Effects of exposure to trace pyriproxyfen on the intestinal bacterial diversity and immune signal pathways of silkworm (Bombyx mori) larvae

Abstract

Silkworm (Bombyx mori) is a widely used lepidopteran model insect. Pyriproxyfen is an insect growth regulator (IGR) that can be used to control pests such as lepidoptera and diptera, and there is no research about its influence on the intestinal bacterial diversity and immune signal pathway of non-target lepidopteran insect larvae. In this study, we treated fifth-instar silkworms with trace pyriproxyfen (10−4 mg/L). The results showed that the abundance and diversity of silkworm larvae intestinal flora at the level of phylum, class, order, family and genus were all changed. The function prediction result showed that the functional changes mainly focused on transcription, amino acid transport and metabolism, carbohydrate transport and metabolism, signal transduction mechanisms, energy production and conversion et al. after exposure to trace pyriproxyfen. Furthermore, qRT-PCR results showed that trace pyriproxyfen exposure activated the transcriptions of antimicrobial peptides (AMPs) genes regulated by Toll and IMD pathways. This research can lay the foundation for the study on the resistance of lepidopteran insects to pyriproxyfen and other juvenile hormone pesticides.