“Sítios frágeis” espontâneos e induzidos nos cromossomos de espécies do complexo Lolium-Festuca

Abstract

The fragile sites (FSs) are considered weak regions of the genome and may be prone to form lesions or chromosomal breaks in addition to being related to instability in the human genome, other animals, fish, and yeast. In plants, these sites have been described in some species of grasses such as the genus Lolium, taking place in the sites of 45S rDNA. However, the consequences of fragile sites in the genome of plants are not well-known. Thus, the aims of this study were to evaluate if there is instabilityin the genome of species of Lolium-Festuca complex with spontaneous expression of FSs and through the induction of chromosomal breaks by ionizing radiation and also to check if the genome is recovering from these induced breaks through the synthesis of new telomere. The results showed that the weakened regions in 45S rDNA sites does not present neocentromeric activity, but showed thin and long chromatin fibers, not visible with DAPI staining, connecting the acentric chromosome fragments to chromosome region containing the centromere, not promoting instability in the genome of these species. The same was observed for the species of F. arundinaceae Festulolium hybrids. Fragile sites are not regions prone to breaks afterirradiation with X-ray and there was no formation of new telomeres during the evaluation of cmetaphase.