The transcription factor RUNT-like regulates pupal cuticle development via promoting a pupal cuticle protein transcription

Holometabolous insects undergo morphological remodeling from larvae to pupae and to adults with typical changes in the cuticle; however, the mechanism is unclear. Using the lepidopteran agricultural insect Helicoverpa armigera, cotton bollworm, as a model, we revealed that the transcription factor RUNT-like (encoded by Runt-like) regulates the development of the pupal cuticle via promoting a pupal cuticle protein gene (HaPcp) expression. The HaPcp was highly expressed in the epidermis and wing during metamorphosis and was found being involved in pupal cuticle development by RNA interference (RNAi) analysis in larvae. Runt-like was also strongly upregulated in the epidermis and wing during metamorphosis. Knockdown of Runt-like produced similar phenomena, a failure of abdomen yellow envelope and wing formation, to those following HaPcp knockdown. The insect molting hormone 20-hydroxyecdysonen (20E) upregulated HaPcp transcription via RUNT-like. 20E upregulated Runt-like transcription via nuclear receptor EcR and the transcription factor FOXO. Together, RUNT-like and HaPCP are involved in pupal cuticle development during metamorphosis under 20E regulation. Holometabolous insects develop pupal cuticle during metamorphosis; however, the mechanism is unclear. Using the lepidopteran agricultural insect Helicoverpa armigera, cotton bollworm, as a model, we revealed that the transcription factor RUNT-like regulates a pupal cuticle protein gene, HaPcp, expression therefore regulates the development of the pupal cuticle under insect molting hormone 20-hydroxyecdysonen (20E) regulation. HaPcp is an insect specific gene without homologue in humans, and the insect Runt-like is different from vertebrate, too. This work deeply addresses the mechanism that 20E regulates development of insect pupal cuticle and presents new gene targets to explore the new growth regulators to control the pest.