Kr-h1 Encoding Juvenile Hormone Transcription Factor Impacts Reproductive Functions in Coccinella septempunctata

The gene encoding juvenile hormone transcription factor Krüppel homolog 1 (Kr-h1) was studied for its effects on ovary development and reproduction in the ladybug beetle, Coccinella septempunctata. Kr-h1 expression in C. septempunctata was evaluated in females supplied with a juvenile hormone (JH) amended diet using quantitative PCR, and the function of Kr-h1 in female reproduction was assessed using RNAi technology. Expression of Kr-h1 in females supplied with a JH diet was significantly higher at 5 and 10 d than in females not supplied with JH. At 5 and 10 d post-injection with Kr-h1-dsRNA, Kr-h1 expression levels were 30.97% and 38.32% lower, respectively, than expression in controls injected with GFP-dsRNA. Development of ovaries and vitellogenesis in ladybugs microinjected with Kr-h1-dsRNA was significantly delayed in comparison to controls. At 20 d post-injection, mean egg production decreased by 28.74% relative to controls. These results prove that Kr-h1 has a vital role in modulating ladybug fecundity by impacting ovary development and egg production.