title: The Chironomus tentans genome sequence and the organization of the Balbiani ring genes.
abstract: BACKGROUND
  The polytene nuclei of the dipteran Chironomus tentans (Ch. tentans) with their Balbiani ring (BR) genes constitute an exceptional model system for studies of the expression of endogenous eukaryotic genes. Here, we report the first draft genome of Ch. tentans and characterize its gene expression machineries and genomic architecture of the BR genes.
  
  
  RESULTS
  The genome of Ch. tentans is approximately 200 Mb in size, and has a low GC content (31%) and a low repeat fraction (15%) compared to other Dipteran species. Phylogenetic inference revealed that Ch. tentans is a sister clade to mosquitoes, with a split 150-250 million years ago. To characterize the Ch. tentans gene expression machineries, we identified potential orthologus sequences to more than 600 Drosophila melanogaster (D. melanogaster) proteins involved in the expression of protein-coding genes. We report novel data on the organization of the BR gene loci, including a novel putative BR gene, and we present a model for the organization of chromatin bundles in the BR2 puff based on genic and intergenic in situ hybridizations.
  
  
  CONCLUSIONS
  We show that the molecular machineries operating in gene expression are largely conserved between Ch. tentans and D. melanogaster, and we provide enhanced insight into the organization and expression of the BR genes. Our data strengthen the generality of the BR genes as a unique model system and provide essential background for in-depth studies of the biogenesis of messenger ribonucleoprotein complexes.
authors.forename: Alexey
authors.initials: A
authors.lastname: Kutsenko
authors.forename: Thomas
authors.initials: T
authors.lastname: Svensson
authors.forename: Björn
authors.initials: B
authors.lastname: Nystedt
authors.forename: Joakim
authors.initials: J
authors.lastname: Lundeberg
authors.forename: Petra
authors.initials: P
authors.lastname: Björk
authors.forename: Erik
authors.initials: E
authors.lastname: Sonnhammer
authors.forename: Stefania
authors.initials: S
authors.lastname: Giacomello
authors.forename: Neus
authors.initials: N
authors.lastname: Visa
authors.affiliation: Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, SE-106 91 Stockholm, Sweden. lars.wieslander@su.se.
authors.forename: Lars
authors.initials: L
authors.lastname: Wieslander
mesh_terms: D000818:Animals; D002683:Chironomidae / Q000235:genetics*; D059045:Chromosomal Puffs; D020451:Contig Mapping; D004331:Drosophila melanogaster / Q000235:genetics; D056426:Genetic Loci; D016678:Genome; D046529:Microscopy, Electron, Transmission; D058977:Molecular Sequence Annotation; D017422:Sequence Analysis, DNA; D059467:Transcriptome