Convergent olfactory circuits for courtship in Drosophila revealed by the circuit-tracing tool ds-Tango.

Animals exhibit sex-specific behaviors that are governed by sexually dimorphic circuits. One such behavior in male Drosophila melanogaster, courtship, is regulated by various sensory modalities, including olfaction. Here, we reveal how sexually dimorphic olfactory pathways in male flies converge onto lateral horn output neurons, third-order neurons in the olfactory circuit, to regulate courtship. To achieve this, we developed ds-Tango, a modified version of the monosynaptic tracing and manipulation tool trans-Tango. In ds-Tango, two distinct configurations of trans-Tango are positioned in series, thus providing selective genetic access not only to the monosynaptic partners of starter neurons but also to their disynaptic connections. Using ds-Tango, we identified a node of convergence for three sexually dimorphic olfactory pathways. Males in which this node is silenced aberrantly court other males, unless a female is present. Thus, our results identify lateral horn output neurons important for proper courtship behavior and establish ds-Tango as a tool for disynaptic circuit tracing.