UAS regulatory sequences (derived from the pValium20 vector) drive expression of 'LOCa3', an engineered light-operated Ca[2+] channel that consists of a constitutively active form of Hsap\ORAI1 (carries amino acid substitution P245T) that has the light-regulated Tag:AsLOV2 tag inserted into the intracellular loop (insertion is between residues S163 and P164) and also carries the additional amino acid substitution H171D.