Insect immunity: A genetic factor (hrtp) is essential for antibacterial peptide expression inDrosophila after infection by parasitoid wasps

Abstract

We have used a parasitoid wasp Drosophila melanogaster system to investigate the relationship between the humoral and cellular immune responses in insects. Expression of the gene encoding diptericin, an antibacterial peptide in various D. melanogaster strains parasitized by several species of parasitoid wasps, was studied by Northern blot. These strains have the capacity to encapsulate parasitoid eggs. Two strains appeared to produce diptericin mRNA after parasitoid challenge, regardless of their cellular immune reaction to the wasp species. This suggests that a specific genetic factor, or factors, here designated humoral response to parasitoid (hrtp), is present in these two strains of D. melanogaster and is implicated in the expression of the antibacterial gene after parasite infection. This hrtp genetic factor is recessively expressed and located on the second chromosome, suggesting that it is monofactorial. The transgenic strain Dipt.2.2‐lacZ:1, in which the transgene is present on the first chromosome, is normally susceptible to the parasitoid wasp. The chromosome bearing the hrtp factor was transferred to this transgenic strain, which then became reactive when triggered by wasp infection. The hrtp factor appears necessary for the activation of diptericin by the parasitoid wasp. No correlation between the cellular immune capacity and the humoral response was observed, suggesting that the two components of insect immunity are regulated independently. Arch. Insect Biochem. Physiol. 43:64–71, 2000. © 2000 Wiley‐Liss, Inc.

Cellular and humoral immune interactions betweenDrosophilaand its parasitoids

“…By using fly mutants defective in Toll and Imd signaling, the authors discovered that some immune genes were not affected and inferred that other unidentified signaling pathways were activated by infection (Gregorio, 2002). Another genetic factor, humoral response to parasitoid ( hrtp ), which is strongly induced by wasp parasitism, was identified in Drosophila (Benassi et al ., 2000). Hrtp contributes to the production of the AMP, diptericin, which the authors inferred was associated with the encapsulation of parasitoid eggs (Benassi et al ., 2000).…”

“…Another genetic factor, humoral response to parasitoid ( hrtp ), which is strongly induced by wasp parasitism, was identified in Drosophila (Benassi et al ., 2000). Hrtp contributes to the production of the AMP, diptericin, which the authors inferred was associated with the encapsulation of parasitoid eggs (Benassi et al ., 2000).…”

Insect immune resistance to parasitoids

“…Interestingly, the response might also depend on whether a genetic factor, called hrtp, is present. This factor has been described in some but not all D. melanogaster host strains and has been localized on the second chromosome (Benassi et al, 2000). It could be part of one of the host pathways involved in response to parasitism.…”

Genes identified by an expression screen of the vector mosquito Anopheles gambiae display differential molecular immune response to malaria parasites and bacteria

“…Fungi and bacteria induce distinct immune signaling pathways in Drosophila and cause differential transcriptional responses of antimicrobial peptides (20,21). Drosophila immune gene expression in response to protozoan or other eukaryotic pathogens has not been examined in detail, although genetic studies identified a locus that seems to control response to parasitoid wasp eggs independently of the antibacterial response (22).…”