Krüppel homolog 1 represses insect ecdysone biosynthesis by directly inhibiting the transcription of steroidogenic enzymes

Significance Two major endocrine hormones in insects, juvenile hormone (JH) and ecdysone, regulate developmental transitions and growth duration in an opposite manner. Deciphering the mechanisms underlying cross-talk between JH and ecdysone is key to understanding the control of insect growth and development. We show that in both Drosophila and Bombyx , JH directly acts on the prothoracic gland to induce Krüppel homolog 1 ( Kr-h1 ) expression, which in turn represses ecdysone biosynthesis by reducing the transcription of steroidogenic enzymes. This transcriptional repression is mediated by direct binding of Kr-h1 to target gene-promoter regions, inducing epigenetic promoter DNA methylation. Our findings provide insights into the direct repression of ecdysone biosynthesis by Kr-h1–mediated JH signaling in insect prothoracic gland.