Two Doublesex1 mutants revealed a tunable gene network underlying intersexuality in Daphnia magna

In recent years, the binary definition of sex is being challenged by repetitive reports about individuals with ambiguous sexual identity from various animal groups. This has created an urge to decode the molecular mechanism underlying sexual development. However, sexual ambiguities are extremely uncommon in nature, limiting their experimental value. Here, we report the establishment of a genetically modified clone ofDaphnia magnafrom which intersex daphniids can be readily generated. By mutating the conserved central sex determining factorDoublesex1, body-wide feminization of male daphniid could be achieved. Comparative transcriptomic analysis also revealed a genetic network correlated withDoublesex1activity which may account for the establishment of sexual identity inD.magna. We found that Dsx1 repressed genes related to growth and promoted genes related to signaling. We infer that different intersex phenotypes are the results of fluctuation in activity of these Dsx1 downstream factors. Our results demonstrated that theD.magnagenome is capable of expressing sex in a continuous array, supporting the idea that sex is actually a spectrum.