Influence of dietary aconitine and nicotine on the gut microbiota of two lepidopteran herbivores

Gut microbiota plays an important role in pheromone production, pesticide degradation, vitamin synthesis, and pathogen prevention in the host animal. Therefore, similar to gut morphology and digestive enzyme activity, gut microbiota may also get altered under plant defensive compound-induced stress. To test the hypothesis, Dendrolimus superans larvae were fed either aconitine- or nicotine-treated fresh leaves of Larix gmelinii, and Lymantria dispar larvae were fed either aconitine- or nicotine-treated fresh leaves of Salix matsudana. Subsequently, larvae were sampled 72 h after diet administration, and DNA extracted from larval enteric canals were employed for gut microbial 16S rRNA gene sequencing (338F and 806R primers). Sequence analysis revealed that dietary nicotine and aconitine influenced the dominant bacteria in the larval gut and determined their abundance. Moreover, the effect of either aconitine or nicotine on Dendrolimus superans and Lymantria dispar larvae had greater dependence on insect species than on secondary plant metabolites. These findings indicate the importance of gut microbiota in the interaction between an herbivore and its host plant and in the coevolution of plants and insects.