A humoral immune response to parasitoid wasps inDrosophilais regulated by JAK/STAT, NF-κB and GATA

Abstract

The two arms of innate immunity consist of the cell-mediated cellular defenses and the systemic humoral immune responses.Drosophilahumoral immune defenses in the context of antimicrobial immunity, particularly the regulation and activation of antimicrobial peptide secretion from the fat body, have been studied extensively. HowDrosophilaregulates humoral immunity against another major natural enemy, the parasitoid wasp, is less well-characterized. In this study, we focused on a gene crucial in anti-parasitoid immunity,lectin-24A, which is specifically induced following parasitization. We found that a fluorescent reporter driven by the region upstream oflectin-24Ashowed localized posterior expression in the larval fat body, theDrosophilatissue mediating humoral immunity. Furthermore, with RNA sequencing of the anterior and posterior fat body sections, we found that components of JAK/STAT, GATA, and Toll pathways were regulated differentially in the anterior-posterior axis of the fat body and/or by infection. Predicted binding motifs for transcription factors in all three of these pathways were identified in the 444bp upstream region of thelectin-24Agene, where scrambling these motifs leads to reduced basal or induced expression of the fluorescent reporter. Investigating each of these pathways, we found that JAK/STAT, the GATA factor Pannier, and the NF-κB factor dorsal all modulate the expression oflectin-24A. The binding motifs associated with these transcription factors were also enriched in the upstream sequences of parasitism-induced genes in the fat body. Taken together, these results indicate that JAK/STAT, Pannier, and NF-κB signaling are involved in the regulation oflectin-24Aand, more generally,Drosophilahumoral anti-parasitoid immunity after infection.