P1 interneurons promote a persistent internal state that enhances inter-male aggression in Drosophila

How brains are hardwired to produce aggressive behavior, and how aggression circuits are related to those that mediate courtship, is not well understood. A large-scale screen for aggression-promoting neurons in Drosophila identified several independent hits that enhanced both inter-male aggression and courtship. Genetic intersections revealed that P1 interneurons, previously thought to exclusively control male courtship, were responsible for both phenotypes. The aggression phenotype was fly-intrinsic, and required male-specific chemosensory cues on the opponent. Optogenetic experiments indicated that P1 activation promoted aggression vs. wing extension at low vs. high thresholds, respectively. High frequency photostimulation promoted wing extension and aggression in an inverse manner, during light ON and OFF, respectively. P1 activation enhanced aggression by promoting a persistent internal state, which could endure for minutes prior to social contact. Thus P1 neurons promote an internal state that facilitates both aggression and courtship, and can control these social behaviors in a threshold-dependent manner

A molecular analysis of three unstable alleles in drosophila : (transposable elements, mutable alleles, white locus)

We have determined the structure of several unstable mutant alleles of the white locus in Drosophila melanogaster. The white ivory (w[superscript i]) allele is a moderately unstable allele, which gave rise to the highly unstable white-crimson (w[superscript C]) allele. We have determined that the w[superscript i] mutation is due to the duplication of 2.9 kilobases (kb) of DNA within the white locus, and that reversion of w[superscript i] to wild type usually occurs by simple loss of one copy of the duplication. We have also analyzed two highly unstable alleles of the white locus, we and white dominant zeste-like (w[superscript DZL]) and have shown that both are insertion mutations. The w[superscript C] mutation results from the insertion of 10 kb of DNA into the w[superscript i] duplication, and the w[superscript DZL] mutation results from the insertion of 13 kb of DNA at or near the right end of the white locus. The w[superscript C] and w[superscript DZL] insertions are structurally related, but not identical, and are related to a previously characterized family of transposable elements, the fold back(FB) elements. The we insertion consists of a single FB elementwith a low eopy number sequence between the moderately repetitive terminal inverted repeats. The wDZL insertion contains two FB elements which flank a single copy sequence in the middle of the insertion. Reversion of w[superscript C] to w[superscript i] is mediated by an apparently precise excision event, while reversion of w[superscript DZL] to wild type occurs by an imprecise excision of the insertion. We suggest that structural differences in the two insertions may account for these different modes of reversion.Mary Collins, Robert Levis, Roger Karess, and Gerald M. Rubin, Department of Embryology Carnegie Institute of Washington, 115 West University Parkway, Baltimore, Maryland

Global analysis of patterns of gene expression during Drosophila embryogenesis

Embryonic expression patterns for 6,003 (44%) of the 13,659 protein-coding genes identified in the Drosophila melanogaster genome were documented, of which 40% show tissue-restricted expression

Computational identification of developmental enhancers: conservation and function of transcription factor binding-site clusters in Drosophila melanogaster and Drosophila pseudoobscura

BACKGROUND: The identification of sequences that control transcription in metazoans is a major goal of genome analysis. In a previous study, we demonstrated that searching for clusters of predicted transcription factor binding sites could discover active regulatory sequences, and identified 37 regions of the Drosophila melanogaster genome with high densities of predicted binding sites for five transcription factors involved in anterior-posterior embryonic patterning. Nine of these clusters overlapped known enhancers. Here, we report the results of in vivo functional analysis of 27 remaining clusters. RESULTS: We generated transgenic flies carrying each cluster attached to a basal promoter and reporter gene, and assayed embryos for reporter gene expression. Six clusters are enhancers of adjacent genes: giant, fushi tarazu, odd-skipped, nubbin, squeeze and pdm2; three drive expression in patterns unrelated to those of neighboring genes; the remaining 18 do not appear to have enhancer activity. We used the Drosophila pseudoobscura genome to compare patterns of evolution in and around the 15 positive and 18 false-positive predictions. Although conservation of primary sequence cannot distinguish true from false positives, conservation of binding-site clustering accurately discriminates functional binding-site clusters from those with no function. We incorporated conservation of binding-site clustering into a new genome-wide enhancer screen, and predict several hundred new regulatory sequences, including 85 adjacent to genes with embryonic patterns. CONCLUSIONS: Measuring conservation of sequence features closely linked to function - such as binding-site clustering - makes better use of comparative sequence data than commonly used methods that examine only sequence identity

