An immune signal pathway using Toll receptor in response to Gram positive bacterial or fungal challenge induces cellularimmunity and production of antimicrobial peptides (AMPs) in insects. Here we tested an hypothesis that Toll signal downstreamfactors, MyD88 and Pelle, influence eicosanoid signal by activating phospholipase A2 (PLA2) activity in the beet armywormSpodoptera exigua. We knocked-down MyD88 and Pelle expressions using specific dsRNAs and assessed their effect onPLA2 activity in immune-challenged S. exigua larvae. The RNAi-treated larvae failed to induce AMP gene expressionand PLA2 activity under immune challenge. These results shed light on cross-talk between Toll pathway and eicosanoidsignal.

Phospholipase A2 (PLA2) hydrolyzes phospholipids at sn-2 position to release free fatty acids. PLA2 consists of a superfamily mainly categorized as secretory PLA2 (sPLA2), cellular Ca 2+ -dependent PLA2 (cPLA2), and cellular Ca 2+ -independent PLA2 (iPLA2). We are the first to report iPLA2 in insect. Here an objective of our study is to purify a recombinant iPLA2 protein (SeiPLA2) of Spodoptera exigua using bacterial expression system. An open reading frame of SeiPLA2 was cloned into an expression vector and then transformed into Escherichia coli BL21. Over-expression with IPTG yielded recombinant SeiPLA2 (rSeiPLA2), which was then purified by an affinity chromatography using Ni-NTA column. The purified rSeiPLA2 gave significant PLA2 activity using a pyrene substrate. Its activity was inhibited by an iPLA2 specific inhibitor (BEL), but not by sPLA2 inhibitor (BPB) or cPLA2 inhibitor (MAFP

Differential gene regulation is crucial for development. Indianmeal moth is a global pest of stored and processed food products. Here, we determined the whole developmental expression patterns of 13 genes (shsp, hsp70, grp78, and hsp90), ecdysone receptor (EcR), ultraspiracle (USP), hemolin, β-1,3-glucan recognition protein (βgrp), prophenoloxidase (ProPO), superoxide dismutase (SOD) and thioredoxin peroxidase (Tpx), and two hexamerin storage protein genes (SP1 and SP2) related to growth, stress, metabolism, and host defense. We also studies effects of Bracon hebetor envenomation on these gene expressions to explore their role in host regulation. We found unexpected transcriptional peaks especially hsps which were high in egg and adult stages. This study provides comprehensive understanding about development and parasitoid regulation at molecular level.

Indianmeal moth Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae) is an economical pest of stored grains and their products, causing severe loss by feeding and producing silken web containing frass and exuvia. An ectoparasitoid Bracon hebetor Say (Hymenoptera, Braconidae) attacks this pest as a natural enemy and induce paralysis and developmental arrest in it. At molecular level its venom induce many physiological changes in host P. interpunctella to make it suitable source of food and development for its young ones. To explore these physiological changes at molecular level in P. interpunctella, we observed expression level of different genes having different functions related to immunity, defense and development at different intervals followed by B. hebetor envenomation. Fifth instar day 5 old larvae of P. interpunctella were used in experiment. Our results showed that B. hebetor envenomation effect the gene expression differently in host P. interpunctella. This basic study will be the starting point to understand the role of envenomation in host regulation studies.

Indianmeal moth Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae) is an important pest of stored grains products. As a natural enemy, an ectoparasitoid Bracon hebetor Say (Hymenoptera, Braconidae) has been used to control Lepidopteran pest insects. Venom from parasitoid female alters many physiological functions in host insects. However, mechanism of physiological response of host insects against envenomation and parasitization is not clear. Here we observed the effect of B. hebetor envenomation on the gene expression (shsp, hsp70, grp78 and hsp90) in P. interpunctella at different time intervals of post envenomation. Fifth instar day 5 larvae of P. interpunctella were used in experiment to observe the effect of envenomation. Our results showed that parasitoid envenomation affected the gene expression differently in host insect. This study will provide comprehensive insights on physiological and biochemical mechanism in host-parasitoid relationships.