RNA interference knockdown of the nuclear receptor HR3 suppresses vitellogenesis in Chilo suppressalis

Developmental and reproductive processes are the most critical physiological processes in insects, with the insect hormone 20-hydroxyecdysone (20E, the major active form of ecdysone) playing a central regulatory role in key developmental events such as embryonic development, larval molting, metamorphosis, and reproduction. As an early-late gene within the ecdysone-mediated genetic regulatory network, the orphan nuclear receptor HR3, which exhibits characteristics of both early and late genes, serves as a critical regulator of insect metamorphosis and development. However, the precise molecular mechanisms underlying HR3's function in the reproduction of non-model insects remain poorly understood.

We cloned Chilo suppressalis HR3 (CsHR3) and phylogenetic analysis demonstrates that CsHR3 shares the highest sequence homology with its ortholog in Ostrinia furnacalis. Spatiotemporal expression profiling revealed that CsHR3 expression peaked during day 4 of the female pupal stage, with the highest tissue-specific expression observed in the heads of female pupae. RNA-interference (RNAi) mediated silencing of CsHR3 resulted in delayed oocyte maturation, reduced yolk deposition, and decreased fecundity. Concurrently, transcriptional levels of key genes involved in yolk formation vitellogenin (Vg), 20E and juvenile hormones (JH) signaling pathways, including chitin synthase 1 (CHS1), were significantly downregulated in the CsHR3-knockdown group.

These findings collectively demonstrate that CsHR3 plays an essential role in the reproductive regulation of C. suppressalis, potentially mediating transcriptional control of 20E and JH pathway-related genes and chitin biosynthesis-related targets. This study not only advances the understanding of reproductive regulation in Lepidoptera but also highlights HR3 as a potential molecular target for pest management strategies.