Spatiotemporal compartmentalization of NADPH oxidase signaling coordinates cell fusion and predatory behavior in nematode-trapping fungi

Reactive oxygen species (ROS) act both as cytotoxic agents and essential signaling molecules. In the nematode-trapping fungus Arthrobotrys flagrans, we investigated how ROS coordinate the development and function of adhesive trapping networks used to capture Caenorhabditis elegans. We demonstrate a distinct functional specialization between the two NADPH oxidases NoxA and NoxB, which are both activated by the regulatory subunit NoxR. The NoxB-NoxR complex was specifically active in trap cells, where it was required for producing the adhesive “glue” for prey capture. In contrast, NoxA localized to the plasma membrane of vegetative hyphae and was required for hyphal fusion and trap closure. NoxA was activated by the pulsatile recruitment of NoxR to the hyphal tip, suggesting oscillatory ROS production during hyphal expansion and hyphal fusion. Nox complexes initially generate superoxide, which is probably converted to more stable hydrogen peroxide (H₂O₂) and serves as a key spatial signal. Together, these findings reveal a remarkable division of labor between Nox isoforms, where spatial compartmentalization of ROS signaling drives fungal morphogenesis and predatory behavior.