The Drosophila fos (Dfos)/kayak gene has been previously identified as a key regulator of epithelial cell morphogenesis during dorsal closure of the embryo and fusion of the adult thorax. We show here that it is also required for two morphogenetic movements of the follicular epithelium during oogenesis. Firstly, it is necessary for the proper posteriorward migration of main body follicle cells during stage 9. Secondly, it controls, from stage 11 onwards, the morphogenetic reorganization of the follicle cells that are committed to secrete the respiratory appendages. We demonstrate that DER pathway activation and a critical level of Dpp/TGFbeta signalling are required to pattern a high level of transcription of Dfos at the anterior and dorsal edges of the two groups of cells that will give rise to the respiratory appendages. In addition, we provide evidence that, within the dorsal-anterior territory, the level of paracrine Dpp/TGFbeta signalling controls the commitment of follicle cells towards either an operculum or an appendage secretion fate. Finally, we show that Dfos is required in follicle cells for the dumping of the nurse cell cytoplasm into the oocyte and the subsequent apoptosis of nurse cells. This suggests that in somatic follicle cells, Dfos controls the expression of one or several factors that are necessary for these processes in underlying germinal nurse cells.

We have established a collection of 2460 lethal or semi-lethal mutant lines using a procedure thought to insert single P elements into vital genes on the third chromosome of Drosophila melanogaster. More than 1200 randomly selected lines were examined by in situ hybridization and 90% found to contain single insertions at sites that mark 89% of all lettered subdivisions of the Bridges' map. A set of chromosomal deficiencies that collectively uncover ~25% of the euchromatin of chromosome 3 reveal lethal mutations in 468 lines corresponding to 145 complementation groups. We undertook a detailed analysis of the cytogenetic interval 86E-87F and identified 87 P-element-induced mutations falling into 38 complementation groups, 16 of which correspond to previously known genes. Twenty-one of these 38 complementation groups have at least one allele that has a P-element insertion at a position consistent with the cytogenetics of the locus. We have rescued P elements and flanking chromosomal sequences from the 86E-87F region in 35 lines with either lethal or genetically silent P insertions, and used these as probes to identify cosmids and P1 clones from the Drosophila genome projects. This has tied together the physical and genetic maps and has linked 44 previously identified cosmid contigs into seven “super-contigs” that span the interval. STS data for sequences flanking one side of the P-element insertions in 49 lines has identified insertions in the αγ element at 87C, two known transposable elements, and the open reading frames of seven putative single copy genes. These correspond to five known genes in this interval, and two genes identified by the homology of their predicted products to known proteins from other organisms.

No abstract

In most Eukaryotes, ubiquitin either exists as free monoubiquitin or as a molecule that is covalently linked to other proteins. These two forms cycle between each other and due to the concerted antagonistic activity of ubiquitylating and deubiquitylating enzymes, an intracellular ubiquitin equilibrium is maintained that is essential for normal biological function. However, measuring the level and ratio of these forms of ubiquitin has been difficult and time consuming. In this paper, we have adapted a simple immunoblotting technique to monitor ubiquitin content and equilibrium dynamics in different developmental stages and tissues of Drosophila. Our data show that the level of total ubiquitin is distinct in different developmental stages, lowest at the larvalpupal transition and in three days old adult males, and highest in first instar larvae. Interestingly, the ratio of free mono-ubiquitin remains within 30-50% range of the total throughout larval development, but peaks to 70-80% at the larval-pupal and the pupal-adult transitions. It stays within the 70-80% range in adults. In developmentally and physiologically active tissues, the ratio of free ubiquitin is similarly high, most likely reflecting a high demand for ubiquitin availability. We also used this method to demonstrate the disruption of the finely tuned ubiquitin equilibrium by the abolition of proteasome function or the housekeeping deubiquitylase, Usp5. Our data support the notion that the ubiquitin equilibrium is regulated by tissue-and developmental stagespecific mechanisms.