Comparison of the heterochromatin and telomeric sequences distribuition in chromosomes of 11 species of Amazonian marsupials (Didelphimorphia; Didelphidae).

Carlos Eduardo Faresin E Silva,Eduardo Schmidt Eler,Eliana Feldberg,Maria Nazareth Ferreira Da Silva,Érica Martinha Silva De Souza

doi:10.1590/1678-4685-gmb-2019-0357

Carlos Eduardo Faresin E Silva, Eduardo Schmidt Eler + Show 3 more

Open Access

https://doi.org/10.1590/1678-4685-gmb-2019-0357

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Abstract

In recent decades the diploid numbers recorded in the New World marsupials have been widely discussed in the context of the processes of karyotype evolution in these mammals. While Interstitial Telomeric Sequences (ITS) have long been interpreted as remnants of chromosomal fusion, the biological role of these features, together with their intraspecific variation, has raised a number of questions. In the present study, we analyzed the karyotype of 11 species of Amazonian didelphids, comparing the distribution of the heterochromatin with that of the telomeric signals, and found that, in six species, the ITS coincided with the blocks of heterochromatin. While ITS were found in the X chromosomes of all Marmosa murina individuals, they were variable in all the other species, representing a specific character of each lineage. Our results support the conclusion that ITS may not always be a consequence of chromosomal rearrangements, and that the mechanisms that produce them are still unclear.

Highlights

The most common diploid numbers among marsupials are 2n = 14 and 2n = 22, in both New World and Australian species (Sharman, 1961, 1982; Biggers et al, 1965; Hayman and Martin, 1974; Rofe and Hayman, 1985; Hayman, 1990)
Pagnozzi et al (2000, 2002) analyzed these markers in didelphid species, and found that the ITSs overlap with the heterochromatin and varied in number intraspecifically, indicating that they were not necessarily the result of recent fusions
Metcalfe et al (2004) concluded that not all the ITSs found in Australian marsupials of the family Macropodidae are evidence of fusions, except when they are the principal components of the heterochromatin

Summary

Introduction

In the Didelphidae, these sequences have been detected in centromeric regions, in species with both 2n = 14 and 2n = 18 chromosomes, which indicates that they are remnants of fusions from a 2n = 22 karyotype (Svartman and Vianna-Morgante, 1998; Carvalho and Mattevi, 2000). Pagnozzi et al (2000, 2002) analyzed these markers in didelphid species, and found that the ITSs overlap with the heterochromatin and varied in number intraspecifically, indicating that they were not necessarily the result of recent fusions.

Results

Conclusion