WINGLESS CAN BRING ABOUT A MESODERM-TO-ECTODERM INDUCTION IN DROSOPHILA EMBRYOS

By means of nuclear transplantations, we make mosaics in which largely wingless(-) embryos contain patches of wingless(+) cells, In these ge netic mosaics, using a standard assay for wingless function (the maint enance of engrailed expression), we uncover an induction across germ l ayers: Wingless made in the mesoderm can sustain engrailed expression in the ectoderm. This result makes clear that Wingless is expressed in the mesoderm until at least one hour after gastrulation and may funct ion in this germ layer in the wild type.