Visualization of ecdysteroid activity using a reporter gene in the crustacean, Daphnia

- We developed a Daphnia model organism for ecdysone activity biodetection.
- The ecdysone response element was cloned and expressed in Daphnia eggs.
- The effects of ecdysone and antagonists on reporter gene expression were validated.
- This model can facilitate understanding of the ecological impacts of ecdysone.

Ecdysone is a hormone known to play a pivotal role in crustaceans and insects. In order to evaluate the ecdysone activities in the environment and within the organism, we have developed a biomonitoring Daphnia strain by introducing a reporter gene. In this study, the ecdysone response element was inserted in the upstream region of a reporter gene, and the DNA construct was injected into Daphnia eggs. The expression of the reporter gene was detected during the early embryonic development stage. In addition, when the eggs expressing the reporter gene were exposed to ecdysone, there was enhanced expression of the reporter gene at detectable levels, while the presence of an antagonist led to its downregulation. These results suggested that this system could be potentially developed for monitoring ecdysone activities in media.