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

BACKGROUND: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 of the immunodeficiency pathway (IMD) are still poorly understood. RESULTS:In this study, we obtained a Relish gene from our transcriptome analysis. Subsequently, the tissue and instar expression profiles were performed by quantitative real-time PCR. The results showed that Relish has highly expressed levels in eggs, larvae and adults, and especially in fat bodies. The transcripts of the tested antimicrobial peptides (AMPs), defensin1, defensin2 and attacin2 were downregulated by dsRelish. Knockdown of Relish led to a higher mortality in larvae after Staphylococcus aureus infection. In addition, we performed the bacterial 16S rRNA-based high throughput sequencing. The results showed that the relative abundance of some gut bacteria was significantly altered after dsRelish ingestion. CONCLUSION:This study would help further to understand of IMD signaling pathway, facilitating functional studies of the Relish in P. versicolora. Moreover, genetic pest management technique might be develop using Relish as a lethal gene to control the pest of P. versicolora.