Comparative molecular cytogenetics of anurans of the genus Pseudis with emphasis on the study of sex chromosomes

Abstract

The hylid genera Pseudis and Lysapsus together comprise eleven South American species, and all of them were already karyotyped. One remarkable cytogenetic feature of this anuran group is the presence of heteromorphic sex chromosomes Z and W in Pseudis tocantins. Based on the chromosomal morphology and NOR location, previous studies suggested that the sex chromosomes of P. tocantins is homeologous to chromosome 5 of P. cardosoi and chromosome 7 of the remaining species of Pseudis and Lysapsus. Recent researches showed that the heterochromatic blocks of the Z and W chromosomes of P. tocantins differ not only in size, but also in composition. Sequences of the satellite DNA PcP190EcoRI were found in both sex chromosomes, but the sequence mapped by FISH on Wq greatly differed from that which was isolated from microdissected Z chromosomes. Such data suggest an important role of this satellite DNA in the differentiation of these Z and W chromosomes. Despite these intriguing findings regarding P. tocantins, the sex chromosomes of Lysapsus and the remaining species of Pseudis remain unknown. In the present proposal, we will investigate about the presence of the satellite DNA PcP190EcoRI in representative species of the genera Pseudis and Lysapsus, aiming to evaluate the possible involvement of these DNA sequences in the karyotype evolution in this group. We will also employ the comparative genomic hybridization (CGH) in an attempt to identify the sex chromosomes of P. fusca, P. minuta, P. bolbodactyla and of one representative species of the genus Lysapsus. Additionally, we propose the sequencing of the sex chromosomes of P. tocantins, aiming to search for W-specific sequences, including candidate genes for sex determination in this species. Therefore, with the present proposal we intend to provide relevant advance in the study of the sex chromosomes of P. tocantins. (AU)