Tissue-specific transcriptomic and endocrine signatures of obligatory reproductive diapause in Eurygaster integriceps

Obligatory reproductive diapause is a hormonally regulated, developmentally programmed state occurring independently of environmental cues. Despite its prevalence in univoltine insects, the molecular regulation remains unclear. The Sunn pest Eurygaster integriceps (Hemiptera: Scutelleridae), a univoltine wheat and barley pest, alternates between a reproductive phase in early spring and diapause during summer to winter. This study investigated the molecular basis of diapause and reproductive activation in this species. Transcriptomic profiling of brain tissues (including corpora allata and corpora cardiaca) and fat body revealed key components of the juvenile hormone (JH) pathway: juvenile hormone acid methyltransferase (JHAMT), Methoprene-tolerant (Met), and Vitellogenin (Vg). De novo assembly of high-quality RNA-seq data yielded 12,557 and 15,684 contigs from brain and fat body tissues, respectively. BUSCO analysis confirmed completeness of 81.6% and 86.5% of core insect orthologs in these assemblies. The full-length JHAMT cDNA (837 bp) encoded a 278-aa cytoplasmic protein; Met (2031 bp) encoded a 665-aa nuclear protein; and Vg (5220 bp) encoded a 1708-aa secretory protein with a signal peptide. Expression profiling via qPCR revealed synchronized transcriptional dynamics of JHAMT, Met, and Vg, with significantly elevated levels in reproductively active females, and reduced expression during diapause phases. These results indicate that diapause in E. integriceps is orchestrated via a conserved JH-Met pathway, with Vg playing a central role in reproductive competence. This study provides the first molecular evidence for hormonally mediated obligatory diapause in E. integriceps, identifying potential RNAi targets for pest control and offering a model for studying diapause evolution in the Sunn pest.