title: Amplification of microsatellite repeat motifs is associated with the evolutionary differentiation and heterochromatinization of sex chromosomes in Sauropsida.
abstract: The sex chromosomes in Sauropsida (reptiles and birds) have evolved independently many times. They show astonishing diversity in morphology ranging from cryptic to highly differentiated sex chromosomes with male (XX/XY) and female heterogamety (ZZ/ZW). Comparing such diverse sex chromosome systems thus provides unparalleled opportunities to capture evolution of morphologically differentiated sex chromosomes in action. Here, we describe chromosomal mapping of 18 microsatellite repeat motifs in eight species of Sauropsida. More than two microsatellite repeat motifs were amplified on the sex-specific chromosome, W or Y, in five species (Bassiana duperreyi, Aprasia parapulchella, Notechis scutatus, Chelodina longicollis, and Gallus gallus) of which the sex-specific chromosomes were heteromorphic and heterochromatic. Motifs (AAGG)n and (ATCC)n were amplified on the W chromosome of Pogona vitticeps and the Y chromosome of Emydura macquarii, respectively. By contrast, no motifs were amplified on the W chromosome of Christinus marmoratus, which is not much differentiated from the Z chromosome. Taken together with previously published studies, our results suggest that the amplification of microsatellite repeats is tightly associated with the differentiation and heterochromatinization of sex-specific chromosomes in sauropsids as well as in other taxa. Although some motifs were common between the sex-specific chromosomes of multiple species, no correlation was observed between this commonality and the species phylogeny. Furthermore, comparative analysis of sex chromosome homology and chromosomal distribution of microsatellite repeats between two closely related chelid turtles, C. longicollis and E. macquarii, identified different ancestry and differentiation history. These suggest multiple evolutions of sex chromosomes in the Sauropsida.
authors.affiliation: Institute for Applied Ecology, University of Canberra, Bruce, Australian Capital Territory, 2601, Australia. baramaty@nuagr1.agr.nagoya-u.ac.jp.|Laboratory of Animal Genetics, Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, 464-8601, Japan. baramaty@nuagr1.agr.nagoya-u.ac.jp.
authors.forename: Kazumi
authors.initials: K
authors.lastname: Matsubara
authors.affiliation: Institute for Applied Ecology, University of Canberra, Bruce, Australian Capital Territory, 2601, Australia.
authors.forename: Denis
authors.initials: D
authors.lastname: O'Meally
authors.affiliation: Institute for Applied Ecology, University of Canberra, Bruce, Australian Capital Territory, 2601, Australia.|The John Curtin School of Medical Research, The Australian National University, Garran Road, Acton, Australian Capital Territory, 2601, Australia.
authors.forename: Bhumika
authors.initials: B
authors.lastname: Azad
authors.affiliation: Institute for Applied Ecology, University of Canberra, Bruce, Australian Capital Territory, 2601, Australia.
authors.forename: Arthur
authors.initials: A
authors.lastname: Georges
authors.affiliation: Institute for Applied Ecology, University of Canberra, Bruce, Australian Capital Territory, 2601, Australia.
authors.forename: Stephen D
authors.initials: SD
authors.lastname: Sarre
authors.affiliation: Institute for Applied Ecology, University of Canberra, Bruce, Australian Capital Territory, 2601, Australia.|School of Life Sciences, La Trobe University, Melbourne, 3086, Victoria, Australia.
authors.forename: Jennifer A Marshall
authors.initials: JA
authors.lastname: Graves
authors.affiliation: Laboratory of Animal Genetics, Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, 464-8601, Japan.
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Matsuda
authors.affiliation: Institute for Applied Ecology, University of Canberra, Bruce, Australian Capital Territory, 2601, Australia. Tariq.Ezaz@canberra.edu.au.
authors.forename: Tariq
authors.initials: T
authors.lastname: Ezaz
mesh_terms: D000818:Animals; D002645:Chickens / Q000235:genetics*; D002874:Chromosome Mapping; D004303:Dosage Compensation, Genetic; D019143:Evolution, Molecular; D005260:Female; D006570:Heterochromatin; D008297:Male; D018895:Microsatellite Repeats; D012104:Reptiles / Q000235:genetics*; D012730:Sex Chromosomes
chemical_list: D006570:Heterochromatin