D3025: Autophagy role in midgut remodeling in the yellow fever mosquito, Aedes aegypti

Autophagic cell death is an evolutionally conserved process mediated by the lysosomal hydrolysis proteinases and plays important role during insect metamorphosis and development. Midgut remodeling is a critical process in metamorphosis and disease progression in Aedes aegypti mosquito, which is coordinately regulated by two major developmental hormones, 20-hydroxyecdysone (20E) and Juvenile hormone (JH). Nevertheless, the function of autophagy in midgut metamorphosis remains not well understood. Treatment with JH analog, methoprene, or RNAi-mediated silencing of two autophagy genes (genes coding for activating molecule in BECN1-regulated autophagy protein 1, AMBRA1 and Autophagy-related protein 8, ATG8) inhibited autophagy and blocked midgut remodeling in Ae. aegypti. RNA sequencing and reverse-transcriptase quantitative PCR (RT-qPCR) analysis revealed that methoprene affects midgut remodeling by inducing the expression of JH-regulated genes, Kr-h1 and Broad complex and suppressing the expression of AMBRA1 and autophagy genes ATG8, ATG 10, ATG 12 and ATG13. Histology studies showed that JHA treatment or knockdown of autophagy genes blocked larval cell death. The pupae developed from the treated insects contained two layers of midgut epithelium, inner larval and outer pupal/adult. Taken together, the results from histology, JHA treatment, RNAi and RT-qPCR studies revealed that JHA blocks Ae. aegypti midgut remodeling during metamorphosis by interfering with the expression of essential autophagy genes.