TORSO SIGNALING REGULATES TERMINAL PATTERNING IN DROSOPHILA BY ANTAGONIZING GROUCHO-MEDIATED REPRESSION

Patterning of the non-segmental termini of the Drosophila embryo depen ds on signalling via the Torso receptor tyrosine kinase (RTK), Activat ion of Torso at the poles of the embryo triggers restricted expression of the zygotic gap genes tailless (tll) and huckebein (hkb). In this paper, we show that the Groucho (Gro) corepressor acts in this process to confine terminal gap gene expression to the embryonic termini, Emb ryos lacking maternal gro activity display ectopic tll and hkb transcr iption; the former leads, in turn, to lack of abdominal expression of the Kruppel and knirps gap genes, We show that torso signalling permit s terminal gap gene expression by antagonising Gro-mediated repression , Thus, the corepressor Gro is employed in diverse developmental conte xts and, probably, by a variety of DNA-binding repressors.