The modulation effect of the Steinernema carpocapsae- Xenorhabdus nematophila complex on immune-related genes in Drosophila suzukii larvae

Larvae of the invasive pest Drosophila suzukii are susceptible to the Steinernema carpocapsae - Xenorhabdus nematophila complex and an assessment of the immune-regulatory system activation in this insect was performed to understand the response to the nematode infection. The expressions of 14 immune-related genes of different pathways (Imd, Toll, Jak-STAT, ProPO, JNK, TGF-beta) were analyzed using qRT-PCR to determine variations after nematode penetration (90 min and 4 h) and after bacterial release (14 h). Before the bacteria were present, the nematodes were not recognized by the immune system of the larvae and practically none of the analyzed pathways presented variations when compared with the non-infected larvae. However, after the X. nematophila were released, PGRP-LC was activated leading to the gene upregulation of antimicrobial peptides of both the Toll and Imd pathways. Interestingly, the cellular response was inactive during the infection course as Jak/STAT and pro-phenoloxidase genes remained unresponsive to the presence of both pathogens. These results illustrate how D. suzukii immune pathways responded differently to the nematode and bacteria along the infection course.

Automated summary

An assessment of the immune-regulatory system activation in the invasive pest Drosophila suzukii was performed after infection with the Steinernema carpocapsae - Xenorhabdus nematophila complex. The expressions of 14 immune-related genes were analyzed to understand the response to the nematode infection. The study found that the immune system of the larvae did not recognize the nematodes until the release of X. nematophila, which resulted in the activation of PGRP-LC and upregulation of antimicrobial peptides.