Affiliation:
1. Department of Plant Medicals, College of Life Sciences, Andong National University, Andong 36729, Korea
Abstract
In insect midgut, prostaglandins (PGs) play a crucial role in defending bacterial and malarial pathogens. However, little is known about the PG signalling pathway in the midgut. A dual oxidase (
Se-Duox
) with presumed function of catalysing reactive oxygen species (ROS) production in the midgut was identified in beet armyworm,
Spodoptera exigua
.
Se-Duox
was expressed in all developmental stages, exhibiting relatively high expression levels in the midgut of late larval instars.
Se-Duox
expression was upregulated upon bacterial challenge. RNA interference (RNAi) of
Se-Duox
expression significantly suppressed ROS levels in the midgut lumen. The suppression of ROS levels increased insecticidal activity of
Serratia marcescens
after oral infection. Interestingly, treatment with a PLA
2
inhibitor prevented the induction of
Se-Duox
expression in response to bacterial challenge. On the other hand, addition of its catalytic product rescued the induction of
Se-Duox
expression. Especially, PG synthesis inhibitor significantly suppressed
Se-Duox
expression, while the addition of PGE
2
or PGD
2
rescued the inhibition. Subsequent PG signals involved cAMP and downstream components because specific inhibitors of cAMP signal components such as adenylate cyclase (AC) and protein kinase A (PKA) significantly inhibited
Se-Duox
expression. Indeed, addition of a cAMP analogue stimulated
Se-Duox
expression in the midgut. Furthermore, individual RNAi specific to PGE
2
receptor (a trimeric G-protein subunit), AC, PKA or cAMP-responsive element-binding protein resulted in suppression of
Se-Duox
expression. These results suggest that PGs can activate midgut immunity via cAMP signalling pathway by inducing
Se-Duox
expression along with increased ROS levels.
Funder
National Research Foundation of Korea
Subject
General Biochemistry, Genetics and Molecular Biology,Immunology,General Neuroscience
Cited by
13 articles.
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