Identification of target genes and pathways related to heat tolerance in Chinese Holstein cows

Heat stress has detrimental effects on the production and reproduction of dairy cows. The present work reveals the role of differentially expressed (DE) miRNAs on the heat stress tolerance of bovine blood using RNA sequencing. Twelve dairy cows were divided into heat-resistant and heat-stressed groups according to rectal temperature and reduction of milk yield. Using the ACGT101-miR program, 1262 known miRNAs and 719 novel miRNAs were identified. Of the 719 novel miRNAs, 144 significantly DE miRNAs (67 up-regulated and 77 down regulated) (P < 0.05) were screened between heat-resistant and heat-stressed cows using edgeR software. Eleven high DE miRNAs (bta-miR-455-3p, bta-miR-455-5p, mmu-mir-6240, bta-miR-106b, bta-miR-11,971, bta-miR29a, bta-miR-142-5p, bta-miR-15b, bta-miR-342, bta-miR-32, and bta-miR-6524) were verified by qRT-PCR, an outcome which was consistent with the sequencing results. The target genes related to heat tolerance of the heat shock protein (HSP) family, malonyl CoA-acyl carrier protein transacylase (MACT), and prolactin receptor (PRLR), were predicted using the TargetScan and miRanda software. Furthermore, KEGG analyses with the R package OmicStudio and on the basis of DE miRNAs revealed an enriched MAPK signaling pathway, endocytosis, Th17 cell differentiation, cellular senescence, peroxisome, and Fc gamma R-mediated phagocytosis. These findings could help in screening for heat tolerance genes for improved dairy cow heat tolerance.