Sublethal effects of the neonicotinoid insecticide thiamethoxam on the transcriptome of the honeybee (Apis mellifera)

Neonicotinoid insecticides are now the most widely used insecticides in the world. 10 Previous studies have indicated that sublethal doses of neonicotinoids impair learning, memory 11 capacity, foraging and immunocompetence in honeybees (Apis mellifera). Despite this, few 12 studies have been carried out on the molecular effects of neonicotinoids. In this study, we focus on 13 the second-generation neonicotinoid thiamethoxam, which is currently widely used in agriculture 14 to protect crops. Using high-throughput RNA-Seq, we investigated the transcriptome profile of 15 honeybees after subchronic exposure to thiamethoxam (10 ppb) over 10 days. In total, 609 16 differentially-expressed genes (DEGs) were identified, of which 225 were up-regulated and 384 17 were down-regulated. The functions of some DEGs were identified, and GO enrichment analysis 18 showed that the enriched DEGs were mainly linked to metabolism, biosynthesis and translation. 19 KEGG pathway analysis showed that thiamethoxam affected biological processes including 20 ribosomes, the oxidative phosphorylation pathway, tyrosine metabolism pathway, pentose and 21 glucuronate interconversions and drug metabolism. Overall, our results provide a basis for 22 understanding the molecular mechanisms of the complex interactions between neonicotinoid 23 insecticides and honeybees. 24