UASt regulatory sequences drive expression of Syt1 (the protein may carry a S265G substitution, which does not affect its localization) fused at its C-terminal end to five tandem copies of the miniSOG photosensitizer, which can be used for labeling of subcellular components for electron microscopy. The fusion protein localizes to the synapses and is tagged at the C-terminal end with mKate2.