| Summary: | 碩士 === 國立中興大學 === 動物科學系所 === 107 === Acute heat stress leads to higher mortality, lower production performance and great economical loss in poultry production. To deal with the problem, we need to realize the bio-molecular mechanism for heat stress response. The hypothalamus is a critical center of body temperature regulation which is responsible for maintaining the homeostasis of body temperature. Heat stress may change gene expression by histone post-translational modifications (HPTMs) that play a role in transcriptional regulation and epigenetics. This study analyzed the differentially expressed proteins (DEPs) and HPTMs in the hypothalamus of layer-type L2 strain Taiwan country chickens (TCCs) after acute heat stress. A total of 192 30-wk-old L2 strain TCCs were subjected to acute heat stress at 38°C for 4 hours. Five control roosters were maintained at 25°C. The heat-stressed roosters were divided into a resistant group and a susceptible group according to body temperature change before and during heat stress. Roosters died during heat stress were defined as dead group. Hypothalamus of five roosters in each group were used for proteomic analysis by isobaric tags for relative and absolute quantitation (iTRAQ) and histone modification analysis by label-free quantification. Histones were extracted by sulfuric acid, derivatized with propionic anhydride and then analyzed by liquid chromatography coupled with tandem mass spectrometry. The results showed that there were 125 DEPs (fold change ≥ 1.3 or ≤ 0.76) in iTRAQ analysis and 33 HPTMs were identified. Gene ontology analysis showed that the DEPs were mainly related to cellular component organization, cellular metabolic process and cell adhesion. Functional pathway analysis showed that the DEGs were mainly involved in pyruvate metabolism, extra cellular matrix-receptor interaction, focal adhesion. Compared to susceptible and dead groups, the DEPs of resistant group are associated with intermediate filament (GFAP, VIM, NEFM, KRT7 and MBP), energy metabolism (LDHA and LDHD), cellular community (COLA3, COLA6 and ZYX), ion homeostasis (ATP1A2, ATP1B1 and ATP1B3) and the degradation of damaged proteins (UBQLN1, UBFD1, HECW2 and DNAJC5). The level of total HPTMs was not significantly different among treatments. Four active histone marks (H3.3K23ac, H3K23ac, H3.3K79me and H2AK5ac) and two repressive marks (H3K9me2 and H3K9me3) among the quantifiable HPTMs were observed. In conclusion, the chickens with better capacity of thermotolerance may respond to acute heat stress by changing the protein expressions associated with maintenance of cell structure and function, energy metabolism, and stress response in the hypothalamus to cope with the adversity. The contribution of HPTMs and their correlation with protein expressions remain unclear and requires further exploration.
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