Insertion of a PvuII fragment containing the y intron, upstream of the y 5' sequences present in Ecol\lacZy.SB.
EcollacZ reporter gene expression issimilar, both spatially and temporally, to the wild type pattern of yantibody staining. The regions at the anterior of all abdominal segmentscorrsponding to the denticle belts, the anal plates, the anterior part ofthe pharynx, and the hairs associate with Keilin's organs are allintensely stained.