UAS regulatory sequences drive expression of the Cameleon(D1) Ca[2+] indicator. To target the protein to the ER, the calreticulin signal sequence MLLPVLLLGLLGAAAD (Tag:SS(hCALR)) has been added at the N-terminal end of the coding sequence, and an ER retention sequence (Tag:ER(KDEL)) has been added to the C-terminal end.