UAS regulatory sequences drive expression of a fluorescence resonance energy transfer (FRET)-based tension-sensing module followed by a Ggal\Vinc tail domain. 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). This is a control construct to determine the basal FRET level of the tension-sensing module: only one end of the protein will bind F-actin and thus the level of FRET is not regulated by pulling and stretching of F-actin filaments.