下耐热猪和热敏感猪的精液质量参数。结论本研究利用精液对热应激的敏感性来判别猪的耐热能力。在耐热和热敏感公猪中记录了热中性和热应激条件下的基因表达谱。研究结果有助于了解与猪热应激反应相关的基因和生物机制，并为未来猪繁殖性能的研究提供潜在的生物标志物。