Peptide antigens (epitopes) and fluorescent proteins (FPs) are the most commonly used protein tags. To overcome the limitations of existing FP and peptide epitopes, Looger's group developed new molecular tags called 'spaghetti monster' fluorescent proteins (smFPs) that combine the advantages of both. smFPs have multiple copies of single epitope tags inserted into an FP scaffold with either an intact or a darkened chromophore. They distribute well in neurons, notably into small dendrites, spines and axons, and can be readily detected by immunolabeling. This tool set expands options for labeling and following defined populations of neurons and other cell types through brain tissue. They also perform well in preparations such as array tomography, super-resolution fluorescence imaging and electron microscopy. In living cells, the probes improve single-molecule image tracking and increase yield for RNA-seq (Viswanathan et al., 2015).

Rubin's group has generated a set of smFP transgenes using the darkened chromophore (FlyBase uses the symbol smGdP for 'spaghetti monster Green darkened Protein') (Nern et al., 2015). One line that carries both the P{10xUAS-IVS-myr::smGdP-HA}attP18 and P{13xLexAop2-IVS-myr::smGdP-V5}su(Hw)attP8 has been combined with GAL4.DBD constructs in the split-GAL4 collection