Characterization and Seasonal Expression Profiling of a Takeout/Juvenile Hormone-Binding Protein-Family Gene...

Diapause in the Sunn pest, Eurygaster integriceps, is a key seasonal adaptation associated with migration, overwintering survival, and reproductive timing. However, the molecular components associated with this physiological state remain poorly characterized in this hemipteran pest. In this study, we identified and characterized a takeout-family transcript from E. integriceps (EiTO1; GenBank OP913374.1) and combined evolutionary, structural, and expression analyses to examine its association with seasonal physiological states. EiTO1 contained a 738-bp open reading frame encoding a 245-amino acid protein and was assigned to the juvenile hormone-binding protein (JHBP) superfamily based on conserved-domain analysis. Phylogenetic reconstruction recovered EiTO1 as sister to the Nilaparvata lugens-Bemisia tabaci clade; however, the low bootstrap support for this placement prevented confident inference of its closest evolutionary relationship. Structural comparison of the predicted EiTO1 model with experimentally resolved takeout/JHBP-family proteins indicated a conserved barrel-like fold and a corresponding internal cavity, consistent with structural features of this protein family. Quantitative PCR profiling revealed marked seasonal and tissue-specific variation in EiTO1 expression. In female whole-body samples, EiTO1 transcript abundance was low during spring field activity and in newly emerged adults sampled in June, reached its maximum during the refuge-associated phase in August (160-fold), and showed a secondary increase during the late-overwintering/premigration transition in March (21.5-fold). Tissue-resolved assays in females showed the highest expression in the head and intermediate expression in the fat body. Ovarian expression remained at or below the April baseline at most sampling points but showed a transient increase in August. Together, these findings identify EiTO1 as a takeout/JHBP-family gene whose expression is associated with seasonal physiological transitions in E. integriceps.