# Expression Analysis of Hormone Receptor 38 (HR38) and Ecdysone-Induced Protein 75 (E75) Genes and Their Functional Implications in the Development of Heortia vitessoides Moore

## TL;DR

This study identifies two hormone-responsive genes in a forest pest insect and shows that they are crucial for development, suggesting they could be used for targeted pest control.

## Contribution

The study characterizes HR38 and E75 genes in Heortia vitessoides and demonstrates their essential roles in development through RNA interference.

## Key findings

- HR38 and E75 genes in Heortia vitessoides show stage- and tissue-specific expression patterns.
- Silencing HR38 or E75 causes developmental defects and reduced survival in Heortia vitessoides.
- Both genes are strongly activated by the molting hormone 20-hydroxyecdysone.

## Abstract

Insect growth and development are controlled by steroid hormones that regulate molting and metamorphosis. Two hormone-responsive genes, HR38 and E75, act as key regulators in converting hormonal signals into developmental responses. However, their roles remain largely unexplored in many forest pests. In this study, we identified and characterized the HR38 and E75 genes in Heortia vitessoides, an important defoliating pest of agarwood-producing trees. Both genes showed clear stage- and tissue-specific expression patterns and responded rapidly to the molting hormone 20-hydroxyecdysone. When either gene was silenced using RNA interference, insects exhibited severe developmental abnormalities, including failed molting, malformed pupae, and reduced survival. These findings demonstrate that HR38 and E75 are essential for normal development in Heortia vitessoides. This work improves our understanding of hormone-regulated insect development and highlights HR38 and E75 as potential molecular targets for environmentally friendly pest control strategies.

HR38 and E75 are early 20-hydroxyecdysone (20E)-responsive nuclear receptors that play important roles in insect molting and metamorphosis. Here, we cloned and characterized HvHR38 and HvE75 from Heortia vitessoides and analyzed their conserved domains and phylogenetic positions. Both genes exhibited distinct stage- and tissue-specific expression patterns closely associated with ecdysteroid-regulated developmental processes. Hormone-induction assays further demonstrated that the transcription of HvHR38 and HvE75 was strongly activated by 20E. RNA interference targeting either gene resulted in significant transcript knockdown, accompanied by incomplete molting, pupal deformities, and molting failure, ultimately leading to markedly reduced survival, with dsHvE75 causing the highest lethality. Collectively, these results suggest that HR38 and E75 function as key components of the early 20E-responsive transcriptional network involved in molting regulation, and highlight their potential as RNAi targets for species-specific and environmentally sustainable pest management.