Investigating genetic variability in Hsp70 gene-5'-fragment and its association with thermotolerance in Murrah buffalo (Bubalus bubalis) under sub-tropical climate of India.

Abstract

The present study was undertaken to investigate genetic variability in a fragment comprising 5'UTR along with partial coding sequence of Hsp70 gene and its association with thermotolerance traits in Murrah buffalo at ICAR-Research Complex for Eastern Region, Patna (India). The allelic variants were identified from genomic DNA samples using SSCP technique. The PCR products were sequenced and analyzed. Data on different thermotolerance traits recorded in three seasons were analyzed by least squares ANOVA taking the SSCP genotypes as fixed effect. Two allelic variants (A and B), each of 503-bp in size, were documented with frequency of 0.59 and 0.41, respectively, and three genotypes (AA, AB and BB) with corresponding frequency of 0.30, 0.58 and 0.12. The allelic variants were due to single nucleotide substitution at 55th base position leading to a change of threonine (A) to methionine (B) in amino acid sequence. Both the allelic variants had 99.8% similarity in nucleotide sequence. In phylogenetic tree, allele A was in a cluster while allele B and Gangatiri cattle sequence formed a different cluster. The SSCP genotypes had significant effect on different thermotolerance traits in summer with thermo-humidity index of ≥ 84. Buffaloes with AA genotype had the highest (P˂0.05) summer evening rectal temperature, respiration rate and pulse rate, inferring that the buffaloes carrying AA genotype had more stress in summer than those with AB and BB genotype. These SSCP genotypes might have differential role in heat shock protein response to induce thermotolerance of Murrah buffaloes in Gangetic plains.