Mapeamento cromossomico dos retroelementos AviRTE e CR1 em aves do Sul do Brasil: enfase nos cromossomos Z e W

Abstract

Transposable elements (TEs) are mobile repetitive genetic sequences ubiquitous in almost all living beings, they have the characteristic of moving within and between genomes. TEs are classified into two main classes, according to their mobilization mechanism: I retrotransposons, which use an RNA intermediate, and II transoposons via DNA. In this work, two retrotransposons were studied: AviRTE and CR1, both belonging to the LINE order of TEs, the most abundant in the genome of birds. Among these, the most known and abundant are the CR1. AviRTE were discovered more recently in the avian genome, are less abundant and even less characterized. Birds have a bimodal karyotype with high variation in diploid number, some species have unusually large sex chromosomes, possibly due to the presence of repetitive sequences. Thus, the main objective was to map the sex chromosomes of species that are larger than commonly found, in order to verify the involvement and contribution of these elements in this differentiation. In the first chapter, an AviRTE probe was used in the karyotype of three species: Progne chalybea (PCH), Chloroceryle americana (CAM) and Trogon surrucura (TSU). Additionally, we analyzed the phylogenetic relationships of the element in the genome of birds and other vertebrates. Our results showed that AviRTE distribution patterns were different among species, not being restricted to heterochromatic regions, with accumulation on the Z chromosome of CAM and on the W chromosome of PCH and TSU. The phylogenetic analysis of the sequences of this element in birds followed the phylogeny proposed for the groups in most clades, and allowed detection in a greater number of species, expanding the distribution of the element. In the second chapter, using the CR1 retroelement as a probe, we mapped the chromosomal distribution in the genome of Chloroceryle americana (CAM) and Gallinula melanops (GME). Our data revealed different distribution between species, we detected the presence of CR1-E in the Z sex chromosomes of CAM and in the W of GME, which suggests the probable involvement of these sequences with the increase in the size of these chromosomes.