Niemann–Pick type C2 Proteins Mediate the Perception of Herbivore-Induced Plant Volatiles in the Predatory Mite Neoseiulus californicus

The citrus crop is severely damaged by the citrus red mite, Panonychus citri. The predatory mite Neoseiulus californicus is an effective natural enemy used for its biocontrol. To enhance predator efficiency, this study investigated the role of odorant-binding proteins in recognizing herbivore-induced plant volatiles (HIPVs). We identified two Niemann-Pick type C2 genes, NcNPC2-a and NcNPC2-b, which were highly expressed in adult females, particularly in the legs. RNAi-mediated silencing of NcNPC 2s impaired the mite's ability to locate HIPVs. Fluorescence binding assays and molecular docking confirmed that NcNPC2 proteins strongly bind undecylcyclohexane. Field trials using slow-release dispensers showed that HIPVs attracted predatory mites effectively within 2 m. These findings reveal that NcNPC2 proteins mediate the perception of HIPVs in N. californicus, providing insights for developing attractants to enhance biocontrol efficacy.