Satellite DNAs as potential taxonomic markers for Squirrel Monkeys, genus Saimiri

Abstract

The number of squirrel monkey species (genus Saimiri, Platyrrhini) and their phylogenetic relationships are still uncertain. All squirrel monkeys analyzed to date presented a diploid number of 2n=44 with variable fundamental numbers. The repetitive DNA fraction of Saimiri genomes, as for most eukaryotes, is still poorly explored. Herein, we took advantage of the genome sequence of Saimiri boliviensis to explore the satellite DNAs (satDNAs) of the genus. After clustering Illumina reads of S. boliviensis (NCBI SRA access: SRR317821) by similarity using the Repeat Explorer pipeline, we identified two abundant satDNAs. The first represents nearly 1% of the S. boliviensis genome and is homologous to the alpha satDNA, known to have a centromeric location in primates. PCR and sequence analysis confirmed the ~340 bp monomer size in S. boliviensis, S. vanzolinii, S. sciureus and S. ustus. This result agrees with that found in most New World monkeys, which is a duplication-derivative of the 170 bp monomer found in Old World primates. In addition to the alpha satDNA, we identified a large satDNA (~1500 bp monomers) that comprises 2.2% of the genome and displays similarity with the CapA satDNA first described in Cebus appella. Using fluorescent in situ hybridization, we verified that CapA chromosome location varies among Saimiri species and is mainly located in subtelomeric regions of the short arms and in the interstitial heterochromatin of some chromosome pairs. In S. sciureus CapA was mapped to the interstitial heterochromatin of both arms of chromosome 2 and in the subtelomeric regions of chromosomes 4, 8, 10 and 14. In S. vanzolinii, CapA was located in the subtelomeric regions of chromosomes 4, 5, 8, 10 and 11. S. ustus is the species in which CapA is more ubiquitous, being present in the subtelomeric regions of chromosomes 4, 5, 7, 8, 10, 11 and 15. The CapA signal on pair 2 of S. vanzolinii and S. ustus displayed a much weaker intensity than that found in S. sciureus. The differences in CapA distribution and abundance within Saimiri species may provide valuable insights into the chromosome evolution and phylogenetic relationships within the genus.

Financial support: CNPq, Fapemig, CAPES