Oviposition fluid protein NlOFP1 in the brown planthopper suppresses rice plant defenses

Summary Insect oviposition fluid plays a role in the early recognition of plants and the initiation of plant defense responses. However, the characterization of oviposition fluid proteins and their relationship with plant defenses remains poorly understood. The oviposition fluid protein NlOFP1 in the brown planthopper ( Nilaparvata lugens ) is synthesized in the ovarian follicular cells and can be deposited into rice tissue. Functional studies reveal that NlOFP1 helps eggs resist desiccation stress. Furthermore, it can suppress plant defenses. NlOFP1 ‐silencing leads to decreased honeydew secretion, fecundity, and egg hatching rate. Orthologs of NlOFP1 in other planthopper species exhibit highly conserved functions. Transgenic rice overexpressing NlOFP1 showed reduced lignin and salicylic acid, increased cellulose, and downregulated resistance genes, indicating weakened defense responses of plants. This phenotype effectively compensated for the adaptive loss caused by NlOFP1 silencing in the brown planthopper. NlOFP1 interacted with the photosynthetic electron transport chain component OsFeS. This interaction partially impaired the import of OsFeS into the chloroplasts and might lead to a decline in plant resistance. Our study reveals that NlOFP1 acts as an effector against plant defense responses and provides insights into pest reproduction and host defense evasion.