Retrotransposon BARE-1 and its role in genome evolution in the genus Hordeum

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Abstract
The replicative retrotransposon life cycle offer's the potential for explosive increases in copy number and consequent inflation of genome size. The BARE-I retrotransposon family of barley is conserved, disperse, and transcriptionally active, To: assess the role of BARE-I in genome evolution, we determined the copy number of its integrase, its reverse transcriptase, and its long terminal repeat (LTR) domains throughout the genus Hordeum, On average, BARE-1 contributes 13.7 x 10(3) full-length copies, amounting to 2.9% of the genome. The number increases with genome size. Two LTRs are associated with each internal domain in intact retrotransposons, but surprisingly, BARE-I LTRs were considerably more prevalent than would be expected from the numbers of intact elements, The excess in LTRs increases as both genome sire and BARE-I genomic fraction decrease.: Intrachromosomal homologous recombination between LTRs could explain the excess, removing BARE-1 elements and leaving behind solo LTRs, thereby reducing the complement of functional retrotransposons in the genome and providing at least a partial "return ticket from genomic obesity,".