Genetic analysis of Juvenile hormone epoxide hydrolases in Drosophila
Authors: Felipe Rogalski; Toshiro Aigaki
Affiliation: Tokyo Metropolitan University, Tokyo, Japan
Keywords: b. metabolism; n. hormonal control
Juvenile hormone epoxide hydrolases (JHEHs) are enzymes that inactivate juvenile hormone (JH) in insects. The inactivation occurs through the hydrolysis of the epoxide group within the hormone into diol. JH’s main function is to ensure larval growth while preventing metamorphosis, but it also affects adult processes, such as egg production, fertility, and behavior. The genome of the fruit fly, Drosophila melanogaster, encodes three JHEHs: Jheh1, Jheh2, and Jheh3. It is not known whether those genes play a major role in JH related phenotypes. Jheh1 and Jheh2 have been repeatedly identified as oxidative stress response genes since they are induced by several xenobiotics, like paraquat and caffeine. Recently, JHEH1 and JHEH2 have been shown to interact with a lipid droplet associated protein, suggesting a role in lipid metabolism. Jheh3’s function is completely unknow. To understand the roles of JHEHs in the fruit fly, we investigated the impact of genetic disruption of Jhehs. We focused on Jheh1 and Jheh2 since they might be involved in resistance against stresses. Using the CRISPR/Cas-9 system, we have generated a mutant deleted for Jheh1 and Jheh2. The mutant flies were viable, fertile, showed a normal lifespan and there was no difference in the resistance against paraquat or caffeine between wild-type and Jheh1-Jheh2 KO flies. Jheh1-Jheh2 KO flies showed decreased body weight and reduced amount of triacylglycerol (TAG). Conversely, overexpression of Jheh1 using the Gal4-UAS system increased TAG storage and body weight. JH is known to control developmental speed. Jheh1-Jheh2 KO flies had a slight delay in development, however, the expression level of krüppel-homolog 1 (kr-h1), a JH-responsive gene, was not different between wild-type and mutant flies, suggesting that JH signaling was not involved in the mutant phenotype. To obtain insights into the metabolic processes of Jheh mutant flies, we performed metabolomic analysis using liquid chromatography-mass spectrometry (LC-MS). All glycolytic metabolites were decreased in Jheh1-Jheh2 KO flies, whereas TCA cycle metabolites remain normal. These results indicate that glycolytic activity is low in the mutants. In conclusion, our research shows that Jheh1 and Jheh2 are involved in the regulation of growth rate, glycolysis, and lipid metabolism, demonstrating that they are essential for energy homeostasis in Drosophila.