Dynamic nature of a wheat centromere with a functional gene |
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Authors: | Jasdeep S Mutti Devinder Sandhu Deepak Sidhu Kulvinder S Gill |
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Institution: | (1) Department of Crop and Soil Sciences, Washington State University, 277 Johnson Hall, P. O. Box 646420, Pullman, WA 99164, USA;(2) Department of Biology, University of Wisconsin-Stevens Point, Stevens Point, WI 54481, USA;(3) Present address: NCI-Frederick, Gene Regulation and Chromosome Biology Lab, Building 539/154, PO Box B, Frederick, MD 21702, USA; |
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Abstract: | Centromeric regions of higher eukaryotes are comprised mainly of tandem and non-tandem repeat sequences with variable copy
number, spacing, order and orientation; are heterochromatic in nature, and are believed to be devoid of actively transcribing
genes. Here, we report an actively transcribing wheat homolog of HSP70 gene that maps in the functional wheat centromere, and copy number of which seems to change in response to centromeric breaks.
The HSP70 gene physically maps on the short arm of chromosomes 1A and 1D of Chinese Spring (CS) and 1R of rye. Whereas, on chromosome 1B in both ‘CS’ and Pavon background, the gene maps in the functional centromere as evident from its presence in both cytologically
confirmed true ditelosomic lines Dt1BS and Dt1BL. Sequence comparison of 11 ESTs showed three sequence patterns suggesting
that all three homoeologous copies of the gene are expressing. The cDNA-single stranded conformation polymorphism analysis
confirmed expression of the ‘CS’ 1B copy of the gene. Observed in two independently developed Dt1BL lines, the 1B copy number of the gene showed three to fivefold increase in response to chromosomal breaks around the centromere. Putative
gene duplications seem to involve large chromosomal segments as only one of the ten restriction enzymes used for DNA gel-blot
analysis showed unique extra fragment band in the Dt1BL line. Further investigations are warranted to uncover the nature and
mechanism of these duplications. |
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