Abstract: 【Aim】The apolipoprotein (apoLp) plays an important role in achieving the physiological functions in animals, but how it affects the growth and development of rice planthoppers remains unknown. Our study aims at investigating the role of apoLp in the feeding, survival and reproduction of Nilaparvata lugens. 【Methods】The full-length open reading frame (ORF) sequence of NlapoLp was obtained based on the genome from N. lugens, and its protein sequence was analyzed. The cluster analysis between NlapoLp and homologous sequences from other insect species was conducted using neighbor-joining method. The expression levels of NlapoLp in different developmental stages (egg, 1st-5th instar nymphs, and newly emerged short-winged female and male adults), and different tissues (head without salivary gland, salivary gland, midgut, fat body and ovary) of the short-winged female adults were analyzed using RT-qPCR. After RNAi by microinjection of dsNlapoLp into the 3rd instar nymphs of N. lugens, the expression level of NlapoLp was determined using RT-qPCR. Then the amount of honeydew secreted per female adult, nymphal survival rate and number of eggs laid per female adult of N. lugens on host rice were investigated after RNAi on insects at different developmental stages. 【Results】 Analysis of sequence features revealed that NlapoLp contains one signal peptide and five conserved domains, but has no transmembrane domain. The phylogenetic tree showed that the apoLp orthologs NlapoLp of N. lugens, LsapoLp of Laodelphax striatellus and SfapoLp of Sogatella furcifera shared the closest evolutionary relationships. Additionally, these orthologs also gathered with the apoLps of three other hemiopteran insects (Macrosteles quadrilineatus, Bemisia tabaci and Halyomorpha halys), indicating close relationships among them. RT-qPCR results showed that NlapoLp was expressed in N. lugens at various developmental stages and highly expressed in short-winged female adults. NlapoLp was highly expressed in the midgut, fat body and salivary gland of the short-winged female adults and lowly expressed in other tissues. Microinjection of dsNlapoLp into N. lugens significantly decreased the expression of NlapoLp. After RNAi, the amount of honeydew secreted per female adult, nymphal survival rate and number of eggs laid per female adult of N. lugens on host rice were significantly decreased as compared with those in the control group (dsGFP injection). 【Conclusion】 The apolipoprotein gene NlapoLp is expressed in various developmental stages and tissues of the short-winged female adults of N. lugens, and silencing NlapoLp via RNAi significantly affects the feeding, growth and development, and reproduction of N. lugens. These results lay the foundation for deeply exploring the mechanism of apolipoprotein in rice damage caused by insects, and provide key target for pest effective control.

Key words: Nilaparvata lugens, apolipoprotein, spatiotemporal expression, RNA interference, bioassay