Liver Transcriptome Responses to Heat Stress and Newcastle Disease Virus Infection in Genetically Distinct Chicken Inbred Lines.

Ying Wang,Rodrigo A Gallardo,Perot Saelao,Colin Kern,Terra Kelly,Jack M Dekkers,Sihua Jin,Huaijun Zhou,Susan J Lamont

doi:10.3390/genes11091067

Ying Wang, Rodrigo A Gallardo + Show 7 more

Open Access

https://doi.org/10.3390/genes11091067

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Abstract

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 107 EID50 (One EID50 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.

Highlights

All animals have a range of ambient temperatures that are appropriate to their physiological functions
As a part of the Feed the Future Innovation Lab Genomics to Improve Poultry (GIP) program, the presented study focuses on investigating the host response to the combination of heat stress and Newcastle disease virus (NDV) infection that are commonly experienced by backyard poultry flocks in African countries
Acute heat stress and chronic heat stress combined with NDV infection stimulated distinct physiological responses in the two highly inbred lines

Summary

Introduction

All animals have a range of ambient temperatures that are appropriate to their physiological functions. When the ambient temperature increases above the upper critical range, animals start to suffer heat stress [1]. Heat stress negatively impacts health and performance of poultry, from reduced growth and egg production to decreased meat and egg quality and safety [2,3], which results in significant economic loss for the US poultry industry and in developing countries such as those in Africa [4]. In response to heat stress, visible signs such as panting respiration, spreading wings, decreasing feed intake, drinking more, and shunting blood has been observed in chickens [2]. Decreased food intake is one way to lower production of metabolic heat and to cool body temperature via the gut and intestinal tract [6]. Blood shunting away from gut is another way to reduce production of metabolic heat and increase heat loss [7]. The increase in water intake increases urine excretion and results in the loss of electrolyte balance [8]

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