Abstract
To begin studies on reproduction in common bed bug, Cimex lectularius, we identified three genes coding for vitellogenin (Vg, a protein required for the reproductive success of insects) and studied their hormonal regulation. RNA interference studied showed that expression of Vg3 gene in the adult females is a prerequisite for successful completion of embryogenesis in the eggs laid by them. Juvenile hormone (JH) receptor, Methoprene-tolerant (Met), steroid receptor coactivator (SRC) and GATAa but not ecdysone receptor (EcR) or its partner, ultraspiracle (USP) are required for expression of Vg genes. Feeding and mating working through Vg, Met, SRC, EcR, and GATAa regulate oocyte development. Knockdown of the expression of Met, SRC, EcR, USP, BR-C (Broad-Complex), TOR (target of rapamycin), and GATAa in female adults resulted in a reduction in the number eggs laid by them. Interestingly, Kruppel homolog 1 (Kr-h1) knockdown in the adult females did not reduce their fecundity but affected the development of embryos in the eggs laid by females injected with Kr-h1 double-stranded RNA. These data suggest that JH functioning through Met and SRC regulate both vitellogenesis and oogenesis in C. lectularius. However, JH does not work through Kr-h1 but may work through transcription factors not yet identified.
Highlights
The results presented here identified three Vg genes and elucidated the hormonal regulation of expression of these genes
The mRNA levels of all three Vg genes increase beginning at two days after feeding and mating
Knockdown genes coding juvenile hormones (JH) receptor Methoprene-tolerant protein (Met) and co-activator, steroid receptor co-activator (SRC) and transcription factor, GATAa reduced expression of all three Vg genes (Fig. 4), oocyte growth (Fig. 6) and a number of eggs laid by the females (Fig. 5)
Summary
The significantly lower number of eggs laid by females injected with dsVg2 and dsVg3 hatched when compared to the hatching observed in Vg1 knockdown and control insects (Fig. 2e). Feeding increased growth in the primary oocyte, to a smaller size compared to fed and mated insects (Fig. 3e). Development of primary oocyte was reduced in Vg knockdown insects (Fig. 3f).
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