Genome-wide DNA methylation profiles regulate distinct heat stress response in zebu (Bos indicus) and crossbred (Bos indicus × Bos taurus) cattle

Epigenetic variations result from long-term adaptation to environmental factors. The Bos indicus (zebu) adapted to tropical conditions, whereas Bos taurus adapted to temperate conditions; hence native zebu cattle and its crossbred (B indicus × B taurus) show differences in responses to heat stress. The present study evaluated genome-wide DNA methylation profiles of these two breeds of cattle that may explain distinct heat stress responses. Physiological responses to heat stress and estimated values of Iberia heat tolerance coefficient and Benezra's coefficient of adaptability revealed better relative thermotolerance of Hariana compared to the Vrindavani cattle. Genome-wide DNA methylation patterns were different for Hariana and Vrindavani cattle. The comparison between breeds indicated the presence of 4599 significant differentially methylated CpGs with 756 hypermethylated and 3845 hypomethylated in Hariana compared to the Vrindavani cattle. Further, we found 79 genes that showed both differential methylation and differential expression that are involved in cellular stress response functions. Differential methylations in the microRNA coding sequences also revealed their functions in heat stress responses. Taken together, epigenetic differences represent the potential regulation of long-term adaptation of Hariana (B indicus) cattle to the tropical environment and relative thermotolerance.