Imaginal discs can be recovered from cultured embryos mutant for the segment-polarity genes <i>engrailed, naked</i> and <i>patched</i> but not from <i>wingless</i>

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.