Developmental expression pattern and RNA interference of the vitellogenin receptor in fire ant (Solenopsis invicta Buren) queens

The red imported fire ant, Solenopsis invicta Buren (Hymenoptera: Formicidae) is an invasive, aggressive pest with high reproductive ability. In social insects, control of reproduction is a complex and poorly understood process. The vitellogenin receptor (VgR) is responsible for the receptor-mediated endocytosis of vitellogenin (Vg) for embryonic development. Understanding VgR biology may be useful to elucidate mechanisms leading to high reproductive capacity in fire ant queens and aid in population management. An antibody specific against the fire ant VgR (SiVgR) was developed and the SiVgR expression pattern was investigated in queens. A SiVgR protein of 202 kDa was detected in both virgin (alate) and mated (dealate) queen ovaries by western blot analysis. Immunohistochemistry of SiVgR in queen ovaries showed differential receptor cellular distribution in early and late stage oocytes. The expression of VgR in virgin queen ovaries was detectable before adult eclosion; however, the VgR was localized in the oocyte membrane only after 12 days after adult eclosion. RNA interference (RNAi) of SiVgR caused silencing of the receptor in newly emerged virgin queens. These ovaries showed no egg formation demonstrating that SiVgR is involved in fire ant ovary development even in virgin queens. This is the first report on the developmental expression pattern and RNAi silencing of an Hymenopteran VgR.