Functional characterization of the ecdysone receptor (EcR) in egg diapause termination and embryonic development in...

Calliptamus italicus is a dominant pest in the grasslands of Xinjiang and overwinters as diapausing eggs. Ecdysone (Ecd) is a key hormone for diapause termination in C. italicus eggs, but the function of its receptor EcR in this process remains largely unexplored. Here, whole-mount in situ hybridization (WISH) and RNA interference (RNAi) were used to characterize its function.

WISH revealed that EcR was stably expressed in the mandibles, maxillae, thorax and legs from embryonic Stage II and subsequently expanded to the prothoracic glands, compound eyes, wings, ventral nerve cord and leg segments, with signals localized in the epidermis. RNAi-mediated silencing [2 μg μL^-1 dsEcR; 71.3% efficiency at 48 h post-treatment (hpt)] resulted in disappearance of EcR signals from prothoracic glands and ventral nerve cord, and reduced signals in appendages. At the transcriptional level, silencing of EcR significantly reduced the expression of downstream genes E75 (88.2% at 12 hpt), FTZ-F1 (72.4% at 48 hpt) and Vg (75.6% at 48 hpt). By contrast, HR3 expression was significantly increased at 24-48 hpt. Phenotypically, EcR silencing delayed diapause termination, abnormal yolk absorption and a smaller head compared with the control group.

EcR exhibited tissue-specific expression during embryonic development. EcR silencing was associated with altered expression of 20E signaling-related genes, and with delayed diapause termination and abnormal embryonic development. These findings provide candidate molecular evidence for EcR participation in endocrine regulation of diapause-associated processes, and may represent a candidate target for RNAi-based pest management strategies. © 2026 Society of Chemical Industry.