Lipophorin receptor regulates Nilaparvata lugens fecundity by promoting lipid accumulation and vitellogenin biosynthesis

Insect lipophorin receptor (LpR) belongs to the low-density lipoprotein receptor (LDLR) superfamily and plays an essential role in fecundity by mediating the incorporation of lipophorin into developing oocytes. Here we report the identification and characterization of a full-length cDNA encoding a putative LpR from the brown planthopper, Nilaparvata lugens. The deduced amino acid sequence of NILpR possesses the conserved structural motifs of LDLR family members, and displays a high degree of similarity with sequences from other insect LpRs. NILpR is transcribed throughout oogenesis with its maximum level on day 7 after adult female emergence. NILpR is highly expressed in the fat body and ovary, with relative low levels in the head, epidermis and midgut. Knockdown of NILpR using double-stranded RNA (dsRNA) led to decreased triacylglycerol (TAG) content, retarded development of ovaries and decreased fecundity. Further functional analyses revealed that NILpR works through nutritional signaling pathway -dependent activation of S6 kinase to regulate vitellogenin (Vg) biosynthesis during vitellogenesis and oocyte development. Disrupting of ecdysone receptor (EcR) expression and 20-hydroxyecdysone (20E) topical application demonstrated that NILpR is regulated by ecdysone at transcript level. These results suggest that LpR is essential for Vg synthesis in the fat body and lipid uptake by developing oocytes, thus playing a critical role in insect reproduction.