The salivary protein NlG8 from Nilaparvata lugens induces both direct and indirect resistance in host rice plants

During feeding, piercing-sucking herbivores inject salivary proteins into the plant, but their roles in modulating direct and indirect plant defenses remain poorly understood. Utilizing an integrated approach that combines transcriptomics, immunoassays, genetic transformation, GC-MS analysis, and bioassays, we identified a novel salivary protein that elicits defense responses in rice. Here, we report a salivary protein, NlG8, from the brown planthopper (BPH), a major piercing-sucking pest of rice. NlG8 localizes to the accessory glands of salivary glands and is secreted into rice plants during feeding as a component of the salivary sheath. Knocking down NlG8 impaired BPH performance and reduced induced plant defenses. Conversely, transgenic rice overexpressing NlG8 enhanced direct defense by upregulating phenylalanine pathway genes. Additionally, NlG8 overexpression induced eight volatiles, including (Z)-3-hexen-1-ol, methyl salicylate, and nonanal, which attracted the natural enemy Tytthus chinensis. These findings reveal that the BPH salivary protein NlG8 not only induces direct rice defenses but also promotes indirect defense by enhancing volatile emissions to recruit natural enemies. Our findings provide new insights into tritrophic interactions and their underlying mechanism, offering valuable genetic and chemical resources for the development of pest control strategies.