Abstract: Insect cuticular protein plays a vital role in insect development and molting sclerosis, by combining with chitin as a barrier to the external environment. To study the function of insect cuticular protein in the rice brown planthopper, Nilaparvata lugens, the full-length of Unigene36450 predicted to code an insect cuticular protein was amplified by RT-PCR and rapid-amplification of cDNA ends according to the RNA-seq analysis of transcriptome. Then the real-time quantitative PCR and RNAi experiment was conducted to explore the expression pattern and the function of NlICP. Bioinformatics analysis showed that Unigene36450 contains a 585 bp open reading frame encoding a protein of 194 amino acid residues, with a consensus region of R&R consensus， so we named it NlICP. The transcripts of NlICP were detected only in the nymphal stage of N. lugens, and its expression reached the highest level in the 3rd instar nymph and then decreased with the nymphal development, suggesting that the coded protein of NlICP belongs to larval cuticular protein. RNAi analysis revealed that N. lugens nymph fed with dsNlICP was disturbed, and the expression levels of NlICP decreased by 58.8% and 45.6% after the continuous feeding for 6 and 8 d, respectively, significantly lower than those in the control group (P<0.01). Some nymphs died because of incomplete molting after RNAi, and the survival rate decreased by 26.7% compared to the control group after continuous feeding for 5 d. The results suggest that NlICP is associated with N. lugens nymphal ecdysis and development, and may serve as a potential target gene for controlling N. lugens.

Key words: Nilaparvata lugens, cuticular protein, gene cloning, expression pattern, RNA interference (RNAi), real-time quantitative PCR