Mapeamento genômico de sequências repetitivas em espécies da família Furnariidae (aves): um enfoque citogenético

Abstract

The family Furnariidae, known as ovenbirds, is one of the most diverse families within the order Passeriformes, but cytogenetic research is still in its early stages, limiting our understanding of the evolution of their karyotypes. Traditional and molecular cytogenetic analyses have been conducted on several representative species of this family, including Synallaxis frontalis, Syndactyla rufosuperciliata, Cranioleuca obsoleta, Heliobletus contaminatus, and Anumbius annumbi. In Chapter 1, the results of these analyses revealed that all the studied species have the same diploid number (2n = 82), but differences in chromosomal morphology suggest the presence of intrachromosomal rearrangements. Furthermore, the mapping of repetitive sequences revealed varied patterns of chromosomal distribution, indicating differential accumulation of repetitive DNA after species divergence. Inter-specific comparative genomic hybridization demonstrated the conservation of the karyotype in the Furnariidae family, although the outgroup species Turdus rufiventris showed more advanced sequence divergence. In Chapter 2, the species Heliobletus contaminatus (2n = 82) was described, which possesses morphological characteristics similar to other related species. Some differences in chromosomal morphology indicate intrachromosomal rearrangements. Additionally, the species exhibits differences in heterochromatin distribution compared to other studied ovenbirds. The mapping of repetitive sequences shows variable patterns, including markings on macro and microchromosomes, as well as on the Z and W sex chromosomes. The presence of 18S rDNA sequences on a pair of microchromosomes suggests that this configuration may represent the ancestral state of birds. Through Fluorescent in situ Hybridization (FISH), telomeric sequences were detected in interstitial locations on macrochromosomes, suggesting past chromosomal fusions and rearrangement events during the evolution of this species. In the third and final chapter, further study of the karyotype of A. annumbi (2n = 82) revealed a conserved karyotype but with a peculiarity: a large Z chromosome larger than all other chromosomes in the complement, which is unusual in Passeriformes. Microsatellite sequences were found distributed on the chromosomes of Anumbius annumbi, some of which were accumulated on the Z chromosome. These results indicate a high degree of chromosomal conservation in diploid number of Furnariidae species but also highlight differences in the distribution of repetitive sequences and chromosomal rearrangements. This unique feature of the large Z chromosome in one of the Furnariidae species (Anumbius annumbi) challenges the established view that Passeriformes have a high degree of karyotype conservation, particularly with respect to the Z chromosome. Therefore, the apparent karyotype conservation in Furnariidae may, in part, result from the limited number of species studied in depth. Thus, this research significantly contributes to our understanding of the chromosomal and genomic evolution of birds, especially within the Furnariidae family and the Passeriformes order.