Effects of Rapid Heat Hardening of Honeybee Queens (Apis mellifera) During the Larval Stage on the Oxidative Response of Their Workers During Heat Stress

Abstract

Exposing insects to mild and/or severe heat can protect them from future heat stress by regulating the expression of certain stress markers. In this study, 60 queen larvae, one day old, were divided into the following two groups: a control group of non-heat-treated mother queens (nH-T MQ) kept for 15 min at 34.5 °C and 70% relative humidity (RH) and a pre-heat-treated mother queen group (pH-T MQ) that was kept for 15 min at 41 °C and 70% RH. Then, 500 daughter workers were collected from brood combs of each group and incubated at room temperature (22 °C) for 30 min, then divided into five groups (n = 100); each group was incubated for one hour at 35, 40, 45, 50, and 55 °C, respectively. The expression levels of several antioxidant genes and markers in 10 workers of each treatment were assessed by relative quantitative Real-Time qPCR and/or ELISA. The pH-T MQ showed improved basal and dynamic expression of several genes and enzymes, which indicated a protective response against heat stress and the effectiveness of tissue hardening on the biological process and/or mechanisms in oxidative stress and antioxidant activity response. These recorded changes may have global implications by improving thermotolerance acquisition during heat stress conditions.