Omics Analysis of Odorant-Binding Proteins and Cuticle-Enriched <i>SfruOBP18</i> Confers Multi-Insecticide Tolerance in <i>Spodoptera frugiperda</i>

<i>Spodoptera frugiperda</i> is a notorious pest that develops a high resistance to many insecticides. Recently, insect odorant-binding proteins (OBPs) have been proven to participate in insecticide resistance. However, the functional evidence supporting the cross-link between OBPs and insecticide resistance remains unexplored. Here, we identified 50 SfruOBPs from the larval transcriptome and genome. Notably, <i>SfruOBP18</i> was highly expressed in the larval cuticle and could be induced to upregulate its expression by multi-insecticides. Ligand-binding assays revealed that <i>SfruOBP18</i> bound strongly with four insecticides; RNAi and insecticide bioassay demonstrated that the knockdown of <i>SfruOBP18</i> did not affect larval survival and development. However, it can significantly increase the larval susceptibility to multi-insecticides, suggesting an uncommon role of <i>SfruOBP18</i> in multi-insecticide susceptibility. Our study provides a comprehensive understanding of SfruOBPs and furthermore proves that a larval cuticle-enriched OBP can bind with and confer larval tolerance to multi-insecticides. <i>SfruOBP18</i> could be a new insecticidal target for controlling Lepidoptera pests.