The fungal virulence factor PefD activates sleep neurons of Caenorhabditis elegans

Nematode-trapping fungi such as Arthrobotrys flagrans employ sophisticated strategies to immobilize and digest their prey. A critical, yet poorly understood, step in this interaction is the induction of prey paralysis following capture. Here, we characterize putative effector D (PefD), a small secreted protein from A. flagrans. We demonstrate that pefD expression is specifically upregulated during the early and middle stages of infection of Caenorhabditis elegans (12–24 h post inoculation) and PefD localizes to the infection bulb within the nematode. Deletion of pefD significantly delayed the paralysis of C. elegans, whereas its overexpression accelerated the process. Through heterologous pan-neuronal expression in C. elegans, we show that PefD directly attenuates host locomotion and significantly enhances the activity of the sleep-promoting RIS interneuron. Unlike other effectors such as NipA or CyrA, PefD specifically modulates neuronal activity patterns without inducing general neurodegeneration. Our results identify PefD as a key virulence factor that hijacks the endogenous sleep induction circuitry of the host to facilitate rapid prey immobilization.