ABSTRACT
Drosophila embryos homozygous for strong mutations in each of the segment-polarity genes wingless (wg), engrailed (en), naked (nkd) and patched (ptc) form a larval cuticle in which there is a deletion in every segment. The mutant embryos normally fail to hatch but by in vivo culture we were able to show which could produce adult structures. Cultured wg− embryos did not produce any adult structures. Cultured en− embryos produced eye-antennal derivatives and rarely produced partial thoracic structures. nkd− and ptc− embryos produced eye-antennal and thoracic derivatives. The nkd− and ptc− thoracic imaginal discs developed with an abnormal morphology and abnormal pattern of en-expression. Our findings are consistent with the idea that the thoracic imaginal discs derive from two adjacent groups of cells that express wg and en respectively in the embryo.
