PGE2 mediation on choriogenesis during late ovarian development of the Asian tiger mosquito, Aedes albopictus

Chorion, the egg shell, is formed at the late stage of oogenesis by follicular epithelium in the ovary. Although it remains unclear in endocrine signal(s) driving the choriogenesis, a mediation of prostaglandins (PGs) in this process has been suspected in some other insects. This study tested its role in the choriogenesis of the Asian tiger mosquito, Aedes albopictus, and its influence on controlling expressions of genes associated with chorion formation by transcriptome analysis. An immunofluorescence assay showed that PGE₂ is localized in follicular epithelium. Treatment of aspirin, an inhibitor of PG biosynthesis, after early oogenesis post blood meal (PBM) suppressed the PGE₂ signal in the follicular epithelium and significantly inhibited chorion formation. This aspirin treatment resulted in significant reduction in egg hatching rate due to malformed egg shell. Ovary transcriptomes were assessed by RNASeq at mid (36 h PBM) and late (60 h PBM) ovarian developmental stages. Differentially expressed genes (DEGs) more than 2 fold changes in expression levels included 297 genes at 36 PBM and 500 genes at 60 h PBM. These DEGs at the two developmental stages included genes associated with egg and chorion proteins of Ae. albopictus. Aspirin treatment significantly suppressed the expression of the chorion-associated genes. An addition of PGE₂ to the aspirin-treated females rescued the gene expressions and led to recovery of the choriogenesis. These results suggest that PGE₂ mediates the choriogenesis of Ae. albopictus.