SEIJO Jose Guillermo
congresos y reuniones científicas
Analysis of the A-TR2 variability and chromosome localization in different species of Arachis section.
SAMOLUK, S; CARISIMO DA; ROBLEDO, G; J. G. SEIJO
Congreso; 5h International Conference of the Peanut Research Community on Advances in Arachis through Genomics and Biotechnology (AAGB).; 2011
Section Arachis has 29 wild diploid and two allotetraploid species belonging to five different genomes (A,B,D,F y K). Based on molecular mapping and GISH analysis it was proposed that changes in the repetitive fractions may have been a main force leading to genomic differentiation in Arachis. To test this hypothesis, we focused on the tandemly repeated fraction, particularly in a sequence previously isolated from the centromeric heterochromatin of A.duranensis, A-TR2. We isolated and characterized 67 sequences from peanut and from diploid species representative of all the genomes of the section and, also, from the three different karyotype groups recognized within the A genome. The sequence was highly conserved with only 14 variable sites. None of the A-TR2 variants was species specific; however, the polymorphism detected within each species tends to be largely distinct from those of other taxa. FISH analysis detected hybridization of A-TR2 only on chromosomes of the species belonging to the three A-genome karyotype groups and of the F-genome. However, in none of these species we observed hybridization onto all the heterochromatic bands, but each species was particular in the number A-TR2 signals. These results suggest a differential composition of the centromeric heterochromatin present in the chromosomes within a single species. The bulk of data evidences that A-TR2, although present in all the taxa analysed, has different variants, representation and probably organization among chromosomes, karyotype groups and genomes, suggesting that it was actively involved in the genomic differentiation of Arachis species.