The Drosophila systemic immune response: sensing and signalling during bacterial and fungal infections

Abstract

A hallmark of the potent, multifaceted antimicrobial defence of Drosophila melanogaster is the challenge-induced synthesis of several families of antimicrobial peptides by cells in the fat body. The basic mechanisms of recognition of various types of microbial infections by the adult fly are now understood, often in great detail. We have further gained valuable insight into the infection-induced gene reprogramming by nuclear factor-kappaB (NF-kappaB) family members under the dependence of complex intracellular signalling cascades. The striking parallels between the adult fly response and mammalian innate immune defences described below point to a common ancestry and validate the relevance of the fly defence as a paradigm for innate immunity.

Toll signal transduction pathway in bivalves: Complete cds of intermediate elements and related gene transcription levels in hemocytes of immune stimulated Mytilus galloprovincialis

“…Transcription levels measured in bivalve hemocytes following the single in vivo injection with different bacteria and PAMPs, and resulting from bibliographic analysis, are summarized in Table 5. Few studies are available, with the majority of the challenges involving Gram-negative bacteria or LPS, a fact which might sound surprising as the Toll pathway is reported to be triggered by Gram-positive bacteria in invertebrates (Ferrandon et al, 2007(Ferrandon et al, , 2004. But infections in marine animals have been mainly associated with Gramnegative bacteria, mostly Vibrios, a reason to analyze defense mechanisms towards such bacteria.…”

“…By contrast, the IMD pathway is similar to the tumor-necrosis-factor (TNF) receptor pathway of mammals (Ferrandon et al, 2007;Hoffmann, 2003). After AMPs were discovered in bivalves (reviewed by , regulation of their transcription levels in response to experimental immune stimulation was reported in the Mediterranean mussel, Mytilus galloprovincialis (Mitta et al, 1999a(Mitta et al, ,b, 2000bSonthi et al, 2012;Venier et al, 2011), the deep-sea hydrothermal vent mussel, Bathymodiolus azoricus (Bettencourt et al, 2007), the Pacific oyster, Crassostrea gigas (Gonzalez et al, 2007;Gueguen et al, 2006;Schmitt et al, 2012), the carpet-shell clam, Ruditapes decussatus (Gestal et al, 2007), the hard clam, Mercenaria mercenaria (Perrigault et al, 2009), the triangle-shell pearl mussel, Hyriopsis cumingii (Ren et al, 2011) and the blue mussel, Mytilus edulis (Tanguy et al, 2013).…”

Endogenous egg immune defenses in the yellow mealworm beetle (Tenebrio molitor)

“…However, due to the high expression of the NF-kappa-B factor dorsal, which is well known for its role in immune gene induction (Ferrandon et al, 2007), Chen et al proposed that the serosa might also protect against infection (Chen et al, 2000). Indeed, immune gene expression was shown to be restricted to the extraembryonic regions of the egg in Manduca sexta (Gorman et al, 2004).…”

Innate immune response in insects: recognition of bacterial peptidoglycan and amplification of its recognition signal

“…In Drosophila, the Toll signalling pathway is responsible for defense against Gram-positive bacteria and fungi, while the immune deficiency (Imd) pathway is activated primarily to defend against Gram-negative bacteria. Both of these pathways use NF-κB-like transcription factors for the induction of the expression of antimicrobial peptides (5,(9)(10)(11)(12).…”

“…Three essential, upstream protein components involved in Lys-type PG recognition have been obtained from a large insect, T. molitor larvae Even though Drosophila genetic studies are very powerful for characterizing and ordering the components in the Toll pathway (5,34), the system is limited in its ability to reveal the biochemical mechanisms that regulate this proteolytic cascade. Drosophila uses several alternative routes to the Toll pathway during various developmental stages and under different infection protocols, and it seems difficult to determine the clear activation mechanism of Toll pathway.…”