Drosophila melanogaster MNK/Chk2 and p53 regulate multiple DNA repair and apoptotic pathways following DNA damage

We have used genetic and microarray analysis to determine how ionizing radiation (IR) induces p53-dependent transcription and apoptosis in Drosophila melanogaster. IR induces MNK/Chk2-dependent phosphorylation of p53 without changing p53 protein levels, indicating that p53 activity can be regulated without an Mdm2-like activity. In a genome-wide analysis of IR-induced transcription in wild-type and mutant embryos, all IR-induced increases in transcript levels required both p53 and the Drosophila Chk2 homolog MNK. Proapoptotic targets of p53 include hid, reaper, sickle, and the tumor necrosis factor family member EIGER: Overexpression of Eiger is sufficient to induce apoptosis, but mutations in Eiger do not block IR-induced apoptosis. Animals heterozygous for deletions that span the reaper, sickle, and hid genes exhibited reduced IR-dependent apoptosis, indicating that this gene complex is haploinsufficient for induction of apoptosis. Among the genes in this region, hid plays a central, dosage-sensitive role in IR-induced apoptosis. p53 and MNK/Chk2 also regulate DNA repair genes, including two components of the nonhomologous end-joining repair pathway, Ku70 and Ku80. Our results indicate that MNK/Chk2-dependent modification of Drosophila p53 activates a global transcriptional response to DNA damage that induces error-prone DNA repair as well as intrinsic and extrinsic apoptosis pathways

The transposable elements of the Drosophila melanogaster euchromatin: a genomics perspective.

BACKGROUND: Transposable elements are found in the genomes of nearly all eukaryotes. The recent completion of the Release 3 euchromatic genomic sequence of Drosophila melanogaster by the Berkeley Drosophila Genome Project has provided precise sequence for the repetitive elements in the Drosophila euchromatin. We have used this genomic sequence to describe the euchromatic transposable elements in the sequenced strain of this species. RESULTS: We identified 85 known and eight novel families of transposable element varying in copy number from one to 146. A total of 1,572 full and partial transposable elements were identified, comprising 3.86% of the sequence. More than two-thirds of the transposable elements are partial. The density of transposable elements increases an average of 4.7 times in the centromere-proximal regions of each of the major chromosome arms. We found that transposable elements are preferentially found outside genes; only 436 of 1,572 transposable elements are contained within the 61.4 Mb of sequence that is annotated as being transcribed. A large proportion of transposable elements is found nested within other elements of the same or different classes. Lastly, an analysis of structural variation from different families reveals distinct patterns of deletion for elements belonging to different classes. CONCLUSIONS: This analysis represents an initial characterization of the transposable elements in the Release 3 euchromatic genomic sequence of D. melanogaster for which comparison to the transposable elements of other organisms can begin to be made. These data have been made available on the Berkeley Drosophila Genome Project website for future analyses.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are

The transposable elements of the Drosophila melanogaster

Background: Transposable elements are found in the genomes of nearly all eukaryotes. The recent completion of the Release 3 euchromatic genomic sequence of Drosophila melanogaster by the Berkeley Drosophila Genome Project has provided precise sequence for the repetitive elements in the Drosophila euchromatin. We have used this genomic sequence to describe the euchromatic transposable elements in the sequenced strain of this species. Results: We identified 85 known and eight novel families of transposable element varying in copy number from one to 146. A total of 1,572 full and partial transposable elements were identified, comprising 3.86% of the sequence. More than two-thirds of the transposable elements are partial. The density of transposable elements increases an average of 4.7 times in the centromereproximal regions of each of the major chromosome arms. We found that transposable elements are preferentially found outside genes; only 436 of 1,572 transposable elements are contained within the 61.4 Mb of sequence that is annotated as being transcribed. A large proportion of transposable elements is found nested within other elements of the same or different classes. Lastly, an analysis of structural variation from different families reveals distinct patterns of deletion for elements belonging to different classes. Conclusions: This analysis represents an initial characterization of the transposable elements in the Release 3 euchromatic genomic sequence of D. melanogaster for which comparison to the transposable elements of other organisms can begin to be made. These data have been made available on the Berkeley Drosophila Genome Project website for future analyses