An XhoI-EcoRI E(spl)mδ-HLH fragment is placed upstream of the P-element minimal promoter and sequence encoding a GAL4 driver.
Expressed in photoreceptor cell 4 and weakly in photoreceptor 3.
ScerGAL4E(spl)mδ-HLH.0.5 drives expression mainly in photoreceptor cell R4; weaker expression is also observed earlier in photoreceptor cell R3 and later in photoreceptor cell R7.