Activating and repressive actions of the insect steroid hormone, 20-hydroxyecdysone, and ecdysone receptor in the female mosquito, Aedes aegypti

Mosquitoes are potent vectors that transmit some of the world’s deadliest diseases due to their need for a blood meal to initiate egg development.  A greater understanding of the molecular events surrounding mosquito reproduction will lead to more effective control strategies. The reproductive phase is mediated by Juvenile Hormone III (JH) and 20-hydroxyecdysone (20E). Transcriptomic analysis by means of microarray revealed several gene clusters differentially expressed throughout a reproductive cycle. Using experimental approaches of RNA interference, in vitro organ culture and quantitative PCR, we identified the roles of JH and 20E in gene activation or repression throughout the vitellogenic period. Of particular interest, a subset of genes showed repression mediated by either 20E or its receptor EcR. While the mechanisms of gene activation by 20E and EcR are well-established, negative regulation is poorly understood.  Here, we report the application of a multifaceted approach to unravel the mechanisms of negative regulation by the EcR during vitellogenesis in the female mosquito, Aedes aegypti.