Format

Send to

Choose Destination
See comment in PubMed Commons below
BMC Genet. 2012 Apr 20;13:28. doi: 10.1186/1471-2156-13-28.

Comparative karyotype analysis and chromosome evolution in the genus Aplastodiscus (Cophomantini, Hylinae, Hylidae).

Author information

  • 1UNESP, Universidade Estadual Paulista, Instituto de Biociências, Departamento de Biologia, Av, 24A, 1515, 13506-900, Rio Claro, SP, Brazil. sisilgg@hotmail.com

Abstract

BACKGROUND:

The frogs of the Tribe Cophomantini present, in general, 2n = 24 karyotype, but data on Aplastodiscus showed variation in diploid number from 2n = 24 to 2n = 18. Five species were karyotyped, one of them for the first time, using conventional and molecular cytogenetic techniques, with the aim to perform a comprehensive comparative analysis towards the understanding of chromosome evolution in light of the phylogeny.

RESULTS:

Aplastodiscus perviridis showed 2n = 24, A. arildae and A. eugenioi, 2n = 22, A. callipygius, 2n = 20, and A. leucopygius, 2n = 18. In the metaphase I cells of two species only bivalents occurred, whereas in A. arildae, A. callipygius, and A. leucopygius one tetravalent was also observed besides the bivalents. BrdU incorporation produced replication bands especially in the largest chromosomes, and a relatively good banding correspondence was noticed among some of them. Silver impregnation and FISH with an rDNA probe identified a single NOR pair: the 11 in A. perviridis and A. arildae; the 6 in A. eugenioi; and the 9 in A. callipygius and A. leucopygius. C-banding showed a predominantly centromeric distribution of the heterochromatin, and in one of the species distinct molecular composition was revealed by CMA3. The telomeric probe hybridised all chromosome ends and additionally disclosed the presence of telomere-like sequences in centromeric regions of three species.

CONCLUSIONS:

Based on the hypothesis of 2n = 24 ancestral karyotype for Aplastodiscus, and considering the karyotype differences and similarities, two evolutionary pathways through fusion events were suggested. One of them corresponded to the reduction of 2n = 24 to 22, and the other, the reduction of 2n = 24 to 20, and subsequently to 18. Regarding the NOR, two conditions were recognised: plesiomorphy, represented by the homeologous small-sized NOR-bearing pairs, and derivation, represented by the NOR in a medium-sized pair. In spite of the apparent uniformity of C-banding patterns, heterogeneity in the molecular composition of some repetitive regions was revealed by CMA3 staining and by interstitial telomeric labelling. The meiotic tetravalent might be due to minute reciprocal translocations or to non-chiasmatic ectopic pairing between terminal repetitive sequences. The comparative cytogenetic analysis allowed to outline the chromosome evolution and contributed to enlighten the relationships within the genus Aplastodiscus.

PMID:
22520864
PMCID:
PMC3465196
DOI:
10.1186/1471-2156-13-28
[PubMed - indexed for MEDLINE]
Free PMC Article
PubMed Commons home

PubMed Commons

0 comments
How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for BioMed Central Icon for PubMed Central
    Loading ...
    Support Center