The key role of repeated DNAs in sex chromosome evolution in two fish species with ZW sex chromosome system

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Authors

CIOFFI Marcelo de Bello KEJNOVSKÝ Eduard MARQUIONI Vinicius POLTRONIERI Juliana MOLINA Wagner Franco DINIZ Debora BERTOLLO Luiz Antonio Carlos

Year of publication 2012
Type Article in Periodical
Magazine / Source MOLECULAR CYTOGENETICS
MU Faculty or unit

Central European Institute of Technology

Citation
Web http://www.molecularcytogenetics.org/content/5/1/28
Doi http://dx.doi.org/10.1186/1755-8166-5-28
Field Genetics and molecular biology
Keywords Microsatellites; Sex chromosome evolution; Heterochromatin; Fish; ZW systems
Description Despite substantial progress, there are still several gaps in our knowledge about the process of sex chromosome differentiation. The degeneration of sex-specific chromosome in some species is well documented, but it is not clear if all species follow the same evolutionary pathway. The accumulation of repetitive DNA sequences, however, is a common feature. To better understand this involvement, fish species emerge as excellent models because they exhibit a wide variety of sex chromosome and sex determining systems. Besides, they have much younger sex chromosomes compared to higher vertebrates, making it possible to follow early steps of differentiation. Here, we analyzed the arrangement of 9 repetitive DNA sequences in the W chromosomes of 2 fish species, namely Leporinus reinhardti and Triportheus auritus, which present well-differentiated ZZ/ZW sex system, but differ in respect to the size of the sex-specific chromosome. Both W chromosomes are almost fully heterochromatic, with accumulation of repeated DNAs in their heterochromatic regions. We found that microsatellites have strongly accumulated on the large W chromosome of L. reinhardti but not on the reduced-size W chromosome of T. auritus and are therefore important players of the W chromosome expansion. The present data highlight that the evolution of the sex chromosomes can diverge even in the same type of sex system, with and without the degeneration of the specific-sex chromosome, being more dynamic than traditionally appreciated.
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