The toxicological mechanism of emamectin benzoate in Spodoptera frugiperda via regulating gut microbiota

Emamectin benzoate is a highly effective neurotoxic insecticide widely used to control pests, including Spodoptera frugiperda (Lepidoptera: Noctuidae) which is an invasive insect spreading worldwide.However, the toxicological mechanism has yet to be fully elucidated.Particularly, the contribution of host gut microbiota in emamectin benzoate-killing activity had less explored.Here, we demonstrated that the gut microbiota triggered the toxicity of emamectin benzoate in S. frugiperda.Emamectin benzoate changed the diversity and abundance of gut microbiota.It reduced the abundance of immune-related microbes and genes, which disrupted the balance of antioxidant enzymes in the gut and destroyed the gut morphology.Simultaneously, emamectin benzoate reduced the microorganisms abundance of decompose polysaccharides and the gene abundance of active carbohydrate enzyme which affected the metabolic function and growth of insects.Most importantly, emamectin benzoate stimulated the abundance of enzyme genes involved in the anabolism of γ-aminobutyric acid by the microbes and catalyzing the production of more γ-aminobutyric acid which is the key neurotransmitters leading insects to death.This study first provides evidence for the role of gut microbes in promoting the toxicity of EMB and suggests gut microbes as a potential target for insecticide development.