Department of Animal Science, University of California, Davis, CA 95616, USA.
Feed the Future Innovation Lab for Genomics to Improve Poultry, University of California, Davis, CA 95616, USA.
Genes (Basel). 2020 Sep 11;11(9):1067. doi: 10.3390/genes11091067.
Heat stress results in reduced productivity, anorexia, and mortality in chickens. The objective of the study was to identify genes and signal pathways associated with heat stress and Newcastle disease virus (NDV) infection in the liver of chickens through RNA-seq analysis, using two highly inbred chicken lines (Leghorn and Fayoumi). All birds were held in the same environment until 14 days of age. On day 14, half the birds were exposed to 38 °C with 50% relative humidity for 4 h, then 35 °C until the end of the experiment. The remaining birds were kept at 25 °C throughout the experiment. The heat-treated birds were inoculated at 21 days of age with 10 EID (One EID unit is the amount of virus that will infect 50 percent of inoculated embryos) NDV La Sota strain to investigate the effects of both heat stress and NDV infection. Physiological parameters were recorded as blood phenotypes at three stages: acute heat (AH), chronic heat (CH1), and chronic heat combined with NDV infection (CH&NDV), at 4 h, 7 days, and 10 days post-initiation of heat treatment, respectively. Our previous work revealed that the heat-resilient Fayoumi line maintained a more stable acid-base balance in their blood compared to the Leghorn line. Liver samples were harvested on both AH and CH&NDV to characterize the transcriptome profiles of these two inbred lines. Both genetic lines and treatments had large impact on the liver transcriptome. Fayoumi birds had more differentially expressed genes (DEGs) than Leghorn birds for both treatments. Metabolic and immune-related genes were on the DEG list, with Fayoumi having more immune-related DEGs than Leghorns, which was confirmed by gene functional enrichment analysis. Weighted correlation network analysis (WGCNA) indicated that the driver genes such as Solute Carrier Family genes could be very important for stabilizing the acid-base balance in Fayoumi birds during heat stress. Therefore, candidate genes such solute carrier family genes could be potential genetic targets that are regulated by Fayoumis to maintain physical hemostasis under heat stress. Differential gene expression showed that Leghorns mainly performed metabolic regulation in response to heat stress and NDV infection, while Fayoumis regulated both immune and metabolic functions. This study provides novel insights and enhances our understandings of liver response to heat stress of heat resilient and susceptible inbred chicken lines.
热应激会导致鸡的生产力下降、食欲不振和死亡率增加。本研究的目的是通过 RNA-seq 分析，确定与热应激和新城疫病毒（NDV）感染相关的基因和信号通路，使用两个高度近交系鸡（来航鸡和法尤米鸡）。所有鸟类在相同的环境中饲养，直到 14 日龄。第 14 天，一半的鸡暴露在 38°C 下，相对湿度为 50%，持续 4 小时，然后在 35°C 下直到实验结束。其余的鸡在整个实验过程中保持在 25°C。在 21 日龄时，对热处理的鸡进行 10 EID（一个 EID 单位是感染 50%接种胚胎的病毒量）NDV La Sota 株的接种，以研究热应激和 NDV 感染的双重影响。生理参数在三个阶段记录为血液表型：急性热（AH）、慢性热（CH1）和慢性热加 NDV 感染（CH&NDV），分别在热处理开始后 4 小时、7 天和 10 天。我们之前的工作表明，耐热的法尤米鸡在血液中保持更稳定的酸碱平衡，而莱航鸡则不然。在 AH 和 CH&NDV 时分别采集肝脏样本，以描述这两个近交系的转录组图谱。遗传系和处理对肝脏转录组都有很大的影响。法尤米鸡的两种处理方法的差异表达基因（DEGs）都比莱航鸡多。代谢和免疫相关基因在 DEG 列表中，法尤米鸡的免疫相关 DEGs 比莱航鸡多，这通过基因功能富集分析得到了证实。加权相关网络分析（WGCNA）表明，溶质载体家族基因等驱动基因对于法尤米鸡在热应激过程中稳定酸碱平衡可能非常重要。因此，溶质载体家族等候选基因可能是法尤米鸡在热应激下维持生理止血的潜在遗传靶点。差异基因表达表明，莱航鸡主要通过代谢调节来应对热应激和 NDV 感染，而法尤米鸡则调节免疫和代谢功能。本研究为耐热和易感近交系鸡肝脏对热应激的反应提供了新的见解，并加深了我们对其的理解。
