Mapping chromatic pathways in the Drosophila visual system

摘要: In Drosophila, color vision and wavelength-selective behaviors are mediated by the compound eye's narrow-spectrum photoreceptors R7 R8 their downstream medulla projection (Tm) neurons Tm5a, Tm5b, Tm5c, Tm20 in second optic neuropil or medulla. These chromatic Tm project axons to a deeper neuropil, lobula, which insects has been implicated processing relaying information central brain. The synaptic targets of lobula not known, however. Using modified GFP reconstitution across partners (GRASP) method probe connections between 28 known novel types neurons, we identify anatomically visual LT11 LC14 intrinsic Li3 Li4 as neurons. Single-cell GRASP analyses reveal that receives contacts from over 90% all four whereas is postsynaptic with only modest selectivity at lower frequency density. To visualize ultrastructural level, develop apply "two-tag" double-labeling label LT11's dendrites mitochondria Tm5c's presynaptic terminals. Serial electron microscopic reconstruction confirms direct Tm5c. This would be generally applicable map large complex Drosophila other animals.