E74 Is Involved in the Regulation of Chitin Biosynthesis and Development of the Cigarette Beetle, Lasioderma serricorne.

The growth and development of insects are mainly governed by juvenile hormone (JH) and molting hormone, which play essential roles in metamorphosis, reproductive control, and signal transduction. However, it remains uncertain whether E74, a crucial transcription factor within the 20- hydroxyecdysone (20E) signaling pathway, is involved in regulating chitin biosynthesis in Lasioderma serricorne. In this study, the E74 gene was identified in L. serricorne, a damaging and prevalent pest of stored products. The E74 gene features an open reading frame of 1, 266 bp that encodes a protein of 421 amino acids, characterized by a typical Ets domain structure. Phylogenetic analysis indicated that E74 is most closely related to Onthophagus taurus. Analysis of temporal expression patterns revealed that E74 is expressed throughout all developmental stages of L. serricorne, with peak expression occurring during the prepupal stage. Tissue-specific expression studies showed high levels of E74 in the epidermis and head. RNA interference (RNAi) assays demonstrated that silencing E74 led to a mortality rate of 68.33%. Experiments involving hormone treatment confirmed that E74 expression is upregulated by 20E and downregulated by JH analog methoprene. Furthermore, the knockdown of E74 significantly decreased the expression of genes associated with the chitin biosynthesis pathway, which was corroborated by a notable reduction in chitin levels following E74 knockdown. In conclusion, this study established that E74 is not only vital for the growth and development of L. serricorne but also plays a role in regulating chitin biosynthesis. This study enhances the understanding of E74's functional role across various species and offers insights for identifying potential targets for pest control.