Antiviral function of peptidoglycan recognition protein in Spodoptera exigua (Lepidoptera: Noctuidae)

Abstract Peptidoglycan recognition proteins (PGRPs) are a class of molecules that play a critical role in insect immunity. Understanding the function of PGRPs is important to improve the efficiency of microbial insecticides. In this study, we investigated the role of PGRP‐LB (a long type PGRP) in insect immunity against viruses using Spodoptera exigua and Spodoptera exigua multiple nucleopolyhedrovirus (SeMNPV) as an insect–virus model. We cloned and identified a PGRP‐LB gene from S. exigua ; the gene consisted of 7 exons that encoded a polypeptide of 234 amino acids with a signal peptide and a typical amidase domain. Expression analysis revealed that the abundance of SePGRP‐LB transcripts in the fat body was greater than in other tissues. Overexpression of SePGRP‐LB resulted in a significant decrease of 49% in the rate of SeMNPV‐infected cells. In addition, the multiplication of SeMNPV was significantly decreased: a decrease of 79% in the production of occlusion‐derived virion (ODV), and a maximum decrease of 50% in the production of budded virion (BV). In contrast, silencing of SePGRP‐LB expression by RNA interference resulted in a significant 1.65‐fold increase in the rate of SeMNPV‐infected cells, a significant 0.54‐fold increase in ODV production, a maximum 1.57‐fold increase in BV production, and the larval survival dropped to 21%. Our findings show that SePGRP‐LB has an antiviral function against SeMNPV, and therefore this gene may provide a target for lepidopteran pest control using virus insecticides.