LAUSR

BACKGROUND The molting hormone 20-hydroxyecdysone (20E) plays a key role in insect development, metamorphosis, and reproduction. Previous studies have shown that ecdysteroid metabolism is regulated by a series of CYP genes in most of the insect species. However, the roles of these CYP genes in a Coleopteran beetle, Aethina tumida (Small Hive Beetle, SHB) have not yet been explored. RESULTS In the current study, we identified seven CYP genes (six Halloween genes and one AtCYP18A1 gene) related to 20E metabolism. RT-qPCR showed that AtCYP307A1 and AtCYP307B1 were primarily expressed in the embryonic stage and in the cephalothorax of larvae. RNA interference (RNAi) screening revealed that suppression of AtCYP307A1 expression caused a lethal phenotype during the larval-pupal metamorphosis. Furthermore, hematoxylin-eosin staining of the integument showed that the RNAi of AtCYP307A1 inhibited the apolysis and degradation of the old cuticle. In addition, silencing of AtCYP307A1 resulted in significant down-regulation of 20E titers and the expression levels of 20E signaling pathway genes. Finally, the AtCYP307A1 RNAi phenotype was rescued by topical application of 20E. CONCLUSION Our studies suggest that AtCYP307A1 involved in 20E synthesis is indispensable during the larval-pupal metamorphosis of beetles, which could serve as a putative insecticide target for pest control. This article is protected by copyright. All rights reserved.