Receptors that transport vitellogenin into oocytes are of vital importance to egg-laying species because they promote oocyte development. In this study, we describe the cloning of the first hymenopteran vitellogenin receptor (VgR) cDNA. Using reverse transcription polymerase chain reaction and 5’ rapid amplification of cDNA ends, cDNA fragments encompassing the entire coding region of a putative VgR from fire ant (=SiVgR) were cloned and sequenced. The deduced amino acid sequence of the SiVgR revealed that it encoded a protein belonging to the low-density lipoprotein receptor superfamily. The number and arrangement of modular domains of SiVgR are the same as those of mosquito and fruit fly VgRs, except there are only four Class A cysteine-rich repeats in the first ligand binding domain of SiVgR compared to five in the mosquito and fruit fly. The deduced amino acid sequence of the SiVgR exhibited 38% and 32% identity to those of the mosquito and fruit fly VgRs, respectively. Northern blot analysis demonstrated that the 7.5-kb SiVgR mRNA was present only in ovaries of reproductive females - both alates (virgins) and queens (mated) and was more abundant in alates. The developmental profile of transcriptional expression was determined by semiquantitative RT-PCR. It showed that SiVgR transcriptional expression increased with age in alate females. The transcriptional expression of SiVgR was up-regulated more than doubleness by methoprene, a juvenile hormone (JH) analog, using an in vitro system. This suggested SiVgR transcription is JH regulated.
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