qRT-PCR/High Resolution Melting Analyses detected polymorphisms of HSP-70 gene in Zebu cattle

Abstract

28Concerns over environmental heat stress have increased in recent years with the 29 realization of global warming effects on environment and subsequently on animal production. 30 Heat stress indicators help to monitor adaptability and survivability of livestock to thermal 31 assault; a consequent effect of global warming. Heat shock proteins (HSPs) are highly 32 conserved and are classified into six groups. Heat shock protein (HSP) 70 gene is a member of 33 molecular chaperone, known to be highly expressed under stressful environmental and 34 physiological conditions. In this study, we used a one-step qReal-Time PCR, followed by 35 high-resolution melting analyses (HRMA) for detection and identification of polymorphism of 2 36 HSP-70 gene in four extant cattle breeds of (White Fulani, Sokoto Gudali, Red Bororo and 37 Ambala). qRT-PCR/HRMA-based assay detected twelve (12) genetic variant groups of HSP-38 70 gene. Ambala breed of Nigerian Zebu cattle had the highest number (7) of genetic variants 39 of HSP-70 gene followed by Red Bororo breed (6 genetic variants), Sokoto Gudali breed had 40 5 genetic variants while White Fulani breed had the least (4 genetic variants) number of 41 genetic variants in the population of Nigerian Zebu cattle breeds examined. We therefore 42 hypothesize that the detected variant groups can be interrogated for their possible effects on 43 thermo-tolerance performance of zebu cattle bred under thermal assaults of tropical 44 conditions. 45 46 Introduction 47 Cattle industry is a very important sector of livestock husbandry in many developing 48 countries all over the world. Cattle serve as valuable source of animal proteins and hide, and 49 contribute in no small measure to national economy. Heat stress is a significant issue in the 50 livestock industry. 51 The impact of heat stress on livestock, particularly on cattle can be overwhelming [1], 52 resulting in reduced feed intake, reduced fertility, increased respiratory and heart rates, 53 increased peripheral blood flow and profuse sweating, reduced milk production and lower 54 milk quality [2]. These impacts according [2], can result in significant loss of income and 55 increase in management costs. Losses to the cattle industry due to heat stress was estimated at 56 about $900 million per annum [3]. The issue is more exacerbated with increased global 57 warming, as such, the impact of heat stress needs to be addressed and ameliorated to maintain 58 animal health status, adaptability, survivability and performance.59 Heat shock proteins (HSPs), are a group of proteins conserved in both prokaryotic and 60 eukaryotic organisms. The expression of HSP genes are related to thermal stress, they play 61 vital roles in cell response to environmental stress [4, 5]. Studies have shown that the 62 expression of HSP genes affects follicular development, embryonic survival and pregnancy 63 maintenance [6-8]. For this reason, the functional characterization of this gene family is 3 64 important. The HSP-70 protein, also referred to as HSP-70 ge...