RESUMEN
In order to reveal syncytia within the visceral musculature of Drosophila melanogaster, we have combined the GAL4/UAS system with the single-cell transplantation technique. After transplantation of single cells from UAS-GFP donor embryos into ubiquitously GAL4-expressing recipients, the expression of the reporter gene was exclusively activated in syncytia containing both donor- and recipient-derived nuclei. In the first trial, we tested the system in the larval somatic musculature, which is already known to consist of syncytia. By this means we could show that most of the larval somatic muscles are generated by clonally non-related cells. Moreover, using this approach we were able to detect syncytia within the visceral musculature - a tissue that has previously been described as consisting of mononuclear cells. Both the longitudinal visceral musculature of the midgut and the circular musculature of the hindgut consist of syncytia and persist through metamorphosis. This novel application of the transplantation technique might be a powerful tool to trace syncytia in any organism using the GAL4/UAS system.
Asunto(s)
Músculo Liso/citología , Proteínas de Saccharomyces cerevisiae , Animales , Animales Modificados Genéticamente , Proteínas de Unión al ADN , Sistema Digestivo/citología , Sistema Digestivo/crecimiento & desarrollo , Drosophila melanogaster/crecimiento & desarrollo , Proteínas Fúngicas/genética , Genes Reporteros , Proteínas Fluorescentes Verdes , Proteínas Luminiscentes/genética , Músculo Liso/metabolismo , Factores de Transcripción/genética , beta-Galactosidasa/genéticaRESUMEN
We have examined the cell lineage of larval and imaginal precursors of the mesodermal anlage between 10% and 60% egg length (EL) by homotopic single-cell transplantations at the blastoderm stage. Clones in the larval somatic muscles and in the fat body were derived from transplantations everywhere between 10% and 60% EL along the ventral side of the embryo. Clones frequently overlap these tissues and can extend over a maximum of four segments in the larval somatic muscles or over two morphologically-distinct parts in the fat body. Clones in the gonadal mesoderm overlap with other mesodermal derivatives and exhibit different mitotic behaviour in the two sexes. We present a blastoderm fate map for the fat body, the larval somatic muscles and the gonadal mesoderm. Clones in the imaginal muscle precursors of the abdomen, as well as of the thorax, always show a common cell lineage with larval somatic muscles and partly with other mesodermal tissues. These clones of imaginal derivatives are always found within a single segment, while the overlapping clone parts in the larval somatic muscles can label up to three segments.
Asunto(s)
Drosophila melanogaster/embriología , Drosophila melanogaster/genética , Mesodermo/citología , Abdomen/embriología , Animales , Diferenciación Celular/genética , Linaje de la Célula/genética , Células Clonales , Drosophila melanogaster/citología , Cuerpo Adiposo/citología , Cuerpo Adiposo/embriología , Larva/citología , Larva/embriología , Mesodermo/fisiología , Músculos/citología , Músculos/embriología , Tórax/citología , Tórax/embriologíaRESUMEN
We have analysed the cell lineage relationships between larval and imaginal mesodermal primordia at the blastoderm stage by homotopic single cell transplantations. The primordia of adepithelial cells, the precursors of adult thoracic muscles, are restricted to the region from 50 to 65% egg length within the ventrally located mesodermal anlage. Clones of adepithelial cells always show a common cell lineage with larval muscles and in some cases additionally with larval fat body. This proves that at the blastoderm stage the determination of larval vs. imaginal mesodermal primordia has not yet taken place. Larval somatic muscle clones, in contrast to clones in the ectoderm, can overlap several segments, whereas clones of adepithelial cells are always restricted to imaginal discs of one segment.
Asunto(s)
Drosophila melanogaster/embriología , Animales , Blastodermo/citología , Linaje de la Célula , Epitelio/embriología , Larva/citología , Mesodermo/citologíaRESUMEN
FlyView is an image database for Drosophila development and genetics, particularly for gene-expression patterns. Thousands of enhancer-trap lines have now been isolated by different methods, particularly by using a variety of transposons with the resulting flies being kept in a great many laboratories. We are collecting pictures of expression patterns of all lines that are available for use by Drosophila researchers and now offer about 1800 images of about 350 enhancer-trap lines in FlyView. This article also summarizes information on the other main Drosophila resources: FlyBase-the main Drosophila database, Flybrain, an online atlas and database of the Drosophila nervous system, and Interactive Fly, a cyberspace guide to Drosophila genes and their roles in development.Copyright 1997 Academic Press Limited Copyright 1997Academic Press Limited
RESUMEN
In holometabolous development, higher insects have two different life forms, the larva and the imago. Both larval and imaginal cells are derived from cells of the blastoderm stage. After the final embryonic wave of mitosis, however, only the imaginal cells remain diploid, proliferate massively and do not differentiate until metamorphosis. The separation of these two pathways was described by many authors as a fundamental process that must take place at a very early stage of development, most probably the blastoderm stage. Mainly by using single cell transplantations at the blastoderm or early gastrula stages, respectively, we found common cell lineages between larval and imaginal structures by clones overlapping in the ectoderm (i.e. larval epidermal cells and imaginal discs within a segment, or larval and imaginal salivary gland cells), the mesoderm (i.e. larval somatic muscles and adepithelial cells), and the endoderm (i.e. larval and imaginal midgut cells). From these findings we conclude that it seems to be a principle in Drosophila embryogenesis that the separation of larval and imaginal pathways is postponed to a later developmental stage.
