Molecular Cloning And Functional Study Of HR2 And HR38 From Nilapparvata Lugens

The brown planthopper(Nilaparvata lugens St(?)l)is a major migratory pest of rice in East and Southeast Asia.Brown planthopper is rice specific insect pest,and its fecundity is strong and its damage is rampant,which seriously threatens rice production.Therefore,it is necessary to investigate the development and reproduction of N.lugens.Hormone receptors are important genes that regulate and affect insect development and reproduction.Therefore,this study focused on the hormone receptor genes HR2(steroid hormone receptor 2)and HR38(hormone receptor 38)genes of N.lugens.So far,little is known about insect HR2,but it may have similar functions with mammalian homologous genes.The HR38(NlHR38)gene is a member of the hormone receptor superfamily.HR38 regulates metamorphosis,stem cell development,ovarian development.It also has implications for normal egg production and maternal regulation of early embryogenesis.Both NlHR2 and NlHR38 are hormone receptors that regulate insect development and reproduction.In this study,the sequence information of brown planthopper HR2(NlHR2)and HR38(NlHR38)was first obtained by NCBI search,and then the full-length genes of NlHR2 and NlHR38 were cloned.The highly conserved DBD(DNA Binding Domain)and LBD domains(Ligand Binding Domain)in hormone receptors was found.At the same time,a phylogenetic tree was also constructed and phylogenetic analysis was carried out.The results showed that the HR2 of the brown planthopper and the whitefly(Bemisia tabaci)had high homology,while the brown planthopper HR38 shared high conservative with the grass-winged leafhopper(Homalodisca vitripennis).qRT-PCR showed the spatial and temporal expression characteristics of NlHR2 and NlHR38,and found that the expression levels were relatively high in the early stage of N.lugens nymphs.Juvenile hormone(JHIII)and ecdysone(20E)treatment showed that the expression of these two genes had a certain response to hormones.In the RNAi interference experiment,it was found that the expression of NlHR2 and NlHR38 in the third,fourth and fifth instar N.lugens nymphs was down-regulated individually or simultaneously,and the proportion of nymph molting failure and eclosion failure was significantly higher,and the eclosion rate decreased.After down-regulating the expression of NlHR2 and NlHR38 alone or simultaneously,the ovarian development of N.lugens obviously delayed,the egg production decreased,and the expressions of vitellogenin genes Vg and Vg-like1 and Vg-like2 also decreased significantly.In addition,qRT-PCR detection showed that the expression of some DNA replication and cell cycle-related genes was also significantly affected after down-regulating the expression of NlHR2 and NlHR38 alone or simultaneously.Flow cytometry results showed that down-regulation of NlHR2 and NlHR38 expression alone or simultaneously could significantly affect the cell cycle of N.lugens ovary,thereby affecting the development and oviposition of the ovary.After RNAi interference down-regulated NlHR2 and NlHR38,the samples were analyzed for transcriptome data and verified by qRT-PCR.It was found that the expression of cuticular protein genes was greatly affected.The results of this study show that NlHR2 and NlHR38 genes interact with juvenile and ecdysone signaling pathways,and the results have theoretical and practical significance for the discovery of targets that can be used to develop new pesticides for pest control.