Structural characterization and proteomic profiling of oviposition secretions across three rice planthopper species

Insect oviposition secretions play crucial roles during the reproductive process, yet systematic studies on their structural characterization and protein compositions remain limited. This study investigated the oviposition secretions of three major rice pests: the brown planthopper (Nilaparvata lugens, BPH), small brown planthopper (Laodelphax striatella, SBPH), and white-backed planthopper (Sogatella furcifera, WBPH). Ultrastructural observation revealed differences in the oviposition secretions of them. The eggs of BPH and SBPH were adhered to rice tissue by abundant secretions, while WBPH eggs were embedded deeper within the leaf sheath with less secretions. Proteomic analysis identified 111, 98, and 66 oviposition secretion proteins (OSPs) in BPH, SBPH, and WBPH, respectively. 4 common protein subgroups were shared among them, along with varying numbers of shared subgroups between species pairs. Notably, the majority of OSPs were exclusively found in one species, indicating the existence of both similar and specialized functions unique to each planthopper species. The functions of 4 uncharacterized OSPs (Nl.chr07.0363, Nl.chr12.078, Nl.chr11.716, Nl.scaffold.0714) that were uniquely identified in the BPH were studied by maternal RNAi. Downregulation of each of these 4 protein-coding genes led to a significant decrease in egg production and hatchability. Moreover, knockdown of Nl.chr12.078 or Nl.chr07.0363 also disrupt the secretory function of the lateral oviduct. In conclusion, this study provides insights into the structural characteristics and protein components of the oviposition secretions of BPH, SBPH, and WBPH, which could serve as potential targets for RNAi-based pest control and lay a foundation for future studies on insect-plant interactions mediated by oviposition secretions.