UAS regulatory sequences drive expression of a sensor that monitors myosin activity under physiological conditions. The sensor consists of two Ggal\Vinc tail domains, each of which can bind filamentous actin, with a fluorescence resonance energy transfer (FRET)-based tension-sensing module inserted between them. The tension-sensing module comprises two fluorescent proteins - mTFP1 (FRET donor) and Venus (FRET acceptor) - separated from each other by a stretchable domain from spider silk (PMID:20613844). If actin filaments are pulled together due to myosin activity, the sensor will produce high a fluorescence resonance energy transfer (FRET) signal, providing an indirect readout of myosin activity.