Evolutionary dynamics of an at‑rich satellite DNA and its contribution to karyotype differentiation in wild diploid arachis species
Fecha
2016Autor
Samoluk, Sergio Sebastián
Robledo Dobladez, Germán Ariel
Bertioli, David J.
Seijo, José Guillermo
Metadatos
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Satellite DNA (satDNA) is a major component
of the heterochromatic regions of eukaryote genomes and
usually shows a high evolutionary dynamic, even among
closely related species. Section Arachis (genus Arachis) is
composed of species belonging to six different genomes
(A, B, D, F, G and K). The most distinguishing features
among these genomes are the amount and distribution of
the heterochromatin in the karyotypes. With the objective
of gaining insight into the sequence composition and evolutionary
dynamics of the heterochromatin fraction in Arachis,
we investigated here the sequence diversity, genomic abundance, and chromosomal distribution of a satDNA
family (ATR-2) among seven diploid species of section
Arachis. All of the isolated sequences were AT-rich and
highly conserved at both intraspecific and interspecific
levels, without any species-specific polymorphism. Pairwise
comparisons of isolated ATR-2 monomers revealed
that most of the nucleotide sites were in the first two transitional
stages of Strachan’s model. However, the abundance
of ATR-2 was significantly different among genomes
according to the ‘library hypothesis’. Fluorescent in situ
hybridization revealed that ATR-2 is a main component of
the DAPI+ centromeric heterochromatin of the A, F, and
K genomes. Thus, the evolution of the different heterochromatin
patterns observed in Arachis genomes can be
explained, at least in part, by the differential representation
of ATR-2 among the different species or even among
the chromosomes of the same complement. These findings
are the first to demonstrate the participation of satDNA
sequences in the karyotype diversification of wild diploid
Arachis species.
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