Reporter gene expression is observedin the visceral mesoderm. Expression is strongest in the first twoabdominal segments, declines in a shallow gradient posteriorly to the 7thabdominal segment, and declines in a sharper gradient anteriorly to thesecond or third thoracic segment. In a Ubx mutant background, EcollacZexpression is uniform along its expression domain and no longer shows amaximum in the first two abdominal segments.