Mapping the expression of the sex determining factor Doublesex1 in Daphnia magna using a knock-in reporter

Quang Dang Nong,Hajime Watanabe,Tomoaki Matsuura,Nur Syafiqah Mohamad Ishak,Yasuhiko Kato

doi:10.1038/s41598-017-13730-4

Abstract

Sexually dimorphic traits are common and widespread among animals. The expression of the Doublesex-/Mab-3-domain (DM-domain) gene family has been widely studied in model organisms and has been proven to be essential for the development and maintenance of sex-specific traits. However, little is known about the detailed expression patterns in non-model organisms. In the present study, we demonstrated the spatiotemporal expression of the DM-domain gene, doublesex1 (dsx1), in the crustacean Daphnia magna, which parthenogenetically produces males in response to environmental cues. We developed a dsx1 reporter strain to track dsx1 activity in vivo by inserting the mCherry gene into the dsx1 locus using the TALEN-mediated knock-in approach. After confirming dsx1 expression in male-specific traits in juveniles and adults, we performed time-lapse imaging of embryogenesis. Shortly after gastrulation stage, a presumptive primary organiser, named cumulus, first showed male-specific dsx1 expression. This cell mass moved to the posterior growth zone that distributes dsx1-expressing progenitor cells across the body during axial elongation, before embryos start male-specific dsx1 expression in sexually dimorphic structures. The present study demonstrated the sex-specific dsx1 expression in cell populations involved in basal body formation.

Highlights

Sexual reproduction is favoured by eukaryotes to produce offspring
The cladoceran crustacean Daphnia magna presents three major advantages when used as a model species for the analysis of mechanisms underlying the development and evolution of sexually dimorphic traits
Daphnia uses a unique sex-determining system, where environmental cues are primarily considered for sex determination, stimulating germ cells at the late stage of oogenesis and leading to the development of males that are genetically identical to females[17]

Summary

Introduction

Sexual reproduction is favoured by eukaryotes to produce offspring. At the gamete level, the sex can be either male or female[1,2]. The cladoceran clade, arising from as early as the Devonian period[15], is a possible common ancestor of Pancrustaceans, including insects and crustaceans[16] This renders Daphnia a useful model for deducing the origin and evolution www.nature.com/scientificreports/. Knock-down of dsx[1] in males feminised both somatic cells and germ cells This suggested that the sexual fates of most cells in Daphnia were directly dependent on dsx[1] expression, as previously observed in Drosophila. This previous study shows limitations, as it only provides snapshot images of dsx[1] at certain time points[24]. Using a genome editing technique, we successfully introduced an in vivo fluorescent reporter into the dsx[1] locus using the TALEN-mediated knock-in approach

Methods

Results

Conclusion