The Effects of Global Climate Change on Gene Expression in Honey Bees (Apis mellifera)

Global climate change is reshaping the abiotic environment of honey bees and triggering molecular responses that underlie colony health and resilience. This review synthesizes research from the 2000s to the present, summarizing gene expression responses of Apis mellifera to climate-related stressors. The principal drivers include temperature extremes, altered seasonal regimes, elevated atmospheric CO₂, drought, and their interactions. Heat stress induces the expression of heat shock proteins (HSP70/90), antioxidant defenses, and detoxification genes, while suppressing the expression of glandular proteins (MRJPs). Cold stress downregulates genes involved in the peroxisomal and glutathione pathways, thereby increasing oxidative damage. Rising CO₂ levels reduce pollen protein content and indirectly alter the expression of vitellogenin and immune genes. Drought, nutritional scarcity, and pathogen pressure reprogram immune effectors such as defensin-1. Subspecies adapted to hot climates (A. m. jemenetica) exhibit strong HSP responses, although increasing extremes may exceed their adaptive thresholds. Recent studies suggest that epigenetic mechanisms, including DNA methylation and histone modification, play a role in the persistence of these responses. Collectively, the findings provide an integrative framework for selective breeding of stress-tolerant colonies and for omics-based research addressing the complex interplay among multiple climatic stressors.