Abstract
ABSTRACTDrosophila adults have been utilized as a genetically tractable model organism to decipher the molecular mechanisms of humoral innate immune responses. In an effort to promote the utility of Drosophila larvae as an additional model system, in this study, we describe a novel aspect of an induction mechanism for innate immunity in these larvae. By using a fine tungsten needle created for manipulating semi-conductor devices, larvae were subjected to septic injury. However, although Toll pathway mutants were susceptible to infection with Gram-positive bacteria as had been shown for Drosophila adults, microbe clearance was not affected in the mutants. In addition, Drosophila larvae were found to be sensitive to mechanical stimuli with respect to the activation of a sterile humoral response. In particular, pinching with forceps to a degree that might cause minor damage to larval tissues could induce the expression of the antifungal peptide gene Drosomycin; notably, this induction was partially independent of the Toll and immune deficiency pathways. We therefore propose that Drosophila larvae might serve as a useful model to analyze the infectious and non-infectious inflammation that underlies various inflammatory diseases such as ischemia, atherosclerosis and cancer.
Highlights
Drosophila adults have been used as a leading model organism to investigate molecular mechanisms of innate immunity (Lemaitre and Hoffmann, 2007; Buchon et al, 2014) since it was first demonstrated in 1996 that the Toll pathway, which was initially characterized as an essential pathway for dorsoventral patterning in Drosophila embryos (Anderson et al, 1985a,b), was required for the induction of the antifungal peptide gene Drosomycin (Drs) upon fungal infection (Lemaitre et al, 1996)
By pricking larvae with a needle dipped into a pellet of Gram-positive bacteria Staphylococcus saprophyticus, we found that Toll pathway mutants were susceptible to the infection (Fig. 1B), the number of bacteria in the infected whole mutant larvae after any time point was similar to that in the wild type (Fig. 1C)
These results suggest that the Toll pathway is dispensable for bacterial clearance in larvae, showing a sharp contrast to the results from Drosophila adults in which the Toll pathway is required for the removal of bacteria upon Gram-positive bacterial challenge
Summary
Drosophila adults have been used as a leading model organism to investigate molecular mechanisms of innate immunity (Lemaitre and Hoffmann, 2007; Buchon et al, 2014) since it was first demonstrated in 1996 that the Toll pathway, which was initially characterized as an essential pathway for dorsoventral patterning in Drosophila embryos (Anderson et al, 1985a,b), was required for the induction of the antifungal peptide gene Drosomycin (Drs) upon fungal infection (Lemaitre et al, 1996). The IMD pathway recognizes diaminopimelic acid-type peptidoglycans derived from Gramnegative bacteria via peptidoglycan recognition protein (PGRP)-LC and PGRP-LE (Kleino and Silverman, 2014). These receptors facilitate downstream signaling via the adaptor protein IMD, activate the NF-κB protein Relish, and induce the expression of antimicrobial peptides such as Diptericin (Dpt) (Paquette et al, 2010). These pathways are essentially characterized in Drosophila adults
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
