Juvenile Hormone and Ecdysteroids Facilitate the Adult Reproduction Through the Methoprene-Tolerant Gene and Ecdysone Receptor Gene in the Female Spodoptera frugiperda

Insects, as the most diverse and numerous group in the animal kingdom, are at least partly dependent on the reproduction process, which is strictly regulated by the 'classic' insect hormones: juvenile hormone (JH), and 20-hydroxyecdysone (20E). However, the regulatory mechanism governing the reproduction of JH and 20E in <i>Spodoptera frugiperda</i> remains unclear. In this study, ovarian development and ovulation in female <i>S. frugiperda</i> were assessed through dissection of the ovaries following treatment with JH analog (JHA) and 20E. Moreover, the expression patterns of the JH-signal and 20E-signal-related genes were determined by quantitative PCR (qPCR), and RNA interference (RNAi) was used to investigate the role of JH and 20E-induced genes. Ovarian development was observed by microdissection, and JH and 20E titers were determined by ELISA. <i>Kr-h1</i>, <i>Vg</i>, and <i>USP</i> expression were determined by qPCR. Dissection and qPCR results showed that JHA and 20E promoted ovarian development, egg maturation, and egg laying by upregulating <i>Methoprene-Tolerant</i> (<i>Met</i>) and <i>Ecdysone Receptor</i> (<i>EcR</i>)expression. Additionally, the RNAi results showed that the injection of ds<i>Met</i> and ds<i>EcR</i> markedly delayed ovarian development, inhibited egg maturation, and halted egg production. Knockdown of <i>Met</i> and <i>EcR</i> significantly reduced JH and 20E content and inhibited the transcription of <i>Kr-h1</i> and <i>USP</i>. These results indicate that JH and 20E facilitate adult reproduction through the methoprene-tolerant gene and ecdysone receptor gene in female <i>S. frugiperda.</i>