Evolutionary transitions between hermaphroditic and dioecious reproductive states are found in many groups of animals. To understand such transitions, it is important to characterize diverse modes of sex determination utilized by metazoans. Currently, little is known about how simultaneous hermaphrodites specify and maintain male and female organs in a single individual. Here we show that a sex-specific gene, Smed-dmd-1 encoding a predicted doublesex/male- abnormal-3 (DM) domain transcription factor, is required for specification of male germ cells in a simultaneous hermaphrodite, the planarian Schmidtea mediterranea. dmd-1 has a male-specific role in the maintenance and regeneration of the testes and male accessory reproductive organs. In addition, a homologue of dmd-1 exhibits male-specific expression in Schistosoma mansoni, a derived, dioecious flatworm. These results demonstrate conservation of the role of DM domain genes in sexual development in lophotrochozoans and suggest one means by which modulation of sex-specific pathways can drive the transition from hermaphroditism to dioecy.
Bibliographical noteFunding Information:
We thank James Sikes and Labib Rouhana for discussion and comments on the project and manuscript, Ryan King for ideas on in situ optimization, Jason Wever for providing the eyes absent construct, Rachel Roberts-Galbraith and Nayab Abidi for clones and assistance with neuronal markers, Melanie Issigonis for assistance with qPCR analyses, and members of the Newmark Lab for discussion and support; Peter Reddien, Whitehead Institute/Massachusetts Institute of Technology, for the pPR242 RNAi feeding vector; Tony Gamble, University of Minnesota, for advice and assistance with phylogenetic analysis of DM domains. This work was supported by NIH (R01 HD043403 and R21 AI099642), NSF (IOS-0744689), and a Richard and Margaret Romano Professorial Scholar Award to P.A.N. and NIH (R01 GM059152) to D.Z. P.A.N is an investigator of the Howard Hughes Medical Institute.