Expression and Functional Analysis of Niemann-Pick Type C2 Genes in Neoseiulus californicus

Niemann-Pick type C2 protein is a newly discovered odor molecule carrier protein in arthropods and has garnered widespread attention in recent studies. However, its functions in predatory mites remain largely unexplored. In this study, we cloned the coding sequences of nine NPC2 genes from the predatory mite Neoseiulus californicus and designated them as NcNPC2-1 to NcNPC2-9. These genes encode proteins ranging from 146 to 174 amino acids in length, with molecular weights between approximately 15.6 and 19.3 kDa. All proteins possess a conserved ML lipid recognition domain, and their tertiary structures are mainly composed of β-sheets, consistent with the characteristics of the NPC2 protein family. Phylogenetic analysis indicated that these genes are closely related to the NPC2 genes of other mites and spiders. All nine genes were expressed in the olfactory-functional leg I, with NcNPC2-5, NcNPC2-6, and NcNPC2-8 showing higher expression levels in leg I. After excision of leg I or both leg I and the gnathosoma, the expression level of NcNPC2-5, NcNPC2-6, NcNPC2-7, NcNPC2-8, and NcNPC2-9 significantly decreased compared with that in leg I. Next, RNA interference experiments were performed on NcNPC2‑5, NcNPC2‑6, and NcNPC2‑8. Knockdown of NcNPC2‑6 and NcNPC2‑8 did not significantly affect the attack latency of female N. californicus towards Tetranychus urticae eggs compared with the dsGFP control but did significantly reduce their daily predation rate. In contrast, knockdown of NcNPC2‑5 significantly increased attack latency and reduced daily predation rate. Our results support that NcNPC2-5 is involved in the prey recognition and localization process of N. californicus.