The function and evolution of a genetic switch controlling sexually dimorphic eye differentiation in honeybees.

Animals develop sex-specific morphological structures that are diverse between organisms. However, understanding the developmental and evolutionary mechanisms governing these traits is still limited and largely restricted to DM domain genes, which are conserved, sex-specific developmental regulators identified in genetic models. Here, we report a sex-specific developmental regulator gene, glubschauge (glu) that selectively regulates sexually dimorphic eye differentiation in honeybees. We found that the sex determination gene feminizer (fem) controls sex-specific splicing of glu transcripts, establishing a genetic switch in which Glu proteins with a zinc finger (ZnF) domain are only expressed in females. We showed that female coding sequence was essential and sufficient for partial feminization. Comparative sequence and functional studies revealed that the evolutionary origination of the genetic switch was followed by the mutational origin of the essential ZnF domain. Our results demonstrate that glu is a newly evolved sex-specific genetic switch for region-specific regulation of a dimorphic character.