Evolution of RPCS, the major satellite DNA in rodents from the genus Ctenomys (Rodentia, Octodontidae) from Corrientes province, Argentina.

CARABALLO, D. A.; BELLUSCIO, P. M.; GIMÉNEZ, M. D.; BIDAU, C. J.; SEARLE, J. B.; ROSSI, S.

Turín

Congreso; 12th ESEB (European Society for Evolutionary Biology); 2009

European Society for Evolutionary Biology

The rodents of the genus Ctenomys (tuco-tucos) conform an extreme case of chromosomal evolution in mammals. The species and forms of tuco-tucos from the Iberá marsh (Corrientes province), are characterized by named species with stable karyotypes, and a taxonomic undefined complex of populations which exhibit high chromosomal polymorphisms. In previous work, the relation between the nucleotide sequence and the expansion/contraction dynamics of the major satellite DNA of tuco-tucos (RPCS) was studied, for different karyomorphs of the genus. In this work, we studied the nucleotide variability distribution and estimated the RPCS copy number, in specimens from the named species that inhabit Corrientes: C. roigi, C. dorbignyi, C. perrensi, and the forms from the C. sp complex. The study was achieved using a PCR strategy to obtain RPCS genomic consensus sequence (gcs) and also to estimate the RPCS copy number per genome. Genetic distances of RPCS gcs were calculated between pairs, and spanned in a range of 0 ? 12.93%. We corroborated the RPCS ancestral library hypothesis, evidenced by the absence of total fixation in unique variants. This hypothesis also finds support in the fact that all the intragenomic polytypisms share variants with a strict RPCS consensus sequence obtained from a wide spectrum of species.RPCS copy number varies between 2-2,600 x103 copies per haploid genome. The relationship between RPCS copy number, sequence variability and chromosomal evolution resulted not trivial. This fact reveals that RPCS has gone through complex processes during the cladogenesis, which are being elucidated in a phylogenetic context.