TITLE:
ASSOCIATION OF HSP90AA1 GENE POLYMORPHISMS WITH HEAT TOLERANCE, HAEMATOLOGICAL TRAITS AND EVALUATION OF THE REPRODUCTIVE PERFORMANCE OF TWO LAYER CHICKEN STRAINS
NAME: IRIVBOJE, YOUNG IMIENWAIN [View Profile]
MATRIC NO.: PG2011/0013
CENTRE: Centre of Excellence in Agricultural Development and Sustainable Environment
PROGRAMME: Livestock Science and Sustainable Environment
DEGREE-IN-VIEW: PhD.AgSE (Animal Breeding and Biotechnology)
YEAR OF ADMISSION: 2014/2015 SESSION
DATE OF DEFENCE:
ABSTRACT
Chickens, like other vertebrates, react to stress conditions through their cultured cells by expressing heat shock proteins (HSPs). Genetic association of single nucleotide polymorphisms (SNPs) in HSPs with desirable traits will reveal their importance as potential genetic markers. Four hundred eggs per strain- Brown Dominant (BRD) and Hyline Brown (HYL) were incubated per week for ten weeks per season for four seasons. Blood samples were collected from fifty birds per strain for DNA extraction, polymerase chain reaction amplification and sequencing of the HSP90AA1 gene. SNPs were detected using Codoncode Aligner. Association of each SNP with heat tolerance and haematological traits was analysed using Generalized Linear Model procedure of SAS. Retrieval of similar sequences was carried out using Basic Local Alignment Search Tool. Evolutionary relationships, genetic diversity, prediction of subcellular localization, motifs scan and phosphorylation sites were done using Molecular Evolution and Genetic Analysis, DNA sequence polymorphism, CELLO, Scanprosite and NetPhos3.1. A total of seven SNPs were detected, four SNPs; A7T, A160T, T223A and C134T were detected in part of intron 7 to exon 8 of HSP90AA1 gene of BRD while three; A160T, T223A and C134T were detected in HYL. SNP-C134T, a synonymous variant, was detected in exon 8. Only SNP-A7T was in Hardy-Weinberg equilibrium (X2=0.03) but had no association with the traits measured. Polymorphic information content calculated showed SNPA-160T to be moderately polymorphic, other SNPs were lowly polymorphic. Heterozygosity for SNPs-A160T and T223A of BRD showed moderate genetic variation while the other SNPs and those in HYL recorded low genetic variation. Linkage disequilibrium was significant between SNPs-A160T and T223A (p<0.001) with average scores of 0.56 and 0.47 for BRD and HYL. BRD had higher genetic diversity in the intron but in the exon, HYL had a higher genetic diversity. Phylogeny showed Japanese quail to be highly related to BRD and HYL. The HSP90AA1 protein is localized in the cytoplasm. Motifs detected include camp_phospho_site, myristyl, ck2_phospho_site, asn_glycosylation and pkc_phospho_site. Phosphorylation sites were serine and threonine. Results on the reproductive performance revealed that late-wet season had the highest significant effect (p<0.05) on the percent fertile, hatched and hatchability (78.12±0.51, 72.36±0.74, 92.92±0.36). Strain effect on reproductive performance showed BRD to be significantly higher (p<0.05) in percent fertile, hatched and hatchability (74.80±0.72, 67.68±0.98, 90.60±0.48) than HYL (71.02±0.71, 63.01±0.92, 88.38±0.49). For the haematological parameters, wet-season had a higher significant effect (p<0.05) on packed cell volume, red blood cell, haemoglobin and eosinophil than dry-season. For heat tolerance, late-wet (41.37±0.02) and early-dry (41.41±0.02) seasons, had the highest significant effect (p<0.05) on rectal temperature. The respiratory rate recorded its highest significant effect (p<0.05) in the early-dry season while strain effect showed HYL (41.14±0.03) to be significantly higher (p<0.05) than BRD (41.07±0.03). The study concluded that the SNP locus A7T in intron 7 of HSP90AA1 of BRD had no genetic association with haematological and heat tolerance traits. The gene HSP90AA1 is highly conserved in both BRD and HYL. The late-wet season was more favourable to reproductive performance. BRD is well-adapted to the local climate and would perform better.
Word count: 499
DATE OF DEFENCE: 14th August, 2018
YEAR OF ADMISSION: 2014