Heat stress is one of the main factors that influence poultry production. Heat shock proteins (HSPs) are known to affect heat tolerance. The formation of HSPs is regulated by heat shock transcription factor 3 (HSF3) in chicken. A DNA pool was established for identifying single nucleotide polymorphisms (SNPs) of the chicken HSF3, and 13 SNPs were detected. The bioinformatic analysis showed that eight SNPs had the capacity to alter the transcription activity of HSF3. The dual luciferase report gene assay showed that there was a significant difference (P<0.01) in the Firefly luciferase/Renilla luciferase ratio (F/R) of C1703 A>G (S1) and C1388 A>G (S4) sites at the 5′-untranslated region (UTR) of chicken HSF3. The electrophoretic mobility shift assay showed that the S4 site was a transcription binding factor. The analysis of the association of the S1 and S4 sites with heat tolerance index revealed that the S4 site was significantly correlated with the CD 3+ T cell, corticosterone, and T3 levels in Lingshan Chickens and with the heterophil/lymphocyte value in White Recessive Rock. These results showed that the S4 site at the 5′UTR of chicken HSF3 might have an impact on heat tolerance in summer and could be used as a potential marker for the selection of chicken with heat tolerance in the future.

ABSTRACT. Glucose-regulated protein 78 (GRP78) is a molecular chaperone in the endoplasmic reticulum and can be induced by different kinds of environmental and physiological stress. Thus far, the role of the GRP78 gene in thermotolerance in chickens has not been investigated. In the present study, we detected sequence variations in the 5ꞌ-flanking region of the GRP78 gene and evaluated several thermotolerance parameters, such as T3, corticosterone, H/L ratio, and levels of CD3 + , CD4 + , and CD8 + T cells, to further determine its associations at 35° and 15°C. The sequencing results revealed 10 SNPs in the 5'-flanking region of the GRP78 gene, and seven mutations were chosen for further genotyping in a White Recessive Rock (WRR) chicken population. The SNP C.-744C>G in WRR chickens was significantly correlated with heat tolerance parameters under both conditions; it may therefore exert 6111 Chicken GRP78 gene expression and thermotolerance ©FUNPEC-RP www.funpecrp.com.br Genetics and Molecular Research 14 (2): 6110-6123 (2015) a potential hereditary effect on heat tolerance, and the genotype GG may be advantageous for thermotolerance. The heart, liver, brain, and leg muscle tissues of 8-day-old WRR chickens were sampled from heat stress groups, which were defined by exposure to 1, 2, 3, and 6 h of persistent thermal stress, and a control group, which was not exposed to thermal stress. Quantitative real-time polymerase chain reaction assay indicated that the mRNA expression level of the GRP78 gene increased gradually under heat stress, peaked at 3 h, and then decreased. We conclude that the mRNA expression of the GRP78 gene is time-and tissue-dependent.