The endocuticle structural glycoprotein AgSgAbd-2-like is required for cuticle formation and survival in the melon...

Cuticular proteins are essential for cuticle formation, molting, and survival in insects. However, functional analysis of cuticular proteins in the melon aphid has been limited. In this study, we identified an endocuticle structural glycoprotein (ESG) AgSgAbd-2-like in the melon aphid Aphis gossypii, which is a member of the RR-1 subfamily of the CPR (cuticular protein containing the conserved Rebers-Riddiford motif) chitin-binding proteins. When double-stranded RNA is delivered epidermally, AgSgAbd-2-like is knocked down, resulting in molting defects and mortality. The expression of AgSgAbd-2-like is comparatively low prior to molting and increases following molting. Ecdysone signaling consistently suppresses AgSgAbd-2-like. Histologically, the endocuticle and whole cuticle are thinner in AgSgAbd-2-like RNA interference (RNAi) aphids, which is a leading cause of molting defects and mortality. Furthermore, knockdown of any other homolog of ESGs, including AgSgAbd-4, AgSgAbd-4-like, AgSgAbd-8-like, and AgSgAbd-9-like, results in molting defects and death, like that by AgSgAbd-2-like RNAi. These results indicate that the melon aphid ESGs are conserved in cuticle formation and could be potential targets for RNAi-based pest management.