Transcriptomic Analysis of the Head Reveals Molecular Mechanisms Underlying Topical Imidacloprid Effects on Africanized Apis mellifera Forager Bees

The global decline of bees has raised significant concerns due to their crucial role in agroecosystems, rendering their diminishment a potential predisposing factor for a worldwide crisis in the agri-food sector and ecosystems. Multiple factors contribute to the decline of pollinator species, including land-use alterations with monoculture expansion, intensive agricultural practices, and the use of systemic pesticides, such as neonicotinoids, which can impact non-target organisms, including bees. This study aimed to evaluate the effect of the neonicotinoid imidacloprid on the gene expression, through contact bioassays (at lethal and sublethal doses) on Africanized Apis mellifera forager bees, analysing the transcriptome of their heads. The results revealed differential gene expression after one and four hours of imidacloprid exposure. Differentially expressed genes (DEGs) were categorized based on gene ontology, revealing alterations in critical biological processes, molecular functions, and cellular components. These changes were associated with immune response, stress, neurotoxicity, and other vital functions. The study identified genes associated with major royal jelly proteins and Yellow proteins, which play significant roles in bee physiology, development, and behavior. Furthermore, an impact on odorant-binding proteins was observed, suggesting altered sensory abilities in bees. These findings contribute to a deeper comprehension of the molecular mechanisms underlying the effects of imidacloprid on honeybees. The study highlights the importance of considering sublethal pesticide effects and their potential long-term consequences on bee populations and ecosystem functioning.