A tension-sensing module has been inserted into the endogenous shg locus, at the C-terminal end of the coding sequence. The tension-sensing module consists of ECFP (FRET donor) and mEYFP (FRET acceptor) connected by an elastic linker (GPGGA)[[8]], derived from spider silk. This is a control construct as the C-terminal end of shg lies outside of the force transmitting region of the protein.