Study of gene expression of Heat shock proteins HSP-70 and some physiological and immunological aspects of three types of heat-tolerant and non-tolerant insects

Heat shock proteins (HSPs), particularly HSP-70, are critical to insect adaptation under extreme environmental stress. This study evaluated HSP-70 gene expression in three insect species-Apis mellifera (honeybee), Camponotus xerxes (ant), and Musca domestica (housefly)-subjected to heat stress (45°C, 50°C, 55°C) and extreme cold (liquid nitrogen, −96°C). Gene expression was measured using RT-PCR, and fold changes were calculated relative to the control groups. In A. mellifera, HSP-70 expression increased from a baseline of 1.54-fold in controls to 3.00-, 3.30-, and 6.09-fold at 45°C, 50°C, and 55°C, respectively; exposure to liquid nitrogen induced a 4.41-fold increase. In C. xerxes, expression rose from 1.03-fold (control) to 3.07-fold, 3.67, and 7.69-fold with increasing temperatures, while nitrogen exposure led to a 5.61-fold rise. M. domestica exhibited the highest expression at 55°C (5.62-fold) and after nitrogen exposure (4.94-fold), compared to 1.01-fold in controls, although expression at 45°C and 50°C was lower (2.04- and 1.91-fold, respectively).The results indicated that all three species upregulate HSP-70 in response to thermal and cold stress, with the greatest expression observed at 55°C and upon exposure to liquid nitrogen. Notably, C. xerxes showed the strongest heat-induced response, while M. domestica exhibited pronounced expression under both heat and cold, suggesting robust thermal adaptation. These findings underscore the species-specific dynamics of HSP-70 regulation and its pivotal role in cellular protection and survival under extreme environmental conditions.