Abstract: 【Aim】To clarify the function of sulfakinin (SK) and sulfakinin receptor (SKR) in the feeding behavior of Nilaparvata lugens.【Methods】The full-length cDNA sequences of sulfakinin gene Nlsk and sulfakinin receptor gene Nlskr of N. lugens were cloned by PCR and subjected to bioinformatical analysis. The expression levels of Nlsk and Nlskr in different developmental stages (egg, 1st-5th instar nymphs, and male and female adults) and different tissues (head, antenna, wing, proboscis, leg, gut and Malpighian tubules) of the female adult of N. lugens were analyzed by qRT-PCR. The 3rd instar nymphs of N. lugens were injected with dsNlskr for gene silencing and the expression level of Nlskr in the 4th instar nymph was detected by qRT-PCR. The food intake of the 4th instar nymph after the Nlskr silencing was measured. GO and KEGG analyses of differentially expressed genes (DEGs) and qRT-PCR verification of feeding-related genes based on the previously constructed transcriptome database of the 4th instar nymphs after RNAi of Nlskr were performed. 【Results】 The full-length cDNA sequences of Nlsk (GenBank accession number: AB817281) and Nlskr (GenBank accession number: BAO01059.1) of N. lugens were cloned by PCR. Sequence alignment results showed that the NlSK mature peptide of N. lugens has a C-terminal FMRFamide polypeptide structure that is conserved with other species. NlSKR has a highly conserved transmembrane domain with homologous receptors of other insects. The results of qRT-PCR showed that Nlsk and Nlskr were highly expressed in the egg and 1st instar nymph, and mainly in the head. Nlskr was also highly expressed in the proboscis of N. lugens. Silencing Nlskr significantly increased the food intake of the 4th instar nymphs of N. lugens. Based on transcriptome data, GO and KEGG analysis result of DEGs showed that silencing of Nlskr by RNAi significantly affected the expression of the olfactory, gustation, energy metabolism, and feeding-related neuropeptides and receptor genes. The qRT-PCR verification results of feeding-related genes showed that silencing Nlskr decreased the expression levels of Nl7tmOR, NlOAR-3R, NlUH-FAF and NlTRP-161A, and increased the expression levels of NlGr64f, NlUE-E2 and NlTHR.【Conclusion】 This study reveals that sulfakinin and its receptor are involved in regulating the feeding behavior of N. lugens, providing a potential target for the development of pest insect feeding behavior inhibitors.

Key words: Nilaparvata lugens, sulfakinin, sulfakinin receptor, transcriptome, feeding behavior