AN ENTOMOPATHOGENIC BACTERIUM, Xenorhabdus nematophila, SUPPRESSES EXPRESSION OF ANTIMICROBIAL PEPTIDES CONTROLLED BY TOLL AND IMD PATHWAYS BY BLOCKING EICOSANOID BIOSYNTHESIS. Issue 3 (5th June 2013)

• Record Type: Journal Article
• Authors: Hwang, Jihyun; Park, Youngjin; Kim, Yonggyun; Hwang, Jihyun; Lee, Daeweon
• Is Part Of: Archives of insect biochemistry and physiology. Volume 83:Issue 3(2013:Jul.)
• Page Start: 151
• Page End: 169
• Publication Date: 2013-06-05
• Subjects: Insects -- Physiology -- Periodicals; Insect biochemistry -- Periodicals; 595.701572
• DOI: 10.1002/arch.21103
• Languages: English
• ISSNs: 0739-4462

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <p>Immune‐associated genes of the beet armyworm, Spodoptera exigua, were predicted from 454 pyrosequencing transcripts of hemocytes collected from fifth instar larvae challenged with bacteria. Out of 22, 551 contigs and singletons, 36% of the transcripts had at least one significant hit (E‐value cutoff of 1e‐20) and used to predict immune‐associated genes implicated in pattern recognition, prophenoloxidase activation, intracellular signaling, and antimicrobial peptides (AMPs). Immune signaling and AMP genes were further confirmed in their expression patterns in response to different types of microbial challenge. To discriminate the AMP expression signaling between Toll and Imd pathways, RNA interference was applied to specifically knockdown each signal pathway; the separate silencing treatments resulted in differential suppression of AMP genes. An entomopathogenic bacterium, Xenorhabdus nematophila, suppressed expression of most AMP genes controlled by Toll and Imd pathways, while challenge with heat‐killed X. nematophila induced expression of all AMPs in experimental larvae. Benzylideneacetone (BZA), a metabolite of X. nematophila, suppressed the AMP gene inductions when it was co‐injected with the heat‐killed X. nematophila. However, arachidonic acid, a catalytic product of PLA<sub>2</sub>, significantly reversed the inhibitory effect of BZA on the AMP gene expression. This study suggests that X. nematophila suppresses AMP production controlled by Toll and Imd pathways by inhibiting eicosanoid biosynthesis in S. exigua.</p> </abstract>