Subprojeto 7 – Constructing probes for cytogenetic mapping from chromosome segments isolated by laser microdissection

Participantes: Luciana Bolsoni Lourenço and Shirlei Maria Recco-Pimentel

The evolutionary interpretation of cytogenetic data improved a lot after the publication of several phylogenetic studies and it has enabled relevant hypotheses concerning the chromosome differentiation occurred during the anuran evolutionary divergence. For the anurans studied by our research group, many interesting cytogenetic phenomena were already reported, i.e. the presence of sex chromosomes in different stages of differentiation, the conspicuous polymorphysms in nucleolus organizer regions and heterochromatic bands localization, and the presence of different classes of heterochromatin in the genomas. However, in some circumstances the lack of chromosomal markers avoids us to propose a proper evolutionary hypothesis concernig these processes. By using the laser microdissection system we intend to isolate hole chromosomes and chromosomal segments in order to improve our analyses and reaccess some questions previously reported. In this way, initially we will microdissect the sex chromosomes of Physalaemus petersi. This anuran species is the only of its genus to present heteromorphic sex chromosomes and for this reason their study could be very relevant in order to better undestand the evolution of sex chromosomes from homomorphic ones. For this study, the isolated sex chromosomes will be cloned and in situ hybridized in metaphases from species closely related to P. petersi. In another part of this project, we will microdissect heterochromatic bands of several anuran species, including P. petersi, which shows an notorious intra and interpopulational C-band polymorphism. So the laser microdissection system will allow us to prepare highly specific probes to performe more detailed and conclusive analyses besides the use of confocal microscopy.