IR25a-like Receptors are Required for Olfactory Detection of Plant Volatiles in the Carmine Spider Mite

Phytophagous mites are known to possess olfactory sensitivity, enabling them to detect plant volatiles. Unlike insects, which detect plant volatiles primarily via odorant receptors (ORs), Tetranychus cinnabarinus , a highly destructive phytophagous species, lacks ORs and ionotropic receptors (IRs); it may rely on its retained ionotropic co-receptor (IR25a-like) genes for olfactory detection. Whether these IR25a-like receptor mediate plant volatile perception in this species remains unknown. Here, we cloned three IR25a-like genes— TcinIR25a-1 , TcinIR25a-2 , and TcinIR25a-3 —and found that their expression was modulated by exposure to plant volatiles. RNA interference (RNAi) of TcinIR25a-1 or TcinIR25a-2 significantly altered female behavioral responses in Y-tube olfactometer assays, indicating their involvement in detecting plant volatiles. This study demonstrates for the first time that IR25a-like genes mediate plant volatile detection in T. cinnabarinus , offering new insights into mite olfactory mechanisms and potential molecular targets for behavior-based pest management.