title: Comparative Analysis of the Shared Sex-Determination Region (SDR) among Salmonid Fishes.
abstract: Salmonids present an excellent model for studying evolution of young sex-chromosomes. Within the genus, Oncorhynchus, at least six independent sex-chromosome pairs have evolved, many unique to individual species. This variation results from the movement of the sex-determining gene, sdY, throughout the salmonid genome. While sdY is known to define sexual differentiation in salmonids, the mechanism of its movement throughout the genome has remained elusive due to high frequencies of repetitive elements, rDNA sequences, and transposons surrounding the sex-determining regions (SDR). Despite these difficulties, bacterial artificial chromosome (BAC) library clones from both rainbow trout and Atlantic salmon containing the sdY region have been reported. Here, we report the sequences for these BACs as well as the extended sequence for the known SDR in Chinook gained through genome walking methods. Comparative analysis allowed us to study the overlapping SDRs from three unique salmonid Y chromosomes to define the specific content, size, and variation present between the species. We found approximately 4.1 kb of orthologous sequence common to all three species, which contains the genetic content necessary for masculinization. The regions contain transposable elements that may be responsible for the translocations of the SDR throughout salmonid genomes and we examine potential mechanistic roles of each one.
authors.affiliation: Department of Biology, Portland State University School of Biological Sciences, Washington State University Vancouver.
authors.forename: Joshua J
authors.initials: JJ
authors.lastname: Faber-Hammond
authors.affiliation: School of Biological Sciences, Washington State University Vancouver Center for Reproductive Biology, Washington State University, Pullman.
authors.forename: Ruth B
authors.initials: RB
authors.lastname: Phillips
authors.affiliation: Department of Biology, Portland State University kibr2@pdx.edu.
authors.forename: Kim H
authors.initials: KH
authors.lastname: Brown
mesh_terms: D000818:Animals; D029941:Fish Proteins / Q000235:genetics; D008297:Male; D008969:Molecular Sequence Data; D017683:Oncorhynchus / Q000235:genetics; D017686:Oncorhynchus mykiss / Q000235:genetics; D012194:RNA-Directed DNA Polymerase / Q000235:genetics; D018626:Retroelements; D020317:Salmo salar / Q000235:genetics; D012487:Salmonidae / Q000235:genetics*; D019849:Sex Determination Processes; D014998:Y Chromosome
chemical_list: D029941:Fish Proteins; D018626:Retroelements; D012194:RNA-Directed DNA Polymerase
keywords: comparative genomics; retrotransposition; salmonid; sex-chromsome; sex-determination; transposable element