Comparative analysis of structure and variability of the ribosomal genes of the Peanut and their wild diploids parentals for evolutionary studies

AGOSTINI F; SAMOLUK SS; SEIJO JG; CHALUP L; ROBLEDO G.

Mendoza

Congreso; A2B2C 10th Congress; 2019

Sociedad Argentina de Bioinformática y Biología Computacional

The ribosomal DNA repeats are an important fraction of the repetitive DNA of the genomes, which have a direct role in gene expression. 45S rDNA repeat unit contains the sequence for the 26S, 5.8S and 18S rRNA genes, as well as two transcribed spacers (ITS1 and ITS2) and a large intergenic spacer (IGS). Likewise, the 5S rDNA is organized in a transcribable region and a non-transcribable (NTS) region. Both rDNA repeats are organized into arrays and contains hundreds to thousands of repeats. Here, we analysed the structure of the ribosomal genes present in A. hypogaea (AABB), A. monticola (AABB) and their diploid parental species, A. duranensis (AA) and A. ipaënsis (BB) for future studies on amphiplasty and other effects of polyploidization. The characterization of the structures of the rDNA units of the 5S loci was highly conserved. However, the structure of the 45S sequence showed some species-specific differences between diploids. A small fraction of 79 bp towards the 5´ and another 300 bp fraction towards the 3´ of the promoter were exclusive of A. ipaënsis. Differences in the composition and structure of another repetitive region were also observed in the ETS. Both 45S rDNA versions were recovered from the allopolyploids. Ongoing research is centered in quantifying the copy number of both 45S versions in the allotetraploids to provide additional information for the analysis of genome specific NOR activation.