title: The bristle patterning genes hairy and extramacrochaetae regulate the development of structures required for flight in Diptera.
abstract: The distribution of sensory bristles on the thorax of Diptera (true flies) provides a useful model for the study of the evolution of spatial patterns. Large bristles called macrochaetes are arranged into species-specific stereotypical patterns determined via spatially discrete expression of the proneural genes achaete-scute (ac-sc). In Drosophila ac-sc expression is regulated by transcriptional activation at sites where bristle precursors develop and by repression outside of these sites. Three genes, extramacrochaetae (emc), hairy (h) and stripe (sr), involved in repression have been documented. Here we demonstrate that in Drosophila, the repressor genes emc and h, like sr, play an essential role in the development of structures forming part of the flight apparatus. In addition we find that, in Calliphora vicina a species diverged from D. melanogaster by about 100 Myr, spatial expression of emc, h and sr is conserved at the location of development of those structures. Based on these findings we argue, first, that the role emc, h and sr in development of the flight apparatus preceded their activities for macrochaete patterning; second, that species-specific variation in activation and repression of ac-sc expression is evolving in parallel to establish a unique distribution of macrochaetes in each species.
authors.affiliation: Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3 EJ, UK.
authors.forename: Marta
authors.initials: M
authors.lastname: Costa
authors.affiliation: Centro de Biología Molecular Severo Ochoa, C/ Nicolás Cabrera, 1, Universidad Autónoma, 28049 Madrid, Spain.
authors.forename: Manuel
authors.initials: M
authors.lastname: Calleja
authors.affiliation: John Maynard Smith Building, School of Life Sciences University of Sussex, Brighton BN1 9QG, UK. Electronic address: c.alonso@sussex.ac.uk.
authors.forename: Claudio R
authors.initials: CR
authors.lastname: Alonso
authors.affiliation: Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3 EJ, UK. Electronic address: p.simpson@zoo.cam.ac.uk.
authors.forename: Pat
authors.initials: P
authors.lastname: Simpson
mesh_terms: D000818:Animals; D001483:Base Sequence; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics*; D019521:Body Patterning / Q000235:genetics*; D017931:DNA Primers; D004175:Diptera / Q000033:anatomy & histology / Q000235:genetics / Q000502:physiology*; D029721:Drosophila Proteins / Q000235:genetics*; D004331:Drosophila melanogaster; D005426:Flight, Animal; D017403:In Situ Hybridization; D019476:Insect Proteins / Q000235:genetics*; D016133:Polymerase Chain Reaction; D012097:Repressor Proteins / Q000235:genetics*
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D017931:DNA Primers; D029721:Drosophila Proteins; D019476:Insect Proteins; D012097:Repressor Proteins; C063577:emc protein, Drosophila; C061841:hairy protein, insect
keywords: Calliphora vicina; Drosophila; Flight motor; Sensory organs; scute