AUTHOR=Báez Mariana , Vaio Magdalena , Dreissig Steven , Schubert Veit , Houben Andreas , Pedrosa-Harand Andrea 

TITLE=Together But Different: The Subgenomes of the Bimodal Eleutherine Karyotypes Are Differentially Organized

JOURNAL=Frontiers in Plant Science

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2019.01170

DOI=10.3389/fpls.2019.01170

ISSN=1664-462X

ABSTRACT=<p>Bimodal karyotypes are characterized by the presence of two sets of chromosomes of contrasting size. <italic>Eleutherine bulbosa</italic> (2<italic>n</italic> = 12) presents a bimodal karyotype with a large chromosome pair, which has a pericentric inversion in permanent heterozygosity with suppressed recombination, and five pairs of three to four times smaller chromosomes. Aiming to understand whether high copy number sequence composition differs between both chromosome sets, we investigated the repetitive DNA fraction of <italic>E. bulbosa</italic> and compared it to the chromosomal organization of the related <italic>Eleutherine latifolia</italic> species, not containing the pericentric inversion. We also compared the repetitive sequence proportions between the heteromorphic large chromosomes of <italic>E. bulbosa</italic> and between <italic>E. bulbosa</italic> and <italic>E. latifolia</italic> to understand the influence of the chromosome inversion on the dynamics of repetitive sequences. The most abundant repetitive families of the genome showed a similar chromosomal distribution in both homologs of the large pair and in both species, apparently not influenced by the species-specific inversions. The repeat families Ebusat1 and Ebusat4 are localized interstitially only on the large chromosome pair, while Ebusat2 is located in the centromeric region of all chromosomes. The four most abundant retrotransposon lineages are accumulated in the large chromosome pair. Replication timing and distribution of epigenetic and transcriptional marks differ between large and small chromosomes. The differential distribution of retroelements appears to be related to the bimodal condition and is not influenced by the nonrecombining chromosome inversions in these species. Thus, the large and small chromosome subgenomes of the bimodal <italic>Eleutherine</italic> karyotype are differentially organized and probably evolved by repetitive sequences accumulation on the large chromosome set.</p>