Tannic Acid Enhances Cold Resistance in Apis mellifera via Antioxidant Defense and Mitochondrial Oxidative Phosphorylation Activation

Significant losses caused by exacerbating oxidative stress during cold winters have been a persistent challenge in the beekeeping industry. Although tannic acid, a plant-derived compound, is known as a hazardous material with hepatotoxic and nephrotoxic effects, paradoxically, it has also been identified as a bioactive metabolite with potent antioxidant properties. We hypothesized that tannic acid in Rhus chinensis Mill. (a major nectar source plant) may serve a natural functional role in supporting honeybee colony health. Our results suggested that honeybees have a higher survival rate after experiencing cold, and ROS levels of cold-stressed honeybees significantly reduced and CAT and SOD levels significantly increased after treatment by tannic acid. Analysis of qPCR further revealed upregulation of CAT and GSH-Px gene expression in the tannic acid group. Transcriptomic profiling indicated that the oxidative phosphorylation pathway was the most enriched among differentially expressed genes, with key genes (Ndufb2, Ndufa4, SDHD, and SDHB) showing marked upregulation. Moreover, the membrane potential of mitochondria and the ATP content in honeybee heads were significantly enhanced by tannic acid. Our study provided insights for new functions as well as further study and application of tannic acid, providing strategies for improving the cold resistance of honeybees and reducing winter losses in the beekeeping industry.