UAS regulatory sequences drive expression of a functionalized circularly permuted Venus variant (contains the mutations S220E, S31D, Q33E, V89I, Q142M) fused to mCherry (as a reference for ratiometric imaging). Referred to as MagIC (Magnesium Imaging in Cell), this construct acts as a non-FRET based Mg[2+] sensor (see description in PMID: 26244765).