EVOLUTIONARY DYNAMICS OF AN AT-RICH SATELLITE DNA AND ITS CONTRIBUTION TO KARYOTYPE DIFFERENTIATION IN WILD DIPLOID ARACHIS SPECIES

BERTIOLI D.; SAMOLUK SS; SEIJO JG; ROBLEDO G.

MOLECULAR GENETICS AND GENOMICS

SPRINGER HEIDELBERG

Lugar: HEIDELBERG; Año: 2016 p. 283 - 296

1617-4615

Satellite DNA (satDNA) is a major component of the heterochromatic regions ofeukaryote genomes and usually shows a high evolutionary dynamic, even amongclosely related species. Section Arachis (genus Arachis) is composed of speciesbelonging to six different genomes (A, B, D, F, G and K). The most distinguishingfeatures among these genomes are the amount and distribution of the heterochromatin inthe karyotypes. With the objective of gaining insight into the sequence composition andevolutionary dynamics of the heterochromatin fraction in Arachis, we investigated herethe sequence diversity, genomic abundance and chromosomal distribution of a satDNAfamily (ATR-2) among seven diploid species of section Arachis. All of the isolatedsequences were AT rich and highly conserved at both intraspecific and interspecificlevels, without any species-specific polymorphism. Pairwise comparisons of isolatedATR-2 monomers revealed that most of the nucleotide sites were in the first twotransitional stages of Strachan?s model. However, the abundance of ATR-2 wassignificantly different among genomes according to the ?library hypothesis?.Fluorescent in situ hybridization revealed that ATR-2 is a main component of theDAPI+ centromeric heterochromatin of the A, F and K genomes. Thus, the evolution ofthe different heterochromatin patterns observed in Arachis genomes can be explained, atleast in part, by the differential representation of ATR-2 among the different species oreven among the chromosomes of the same complement. These findings are the first todemonstrate the participation of satDNA sequences in the karyotype diversification ofwild diploid Arachis species.