Update information. Insects use innate immunity to defend microbial infection. Toll pathway is a major immune signaling pathway that is associated with antifungal immune response in mosquitoes. Our study identified a fungal-induced deubiquitinase, OTU7B, which, when knocked out, promotes the translocation of the NF-κB factor Rel1 into the nucleus and confers enhanced resistance to fungal infection. We further found the counterpart of OTU7B, TRAF4, which is a component of Toll pathway and acts as an adaptor protein.