Mechanisms of selectivity for azadirachtin in honeybees (Apis cerana): A new strategy for avoiding thiamethoxam ingestion

Abstract

The high toxicity of thiamethoxam (Thi) to foragers has threatened the development of bee populations and the use of neonicotinoid pesticides. In this study, we explored the mechanism of selective feeding on azadirachtin (Aza) by foragers to reduce the feeding of Aza-Thi and improve foragers' safety. The results showed that foragers under selective feeding significantly reduced the Aza sucrose solution intake. The Thi content in foragers was significantly lower, and the mortality rate was significantly reduced. In order to further analyze the selective feeding of foragers on Aza, the classic proboscis extension response (PER) experiment showed that Aza did not affect the learning ability of foragers, and the expression of related genes was not significantly different from the regular PER foragers. Further analysis of transcriptomics and metabolomics showed that compared with the regular PER foragers, treated with Aza were significantly affected in metabolic pathways and peroxisome and 67 differentially expressed genes (DEGs) were up-regulated and 136 were down-regulated. Differential metabolite analysis showed that metabolites primarily enriched in caffeine metabolism and microbial metabolism in diverse environments, and only dibucaine was up-regulated in response to Aza treatment. It is worth noting that dibucaine was significantly positively correlated with differentially expressed genes. Thus, our findings revealed that Aza does not affect the expression of memory genes in foragers. Aza affected the regular metabolic levels of foragers, leading to selective feeding of foragers on Aza, reduced intake of Aza-Thi, and increased safety for foragers. This study provides a reference for applying Aza to selective mechanisms in foragers.