AGRICULTURAL RESEARCH COMMUNICATION CENTRE www.arccjournals.com/www.ijaronline.in *Corresponding author’s e-mail: ++ 1 AG Division, IVRI, Izatnagar, 2 DCP Division, National Dairy Research Institute, Karnal. Indian J. Anim. Res., 50 (6) 2016 : 856-861 Print ISSN:0367-6722 / Online ISSN:0976-0555 Polymorphisms in Hsp90ab1 gene and their association with heat tolerance in Sahiwal and Karan Fries cows Lalrengpuii Sailo 1 , I.D. Gupta*, Archana Verma, Ramendra Das 2 , M.V. Chaudhari 1 and Sohanvir Singh 2 ICAR-National Dairy Research Institure, Karnal-132 001, India. Received: 03-06-2015 Accepted: 15-01-2016 DOI: 10.18805/ijar.v0iOF.6662 ABSTRACT Heat shock protein functions as a molecular chaperone and plays an important role in thermotolerance. The study was undertaken to identify single nucleotide polymorphisms (SNPs) of Hsp90ab1 gene by comparative sequencing and to analyze their association with thermo-physiological parameters, viz. respiration rate (RR), rectal temperature (RT) and heat tolerance coefficient (HTC) in different seasons, viz. winter, spring and summer, at probable extreme hours of the day in Sahiwal and Karan Fries cows. The RR, RT and HTC in summers were significantly (P0.01) higher than the other two seasons. Polymorphism of Hsp90ab1 gene, evaluated by comparative sequencing revealed six SNPs, viz. T17871421C, C17871485del, C17872061T, T17872112C, T17872148G and A17872199C, two each located in exon 8, intron 10 and exon 11. SNP loci T17871421C and C17871485del were found to be monomorphic for allele C and Deletion (-) respectively in experimental population. Individuals with AA genotype showed significantly (P 0.01) lower RR than AC genotype. While, individuals with CT genotype recorded significantly (P  0.01) lower RT than CC genotype. Therefore, it is inferred that propagation of AA and CT genotypes may be an aid to selection and breeding programmes to enhance thermo-tolerance in dairy cattle. Key words: Heat stress, Hsp90ab1, Karan Fries SNP, Sahiwal. INTRODUCTION Climate change represents a critical challenge to both agricultural and livestock production systems. Variation in climatic variables like temperature, humidity and solar radiations are recognized as one of the most potential hazards in growth, health, production and reproduction of all domestic livestock species (Bernabucci et al., 2010; Yatoo et al., 2012; Ganaie et al., 2013). Physiological responses like respiration rate, rectal temperature and pulse rate reflect the degree of stress imposed by climatic parameters on animals (Ganaie et al., 2013). Zebu breeds (Bos indicus) of cattle are better able to regulate body temperature in response to heat stress than European breeds (Bos taurus) due to their long time adaptation to tropical climates (Beatty et al., 2006; Gaughan et al., 2010). The problem of heat stress in dairy cattle has recently received increasing attention because of anticipated increases in environmental temperature by global warming (Hansen, 2004; Hoffmann, 2010). Under thermal stress, multiple cellular mechanisms are displayed to counter the stress conditions by altering the expression of several stress genes (Collier et al., 2008). Mammals respond to heat stress by transcriptional activation of a set of proteins known as heat shock proteins (Kregel, 2002). Heat shock proteins (Hsps) play essential roles in immunity of organisms, particularly in relation to heat- resistance (Song et al., 2006, You et al., 2013). Therefore, identification for SNP markers associated with heat- resistance has mainly concentrated on Hsps as the most suitable candidate genes (Rako et al., 2007; Yang et al., 2011; Chen et al., 2013). The chaperone, Hsp90 is one of the most abundant proteins in eukaryotic cells, comprising two major cytoplasmic isoforms, the inducible (Hsp90) and the constitutive (Hsp90) (Chen et al., 2006). The gene hsp90 has been identified and characterized in diverse species and is involved in a variety of cellular processes, including protein regulation, control of apoptosis, and signal transduction in the stress response (Richter and Buchner, 2001). Recently, novel single nucleotide polymorphisms (SNP) were identified at different positions of the bovine Hsp90ab1 gene in Bos taurus, crossbred and Bos indicus cattle. High prevalence of this gene in zebu cattle enable them to survive and perform better to crossbred cattle due to better heat tolerance (Deb et al., 2013; McManus et al., 2014; Sajjanar et al., 2015) The objective of this study was to identify SNPs in the targeted regions of Hsp90ab1 gene in Sahiwal and Karan Fries cows and to analyze the association of genetic variants with thermal stress related physiological parameters, viz. respiration rate, rectal temperature and HTC.