Functional differentiation of ecdysis triggering hormone receptor variants in development and reproduction of Tribolium castaneum.

Understanding the functional differentiation of hormone receptor variants is crucial for unraveling the complexity of endocrine regulatory networks and developing targeted pest management strategies. By integrating genetic manipulation with phenotypic analysis, we provided multiple lines of evidence for the distinct roles of ecdysis triggering hormone (ETH) receptor splice variants in the development and reproduction of Tribolium castaneum. The study revealed that the TcETH receptor gene was alternatively spliced into 2 variants, TcETHRA and TcETHRB, both of which were highly expressed in early and late pupae, early adults, and the central nervous system. The steroid hormone 20-hydroxyecdysone enhanced the expression of TcETH and its receptors via its nuclear receptor TcEcR. Functional validation experiments demonstrated that TcETHRA was the primary functional receptor. Both TcETH and TcETHRA promoted the shedding of the old cuticle, which was essential for successful molting, pupation, and eclosion. In addition, TcETH and TcETHRA specifically regulated female reproduction by influencing the expression of juvenile hormone acid methyltransferase (TcJHAMT3) and vitellogenin-related genes (TcVg1, TcVg2, and TcVgR). In contrast, knockdown of TcETHRB had no significant impact on development but significantly reduced female embryo hatchability. These findings clarify the functional divergence of receptor splice variants in insect development and reproduction, providing new insights into the plasticity of arthropod endocrine networks and potential targets for pest control strategies.