Imidacloprid exposure disrupts gene expression in<i> Apis</i><i> mellifera,</i> potentially threatening pollination efficiency

Abstract

Bees are indispensable pollinators for maintaining both ecosystems and agricultural productivity. However, their populations have been reduced, potentially attributed to habitat loss, climate change, heightened vulnerability to diseases and parasites, and the use of pesticides. Neonicotinoids, acting as agonists of nicotinic cholinergic receptors, have been associated with detrimental impacts on bees, including decreased survival rates. In this study, Apis mellifera L. in their foraging phase were exposed to lethal or sublethal doses of imidacloprid through ingestion or contact. After 1 and 4 hours, the bees were euthanised and stored in an ultra-freezer (-80 degrees C) for transcriptomic analysis. After 1 hour and 4 hours of all treatments, twenty-four genes were differentially expressed, potentially impacting foraging activity and thus pollination, promoting genetic dysregulation, and affecting genes associated with odorant-binding proteins (OBPs) and chemosensory proteins (CSPs). This suppression suggests compromised olfactory function and chemical communication, essential for foraging and pollination. Additionally, metabolic alterations were observed, influencing crucial enzymes involved in carbohydrate and protein digestion, potentially impacting bee performance. Imidacloprid exposure also disrupted the gene encoding a circadian clock-controlled protein, which regulates circadian rhythms essential for behaviours like orientation, navigation, and sleep, all crucial for colony survival. Evidence of an adaptive response to oxidative stress was observed, indicated by increased expression of genes related to hexamerin 70a and vitellogenin. Beyond threats to bee health, substantial economic and environmental impacts are evident, underscoring the urgent need for sustainable alternatives in pesticide management to ensure bee preservation and global food security.