Effective isolation of retrotransposons and repetitive DNA families from the wheat genome.J Integr Plant Biol 2010; 52(7):679-91JI
New classes of repetitive DNA elements were effectively identified by isolating small fragments of the elements from the wheat genome. A wheat A genome library was constructed from Triticum monococcum by degenerate cleavage with EcoO109I, the recognition sites of which consisted of 5'-PuGGNCCPy-3' multi-sequences. Three novel repetitive sequences pTm6, pTm69 and pTm58 derived from the A genome were screened and tested for high copy number using a blotting approach. pTm6 showed identity with integrase domains of the barley Ty1-Copia-retrotransposon BARE-1 and pTm58 showed similarity to the barley Ty3-gypsy-like retrotransposon Romani. pTm69, however, constituted a tandem array with useful genomic specificities, but did not share any identity with known repetitive elements. This study also sought to isolate wheat D-genome-specific repetitive elements regardless of the level of methylation, by genomic subtraction. Total genomic DNA of Aegilops tauschii was cleaved into short fragments with a methylation-insensitive 4 bp cutter, MboI, and then common DNA sequences between Ae. tauschii and Triticum turgidum were subtracted by annealing with excess T. turgidum genomic DNA. The D genome repetitive sequence pAt1 was isolated and used to identify an additional novel repetitive sequence family from wheat bacterial artificial chromosomes with a size range of 1 395-1 850 bp. The methods successfully led pathfinding of two unique repetitive families.