Expression profiling of hsp70 gene during different seasons in goats (Capra hircus) under sub-tropical humid climatic conditions

Thermal stress alters the normal body homeostasis and causes severe detrimental effects on productivity of animals. Heat shock proteins (HSPs) are a ubiquitous class of highly conserved proteins that play a role in cell survival during different conditions of stress. The present study was conducted to detect hsp70 mRNA and protein of stress tolerance and to quantify the expression in different tissues with respect to seasonal variation. The expression of hsp70 gene was observed in four different tissues e.g., liver, heart, spleen & kidney in different climatic conditions. The temperature-humidity index (THI) were observed thrice i.e. in the month of June (THI > 72), between September-October (THI = 72) and January-February (THI < 72). Quantitative real-time PCR (qPCR) & ELISA were used to investigate the relative expression profile of hsp70 gene during different seasons. GAPDH (Glyceraldehyde 3-phosphate dehydrogenase) was used as a housekeeping gene. It was observed that expression of hsp70 gene was higher in liver & kidney tissues as compared to heart and spleen and the expression of hsp70 protein exhibited that the liver and heart tissues showed over expression as compared to kidney and spleen tissues in both the summer & winter season. Heat and cold stress conditions induced over-expression of hsp70. Different tissues have differential sensibilities to thermal stress. The quantification of hsp70 mRNA and protein were both breed and tissue dependent. The phylogenetic analysis of mammalian HSPA4 gene indicated that goats have close relationship (99-99.7%) with sheep, cattle & buffalo and also share homology (94.6-98%) with pig, camel, dog & human. The mRNA and protein expression in the four different tissues of Barbari & Jamunapari show a statistically significant difference (p < 0.05) in summer as compared to winter. The above study confirmed that hsp70 expression is breed- and tissue-specific and varies with THI and this relationship may play an imperative role in conferring thermotolerance against heat stress during different seasons.