Genome-wide association studies for heat stress response in Bos taurus × Bos indicus crossbred cattle

摘要

Heat stress is an important issue in the global dairyindustry. In tropical areas, an alternative to overcomeheat stress is the use of crossbred animals or syntheticbreeds, such as the Girolando. In this study, we performeda genome-wide association study (GWAS) andpost-GWAS analyses for heat stress in an experimentalGir × Holstein F_2 population. Rectal temperature(RT) was measured in heat-stressed F_2 animals, andthe variation between 2 consecutive RT measurements(ΔRT) was used as the dependent variable. IlluminaBovineSNP50v1 BeadChip (Illumina Inc., San Diego,CA) and single-SNP approach were used for GWAS.Post-GWAS analyses were performed by gene ontologyterms enrichment and gene-transcription factor (TF)networks, generated from enriched TF. The breed originof marker alleles in the F_2 population was assignedusing the breed of origin of alleles (BOA) approach.Heritability and repeatability estimates (± standarderror) for ΔRT were 0.13 ± 0.08 and 0.29 ± 0.06,respectively. Association analysis revealed 6 SNP significantlyassociated with ΔRT. Genes involved withbiological processes in response to heat stress effects(LIF, OSM, TXNRD2, and DGCR8) were identified asputative candidate genes. After performing the BOAapproach, the 10% of F_2 animals with the lowest breedingvalues for ΔRT were classified as low-ΔRT, and the10% with the highest breeding values for ΔRT wereclassified as high-ΔRT. On average, 49.4% of low-ΔRTanimals had 2 alleles from the Holstein breed (HH),and 39% had both alleles from the Gir breed (GG). Inhigh-ΔRT animals, the average proportion of animalsfor HH and GG were 1.4 and 50.2%, respectively. Thisstudy allowed the identification of candidate genes forΔRT in Gir × Holstein crossbred animals. Accordingto the BOA approach, Holstein breed alleles could beassociated with better response to heat stress effects,which could be explained by the fact that Holstein animalsare more affected by heat stress than Gir animalsand thus require a genetic architecture to defend thebody from the deleterious effects of heat stress. Futurestudies can provide further knowledge to uncover thegenetic architecture underlying heat stress in crossbredcattle.