Asunto(s)
Drosophila/embriología , Drosophila/crecimiento & desarrollo , Animales , Blastodermo/citología , Trasplante de Células , Drosophila/genética , Gástrula/citología , Larva/citología , Larva/crecimiento & desarrollo , Túbulos de Malpighi/embriología , Túbulos de Malpighi/crecimiento & desarrollo , Metamorfosis Biológica , MitosisRESUMEN
By marking cells of early gastrula stage embryos, we showed that in embryos mutant for a strong tll allele the fate map is shifted posteriorly and the hindgut anlage is deleted. We therefore used aspects of hindgut development to characterize the phenotype of new and previously described tll alleles. In embryos mutant for the various alleles, relative levels of blastoderm expression of Trg (T-related gene, required to establish the hindgut) and of mature hindgut size were determined; the results of these assays correlated with each other. Of the alleles that map to the sequence encoding the Tailless nuclear receptor protein, all (four) affect the zinc fingers of the DNA binding domain; surprisingly, substitutions of highly conserved residues allow a range of activities as detected by our bioassays.
Asunto(s)
Proteínas de Unión al ADN/fisiología , Proteínas de Drosophila , Drosophila melanogaster/genética , Gástrula/metabolismo , Regulación del Desarrollo de la Expresión Génica , Intestinos/embriología , Proteínas Represoras/fisiología , Alelos , Secuencia de Aminoácidos , Animales , Sitios de Unión , Blastodermo/metabolismo , Linaje de la Célula , ADN/genética , ADN/metabolismo , Proteínas de Unión al ADN/genética , Drosophila melanogaster/embriología , Embrión no Mamífero/metabolismo , Embrión no Mamífero/ultraestructura , Gástrula/citología , Genes de Insecto , Genes Letales , Mucosa Intestinal/metabolismo , Datos de Secuencia Molecular , Fenotipo , Mutación Puntual , Proteínas Represoras/genética , Eliminación de Secuencia , Dedos de Zinc/genética , Dedos de Zinc/fisiologíaRESUMEN
Our previous cell lineage analysis of the thoracic disc primordia of Drosophila showed that at the blastoderm and early gastrula stage, cells are not yet committed to form either larval or imaginal tissue (Meise and Janning, 1993). We have now refined our studies on the cell lineage and have mapped the imaginal primordia in the thoracic region. Homotopic transplantations of single cells within the thoracic region of blastoderm and early gastrula stages show that the precursor cells of thoracic imaginal discs are locally restricted to a small lateral area of the thoracic region. Clones labelling leg discs frequently included the Keilin's organs. Heterotopic transplantations along the dorsoventral axis indicate that cells within the thoracic region are not yet committed with respect to larval or imaginal tissue, their fate being dependent on the position where the transplanted cell had been deposited. On the other hand, cells taken from the abdominal anlagen and transplanted into the region of thoracic disc primordia could not participate in the formation of imaginal discs. This shows that, in contrast to the dorsoventral axis, determinative events had separated primordia along the anterior-posterior axis.
Asunto(s)
Drosophila melanogaster/embriología , Genes de Insecto , Células Madre/citología , Tórax/embriología , Animales , Trasplante de Células , Extremidades/embriología , Gástrula/fisiología , Edad Gestacional , Tórax/citología , Tórax/trasplante , Trasplante HeterotópicoRESUMEN
In Drosophila hindgut, Malpighian tubules and posterior midgut develop from the most posterior region of the blastoderm. One of the genes that influences the differentiation of the Malpighian tubules is Krüppel (Kr), a segmentation gene of the gap class. Kr homozygous embryos lack thoracic and abdominal segments and, depending on the allele, develop nearly normal Malpighian tubules or do not differentiate them at all. In the wild type, injection of horseradish peroxidase (HRP) into cells of the early gastrula at various posterior positions results in labeling of hindgut (93%), Malpighian tubules (46%), and posterior midgut (20%). Malpighian tubules were labeled only in combination with hindgut. In Kr1 homozygous embryos that lack Malpighian tubules, the label was restricted to hindgut (84%) and posterior midgut (24%). Because we could not find significant cell death in the posterior region of Kr1 embryos, we counted the cell nuclei in the hindguts of wild-type and mutant embryos. The results show that the hindgut in Kr1 embryos contains those cells that would differentiate into Malpighian tubules in wild type. Therefore, we conclude that the Krüppel gene exhibits a homeotic function in addition to its role as a segmentation gene and is involved in separating hindgut and Malpighian tubule cells and in the elongation process as well.