HOMEODOMAIN-INDEPENDENT ACTIVITY OF THE FUSHI-TARAZU POLYPEPTIDE IN DROSOPHILA EMBRYOS

THE Drosophila segmentation gene fushi tarazu (ftz) encodes a homeodomain-containing protein, ftz, that can act as a DNA-binding activator of transcription 1-5. In the developing embryo, ftz is expressed in seven stripes 6 which correspond to the even-numbered parasegments 7. These parasegments are missing in ftz- embryos 8. When ftz is expressed throughout blastoderm embryos under the control of a heat-shock promoter, the odd-numbered parasegments are lost 9. This 'anti-ftz' phenotype has been attributed to autoactivation of the endogenous ftz gene by the ectopically expressed protein 10. Here we show that the same phenotype is induced by ectopic expression of a ftz polypeptide containing a deletion in the homeodomain. Thus, ftz can alter gene expression without binding directly to DNA.