FIGURE 6:

Optogenetic activation of yeast galactose signaling. (A) Schematic of the galactose signaling system. Galactose-based activation of the system: presence of galactose removes the repressor Gal80 from the nucleus, allowing transcription (top). Light-based activation of the system: we used the CAAX (plasma membrane)–anchored PhyB and Gal80 tagged with PIF at the endogenous locus; 650-nm light causes Gal80-PIF to localize to the plasma membrane, pulling it out of the nucleus (bottom), thereby activating galactose-based transcriptional targets. (B) Galactose signaling system can be turned ON by 650-nm light even in the presence of glucose and the absence of galactose. Fluorescence represents cyan fluorescent protein expressed from the Gal1 promoter.