In vivo fluorescent adenosine 5'-triphosphate (ATP) imaging of Drosophila melanogaster and Caenorhabditis elegans by using a genetically encoded fluorescent ATP biosensor optimized for low temperatures.

Adenosine 5'-triphosphate (ATP) is the major energy currency of all living organisms. Despite its important functions, the spatiotemporal dynamics of ATP levels inside living multicellular organisms is unclear. In this study, we modified the genetically encoded Förster resonance energy transfer (FRET)-based ATP biosensor ATeam to optimize its affinity at low temperatures. This new biosensor, AT1.03NL, detected ATP changes inside Drosophila S2 cells more sensitively than the original biosensor did, at 25 °C. By expressing AT1.03NL in Drosophila melanogaster and Caenorhabditis elegans, we succeeded in imaging the in vivo ATP dynamics of these model animals at single-cell resolution.