The wheat D-genome HMW-glutenin locus: BAC sequencing, gene distribution, and retrotransposon clusters.
A bacterial-artificial-chromosome (BAC) clone from the genome of Triticum tauschii, the D-genome ancestor of hexaploid bread wheat, was sequenced and the presence of the two paralogous x- and y-type high-molecular-weight (HMW) glutenin genes of the Glu-D1 locus was confirmed. These two genes occur in the same orientation, are 51,893 bp apart, and the separating DNA includes a 31,000-bp cluster of retrotransposons. A second retrotransposon cluster of 32,000 bp follows the x-type HMW-glutenin gene region. Each HMW-glutenin gene is found within a region of mainly unique DNA sequence which includes multiple additional genes including an active endosperm globulin gene not previously reported in the Triticeae family, a leucine-rich-repeat (LRR) type gene truncated at the 5' end of the BAC, a kinase gene of unknown activity, remnants of a paralogous second globulin gene, and genes similar to two hypothetical rice genes. The newly identified globulin genes are assigned to a locus designated Glo-2. Comparison to available orthologous regions of the wheat A and B genomes show rapid sequence divergences flanking the HMW-glutenin genes, and the absence of two hypothetical and unknown genes found 5' to the B-genome x-type ortholog. The region surrounding the Glu-D1 locus is similar to other reported Triticeae BAC sequences; i.e. small gene islands separated by retrotransposon clusters.
Anderson
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Western Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, 800 Buchanan Street, Albany, CA 94710, USA. oandersn@pw.usda.gov
Rausch
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Moullet
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Lagudah
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D000595:Amino Acid Sequence; D001483:Base Sequence; D022202:Chromosomes, Artificial, Bacterial; D003001:Cloning, Molecular; D004247:DNA / Q000648:ultrastructure; D004251:DNA Transposable Elements; D015723:Gene Library; D018745:Genome, Plant; D005983:Glutens / Q000031:analogs & derivatives* / Q000235:genetics*; D007930:Leucine / Q000737:chemistry; D008957:Models, Genetic; D008969:Molecular Sequence Data; D011494:Protein Kinases / Q000235:genetics; D017434:Protein Structure, Tertiary; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014908:Triticum / Q000235:genetics*
D004251:DNA Transposable Elements; D005983:Glutens; D004247:DNA; D011494:Protein Kinases; C037302:glutenin; D007930:Leucine