Juvenile hormone degradation enzymes have shared and unique requirements in Drosophila development

Precise control of hormones is essential for animal development. Hormone bioavailability is regulated by their synthesis, transport, sequestration, natural turnover, and programmed degradation. Here, we use Drosophila melanogaster to investigate developmentally programmed degradation of the retinoid-like juvenile hormones (JHs). JHs promote juvenile growth and timely development by functionally opposing the steroid hormone, ecdysone. Despite well-characterized biochemistry, the developmental requirements for programmed JH degradation are poorly understood due to paralogue expansion. To close this knowledge gap, we generated double and triple knockout animals lacking one of two classes of JH degradation enzymes: JH esterases (JHEs) and JH epoxide hydrolases (JHEHs). We found that while both JHEs and JHEHs restrain JH signaling during Drosophila juvenile development, each has separate requirements in the regulation of developmental timing and growth. Strikingly, loss of all three JHEHs doubled the length of juvenile development, and the resulting pupae were smaller. Through targeted and genome-wide transcriptome analysis, measurements of hormone-producing glands, and rescue experiments, we uncovered both shared and unique dysregulated gene networks, some of which have established roles in the regulation of both body size and developmental timing. Our comparative analysis of both JH degradation pathways demonstrated that loss of JHEH, but not JHE, activates multiple levels of compensatory feedback to maintain homeostasis within JH and ecdysone axes. These data not only suggest that JHEH-mediated degradation is the dominant programmed JH degradation pathway in D. melanogaster development, but they also revealed new JH homeostatic mechanisms more generally. Together, this study provides new genetic tools and insights into programmed hormone degradation.

Hormones control the timing of developmental transitions and growth. As such, multiple mechanisms ensure precise amounts of a hormone are available at the right time and place. Here, we investigated the poorly understood process of developmentally programmed hormone degradation using juvenile hormones (JHs) in Drosophila melanogaster as a model. We generated double and triple knockout strains to disrupt JH degradation and found an unexpected separation of requirements in regulating developmental growth and timing. Through phenotypic and transcriptomic analysis, this study provides insights into the mechanisms and complexities of programmed hormone degradation in animal development.