Max-Planck-Institut für Entwicklungsbiologie, Abteilung Genetik, Tübingen, FRG.
The organization of the anterior pattern in the Drosophila embryo is mediated by the maternal effect gene bicoid. bcd has been identified in an 8.7-kb genomic fragment by germ line transformants that completely rescue the mutant phenotype. The major transcript of 2.6 kb includes a homeobox with low homology to previously known homeoboxes, a PRD-repeat and a M-repeat. In situ hybridizations reveal that bcd is transcribed in the nurse cells. The mRNA is localized at the anterior tip of oocyte and early embryo until the cellular blastoderm stage. The localization of the transcript requires the function of the maternal effect genes exuperantia and swallow while transcript stability is reduced by functions depending on posterior group genes.