| Popis: |
Innate immune responses depend on the action of multiple conserved signaling pathways. Pathways important for activation of humoral immune responses following microbial infection are well-characterized in the genetic model species Drosophila melanogaster, but our understanding of fly cellular immunity, and how parasites suppress it, is relatively fragmentary. Fly larvae mount a coordinated cellular immune response following infection by endoparasitoid wasps, characterized by the production of specialized blood cells called lamellocytes that form a tight capsule around wasp eggs in their hemolymph. The conserved JAK/Stat signaling pathway has been implicated in lamellocyte proliferation and is required for successful encapsulation of wasp eggs. Here we show that activity of Stat92E, the D. melanogaster Stat ortholog, is induced in the fat body and hemocytes following wasp infection. Virulent wasp species are able to suppress activation of a Stat92E activity reporter during infection, suggesting they target upstream activation of this pathway as part of their virulence strategies. Furthermore, two wasp species (Leptopilina guineaensis and Ganaspis xanthopoda) suppress phenotypes associated with gain-of-function mutations in hopscotch, the D. melanogaster JAK ortholog, showing that they inhibit JAK/Stat activity downstream of JAK. Our data demonstrate that endoparasitoid wasp virulence factors block JAK/Stat signaling to overcome fly immune defenses. |
