We describe a collection of P-element insertions that have considerable utility for generating custom chromosomal aberrations in Drosophila melanogaster. We have mobilized a pair of engineered P elements, p{RS3} and p{RS5}, to collect 3243 lines unambiguously mapped to the Drosophila genome sequence. The collection contains, on average, an element every 35 kb. We demonstrate the utility of the collection for generating custom chromosomal deletions that have their end points mapped, with base-pair resolution, to the genome sequence. The collection was generated in an isogenic strain, thus affording a uniform background for screens where sensitivity to genetic background is high. The entire collection, along with a computational and genetic toolbox for designing and generating custom deletions, is publicly available. Using the collection it is theoretically possible to generate >12,000 deletions between 1 bp and 1 Mb in size by simple eye color selection. In addition, a further 37,000 deletions, selectable by molecular screening, may be generated. We are now using the collection to generate a second-generation deficiency kit that is precisely mapped to the genome sequence.

Upon apoptotic stimuli, epithelial cells compensate the gaps left by dead cells by activating proliferation. This has led to the proposal that dying cells signal to surrounding living cells to maintain homeostasis. Although the nature of these signals is not clear, reactive oxygen species (ROS) could act as a signaling mechanism as they can trigger pro-inflammatory responses to protect epithelia from environmental insults. Whether ROS emerge from dead cells and what is the genetic response triggered by ROS is pivotal to understand regeneration of Drosophila imaginal discs. We genetically induced cell death in wing imaginal discs, monitored the production of ROS and analyzed the signals required for repair. We found that cell death generates a burst of ROS that propagate to the nearby surviving cells. Propagated ROS activate p38 and induce tolerable levels of JNK. The activation of JNK and p38 results in the expression of the cytokines Unpaired (Upd), which triggers the JAK/STAT signaling pathway required for regeneration. Our findings demonstrate that this ROS/JNK/p38/Upd stress responsive module restores tissue homeostasis. This module is not only activated after cell death induction but also after physical damage and reveals one of the earliest responses for imaginal disc regeneration. Regenerative biology pursues to unveil the genetic networks triggered by tissue damage. Regeneration can occur after damage by cell death or by injury. We used the imaginal disc of Drosophila in which we genetically activated apoptosis or physically removed some parts and monitored the capacity to repair the damage. We found that dying cells generate a burst of reactive oxygen species (ROS) necessary to activate JNK and p38 signaling pathways in the surrounding living cells. The action of these pathways is necessary for the activation of the cytokines Unpaired (Upd). Eventually, Upd will turn on the JAK/STAT signaling pathway to induce regenerative growth. Thus, we present here a module of signals that depends on oxidative stress and that, through the p38-JNK interplay, will activate cytokine-dependent regeneration.

We describe a second-generation deficiency kit for Drosophila melanogaster composed of molecularly mapped deletions on an isogenic background, covering ∼77% of the Release 5.1 genome. Using a previously reported collection of FRT-bearing P-element insertions, we have generated 655 new deletions and verified a set of 209 deletion-bearing fly stocks. In addition to deletions, we demonstrate how the P elements may also be used to generate a set of custom inversions and duplications, particularly useful for balancing difficult regions of the genome carrying haplo-insufficient loci. We describe a simple computational resource that facilitates selection of appropriate elements for generating custom deletions. Finally, we provide a computational resource that facilitates selection of other mapped FRT-bearing elements that, when combined with the DrosDel collection, can theoretically generate over half a million precisely mapped deletions.

Regeneration and tissue repair allow damaged or lost body parts to be replaced. After injury or fragmentation of Drosophila imaginal discs, regeneration leads to the development of normal adult structures. This process is likely to involve a combination of cell rearrangement and compensatory proliferation. However, the detailed mechanisms underlying these processes are poorly understood. We have established a system to allow temporally restricted induction of cell death in situ. Using Gal4/Gal80 and UAS-rpr constructs, targeted ablation of a region of the disc could be performed and regeneration monitored without the requirement for microsurgical manipulation. Using a ptc-Gal4 construct to drive rpr expression in the wing disc resulted in a stripe of dead cells in the anterior compartment flanking the anteroposterior boundary, whereas a sal-Gal4 driver generated a dead domain that includes both anterior and posterior cells. Under these conditions, regenerated tissues were derived from the damaged compartment, suggesting that compartment restrictions are preserved during regeneration. Our studies reveal that during regeneration the live cells bordering the domain in which cell death was induced first display cytoskeletal reorganisation and apical-to-basal closure of the epithelium. Then, proliferation begins locally in the vicinity of the wound and later more extensively in the affected compartment. Finally, we show that regeneration of genetically ablated tissue requires JNK activity. During cell death-induced regeneration, the JNK pathway is activated at the leading edges of healing tissue and not in the apoptotic cells, and is required for the regulation of healing and regenerative growth.

EMBO Press is an editorially independent publishing platform for the development of EMBO scientific publications.