Identification and Functions of JHE 6 Specifically Expressed in Bombyx mori Silk Gland

Juvenile hormone esterase (JHE) is the specific enzyme that degrades juvenile hormone (JH) and regulates the JH titer in insects. JH also regulates the development of the silk gland and the synthesis and secretion of silk proteins in . Here, we identified nine possible JHE family members, Bmjhe1-9. Notably, is specifically expressed in the silk gland. Using semi-quantitative, quantitative real-time RT-PCR and Western blot, it was confirmed that was specifically expressed in the middle silk gland (MSG) with high levels in the anterior region of the MSG (A-MSG). The immunofluorescence localization analysis revealed that Bmjhe6 is produced within cells, secreted into the gland lumen, and co-transported with silk proteins into the anterior silk gland (ASG). In vitro hormone induction experiments demonstrated that responds to a JH analog, increasing its expression after 12-24 h, whereas 20-hydroxyecdysone inhibited it. In addition, Bmjhe6 knockdown using dsBmjhe6 injections accelerated larval development, resulting in increased larval body and silk gland weight. This induced disordered sericin genes ( , ) expression, and key genes in the JH synthesis pathway ( and ) were significantly upregulated along with the transcription factors ( and ). These results indicate that Bmjhe6 plays an important role in silk gland growth and silk protein synthesis by modulating JH signal.