Relish involved in immunity and larval survival in the willow leaf beetle Plagiodera versicolora.

Abstract

Insects mainly rely on innate immunity against pathogen infection. Plagiodera versicolora (Coleoptera: Chrysomelidae), is a worldwide leaf-eating forest pest in salicaceous trees. However, the mechanisms behind the immunodeficiency pathway (IMD) remain poorly understood. In this study, we obtained a Relish gene from transcriptome analysis. Tissue and instar expression profiles were subsequently obtained using quantitative real-time polymerase chain reaction analysis. The results showed that Relish has high expression levels in eggs, larvae and adults, and especially in fat bodies. Transcripts of the tested antimicrobial peptides (AMPs), defensin1, defensin2 and attacin2 were downregulated by dsRelish. Knockdown of Relish led to greater mortality in larvae after Staphylococcus aureus infection. In addition, we performed bacterial 16S ribosomal RNA-based high-throughput sequencing. The results showed that the relative abundance of some gut bacteria was significantly altered after dsRelish ingestion. This study provides a greater understanding of the IMD signaling pathway, facilitating functional studies of Relish in P. versicolora. Moreover, a genetic pest management technique might be developed using Relish as a lethal gene to control the pest P. versicolora. © 2024 Society of Chemical Industry.