Comparative ovarian microarray analysis of juvenile hormone-responsive genes in water fleaDaphnia magna: potential targets for toxicity

Abstract

The freshwater zooplankton Daphnia magna has been extensively employed in chemical toxicity tests such as OECD Test Guidelines 202 and 211. Previously, it has been demonstrated that the treatment of juvenile hormones (JHs) or their analogues to female daphnids can induce male offspring production. Based on this finding, a rapid screening method for detection of chemicals with JH-activity was recently developed using adult D. magna. This screening system determines whether a chemical has JH-activity by investigating the male offspring inducibility. Although this is an efficient high-throughput short-term screening system, much remains to be discovered about JH-responsive pathways in the ovary, and whether different JH-activators act via the same mechanism. JH-responsive genes in the ovary including developing oocytes are still largely undescribed. Here, we conducted comparative microarray analyses using ovaries from Daphnia magna treated with fenoxycarb (Fx; artificial JH agonist) or methyl farnesoate (MF; a putative innate JH in daphnids) to elucidate responses to JH agonists in the ovary, including developing oocytes, at a JH-sensitive period for male sex determination. We demonstrate that induction of hemoglobin genes is a well-conserved response to JH even in the ovary, and a potential adverse effect of JH agonist is suppression of vitellogenin gene expression, that might cause reduction of offspring number. This is the first report demonstrating different transcriptomics profiles from MF and an artificial JH agonist in D. magna ovary, improving understanding the tissue-specific mode-of-action of JH. Copyright © 2016 John Wiley & Sons, Ltd.

Fenoxycarb exposure disrupted the reproductive success of the amphipod Gammarus fossarum with limited effects on the lipid profile

“…Indeed, crustaceans have a juvenile hormone methyl farnesoate that has a similar chemical structure and may play a role in development similar to the juvenile hormone in insects [ 6 ]. In line with this, lipids profile perturbation [ 7 ], morphological abnormalities [ 8 ], reproduction impairment [ 9 ] and reduced vitellogenin genes expression [ 10 , 11 ] were reported in the cladoceran Daphnia magna exposed to juvenoid insecticides. In addition, the juvenoid insecticide fenoxycarb was responsible for both growth and lipid content impairment in the mud crab Rhithropanopeus harrisii [ 12 ] and for reduced fertility in the hymenoptera Aphytis melinus [ 13 ].…”

“…Similarly, an impairment of vitellogenin genes expression was reported in the cladorecan D . magna exposed to fenoxycarb [ 10 , 11 ].…”

Identification of General Patterns of Sex-Biased Expression in Daphnia, a Genus with Environmental Sex Determination

“…Since the publication of the D. pulex genome ( Colbourne et al 2011 ), the amount of genomic and transcriptomic resources for the genus has markedly increased ( Routtu et al 2014 ; Xu et al 2015 ; Dukić et al 2016 ; Orsini et al 2016 ; Huylmans et al 2016 ; Giraudo et al 2017 ; Lynch et al 2017; Spanier et al 2017 ; Toyota et al 2017 ; Ye et al 2017 ; Herrmann et al 2018 ). Previous studies have investigated sex-biased gene expression in two Daphnia species ( Colbourne et al 2011 ; Eads et al 2007 ; Huylmans et al 2016 ).…”

Identification of general patterns of sex-biased expression inDaphnia, a genus with environmental sex determination

“…Since the publication of the D. pulex genome (Colbourne et al 2011), the amount of 63 genomic and transcriptomic resources for the genus has markedly increased (Routtu et al 2014;64 Xu et al 2015;Dukić et al 2016 ;Orsini et al 2016;Huylmans et al 2016;Giraudo et al 65 2017;Lynch et al 2017;Spanier et al 2017;Toyota et al 2017;Ye et al 2017;Herrmann et 66 al. 2018).…”

“…it is important to remember that we performed RNA-sequencing on whole animals and hence 328 included all tissues present at that the time of sampling in adult males and females. Patterns of 329 sex-specific gene expression are known to be tissue-specific in many cases (Ellegren & Parsch 330 2007;Toyota et al 2017), with strongest differences being found in brains (at least in mammals) 331 and, unsurprisingly, in gonad tissues (Mank 2009). Thus, it is difficult to compare our results 332 with those in larger animals, where studies have mostly been carried out on specific tissues 333 (e.g., 54.5 % of genes were found to be sex-DE in Mus musculus liver, (Yang et al 2006)).…”