Ovarian transcriptome analyses indicate that weak juvenile hormone signaling underlies the molecular basis of oogenesis deficiencies in mosquitoes.

Juvenile hormone (JH) is synthesized by the corpora allata (CA) and controls development and reproduction in insects. We recently utilized CRISPR/Cas9 to establish a line lacking the enzyme that catalyzes the final step of JH biosynthesis in mosquitoes, a P450 epoxidase. The CA of the epox-/- mutants do not synthesize epoxidated JH III but methyl farneosate (MF), a weak agonist of the JH receptor. Female epox-/- mosquitoes have reduced JH signaling and show a substantial reproductive fitness cost. To understand the molecular bases of this fitness cost, we generated ovarian mRNA libraries of wild type (WT) and epox-/- mutants, and studied the differential expression of reproductive genes. We performed triplicate RNA-seq analyses of female WT and epox-/- ovaries dissected at four critical stages of oogenesis, ovaries from newly eclosed females (0h), from sugar-fed females 4 days post-eclosion (4d SF), from females 16 hours (16h BF) and 48 hours after a blood meal (48h BF). The epoxidase knockdown caused a drastic change in the expression of thousands of genes. Our results suggest that epoxidase deficiency leads to a reduction in JH signaling that has significant effects on the transcriptome profiles of Ae. aegypti ovaries. Ecdysteroid titers are dysregulated in mutants, causing a significant delay in the expression of vitelline membrane genes and other transcripts.