SAMOLUK Sergio Sebastian
Heterochromatin evolution in Arachis investigated through genome-wide analysis of repetitive DNA
SAMOLUK, SERGIO S.; CHALUP, LAURA M. I.; CHAVARRO, CAROLINA; ROBLEDO, GERMÁN; BERTIOLI, DAVID J.; JACKSON, SCOTT A.; SEIJO, GUILLERMO
Main conclusion The most conspicuous difference among chromosomes and genomes in Arachis species, the patternsof heterochromatin, was mainly modeled by differential amplification of different members of one superfamily ofsatellite DNAs.Divergence in repetitive DNA is a primary driving force for genome and chromosome evolution. Section Arachis is karyotypicallydiverse and has six different genomes. Arachis glandulifera (D genome) has the most asymmetric karyotype andthe highest reproductive isolation compared to the well-known A and B genome species. These features make A. glanduliferaan interesting model species for studying the main repetitive components that accompanied the genome and chromosomediversification in the section. Here, we performed a genome-wide analysis of repetitive sequences in A. glandulifera andinvestigated the chromosome distribution of the identified satellite DNA sequences (satDNAs). LTR retroelements, mainlythe Ty3-gypsy families ?Fidel/Feral? and ?Pipoka/Pipa?, were the most represented. Comparative analyses with the A andB genomes showed that many of the previously described transposable elements (TEs) were differently represented in theD genome, and that this variation accompanied changes in DNA content. In addition, four major satDNAs were characterized.Agla_CL8sat was the major component of pericentromeric heterochromatin, while Agla_CL39sat, Agla_CL69sat, andAgla_CL122sat were found in heterochromatic and/or euchromatic regions. Even though Agla_CL8sat belong to a differentfamily than that of the major satDNA (ATR-2) found in the heterochromatin of the A, K, and F genomes, both satDNAs aremembers of the same superfamily. This finding suggests that closely related satDNAs of an ancestral library were differentiallyamplified leading to the major changes in the heterochromatin patterns that accompanied the karyotype and genomedifferentiation in Arachis.