Comparative analysis of repetitive DNA in Phaseolus beans and its impact on the karyotype evolution of the dysploid Leptostachyus group

Abstract

Abstract Structural karyotype changes result from ectopic recombination events frequently associated to repetitive DNA. Although most Phaseolus species have 2n = 22 and a relatively stable karyotype, the species cytogenetically studied so far that belong to the Leptostachyus group, as P. leptostachyus and P. macvaughii, show high rates of rearrangements, including a nested chromosome fusion which led to the dysploid chromosome number of the group (2n = 20). In this study, aiming to test the role of the repetitive landscape in the rearrangements of the Leptostachyus group, we used genome skimming to characterize the repeatome of a range of Phaseolus species in comparison to P. leptostachyus and P. macvaughii. LTR retrotransposons, especially the Ty3/gypsy lineage Chromovirus, were the most abundant elements in the genomes. Remarkable diferences in the abundance of Tekay, Retand and SIRE between P. macvaughii and P. leptostachyus reflected in the total amount of Ty3/gypsy and Ty1/copia in both species. The satellite DNA fraction was the most divergent among species, varying both in abundance and distribution even between P. leptostachyus and P. macvaughii. The rapid turnover of repeats in the Leptostachyus group might be associated with the several rearrangements observed in the group.