Novel SNPs in HSPB8 gene and their association with heat tolerance traits in Sahiwal indigenous cattle.

Heat shock proteins (HSPs) are expressed in response to heat stress, and the polymorphism in HSP genes at single-nucleotide level has been reported to be associated with heat tolerance and production performance traits in cattle. HSPB8 gene has been mapped on Bos taurus autosome 17 (BTA-17) spanning nearly 13,252 bp and comprising three exons and two introns. The present study was conducted in Sahiwal cows (n = 108) reared in subtropical climate with the objectives to identify SNPs in all three exons and part of intron 1 of HSPB8 gene and to analyze their association with heat tolerance traits in Sahiwal cows. Respiration rate (RR) and rectal temperature (RT) were recorded once during probable extreme hours in different seasons or Temperature-Humidity Index (THI), i.e., winter, spring, and summer. Heat tolerance coefficient (HTC) was also calculated to check the adaptability of the animals during the period of heat stress. The comparative sequence analysis revealed a total two single-nucleotide polymorphisms (SNPs), i.e., g.507G>A in exon 1 and g.881T>C in intron 1 of HSPB8 gene. Out of these two identified SNPs, only one SNP, i.e., g.507G>A, was found to be significantly associated with heat tolerance indicator traits (RR, RT, and HTC) in Sahiwal cows. The perusal of results across different seasons showed the significant (P < 0.01) difference in RR, RT, and HTC between winter, spring, and summer seasons. RR, RT, and HTC were found to be significantly lower (P < 0.01) in GA as compared to GG genotype of g.507G>A SNP of HSPB8 gene. However, in case of another SNP, i.e., g.881T>C, located on intron 1, the RR, RT, and HTC were having non-significant association with the different genotypes, i.e., TT and TC. These findings may partly suggest that GA genotype of SNP g.507G>A of HSPB8 gene has a probable role in heat tolerance in Sahiwal cattle and can therefore be utilized as a marker in propagation of thermo-tolerance cattle in hot tropical and subtropical climate. Nevertheless, the involvement of other regulatory mechanisms cannot be overruled.

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