Dispersion of transposable elements and multigene families: Microstructural variation in Characidium (Characiformes: Crenuchidae) genomes.

Marcela Baer Pucci,Viviane Nogaroto,Orlando Moreira-Filho,Marcelo Ricardo Vicari

doi:10.1590/1678-4685-gmb-2017-0121

Marcela Baer Pucci, Viviane Nogaroto + Show 2 more

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https://doi.org/10.1590/1678-4685-gmb-2017-0121

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Abstract

Eukaryotic genomes consist of several repetitive DNAs, including dispersed DNA sequences that move between chromosome sites, tandem repeats of DNA sequences, and multigene families. In this study, repeated sequences isolated from the genome of Characidium gomesi were analyzed and mapped to chromosomes in Characidium zebra and specimens from two populations of C. gomesi. The sequences were transposable elements (TEs) named retroelement of Xiphophorus (Rex); multigene families of U2 small nuclear RNA (U2 snRNA); and histones H1, H3, and H4. Sequence analyses revealed that U2 snRNA contains a major portion corresponding to the Tx1-type non-LTR retrotransposon Keno, the preferential insertion sites of which are U2 snRNA sequences. All histone sequences were found to be associated with TEs. In situ localization revealed that these DNA sequences are dispersed throughout the autosomes of the species, but they are not involved in differentiation of the specific region of the W sex chromosome in C. gomesi. We discuss mechanisms of TE invasion into multigene families that lead to microstructural variation in Characidium genomes.

Highlights

The genomes of all studied eukaryotic species primarily consist of repetitive sequences that are dispersed or found in tandem (Sumner, 2003)
The partial sequences of Rex1, Rex3, U2 snRNA, and the H1, H3, and H4 genes were isolated from the genomes of C. gomesi and C. zebra, and consensus sequence of each gene was constructed (Table S2)
Rex1 and Rex3 elements were dispersed in small clusters throughout the chromosomes, and they did not display significant chromosome reorganization between Characidium species

Summary

Introduction

The genomes of all studied eukaryotic species primarily consist of repetitive sequences that are dispersed or found in tandem (Sumner, 2003). Dispersed DNA sequences can move between chromosome sites, with this movement occurring in the presence or absence of RNA as a transposition intermediate (Tollis and Boissinot, 2012). These mobile segments are called transposable elements (TEs) and are classified as retrotransposons (class I elements, RNA intermediates of the transposition process) or transposons (class II elements, DNA intermediates of the transposition process) (Wicker et al, 2007). These mobile elements can drive genetic and

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