Broilers are more vulnerable to high temperatures than mammals due to the feather cover, lack of sweat glands, fast growth and intensive breeding in commercial systems. Thermal stresses affect the function of various organs and change the expression profiles of hundreds of genes in the different tissues of broilers. Thermal manipulation (TM) during embryogenesis can increase heat tolerance in growing broilers. Small heat shock proteins (SHSPs) are a group of HSPs which participate in many cellular functions like response to different stressors. However, their role in the thermotolerance has not been fully elucidated. Ninety fertilized eggs were randomly divided into three groups (30 eggs/group; 10 eggs/replicate). Normal control (NC) eggs were incubated at 37.5 °C throughout the incubation period whereas heat stress (HS) and cold stress (CS) groups were kept at 41 °C and 33 °C from 15 to 17th day of incubation for 3 h each day, respectively. On day 20, samples from the cerebrums were harvested for histopathology and mRNA expression analyses of HSPB1, HSPB5, HSPB8, and HSPB9. There were no significant differences in survivability, defected embryos, hatchability, and body weight among treatments. TM had no major deleterious effects on the cerebral tissue except for mild degeneration in the HS group. HSPB1, HSPB5, HSPB8, and HSPB9 were expressed in the presence and absence of TM. All SHSP genes tested were downregulated in response to TM except for HSPB9 which was upregulated in the HS group. The highest change in gene expression due to TM observed for HSPB1. This study presents a broader understanding of mechanisms underlying response to TM in broilers. The results suggest that HSPB1, HSPB5, HSPB8, and HSPB9 are involved in thermotolerance in broilers and SHSPs could be involved in the gene expression profiling of TM. It may propose the use of nutritional supplements in the poultry industry to modulate SHSPs.

中文翻译：

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小热休克蛋白在肉鸡胚脑中的差异表达 胚胎热操作的影响

由于羽毛覆盖、缺乏汗腺、快速生长和商业系统中的密集繁殖，肉鸡比哺乳动物更容易受到高温的影响。热应激影响各种器官的功能并改变肉鸡不同组织中数百个基因的表达谱。胚胎发生过程中的热操作 (TM) 可以提高生长肉鸡的耐热性。小热休克蛋白 (SHSP) 是一组 HSP，它们参与许多细胞功能，如对不同压力源的反应。然而，它们在耐热性中的作用尚未完全阐明。将 90 个受精卵随机分为三组（30 个卵/组；10 个卵/重复）。正常对照 (NC) 鸡蛋在 37 岁时孵化。整个潜伏期为 5°C，而热应激 (HS) 和冷应激 (CS) 组分别在 41°C 和 33°C 下从孵化的第 15 天至第 17 天每天保持 3 小时。在第 20 天，从大脑中采集样本用于 HSPB1、HSPB5、HSPB8 和 HSPB9 的组织病理学和 mRNA 表达分析。不同处理间在存活率、缺陷胚胎、孵化率和体重方面没有显着差异。除了 HS 组轻度变性外，TM 对脑组织没有重大的有害影响。HSPB1、HSPB5、HSPB8 和 HSPB9 在存在和不存在 TM 的情况下表达。除了 HSPB9 在 HS 组中上调外，所有测试的 SHSP 基因都响应 TM 下调。对于 HSPB1 观察到的由 TM 引起的基因表达的最高变化。本研究提供了对肉鸡 TM 反应机制的更广泛理解。结果表明 HSPB1、HSPB5、HSPB8 和 HSPB9 与肉鸡的耐热性有关，而 SHSP 可能参与 TM 的基因表达谱分析。它可能会建议在家禽业中使用营养补充剂来调节 SHSP。