ABSTRACT
Transcriptional quiescence, an evolutionarily conserved trait, distinguishes the embryonic primordial germ cells (PGCs) from their somatic neighbors. In Drosophila melanogaster, PGCs from embryos maternally compromised for germ cell-less (gcl) misexpress somatic genes, possibly resulting in PGC loss. Recent studies documented a requirement for Gcl during proteolytic degradation of the terminal patterning determinant, Torso receptor. Here we demonstrate that the somatic determinant of female fate, Sex-lethal (Sxl), is a biologically relevant transcriptional target of Gcl. Underscoring the significance of transcriptional silencing mediated by Gcl, ectopic expression of a degradation-resistant form of Torso (torsoDeg) can activate Sxl transcription in PGCs, whereas simultaneous loss of torso-like (tsl) reinstates the quiescent status of gcl PGCs. Intriguingly, like gcl mutants, embryos derived from mothers expressing torsoDeg in the germline display aberrant spreading of pole plasm RNAs, suggesting that mutual antagonism between Gcl and Torso ensures the controlled release of germ-plasm underlying the germline/soma distinction.
Subject(s)
Drosophila Proteins/genetics , Drosophila melanogaster/embryology , Intercellular Signaling Peptides and Proteins/genetics , RNA-Binding Proteins/genetics , Receptor Protein-Tyrosine Kinases/genetics , Sex Determination Processes , Animals , Drosophila Proteins/metabolism , Drosophila melanogaster/genetics , Drosophila melanogaster/metabolism , Embryo, Nonmammalian/embryology , Female , Intercellular Signaling Peptides and Proteins/metabolism , Male , RNA-Binding Proteins/metabolism , Receptor Protein-Tyrosine Kinases/metabolism , Transcription, GeneticABSTRACT
Species of the Drosophila melanogaster species subgroup, including the species D. simulans, D. mauritiana, D. yakuba, and D. santomea, have long served as model systems for studying evolution. However, studies in these species have been limited by a paucity of genetic and transgenic reagents. Here, we describe a collection of transgenic and genetic strains generated to facilitate genetic studies within and between these species. We have generated many strains of each species containing mapped piggyBac transposons including an enhanced yellow fluorescent protein (EYFP) gene expressed in the eyes and a ÏC31 attP site-specific integration site. We have tested a subset of these lines for integration efficiency and reporter gene expression levels. We have also generated a smaller collection of other lines expressing other genetically encoded fluorescent molecules in the eyes and a number of other transgenic reagents that will be useful for functional studies in these species. In addition, we have mapped the insertion locations of 58 transposable elements in D. virilis that will be useful for genetic mapping studies.
Subject(s)
Drosophila/genetics , Alleles , Animals , Animals, Genetically Modified , DNA Transposable Elements/genetics , Drosophila simulans/genetics , Eye/metabolism , Gene Expression Regulation , Genomics , Green Fluorescent Proteins/metabolism , Mutagenesis, Insertional/genetics , Species Specificity , TransgenesABSTRACT
The binary switch gene Sex-lethal (Sxl) controls sexual identity in Drosophila. When activated, Sxl imposes female identity, whereas male identity ensues by default when the gene is off. The decision to activate Sxl is controlled by an X chromosome counting system that regulates the Sxl establishment promoter, Sxl-Pe. The counting system depends upon the twofold difference in the gene dose of a series of X-linked transcription factors or numerators. Because of this difference in dose, early female embryos express twice the amount of these transcription factors, and the cumulative action of these transcription factors turns on Sxl-Pe. Here we show that the Drosophila Myc gene diminutive is an X-linked numerator.
Subject(s)
DNA-Binding Proteins/genetics , Drosophila Proteins/genetics , Promoter Regions, Genetic/genetics , RNA-Binding Proteins/genetics , Transcription Factors/genetics , Animals , Base Sequence , Basic Helix-Loop-Helix Transcription Factors/genetics , Basic Helix-Loop-Helix Transcription Factors/metabolism , Chromatin Immunoprecipitation , DNA-Binding Proteins/metabolism , Drosophila Proteins/metabolism , Drosophila melanogaster/embryology , Drosophila melanogaster/genetics , Drosophila melanogaster/metabolism , Embryo, Nonmammalian/embryology , Embryo, Nonmammalian/metabolism , Female , Gene Expression Regulation, Developmental , Genes, Lethal/genetics , Genes, X-Linked/genetics , Male , Mutation , Nuclear Proteins/genetics , Nuclear Proteins/metabolism , Protein Binding , RNA-Binding Proteins/metabolism , Response Elements/genetics , Reverse Transcriptase Polymerase Chain Reaction , Sex Factors , Transcription Factors/metabolismABSTRACT
Boundary elements or insulators subdivide eukaryotic chromosomes into a series of structurally and functionally autonomous domains. They ensure that the action of enhancers and silencers is restricted to the domain in which these regulatory elements reside. Three models, the roadblock, sink/decoy, and topological loop, have been proposed to explain the insulating activity of boundary elements. Strong predictions about how boundaries will function in different experimental contexts can be drawn from these models. In the studies reported here, we have designed assays that test these predictions. The results of our assays are inconsistent with the expectations of the roadblock and sink models. Instead, they support the topological loop model.
