Effects of the Ecdysone Receptor on the Regulation of Reproduction in Coccinella septempunctata

The effects of the gene encoding the ecdysone receptor (<i>EcR</i>) on the reproduction of the ladybug <i>Coccinella septempunctata</i> was evaluated. <i>EcR</i> transcription was measured by quantitative real-time PCR in ladybug adults reared on artificial diets with and without 20-hydroxyecdysone (20E). <i>EcR</i> expression levels in 5 d old male and female ladybugs supplied with the 20E-amended artificial diet were lower than expression levels in ladybugs reared on an artificial diet lacking 20E. However, <i>EcR</i> expression levels in 10 d old ladybugs supplied with the 20E artificial diet were higher than those lacking 20E supplementation. The regulatory effects of <i>EcR</i> were studied in female and male ladybugs by RNA interference. <i>EcR</i> expression in female ladybugs injected with <i>EcR</i>-dsRNA was significantly downregulated after 5 d but remained unaffected in 10 d old females. <i>EcR</i> expression levels in males microinjected with <i>EcR</i>-dsRNA were significantly lower at 5 and 10 d after microinjection than <i>GFP</i>-dsRNA-treated males. The ovary volume in females injected with <i>EcR</i>-dsRNA at 5 d was smaller than females microinjected with <i>GFP</i>-dsRNA, but volumes at 10 d were larger than in <i>GFP</i>-dsRNA-treated females. The testes of males injected with <i>EcR</i>-dsRNA were larger than those injected with <i>GFP</i>-dsRNA at 5 d but the testes at 10 d after injection with <i>EcR</i>-dsRNA were smaller than those injected with <i>GFP</i>-dsRNA. When females were microinjected with <i>EcR</i>-dsRNA and mated with noninjected males, egg production decreased by 34.80% for 20 days. When males were microinjected with <i>EcR</i>-dsRNA and mated with noninjected females, egg production decreased by 30.38% for 20 days. Injection of female and male ladybugs with <i>EcR</i>-dsRNA had no significant effect on egg hatching rates. Our results show that <i>EcR</i> plays an important role in the development of reproductive organs and egg development in <i>C. septempunctata</i>.