Abstract
The red flour beetle, Tribolium castaneum, is an established
genetically tractable model insect for evolutionary and developmental
studies. Therefore, it may also represent a valuable model for
comparative analysis of insect immunity. Here, we used the suppression
subtractive hybridization method to identify Tribolium genes that are
transcriptionally induced in response to injection of crude
lipopolysaccharide (LPS). Determined genes encode proteins that share
sequence similarities with counterparts from other insects known to
mediate sensing of infection (e.g. Toll and PGRP) or to represent
potential antimicrobial effectors (e.g. ferritin, c-type lysozyme,
serine proteinase inhibitors, and defensins). Especially significant is
the identification of thaumatin-like peptides, representing ancient
antifungal peptides originally reported from plants, that are absent
from the genomes of many other insects such as Drosophila, Anopheles,
and Apis. We produced recombinant thaumatin-1 in bacteria and we found
that it represents an antimicrobial peptide against filamentous fungi
in Tribolium. Additionally, septic injury induces expression of genes
involved in stress adaptation (e.g. heat-shock proteins) or insecticide
resistance (e.g. cytochrome P450s) in Tribolium, suggesting that there
may be crosstalk between the immune and stress responses. (c) 2007
Elsevier Ltd. All rights reserved.
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