Diversity and chromosomal distribution of Long interspersed non- LTR elements (LINEs) in the A genome of Arachis species

SAMOLUK, S.; CARÍSIMO D.; ROBLEDO, G.; SEIJO, G.

Bento Gonçalves

Congreso; Sixth International Crop Science Congress; 2012

Retroelements constitute part of the repetitive DNA and play an important role in both the evolution and structure of plant genomes. Section Arachis has 31 described species belonging to different genomic groups (A,B,D,F y K), 29 are wild diploids and two are allotetraploids. Even though there is a conserved colinearity of different molecular markers among Arachis species with different genomes, GISH analysis showed a large divergence at the sequence level. On these bases it has been hypothesized that the repetitive fraction may have driven or participated in the genome differentiation of Arachis. Considering that, and as a first step to test this hypothesis, we analyzed the diversity of a group of LINEs retroelements in Arachis species belonging to the A genome (A. duranensis, A. cardenasii and A. helodes). For this purpose, a conserved region of the reverse transcriptase gene was amplified from genomic DNA using degenerate primers. The amplified sequences showed 81% of variable sites and stop codons in 40% of them. However, they had high homology at the amino acid level. These sequences also showed high homology with the amino acid motifs of the reverse transcriptase of LINEs elements present in other angiosperms and in gymnosperms. Despite the wide distribution of these elements in different groups of plants, the N-J dendrogram revealed that the Arachis sequences form a unique cluster, although nonspecific subclusters were observed for each species. The fluorescent in situ hybridization revealed a dispersed pattern of weak signals over most of the chromosomes of the three species. From these results we concluded that even though these elements are ubiquitous they have a low representation in the A genome. Moreover, the results suggest that the diversification of these elements took place before the origin of this genome.