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

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.

Localization and Functional Analysis of SeMNPV IE1 in Mammalian Cells

In this paper, the function of the iel gene from baculovirus Spodoptera exigua multiple nucleopolyhedrovirus （SeMNPV）, belonging to group II nucleopolyhedrovirus, was studied in mammalian cells We amplified the SeMNPV iel gene and expressed it by fusing to the C terminal of enhanced GFP protein in HEK 293 cells. Confocal microscopy revealed that the IE1-GFP fusion protein was localized in the nucleus of the mammalian cells. The promoter sequences of AcMNPV gp64, SeMNPV F protein and Drosophila hsp70 were also analyzed, to further study the function of SeMNPV IE1. The results showed that, in the absence of the hr sequence, IE1 improved the expression of the F promoter but didn＇t influence the gp64 promoter significantly, but IE1 moderately stimulated the hsp70 promoter.