The water fleas (daphnids, such as Daphniamagna and D.pulex) reproduce primarily by cyclic parthenogenesis in which only female offspring are produced. However, the daphnids switch to bisexual reproduction producing dormant resting eggs under the adverse environmental conditions, such as low food availability, low temperature, and hypoxic condition. Although juvenile hormones (JHs) are one of the hormones that control growth and development of arthropods, methyl farnesoate (MeFa: JH in daphnids) induces male offspring production in daphnids via JH-receptor methoprene-tolerant (Met). Therefore, chemicals with JH-like activity probably affect the endocrine system of daphnids, leading the reduction in population density. However, there are no invitro screening tests using juvenile hormone response element (JHRE) currently available for the detection of JH in D.magna. In this study, we found a novel JHRE, located upstream region of gene encoding Vrille [the transcriptional activator of doublesex-1 (Dsx1)] of D.magna and established reporter gene assay using the JHRE to detect JH-like substances in yeast expressing Met and steroid receptor coactivator SRC derived from D.magna.
We found a novel JHRE in the upstream region of the Vrille gene, and established yeast strain transformed JHRE reporter plasmid, D.magna Met expression plasmid, and D.magna steroid receptor coactivator expression plasmid. In this study, we evaluated the JH activity of the various compounds using the yeast reporter gene assay. The reporter gene assay was able to selectively and sensitively detect JH-like compounds.
