| Research Abstract |
A new class of transposable element with 3 kb length have been identified in the Triticeae genome. The transposon contains a single ORF of a transposase encoding 118 amino acid residues, which is conferred by a processed mRNA (726 nt). Firstly, a partial DNA fragment (89 bp) of the transposon enriched in the rye genome was isolated via the genomic subtraction of common DNA sequences between rye and wheat. Then, the whole structure of the rye genome-specific element is determined by sequencing genomic clones, which include the 89 bp segment. The consensus sequence of the element encompasses 3041 bp and it exists dispersedly in the rye genome by flanking with 20 bp of terminal inverted repeated sequence in the both ends. The transposon-like element is actively transcribed by Northern analysis. Moreover, cDNA clones (726 bp) derived from the transposon has identified in Triticeae plants, elucidating that the transposon bears 3 exons (342 bp, 88 bp, 296 bp) and 2 introns (750 bp, 1,237 bp). The entire structure of the transposon dose not share identity with known transposable elements, then the transposon is designated as Revolver. The deduced gene of Revolver encodes a protein featuring transcriptional regulators, having DNA binding ability. Genomic Southern blots on the Triticeae plants revearls that Revolver is abundant in the genomes of wheat relatives, rye, Dasypyrum, as well as wheat ancestor species, T.monococcum and Ae. squarrosa. At least ten thousand copies of Revolver are distributed along with each chromosome of wheat relatives. However, Revolver is quite rare in bread wheat varieties. These facts indicates that Revolver have been existed through the evolution since the ancestor of wheat, then it has been amplifing in some species, while disappearing in bread wheat. A new class of transposon-like gene Revolver is effective to develop DNA markers for wild wheat relatives, useful gene sources of wheat, and to evaluate phylogenetic evolution among the Triticeae
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