title: Regulation of Easter activity is required for shaping the Dorsal gradient in the Drosophila embryo.
abstract: Dorsoventral polarity of the Drosophila embryo requires maternal spätzle-Toll signaling to establish a nuclear gradient of Dorsal protein. The shape of this gradient is altered in embryos produced by females carrying dominant alleles of easter (ea(D)). The easter gene encodes a serine protease that generates processed Spätzle, which is proposed to act as the Toll ligand. By examining the expression domains of the zygotic genes zen, sog, rho and twist, which are targets of nuclear Dorsal, we show that the slope of the Dorsal gradient is progressively flattened in stronger ea(D) alleles. In the wild-type embryo, activated Easter is found in a high M(r) complex called Ea-X, which is hypothesized to contain a protease inhibitor. In ea(D) embryo extracts, we detect an Easter form corresponding to the free catalytic domain, which is never observed in wild type. These mutant ea(D) proteins retain protease activity, as determined by the production of processed Spätzle both in the embryo and in cultured Drosophila cells. These experiments suggest that the ea(D) mutations interfere with inactivation of catalytic Easter, and imply that this negative regulation is essential for generating the wild-type shape of the Dorsal gradient.
authors.affiliation: Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA.
authors.forename: Andy J
authors.initials: AJ
authors.lastname: Chang
authors.forename: Donald
authors.initials: D
authors.lastname: Morisato
mesh_terms: D000483:Alleles; D000818:Animals; D001755:Blastocyst / Q000378:metabolism; D019521:Body Patterning; D020134:Catalytic Domain; D018076:DNA, Complementary / Q000378:metabolism; D004330:Drosophila / Q000196:embryology*; D029721:Drosophila Proteins / Q000378:metabolism; D005260:Female; D018507:Gene Expression Regulation, Developmental; D005799:Genes, Dominant; D005838:Genotype; D019476:Insect Proteins / Q000378:metabolism; D008024:Ligands; D009154:Mutation; D017434:Protein Structure, Tertiary; D011956:Receptors, Cell Surface / Q000378:metabolism; D012697:Serine Endopeptidases / Q000378:metabolism*; D013997:Time Factors; D051193:Toll-Like Receptors
chemical_list: D018076:DNA, Complementary; D029721:Drosophila Proteins; D019476:Insect Proteins; D008024:Ligands; D011956:Receptors, Cell Surface; C068721:Tl protein, Drosophila; D051193:Toll-Like Receptors; C086179:spz protein, Drosophila; D012697:Serine Endopeptidases; C078099:ea protein, Drosophila