Single nucleotide polymorphisms in Heat Shock Protein (HSP) 90AA1 gene and their association with heat tolerance traits in Sahiwal cows

Heat Shock Proteins (HSPs) are group of proteins which are synthesized during heat stress. HSP genes have been reported to be associated with heat tolerance and production performance in cattle. HSP90AA1 gene has been mapped on Bos taurus autosome 21 (BTA 21) and spans nearly 5368 bp comprising 11 exons out of which first exon does not translate. The present study was carried out in Sahiwal cows (n=100) with the objectives to identify SNPs in targeted regions (exon 3, 7, 8 & 11) of HSP90AA1 gene and to analyze their association with heat tolerance traits in Sahiwal cows. Respiration rate (RR) and rectal temperature (RT) was recorded once during probable extreme hours in winter, spring and summer season. Further, heat tolerance coefficient (HTC) also calculated to see the adaptability of the animals during the period of heat stress. On the basis of comparative sequence analysis, total five SNPs were revealed at position of A1209G; A3292C, T4935C, T5218C and A5224C in the targeted region of HSP90AA1 gene. Out of these, only two SNPs at A1209G and A3292C loci were found significantly associated with heat tolerance traits in Sahiwal cows. Whereas, THI has a highly significant associated with RR, RT and HTC in all the seasons. At A1209G locus in Sahiwal cows for traits RR, genotype AA (18.40 +/- 0.46(a)), AG (19.60 +/- 10.85(b)) and GG (21.18 +/- 0.64(ab)) and trait HTC AA (1.78 +/- 0.04(a)), AO (1.85 +/- 0.03(b)) and GG (1.91 +/- 0.02(c)) differ significantly (p<0.01) while trait RT, AG (38.32 +/- 0.10(b)) and GG (38.27 +/- 0.08(ab)) didn't differ significantly. For a locus A3292C for traits RR, genotype AA (21.55 +/- 1.01(a)), AC (19.66 +/- 1.59(b)) and CC (18.40 +/- 1.03(c)) differ significantly (p<0.05), while traits RT, genotype AA (38.41 +/- 0.12), AC (38.28 +/- 0.20) and CC (37.96 +/- 0.15) didn't differ significantly. For trait HTC, AA (1.93 +/- 0.04(a)), AC (1.85 +/- 0.06(b)) and CC (1.79 +/- 0.05(c)) found significantly (p<0.05) differ with each other. Our study indicated that Sahiwal cows of AA and AC genotype had better thereto-tolerance capacity, which had been useful for genetic improvement of Sahiwal cattle for heat tolerance traits.