The ncd promoter drives expression of a fluorescence resonance energy transfer (FRET)-based sensor that is designed to measure tension along a dominant-negative ncd kinesin motor. The sensor consists of the full-length ncd coding sequence, with a N600K mutation that results in a dominant-negative protein that binds more tightly to microtubules than wild type but is blocked in microtubule motility. A tension-sensing module (TSmod) has been inserted at K210 near the ncd tail-stalk junction. 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). Under low tension high FRET is produced, but under high tension, the two fluorophores move further apart, reducing the FRET signal.