Cross-talk of insulin-like peptides, juvenile hormone, and 20-hydroxyecdysone in regulation of metabolism in the mosquito Aedes aegypti

Abstract

Significance In hematophagous female mosquitoes, each reproductive cycle is linked to a separate blood intake, serving as a foundation for the transmission of dangerous human diseases. During each reproductive cycle, female mosquitoes sequentially feed on carbohydrates and protein (blood). Metabolic flux is alternated to support the reproductive cyclicity. We have established that insulin-like peptides (ILPs), critical for regulating metabolism, are genetically controlled by juvenile hormone (JH) and 20-hydroxyecdysone (20E), the key hormones governing the reproduction of female mosquitoes. CRISPR gene-tagging experiments revealed that the JH and 20E pathways coordinate the production of ILPs. This study has uncovered the link between ILPs and JH and 20E pathways in controlling mosquito metabolism during reproduction of the Aedes aegypti mosquito. Female mosquitoes feed sequentially on carbohydrates (nectar) and proteins (blood) during each gonadotrophic cycle to become reproductively competent and effective disease vectors. Accordingly, metabolism is synchronized to support this reproductive cyclicity. However, regulatory pathways linking metabolism to reproductive cycles are not fully understood. Two key hormones, juvenile hormone (JH) and ecdysteroids (20-hydroxyecdysone, 20E, is the most active form) govern female mosquito reproduction. Aedes aegypti genome codes for eight insulin-like peptides (ILPs) that are critical for controlling metabolism. We examined the effects of the JH and 20E pathways on mosquito ILP expression to decipher regulation of metabolism in a reproducing female mosquito. Chromatin immunoprecipitation assays showed genomic interactions between ilp genes and the JH receptor, methoprene-tolerant, a transcription factor, Krüppel homolog 1 (Kr-h1), and two isoforms of the ecdysone response early gene, E74. The luciferase reporter assays showed that Kr-h1 activates ilps 2, 6, and 7, but represses ilps 4 and 5. The 20E pathway displayed the opposite effect in the regulation of ilps. E74B repressed ilps 2 and 6, while E74A activated ilps 4 and 5. Combining RNA interference, CRISPR gene tagging and enzyme-linked immunosorbent assay, we have shown that the JH and 20E regulate protein levels of all eight Ae. aegypti ILPs. Thus, we have established a regulatory axis between ILPs, JH, and 20E in coordination of metabolism during gonadotrophic cycles of Ae. aegypti.