Rnai-mediated knockdown of nuclear receptors impairs cuticle formation by disrupting chitin metabolic pathway in Holotrichia oblita.

Nuclear receptors (NRs) are ligand-regulated transcription factors that play crucial roles in insect growth and development. However, their functions in Holotrichia oblita Faldermann remain uncharacterized. In this study, we identified and characterized three HoNRs from H. oblita. Spatiotemporal expression analysis revealed that all three HoNRs were predominantly expressed in eggs and first-instar larvae. Tissue localization showed high expression in the epidermis, fat body, and rectum. RNA interference (RNAi) experiments demonstrated that silencing these HoNRs reduced larval feeding, impaired molting, and resulted in a 37-50 % weight inhibition rate and a 73-93 % mortality rate. Hematoxylin-eosin staining showed that knockdown of HoHR3, HoE75, and HoEcR led to the formation of a thinner cuticle compared to controls, accompanied by a 46-48 % reduction in chitin content and downregulation of chitin metabolic Pathway genes. Additionally, the expression of these HoNRs was influenced by 20E at different time points. Therefore, these findings demonstrate that these three HoNRs are essential for normal molting in H. oblita through chitin metabolic pathway regulation.