Salivary proteins NlSP5 and NlSP7 are required for optimal feeding and fitness of the brown planthopper, Nilaparvata lugens.

Background: Saliva has a crucial role in determining the compatibility between piercing-sucking insects and their hosts. The brown planthopper (BPH) Nilaparvata lugens, a notorious pest of rice in East and Southeast Asia, secretes gelling and watery saliva when feeding on rice sap. Nlsalivap-5 (NlSP5) and Nlsalivap-7 (NlSP7) were identified as potential planthopper-specific gelling saliva components, but their biological functions remain unknown.
Results: Here, we showed by transcriptomic analyses that NlSP5 and NlSP7 were biasedly expressed in the salivary glands of BPHs. Using the clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9-mediated genome-editing system, we constructed NlSP5 and NlSP7 homozygous mutants (NlSP5 ^-/- and NlSP7 ^-/- ). Electrical penetration graph assay showed that NlSP5 ^-/- and NlSP7 ^-/- mutants exhibited abnormal probing and feeding behaviors. Bioassays revealed that the loss-of-function of NlSP5 and NlSP7 significantly reduced the fitness of BPHs, with extended developmental duration, shortened lifespan, reduced weight, and impaired fecundity and hatching rates.
Conclusion: These findings deepen our understanding of the BPH-host interaction and may provide potential targets for the management of rice planthoppers. © 2024 Society of Chemical Industry.
(© 2024 Society of Chemical Industry.)