RESUMEN
The UAS/GAL4 ectopic expression system is widely used in Drosophila melanogaster for the overexpression of transgenes. This system operates under the assumption that the yeast transcription factor, GAL4, is inactive in D. melanogaster. Thus, GAL4 can be expressed under the control of D. melanogaster -specific promoters with little effect upon the organism. We have shown that expression of GAL4 in the developing eye under the control of the glass multiple reporter (GMR) promoter element does have an effect on eye development. Although GMR-GAL4 heterozygotes appear normal when raised at 25 degrees C, the homozygotes have a highly disorganized ommatidial array. In addition, the levels of apoptosis in the third-instar larval eye imaginal disc (where GAL4 is expressed) are slightly higher in GMR-GAL4 heterozygotes, and much higher in GMR-GAL4 homozygotes when compared to wild type discs. The morphological eye defects caused by GMR-GAL4 are significantly enhanced when flies are raised at 29 degrees C (presumably due to the higher activity of GAL4 at this temperature); however, the levels of apoptosis appear to be similar at these two temperatures. Taken together, these data suggest that GAL4 can have adverse effects on D. melanogaster development, especially at high expression levels. In addition, GAL4 appears to induce apoptosis even in the absence of any visible morphological defects. Thus, despite the benefits of the UAS/GAL4 ectopic expression system, one must use caution in the design and interpretation of experiments
Asunto(s)
Animales , Drosophila melanogaster/crecimiento & desarrollo , Factores de Transcripción/genética , Ojo/crecimiento & desarrollo , Proteínas de Saccharomyces cerevisiae/genética , Apoptosis , Anomalías del Ojo/etiología , Drosophila melanogaster/citología , Drosophila melanogaster/metabolismo , Factores de Transcripción/metabolismo , Regulación de la Expresión Génica , Ojo/citología , Ojo/metabolismo , Regiones Promotoras Genéticas , Proteínas de Saccharomyces cerevisiae/metabolismoRESUMEN
Roller mutants of Caenorhabditis elegans rotate around their long axis and move in circular paths. Isolation and sequence of the rol-6 gene of C. elegans have shown that it encodes a cuticle collagen. In this paper, we describe the morphological alterations seen in the cuticle of the right roller mutant rol-6 (su1006) at the ultrastructural level. Deep-etched replica analyses showed that the honeycomb elements, fibers organized in a pentagonal fashion above the fishbone fibrous layer, completely fill the intermediate layer, which is observed to be largely empty spaces in the wild-type strain. The honeycomb fibers appear to connect the cortical and basal regions of the mutant cuticle. These fibers are likely to be involved in generating the helical twist of the mutant animals. Deep-etched replicas also revealed a delicate network of filaments on the nematode surface.
Asunto(s)
Proteínas de Caenorhabditis elegans , Caenorhabditis elegans/ultraestructura , Colágeno/genética , Proteínas del Helminto/genética , Animales , Caenorhabditis elegans/genética , Grabado por Congelación , Microscopía Electrónica , Microscopía Electrónica de Rastreo , Mutación , FenotipoRESUMEN
At the ultrastructural level, the Caenorhabdits elegans cuticle shows the presence of well defined layers; 1 of them is the fibrous layer composed by 2 strands of fibers that meet each other at a 60 degrees angle and resembling a fish-bone pattern. In this paper, we describe new elements of the fibrous layer. When thin sections were obtained at a very low angle, i.e., almost tangential, fibers of wavy appearance could be observed. Those elements were 300 nm in length and 20 nm thick and were linked to each other by delicate dots. Deep-etched replicas of C. elegans revealed more details of the arrangement of new elements in the fibrous layer. The wavy fibers were organized in 5-sided, honeycomblike figures. Each pentagonal fiber was 145 nm across and was composed of tightly packed globular structures arranged linearly.