ORIGINAL ABSTRACT

Due to their role as the main pollinators in agricultural environments, honeybees help improve crop quality and yield and also help maintain global and ecosystem biodiversity. However, pesticide exposure during foraging has resulted in declining honeybee populations, and there are increasing concerns about the potential adverse effects of the herbicide glyphosate (Gly) on honeybees. In this study, we show that exogenous melatonin (Mel) alleviated Gly toxicity in honeybees, and we investigated the mechanisms underlying Mel's effects using RNA-seq and 16S rRNA sequencing. We show that the survival rate of honeybees exposed to Gly increased significantly after pretreatment with 10 mg/L exogenous Mel in the laboratory. RNA-seq showed that genes involved in immunity, digestion, the nervous system, carbohydrate and amino acid metabolism, and development were altered after Gly treatment; interestingly, pretreatment with Mel had a compensatory effect on transcription in response to Gly. 16S rRNA sequencing revealed that Mel treatment dramatically improved the abundance of lactic acid bacteria in honeybees. These findings reveal how melatonin protects honeybee intestines from glyphosate-induced damage, offering practical strategies for honeybee conservation.