Elevated developmental temperature affects gene expression and oxidative stress in bumblebee (Bombus terrestris) workers

Climate change can negatively impact bumblebee populations, which are crucial pollinators in agricultural systems and natural ecosystems. Bumblebee nest temperatures typically range from 27 to 32 °C, and workers engage in wing fanning to maintain a nest temperature below 32 °C. We investigated the gene expression profile in queen, worker, and male bumblebees (Bombus terrestris) at 27 °C, which is the optimal ambient temperature, and 32 °C, which is the upper-temperature limit requiring wing fanning. We found that a developmental temperature of 32 °C significantly increased the expression of genes related to growth, immune response, antioxidants, and chaperones in workers. Compared to workers reared at 27 °C, those reared at 32 °C exhibited a significant increase in reactive oxygen species (ROS) and iron concentrations in the hemolymph. Additionally, the gene expression of superoxide dismutase (SOD) and transferrin (Tf) was significantly increased in workers at 32 °C. These findings indicate that a developmental temperature of 32 °C in bumblebees, especially workers, leads to an increase in gene expression, including SOD and TF, in response to thermal stress.