A novel mode of induction of the humoral innate immune response in Drosophila larvae

Abstract

Drosophila 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.

Innate immune signaling inDrosophilashifts anabolic lipid metabolism from triglyceride storage to phospholipid synthesis in an ER stress-dependent manner

“…To test this hypothesis, we asked whether induction of Kennedy pathway enzymes occurs downstream of AMP synthesis. The Bom D55C mutation deletes a cluster of ten highly-induced genes, the bomanins, that are critical for survival during infection (Clemmons et al, 2015), and the Drs D7-17 mutation is a deletion of Drs (Kenmoku et al, 2017).…”

“…Except where noted, experiments were performed using mid-to late-third instar larvae (96-108 h after egg lay). The UAS-Toll 10b (Hu et al, 2004), UAS-Dif (Yagi and Ip, 2005), UAS-Lipin (Schmitt et al, 2015), Clemmons et al, 2015), and Drs D7-17 (Kenmoku et al, 2017).…”

The Toll Signaling Pathway Targets the Insulin-like Peptide Dilp6 to Inhibit Growth in Drosophila

“…Mid-third instar Dilp6 HF larvae were removed from bottles, rinsed in PBS and transferred to fresh food. Because injury activates innate immune signaling (Kenmoku et al, 2017;Lemaitre et al, 1997), uninfected controls were not manipulated further until sample collection. Larvae were infected with the Gram-positive bacteria Enterococcus faecalis (strain OG1RF, ATCC 47077), grown in brain heart infusion media with rifampicin, and concentrated to OD 600 10.0 in PBS, a dose shown to strongly activate Toll signaling in adult flies (Issa et al, 2018).…”

Dense time-course gene expression profiling of the Drosophila melanogaster innate immune response

“…These IM genes are located in the 55C4 region of chromosome 2R and have been recently labeled as "Bomanins" ( Clemmons et al 2015 ). CG33470 is an uncharacterized transcript located 3.3 kb downstream of IMPPP and might belong to the same open reading frame, as both are sometimes referred to as IM10 ( Kenmoku et al 2017 ), and show nearly identical gene counts in our dataset. This cluster of immune-induced molecules was characterized by an early induction (but not as immediate as the AMP cluster) of ~6 to 11 fold changes within the first two hours, reaching a max of 6 to 32 fold changes, and returning to a steady state after 3-5 days ( Figure 6B ).…”