EcollacZ reporter gene expression isobserved from embryonic stage 13 in a thin stripe of cells in the midgutepithelium that coextends approximately with Ubx expression inparasegment 7 of the adhering visceral mesoderm. The pattern differs fromthat of constructs carrying additional 5' sequences in two respects.Unlike lab expression, the intensity of the stripe is not graded andthere is no 2-3 cell wide gap between the posterior boundary of EcollacZexpression and the second midgut constriction. In lab mutants, onset ofexpression is decreased and slightly delayed. Expression is completelyeliminated in dpp mutant embryos. Ectopic expression is seen posteriorlyin an abd-A mutants and anteriorly in a Pc mutant. Expression isreduced in a wg mutant and is derepressed posteriorly.