Genomic and epigenetic differentiation at diploid and polyploid levels in Arachis species (sect. Arachis), a molecular cytogenetic approach.

J. G. SEIJO; SAMOLUK, S; CHALUP, L.; GERMÁN ROBLEDO

Foz Iguazu

Conferencia; International Plant Molecular Biology Congress Iguazú.; 2015

International Plant Molecular Biology Society

Section Arachis includes ca. 30 diploid species (2n=20, 18) arranged into the A, B, D, F, G and K genomes. It also includes the peanut and one wild tetraploid, both with 2n=40 (AABB). Genetic maps revealed a high colinearity among the species assigned to different genome and the transference of molecular markers are very high among them. However GISH analyses revealed a high genomic differentiation. On these bases, it was hypothesized that the repetitive fraction has played an important role in the differentiation of the genomes and allopolyploidization. This was tested by the isolation, characterization, quantification and chromosome mapping of different repetitive sequences in representative species of each genome formula. The global pattern of 5-methylcytosine was also analyzed. The retroelements Ty3-Gypsy and LINES, the CACTA-like transposons, and the satellite sequence TR2 showed a differential representation in dot-blot analysis and genome distribution by FISH at the diploid level. The distribution pattern of the 5-methylcytosine by immunocytochemistry was distinctive between the A and B genomes. Comparing the allotetraploids with its diploid progenitors, all the markers analyzed evidenced clear genome additivity. However, the cytosines of the B-genome of the tetraploids appeared hipermethylated with respect to its wild progenitor. These results support the formulated hypothesis at the diploid level with significant changes in sequences and epigenetic patterns. However, the results suggest that allopolyploidization did not affect the sequence arrangement but its trigger a major change of the epigenetic pattern of one of the peanut genomes.