Sensing microbial infections in the Drosophila melanogaster genetic model organism

Abstract

Insects occupy a central position in the biosphere. They are able to resist infections even though they lack an adaptive immune system. Drosophila melanogaster has been used as a potent genetic model to understand innate immunity both in invertebrates and vertebrates. Its immune system includes both humoral and cellular arms. Here, we review how the distinct immune responses are triggered upon sensing infections, with an emphasis on the mechanisms that lead to systemic humoral immune responses. As in plants, the components of the cell wall of microorganisms are detected by dedicated receptors. There is also an induction of the systemic immune response upon sensing the proteolytic activities of microbial virulence factors. The antiviral response mostly relies on sensing double-stranded RNAs generated during the viral infection cycle. This event subsequently triggers either the viral short interfering RNA pathway or a cGAS-like/STING/NF-kB signaling pathway.

The Toll pathway mediates Drosophila resilience to Aspergillus mycotoxins through specific Bomanins

“…Drosophila melanogaster represents a genetically amenable model system that is well‐suited to study infections and innate immunity as there is no vertebrate‐like adaptive immunity. Its innate immune system comprises several arms: a cellular response mediated by plasmatocytes in the adult, melanization, which depends on the cleavage of pro‐phenol oxidases by Hayan, and the humoral systemic immune response (Lemaitre & Hoffmann, 2007 ; Liegeois & Ferrandon, 2022 ). A landmark study published 25 years ago established the central role of the Toll pathway in mediating the humoral immune response against fungal infections, as represented by A. fumigatus (Lemaitre et al , 1996 ).…”

Lipopolysaccharide -mediated resistance to host antimicrobial peptides and hemocyte-derived reactive-oxygen species are the major Providencia alcalifaciens virulence factors in Drosophila melanogaster

“…Forward and reverse genetics approaches identified and characterized multiple defense reactions in fruit flies that are conserved throughout evolution [ 6 , 7 ]. The immune system of fruit flies consists of both cellular immune responses, which eliminate foreign invaders via phagocytosis and encapsulation by specialized hemocytes [ 8 ], and humoral immune responses leading to the inducible production of antimicrobial peptides (AMPs) and other effector molecules [ 6 , 9 , 10 ]. Moreover, cuticle injury and recognition of microbial ligands trigger a serine protease cascade resulting in the activation of phenol oxidases and the melanisation reaction.…”

The Toll pathway mediates Drosophila resilience to Aspergillus mycotoxins through specific Bomanins

“…Drosophila melanogaster represents a genetically amenable model system that is well-suited to study infections and innate immunity as there is no vertebrate-like adaptive immunity. Its innate immune system comprises several arms, including a cellular response mediated by plasmatocytes in the adult, melanization, which depends on the cleavage of pro-phenol oxidases by Hayan, and the humoral systemic immune response (Lemaitre and Hoffmann, 2007; Liegeois and Ferrandon, 2022). A landmark study published 25 years ago established the central role of the Toll pathway in mediating the humoral immune response against fungal infections, as represented by A. fumigatus (Lemaitre et al, 1996).…”