Integrating miRNA and mRNA expression profiles in plasma of laying hens associated with heat stress.

High temperature is one of the most common environmental stressors plaguing animal husbandry worldwide. Little is known about the regulatory roles of miRNAs in response to heat stress in laying hens. To systematically identify heat stress-responsive miRNAs and their targets in laying hens, the differential expression of miRNAs and mRNAs was compared under heat stress and normal temperature. We identified 16 miRNAs and 502 genes that were significantly changed in heat-stressed laying hens. By comparing the differentially expressed genes (DEGs) and the putative targets of the altered miRNAs based on bioinformatics prediction, 82 coordinated genes were identified. Gene ontology classification analyses of the 82 putative target genes showed that the biological category 'cellular response to stress' was prominently annotated. Notably, the response-related gene autophagy-related protein 9A was most likely controlled by the upregulated miRNAs gga-miR-92-5p, gga-miR-1618-5p, gga-miR-1737, and gga-miR-6557 in response to heat stress. Analysis of DEGs also revealed an increase in lipid metabolism in heat-stressed laying hens. Some of these genes were negatively correlated with the altered miRNAs, suggesting that they are potential targets of the miRNAs. Taken together, our results advance our understanding of the regulatory mechanism of heat-stress-induced injury in laying hens, specifically with regard to miRNAs.