Transcriptome profiling analysis of heat-adapted and heat-sensitive breeder hen jejunal mucosal tissues in response to acute heat stress

<title>Abstract</title> Background Heat stress impairs intestinal integrity in poultry, compromising nutrient digestion and absorption. Nevertheless, the individual variation in heat tolerance suggests distinct molecular responses that are still not well understood. Materials and methods This study investigated the molecular basis of differential heat tolerance by comparing jejunal transcriptomes in heat-adapted ( <bold>HA</bold> ) and heat-sensitive ( <bold>HS</bold> ) breeder hens under acute heat stress (36°C for a 6-h). Fifty 28-week-old hens were randomly allocated to the HA and HS groups (25 hens each). After exposure to acute heat stress for 6 hours, the respiratory rate and cloacal temperature were measured, and jejunal mucosal samples were collected for RNA sequencing ( <bold>RNA-seq</bold> ). Results The results indicated that, under acute heat stress, the respiratory rates and cloacal temperatures of HS hens were significantly higher than those of HA hens ( <italic>P</italic> = 0.002). RNA-seq analysis identified 284 differentially expressed genes ( <bold>DEGs</bold> ), with 155 genes upregulated and 129 downregulated in the HS group compared to the HA group. Gene Ontology analysis revealed significant enrichment in 555 GO terms. Kyoto Encyclopedia of Genes and Genomes pathway analysis identified five pathways that were enriched in upregulated DEGs (VEGF signaling pathway, MAPK signaling pathway, steroid biosynthesis, neuroactive ligand-receptor interaction, and cell cycle) and one pathway enriched in downregulated DEGs (cell adhesion molecules). Protein-protein interaction network identified key genes ( <italic>PLK1</italic> , <italic>CDC7</italic> , <italic>CDC20</italic> , <italic>HSPA2</italic> , <italic>IL6</italic> , <italic>SLC22A19A</italic> , <italic>LBFABP</italic> , <italic>SLC6A19</italic> , and <italic>SLC2A2</italic> ), involved in cell division, immune function, energy and lipid metabolism, as well as organic acid, glucose, and amino acids transport. Conclusions These findings suggest that acute heat stress differentially affects intestinal function in HA and HS hens, potentially through alterations in cell division, immune function, energy and lipid metabolism, and organic acid and glucose transport mechanisms. The identified DEGs and pathways offer valuable insight into the molecular basis of heat stress susceptibility and may inform nutritional or management strategies to enhance poultry resilience.