Cotesia plutellae bracovirus suppresses expression of an antimicrobial peptide, cecropin, in the diamondback Moth, Plutella xylostella, challenged by bacteria

Abstract

An endoparasitoid wasp, Cotesia plutellae, induces significant immunosuppression of host insect, Plutella xylostella. This study was focused on suppression in humoral immune response of P. xylostella parasitized by C. plutellae. An EST database of P. xylostella provided a putative cecropin gene (PxCec) which is 627 bp long and encodes 66 amino acids. A signal peptide (22 amino acids) is predicted and two putative O-glycosylation sites in threonine are located at positions 58 and 64. Without bacterial infection, PxCec was expressed in pupa and adult stages but not in the egg and larval stages. Upon bacterial challenge, however, the larvae expressed PxCec as early as 3 h post infection (PI) and maintained high expression levels at 12-24 h PI. By 48 h PI, its expression noticeably diminished. All tested tissues of bacteria-infected P. xylostella showed PxCec expression. However, other microbes, such as virus and fungus, did not induce the PxCec expression. Parasitization by C. plutellae suppressed the expression of PxCec in response to bacterial challenge. Among the parasitic factors of C. plutellae, its symbiotic virus (C. plutellae bracovirus: CpBV) alone was able to inhibit the expression of PxCec of P. xylostella challenged by bacteria. These results indicate that PxCec expression is regulated by both immune and developmental processes in P. xylostella. The parasitization by C. plutellae inhibited the expression of PxCec by the wasp's symbiotic virus.

Transcriptome Immune Analysis of the Invasive Beetle Octodonta nipae (Maulik) (Coleoptera: Chrysomelidae) Parasitized by Tetrastichus brontispae Ferrière (Hymenoptera: Eulophidae)

“…Similarly, cecropin and gloverin in the Manduca sexta egg were down-regulated following parasitization by Trichogramma evanescens [28]. Barandoc et al found that parasitization by Cotesia plutellae suppressed the expression of cecropin in P. xylostella larvae [29]. In contrast, some studies demonstrated that parasitoid challenge induces AMP transcript levels in the host.…”

Production, purification, and characterization of the cecropin from Plutella xylostella, pxCECA1, using an intein-induced self-cleavable system in Escherichia coli

“…Since insects have no adaptive immunity, their innate immune system must build both cellular and humoral responses against various pathogens; inducible AMPs play an important role in this humoral response (Barandoc et al 2010). Upon injury or infection, most AMPs are co-expressed as groups that act together (Lai and Gallo 2009).…”

“…The post-translation process in the native host includes the cleavage of signal peptide by signal peptidase, then deletion of the following two residues, Ala-Pro, by dipeptidyl peptidase (Fig. 2) (Lidholm et al 1987;Barandoc et al 2010). According to the secondary structure by PredictProtein and Antimicrobial Peptide Predictor, the mature peptide can be classified as an all-alpha helix structure with amphipathic properties and a total net charge of +8.…”

“…To test this system for production of AMPs, we chose to purify and characterize a promising candidate AMP: cecropin-like peptide from Plutella xylostella (pxCECA1). pxCECA1 has been previously reported (Eum et al 2007;Barandoc et al 2010), but to date, there have been no studies on its biological activity.…”

Deep sequencing-based transcriptome analysis of Plutella xylostella larvae parasitized by Diadegma semiclausum

“…PDVs are the most highly characterized of the known mutualistic viruses [10], replicating only within the calyx cells of the reproductive tract of female wasps [11]. No virus replication occurs in parasitized larvae; however expression of encapsidated PDV genes induces different physiological modifications such as interruption of the larval endocrine system and suppression of the host immune system [12-15]. …”