EcollacZ reporter gene expression isobserved from embryonic stage 13. The pattern closely resembles labexpression in a thin stripe of cells in the midgut epithelium thatcoextends approximately with Ubx expression in parasegment 7 of theadhering visceral mesoderm. The stripe widens and displays a gradedpattern with the strongest expression posteriorly. As with labexpression, a 2-3 cell wide gap is present between the posterior boundaryof EcollacZ expression and the second midgut constriction. In lab mutants,midgut expression is eliminated prior to stage 15 and occurs at low levelsthereafter. Expression is completely eliminated in dpp mutant embryos.Ectopic expression is seen posteriorly in an abd-A mutants andanteriorly in a Pc mutant. Expression is reduced in a wg mutant and isderepressed posteriorly.