title: A late phase of Oskar accumulation is crucial for posterior patterning of the Drosophila embryo, and is blocked by ectopic expression of Bruno.
abstract: In Drosophila, posterior embryonic body patterning and germ cell formation rely on Oskar, a protein that is concentrated at the posterior pole of the oocyte. A program of mRNA localization and translational regulation ensures that Oskar is only expressed at the proper location. One key regulatory factor is Bruno, which represses translation of oskar mRNA before its localization. Ectopic expression of a bruno cDNA prolongs repression, even after oskar mRNA is localized, and posterior body patterning is efficiently and selectively blocked. Surprisingly, the initial accumulation of Oskar, while frequently reduced, is not eliminated, arguing that levels of Oskar previously thought to be sufficient for patterning do not suffice, or that Bruno acts at a downstream step in patterning. Expression of the bruno cDNA does not inhibit posterior patterning when Oskar is expressed independent of Bruno-mediated regulation, ruling out a downstream requirement for Bruno. Notably, an Oskar::GFP reporter protein reveals continual accumulation during the late phases of oogenesis. Taken together, these results strongly argue that a late phase in accumulation of Osk protein, typically not monitored because of imperviousness of late stage oocytes to antibodies, is crucial for body patterning.
authors.affiliation: Section of Molecular, Cell, and Developmental Biology, Institute for Cellular and Molecular Biology, University of Texas, Austin, TX 78712, USA.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Snee
authors.forename: Dianne
authors.initials: D
authors.lastname: Harrison
authors.forename: Nan
authors.initials: N
authors.lastname: Yan
authors.forename: Paul M
authors.initials: PM
authors.lastname: Macdonald
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D019521:Body Patterning / Q000235:genetics* / Q000502:physiology; D018076:DNA, Complementary / Q000378:metabolism; D004330:Drosophila / Q000196:embryology* / Q000378:metabolism; D029721:Drosophila Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D004625:Embryo, Nonmammalian / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D009865:Oocytes / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D016211:Transforming Growth Factor alpha / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D018076:DNA, Complementary; D029721:Drosophila Proteins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D016211:Transforming Growth Factor alpha; C093437:bru1 protein, Drosophila; C433983:btz protein, Drosophila; C083730:grk protein, Drosophila; C091675:osk protein, Drosophila; D049452:Green Fluorescent Proteins