Avaliação citogenômica do cromossomo B em Psalidodon scabripinnis (Teleostei: Characidae): implicações para o drive meiótico

Abstract

B chromosomes are supernumerary elements in the genome that occur in a wide variety of eukaryotic organisms, they are important for their role in evolutionary history, and the fact that these elements in many cases have preferential segregation mechanisms increases their frequency in populations, a phenomenon known as “Drive”. Fish from the Psalidodon scabripinnis complex have B chromosomes, where several aspects related to this additional genetic element have already been studied, but it is not known whether this chromosome has the drive capacity. In this sense, the objective of this study was to establish tools for determining the meiotic drive of the B chromosome in P. scabripinnis females from a population in southeastern Brazil. For this, females of P. scabripinnis with chromosome B (B+) and without

chromosome B (B-) were sampled from Ribeirão Grande, municipality of Pindamonhangaba- SP. The individuals were euthanized, their gonads extracted and subjected to the oocyte nuclei

extraction protocol. Additionally, the anterior kidneys were removed to obtain metaphase cells to verify the diploid number. Three markers were tested: SatDNA As51, probe B and microsatellite CA(15) for molecular cytogenetic analysis in metaphase preparations and oocyte nuclei. Flow cytometry was used to evaluate the amount of DNA in gonad tissue samples from females with a B chromosome. Double FISH with probes B and As51 were those that showed the best results in marking the B chromosome in oocyte nuclei and also in mitotic metaphases. Furthermore, the As51 marker helped in the identification of haploid and diploid nuclei, which were corroborated by flow cytometry. The results obtained in the present study present useful tools for determining the existence or not of a drive on the B chromosome. Some advances are still necessary to improve this innovative method, for example, in the differentiation of the polar bodies of mature oocytes and in the maintenance of oocytes by more time under analysis conditions.