Project description:Thomas Hunt Morgan and colleagues identified variation in gene copy number in Drosophila in the 1920s and 1930s and linked such variation to phenotypic differences [Bridges, C. B. (1936) Science 83, 210]. Yet the extent of variation in the number of chromosomes, chromosomal regions, or gene copies, and the importance of this variation within species, remain poorly understood. Here, we focus on copy-number variation in Drosophila melanogaster. We characterize copy-number polymorphism (CNP) across genomic regions, and we contrast patterns to infer the evolutionary processes acting on this variation. Copy-number variation in D. melanogaster is non-randomly distributed, presumably due to a mutational bias produced by tandem repeats or other mechanisms. Comparisons of coding and noncoding CNPs, however, reveal a strong effect of purifying selection in the removal of structural variation from functionally constrained regions. Most patterns of CNP in D. melanogaster suggest that negative selection and mutational biases are the primary agents responsible for shaping structural variation. Keywords: comparative genomic hybridization
Project description:The role natural selection plays in governing the locations and early evolution of copy number mutations remains largely unexplored. Here we employ high-density full-genome tiling arrays to create a fine-scale genomic map of copy number polymorphisms (CNPs) in Drosophila melanogaster. We inferred a total of 2,658 independent CNPs, 56% of which overlap genes. These include CNPs likely to be under positive selection, most notably high frequency duplications encompassing toxin-response genes. The locations and frequencies of CNPs are strongly shaped by purifying selection with deletions under stronger purifying selection than duplications. Among duplications, those overlapping exons or introns and those falling on the X-chromosome seem to be subject to the strongest purifying selection. In order to characterize copy number polymorphisms (CNPs) in Drosophila malanogaster, we applied comparative genome hybridization (CGH) using tiling arrays covering the full euchromatic genome of Drosophila melanogaster. We inferred copy number changes with a Hidden Markov Model (HMM) that returned the posterior probabilities for copy number by comparing DNA hybridization intensities between natural isolates and the reference genome strain. Training data for copy number changes were obtained via hybridization with a line known to contain a ~200kb homozygous duplication and from a set of 52 validated homozygous deletions. The probabilities of mutation were parsed to make CNP calls. Key words: comparative genomic hybridization, CGH, copy number polymorphism, CNP, copy number variation, CNV, duplication, deletion
Project description:These arrays were done in the context of a study to probe gene expression variation across Y-chromosome substitution lines of Drosophila melanogaster Keywords: polymorphism, evolution, chromosome substitution
Project description:In Drosophila melanogaster larval hemolymph, under normal conditions, plasmatocytes and crystal cells represent respectively ~95% and ~5% of hemocytes, while lamellocytes, the third larval cell type, are absent since they are only induced after parasitoid wasp oviposition, their role being the encapsulation-melanization response to eliminate the wasp egg. However, even after induction lamellocytes number remains low, making difficult biochemical studies. Here using the D. melanogaster hopTum-l mutant that constitutively produces a high number of hemocytes, we set up a method to purify lamellocytes and analyzed their major proteins by 2D gel electrophoresis and their biotinylated plasma membrane surface proteins by 1D SDS-PAGE after affinity purification. Mass spectrometry allowed to identify 430 proteins from the 2D spots and 344 from affinity purified proteins, totalizing 639 unique proteins. Known lamellocyte markers such as PPO3 and the integrin myospheroid are among the major proteins and affinity purification led to the detection of other integrins and a large array of integrins associated proteins involved in cell-cell junction formation and function. Overall newly identified proteins indicated that these cells are highly adapted to the encapsulation process but may have also several different physiological functions. This study provides the basis for new lamellocyte studies in vivo and in vitro, and develop markers to search whether different populations coexist, establish their origins and decipher their respective roles in drosophila physiology and immunity.
Project description:Thermal acclimation study on Drosophila melanogaster reared at 3 different temperatures (12, 25, and 31oC). The proteomic profiles of D. melanogaster under these different temperatures were analyzed and compared using label-free tandem mass spectrometry.