Optogenetic Activation of the<i>fruitless</i>-Labeled Circuitry in<i>Drosophila subobscura</i>Males Induces Mating Motor Acts

<jats:p>It remains an enigma how the nervous system of different animal species produces different behaviors. We studied the neural circuitry for mating behavior in<jats:italic>Drosophila subobscura</jats:italic>, a species that displays unique courtship actions not shared by other members of the genera including the genetic model<jats:italic>D. melanogaster</jats:italic>, in which the core courtship circuitry has been identified. We disrupted the<jats:italic>D. subobscura fruitless</jats:italic>(<jats:italic>fru</jats:italic>) gene, a master regulator for the courtship circuitry formation in<jats:italic>D. melanogaster</jats:italic>, resulting in complete loss of mating behavior. We also generated<jats:italic>fru<jats:sup>soChrimV</jats:sup></jats:italic>, which expresses the optogenetic activator Chrimson fused with a fluorescent marker under the native<jats:italic>fru</jats:italic>promoter. The<jats:italic>fru</jats:italic>-labeled circuitry in<jats:italic>D. subobscura</jats:italic>visualized by<jats:italic>fru<jats:sup>soChrimV</jats:sup></jats:italic>revealed differences between females and males, optogenetic activation of which in males induced mating behavior including attempted copulation. These findings provide a substrate for neurogenetic dissection and manipulation of behavior in non-model animals, and will help to elucidate the neural basis for behavioral diversification.</jats:p><jats:p><jats:bold>SIGNIFICANCE STATEMENT</jats:bold>How did behavioral specificity arise during evolution? Here we attempted to address this question by comparing the parallel genetically definable neural circuits controlling the courtship behavior of<jats:italic>Drosophila melanogaster</jats:italic>, a genetic model, and its relative,<jats:italic>D. subobscura</jats:italic>, which exhibits a courtship behavioral pattern unique to it, including nuptial gift transfer. We found that the<jats:italic>subobscura fruitless</jats:italic>circuit, which is required for male courtship behavior, was slightly but clearly different from its<jats:italic>melanogaster</jats:italic>counterpart, and that optogenetic activation of this circuit induced<jats:italic>subobscura</jats:italic>-specific behavior, i.e., regurgitating crop contents, a key element of transfer of nuptial gift. Our study will pave the way for determining how and which distinctive cellular elements within the<jats:italic>fruitless</jats:italic>circuit determine the species-specific differences in courtship behavior.</jats:p>