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

BACKGROUND

Juvenile hormone (JH) is synthesized by the corpora allata (CA) and controls development and reproduction in insects. We recently used 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 epoxidized JH III but methyl farneosate (MF), a weak agonist of the JH receptor. Female epox-/- mosquitoes have reduced JH signaling and show a substantial loss of reproductive fitness. To understand the molecular basis of this loss of fitness, we constructed ovarian mRNA libraries of Ae. aegypti of the Orlando strain wild-type (WT) and epoxidase null mutants (epox-/-) and investigated differential expression of reproductive genes.

RESULTS

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), sugar-fed females at 4 days post-eclosion (4d SF), females 16h (16h BF), and 48 h after a blood meal (48h BF). Silencing of epoxidase resulted in a drastic change in the expression of thousands of genes.

CONCLUSIONS

Our results suggest that epoxidase deficiency leads to a reduction in JH signaling that has significant effects on Ae. aegypti ovarian transcriptome profiles. Ecdysteroid titers are dysregulated in the mutants, leading to a significant delay in the expression of vitelline membrane genes and other transcripts. We discovered changes in the expression of 230 long non-coding RNAs (lncRNAs) that may play an important role in the regulation of ovarian genes.