title: An Unusual Role for doublesex in Sex Determination in the Dipteran Sciara.
abstract: The gene doublesex, which is placed at the bottom of the sex-determination gene cascade, plays the ultimate discriminatory role for sex determination in insects. In all insects where this gene has been characterized, the dsx premessenger RNA (pre-mRNA) follows a sex-specific splicing pattern, producing male- and female-specific mRNAs encoding the male-DSXM and female-DSXF proteins, which determine male and female development, respectively. This article reports the isolation and characterization of the gene doublesex of dipteran Sciara insects. The Sciara doublesex gene is constitutively transcribed during development and adult life of males and females. Sciara had no sex-specific doublesex mRNAs but the same transcripts, produced by alternative splicing of its primary transcript, were present in both sexes, although their relative abundance is sex specific. However, only the female DSXF protein, but not the male DSXM protein, was produced at similar amounts in both sexes. An analysis of the expression of female and male Sciara DSX proteins in Drosophila showed that these proteins conserved female and male function, respectively, on the control of Drosophila yolk-protein genes. The molecular evolution of gene doublesex of all insects where this gene has been characterized revealed that Sciara doublesex displays a considerable degree of divergence in its molecular organization and its splicing pattern with respect to the rest of dipterans as suggested by its basal position within the doublesex phylogeny. It is suggested that the doublesex gene is involved in Sciara sex determination although it appears not to play the discriminatory role performed in other insects.
authors.affiliation: Centro de Investigaciones Biológicas (Consejo Superior de Investigaciones Cientifícas), 28040 Madrid, Spain.
authors.forename: María Fernanda
authors.initials: MF
authors.lastname: Ruiz
authors.affiliation: Centro de Investigaciones Biológicas (Consejo Superior de Investigaciones Cientifícas), 28040 Madrid, Spain.
authors.forename: Mercedes
authors.initials: M
authors.lastname: Alvarez
authors.affiliation: Department of Biological Sciences, Florida International University, North Miami, Florida 33181.
authors.forename: José M
authors.initials: JM
authors.lastname: Eirín-López
authors.affiliation: Centro de Investigaciones Biológicas (Consejo Superior de Investigaciones Cientifícas), 28040 Madrid, Spain.
authors.forename: Francesca
authors.initials: F
authors.lastname: Sarno
authors.affiliation: Department of Immunology and Oncology, Centro Nacional de Biotecnología (Consejo Superior de Investigaciones Cientifícas), 28049 Madrid, Spain.
authors.forename: Leonor
authors.initials: L
authors.lastname: Kremer
authors.affiliation: Centro de Investigaciones Biológicas (Consejo Superior de Investigaciones Cientifícas), 28040 Madrid, Spain.
authors.forename: José L
authors.initials: JL
authors.lastname: Barbero
authors.affiliation: Centro de Investigaciones Biológicas (Consejo Superior de Investigaciones Cientifícas), 28040 Madrid, Spain lsanchez@cib.csic.es.
authors.forename: Lucas
authors.initials: L
authors.lastname: Sánchez
mesh_terms: D000818:Animals; D004175:Diptera / Q000235:genetics* / Q000378:metabolism*; D029721:Drosophila Proteins / Q000235:genetics; D005260:Female; D005786:Gene Expression Regulation; D019476:Insect Proteins / Q000235:genetics / Q000378:metabolism*; D008297:Male; D010802:Phylogeny; D012326:RNA Splicing; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D019849:Sex Determination Processes
chemical_list: D029721:Drosophila Proteins; D019476:Insect Proteins; D012333:RNA, Messenger
keywords: Sciara; gene doublesex; genetics of sex; molecular evolution; sex determination