Comparative ovarian microarray analysis of juvenile hormone-responsive genes in water flea Daphnia magna

The freshwater zooplankton Daphnia magna has been used for the validation of chemical toxicity tests such as OECD Test Guideline 202 and 211. Previously, it has been demonstrated that treatment of juvenile hormones (JHs) or their analogs to mother daphnids could induce male offspring production. Based on this funding, a rapid screening method for detection of chemical with JH-activity was recently developed by using adult D. magna. This screening system can validate whether arbitrary chemical has JH-activity by investigating the male offspring inducibility. Although this short-term screening system will be possible to enhance a throughput of detection efficiency, JH-responsive genes in the ovary including developing oocytes at JH-sensitive period for male sex determination are still largely undescribed. Here, we conducted comparative microarray analyses using ovary treated by fenoxycarb (Fx; artificial JH agonist) and methyl farnesoate (MF; a putative innate JH in daphnids) to make the comprehensive gene catalogs in response to JH molecules in ovary including developing oocytes at JH-sensitive period for male sex determination. We successfully created the comprehensive ovarian gene catalogs in response to Fx and MF. Furthermore, we demonstrated that the hemoglobin genes are well-conserved JH-responsive element even in the ovary, and a potential toxic effect of JH agonist is suppression of vitellogenin gene expression that might cause reduction of offspring number. This is first report demonstrating the differential transcriptomics profiles between MF and artificial JH agonist in D. magna ovary, making it possible for understanding the tissue-specific mode-of-action of JH molecule. Microarray analyses using ovary treated by fenoxycarb and methyl farnesoate were conducted. Ovary samples consisted of three individuals per replicate, and quadruplicates were prepared for both treatments.