Metabolomics reveals an involvement of pantothenate for male production responding to the short-day stimulus in the water flea, Daphnia pulex.

Kenji Toyota,Shinichi Miyagawa,Alex Gavin,Mark R Viant,Taisen Iguchi

doi:10.1038/srep25125

Abstract

Under favorable conditions, the micro-crustacean Daphnia pulex produces female offspring by parthenogenesis, whereas under unfavorable conditions, they produce male offspring to induce sexual reproduction (environmental sex determination: ESD). We recently established a suitable system for ESD studies using D. pulex WTN6 strain, in which the sex of the offspring can be regulated by alterations in day-length; long-day and short-day conditions can induce female and male offspring, respectively. Taking advantage of this system, we have already demonstrated that methyl farnesoate (MF) synthesis is necessary for male offspring production, and identified ionotropic glutamate receptors as an upstream regulator of MF signaling. Despite these findings, the molecular mechanisms associated with MF signaling have not yet been well elucidated. In this study, we analyzed the whole metabolic profiles of mother daphnids reared under long-day (female-producing) and short-day (male-producing) conditions, and discovered that pantothenate (vitamin B5), a known precursor to coenzyme A, was significantly accumulated in response to the short-day condition. To confirm the innate role of pantothenate in D. pulex, this metabolite was administered to mother daphnids resulting in a significantly increased proportion of male offspring producing mothers. This study provides novel insights of the metabolic mechanisms of the ESD system in D. pulex.

Highlights

In spite of large efforts, the induction system for male offspring has not yet been established[1,2,3,4]
Using transcriptome analysis, we revealed that N-methyl-D-aspartic acid (NMDA) receptors are an important factor for male offspring production in D. pulex WTN6 strain acting as an upstream regulator of methyl farnesoate (MF) signaling[11]
Prior to the metabolomics investigation, we evaluated whether the two rearing conditions used in this study impacted the growth of D. pulex through a comparison of body length, as such an effect would likely be accompanied by metabolic changes that could complicate the interpretation of the metabolomics data

Summary

Introduction

In spite of large efforts, the induction system for male offspring has not yet been established[1,2,3,4]. The contribution of endogenous JH signaling on male-fate determination, has so far been elusive due to the lack of a suitable experimental system which allows the modification of offspring sex without the use of exogenous JH To overcome this limitation, we have recently established a reliable system for the induction of both female and male offspring in D. pulex strain WTN6 through alteration of culture day-length. A mother produces female neonates when reared under the long-day condition (14 h light : 10 h dark), while under the short-day condition (10 h light : 14 h dark), male neonate production is induced[10] Using this male offspring induction system, we have recently demonstrated that methyl farnesoate (MF) is likely an innate JH in daphnids[10]. We sought to contribute towards the understanding of how organisms translate external environmental information into biological information

Methods

Results

Conclusion