In constructs driven by either the -310 to +151 or -56 to +151 region of janA (with +1 denoting the start of transcription), EcollacZ expression is detected in follicle cells throughout oogenesis. EcollacZ staining in nurse cells and in oocyte nuclei is intense from stage S1 to stage S7 of oogenesis, but declines sharply at stage S8; the nurse cell cytoplasm stains only faintly. In adult males, staining is detected throughout the testis, but not in male somatic tissue (ejaculatory duct and male accessory gland). However, introduction of for copies of either construct did reveal weak staining in male somatic tissue, indicating that low levels of expression, undetectable in one copy, did exist. In third instar larvae, staining is strong in gonads of both sexes, but weak in other tissues.