The yolk protein precursor, vitellogenin (Vg), provides nutrition for embryonic development whereas the vitellogenin receptor (VgR) is responsible for the uptake of yolk protein by maturing oocytes. These two proteins are key reproduction-related proteins in insects. We cloned and characterized Vg and VgR genes in Sogatella furcifera, and investigated their function in oocyte maturation. Cloned SfVg and SfVgR have open reading frames of 6 114 and 5 796 bp, encoding 2 037 and 1 931 amino acid residues, respectively. Structural analysis indicates that SfVg has the three conserved LPD_N, DUF1943 and VWFD domains, SfVgR contains all conservative motifs of the LDLR superfamily. Both genes were highly expressed in adult females; SfVg was most highly expressed in the fat body whereas SfVgR was mainly expressed in the ovary. Knockdown of either gene reduced yolk protein deposition in oocytes and arrested oocyte maturation. However, silencing one of these two genes did not affect the transcript level of the other. These results demonstrate the role of SfVgR in transporting SfVg into oocytes. Both SfVg and SfVgR are essential for oocyte maturation in S. furcifera and both genes could potentially be targeted as means of controlling this pest.

Plant volatiles play an important role in regulating insect behavior. Odorant binding proteins (OBPs) are involved in the first step of the olfactory signal transduction pathway and plant volatiles recognition. Sogatella furcifera is one of the most destructive pests of rice crops. Understanding the functions of S. furcifera OBPs (SfurOBPs) in the host plant location and the behavioral responses of S. furcifera to rice plant volatiles could lead to improved, more environmentally-friendly, methods for controlling this pest. We found that SfurOBP1 displayed only weak binding with all the tested volatiles. SfurOBP2, SfurOBP3 and SfurOBP11 had different binding affinities to β-ionone. SfurOBP2 and SfurOBP11 had strong binding affinities to β-caryophyllene (K_i = 2.23 µM) and plant alcohol (K_i = 2.98 µM), respectively. The results of Y-olfactometer experiments indicate that S. furcifera was significantly repelled by octanal and n-octane but strongly attracted by (+)-limonene, acetophenone, 2-heptanone, n-hendecane, α-farnesene and β-ionone. Furthermore, the dsRNA-mediated gene silencing of SfurOBP2, SfurOBP3 and SfurOBP11 shifted the olfactory behavior of S. furcifera for β-ionone, α-farnesene and plant alcohol, respectively. These results suggest that the SfurOBPs are involved in the recognition of rice plant volatiles, and several potential repellants and lures for controlling this pest.