title: Chromosomal Mapping of Repetitive DNAs in Myiopsitta monachus and Amazona aestiva (Psittaciformes, Psittacidae) with Emphasis on the Sex Chromosomes.
abstract: Here, for the first time, we describe the karyotype of Myiopsitta monachus (Psittacidae, Arini). We found 2n = 48, corresponding to the lowest diploid number observed in Neotropical Psittaciformes so far, with an uncommonly large W chromosome homomorphic to the Z. In order to better understand the evolution of the sex chromosomes in this species, we applied several molecular cytogenetic approaches, including C-banding, FISH mapping of repetitive DNAs (several microsatellite repeats), and whole-chromosome painting on metaphases of M. monachus. For comparison, another species belonging to the same tribe but with a smaller W chromosome (A. aestiva) was also analyzed. The results show that the constitutive heterochromatin has a very diverse distribution pattern in these species revealing heterochromatic blocks in the centromeric region of all chromosomes and in most of the length of the W chromosome in A. aestiva, while in M. monachus they were found in interstitial and telomeric regions. Concerning the microsatellites, only the sequence (CG)n produced signals on the W chromosome of A. aestiva, in the distal region of both arms. However, in M. monachus, (CAA)n, (CAG)n, and (CG)n probes were accumulated on the W chromosome, and, in addition, the sequence (CAG)n also hybridized to heterochromatic regions in macrochromosomes, as well as in microchromosomes. Based on these results, we suggest that the increase in length of the W chromosome in M. monachus is due to the amplification of repetitive elements, which highlights their significant role in the evolutionary process of sex chromosome differentiation.
authors.affiliation: Programa de Pós Graduação em Genética e Biologia Molecular, Universidade Federal do Pará, Belém, Brazil.
authors.forename: Ivanete
authors.initials: I
authors.lastname: de Oliveira Furo
authors.forename: Rafael
authors.initials: R
authors.lastname: Kretschmer
authors.forename: Michelly S
authors.initials: MS
authors.lastname: Dos Santos
authors.forename: Carlos A
authors.initials: CA
authors.lastname: de Lima Carvalho
authors.forename: Ricardo J
authors.initials: RJ
authors.lastname: Gunski
authors.forename: Patrícia C M
authors.initials: PCM
authors.lastname: O'Brien
authors.forename: Malcolm A
authors.initials: MA
authors.lastname: Ferguson-Smith
authors.forename: Marcelo B
authors.initials: MB
authors.lastname: Cioffi
authors.forename: Edivaldo H C
authors.initials: EHC
authors.lastname: de Oliveira
mesh_terms: D000818:Animals; D002874:Chromosome Mapping; D005260:Female; D006570:Heterochromatin / Q000235:genetics; D007621:Karyotyping; D008297:Male; D011563:Psittaciformes / Q000145:classification* / Q000235:genetics*; D012091:Repetitive Sequences, Nucleic Acid; D012730:Sex Chromosomes / Q000235:genetics*; D016615:Telomere / Q000235:genetics
chemical_list: D006570:Heterochromatin
keywords: Constitutive heterochromatin; Karyotype description; Microsatellites; Neotropical Psittacidae; Sex chromosomes