Genetic Characterization of Juvenile Hormone Degradation Enzyme Mutants

In insects, pacing of growth and development is regulated by Juvenile hormones (JHs). JHs are potent sesquiterpenoids whose titers must be tightly regulated for normal development. One method of controlling JH titers is by enzymatic synthesis and degradation. Little is known about enzymes in the JH degradation cascade. In this study, we use Drosophila melanogaster to understand the contributions of JH degrading enzymes on classic JH developmental functions. We focused on D. melanogaster's five degradation enzyme genes: two JH esterases (Jhes) and three JH epoxide hydrolases (Jhehs). Our lab had previously generated Jhe double knockout (DKO) and Jheh triple knockout (TKO) Drosophila strains. Phenotypic analysis revealed Jhes are required to restrain body size but not developmental timing; while Jhehs are required for developmental pacing but do not affect size. To determine if these phenotypes were related to JH degradation, we performed genetic epistasis experiments with mutations in the gene encoding a key JH synthesis enzyme, JH acid methyltransferase (Jhamt). We didn't find genetic evidence that the delay of Jheh TKO is linked to JH degradation. However, the larger size of Jhe DKO was rescued by Jhamt mutation indicating JH degradation may be involved with this phenotype. Interestingly, Jheh mutants pupate closer to the food while Jhe DKOs do not, yet Jhamt, Jhe DKO pupae had an intermediate phenotype indicating the possible involvement of JH. Future work should focus on a deeper evaluation of the phenotypes of the Jhamt mutant alone to assess the contribution of JH synthesis to degradation enzyme mutant phenotypes.