Broad complex Z2 regulates the group Ⅳ chitinase gene HaCHT4 in the midgut of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae)

Background Chitinases and ecdysone are both crucial for insect growth and development, yet the regulatory interplay between them remains poorly understood. Our previous research demonstrated that the chitinase gene HaCHT4 critically regulates the content of chitin and peritrophic membrane’s (PM) structure in Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae). Results Here, a 1186 bp promoter region of HaCHT4 was cloned to investigate its regulation mechanism. Bioinformatics analysis predicted the presence of several 20-hydroxyecdysone (20E) related cis-regulatory elements (CREs) within this promoter, including Broad-Complex Zinc-Finger isoforms (BRCs), GATA, NF-AT1, and POU1F1. Notably, genome-wide identification and characterization revealed that the H. armigera BRC gene exhibits the highest similarity with that of Bombyx mori . Molecular docking and EMSA demonstrated the specific binding between HaBRC Z2 and HaCHT4 . Expression analysis showed concomitant upregulation of HaBRC Z2 and HaCHT4 during the late (4th to 5th ) instar stages, and were also strongly induced by 20E. In addition, RNA interference (RNAi) experiments further supported this regulatory relationship, a substantial decrease in the transcript levels of both HaBRC Z2 and HaCHT4 were observed after HaBRC Z2 silencing for 24, 48, 72, and 96 h. The knockdown of HaBRC Z2 not only stunted larval growth, evidenced by reduced body length and weight, but also confirmed its role as an activator of HaCHT4 transcription during the larval transition. Conclusion These findings reveal a critical regulatory relationship between chitinase and ecdysone, underscoring the significance of HaBRC Z2 as promising targets for informing future pest control research.