Extensive pericentric rearrangements in the bread wheat (Triticum aestivum L.) genotype "Chinese Spring" revealed from chromosome shotgun sequence data.
Bottom Line: Based on patterns of their homoeologous arm locations, 551 genes indicated the presence of pericentric inversions in at least 10 of the 21 chromosomes.Available data from deletion bin-mapped expressed sequence tags and genetic mapping in wheat indicated that all inversions had breakpoints in the low-recombinant gene-poor pericentromeric regions.These differences could have significant implications in wheat genome research where comparative approaches are used such as in ordering and orientating sequence contigs and in gene cloning.
Affiliation: CSIRO Agriculture Flagship, St Lucia, Queensland, Australia Triticeae Research Institute, Sichuan Agricultural University, Wenjiang, Chengdu, China.Show MeSH
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Mentions: Although there is no easy way to discern whether any single rearrangement is present in euploid CS, our data provide some indication that at least some of the rearrangements must have occurred in the aneuploids. When considering each chromosome independently, pericentric inversions appear to have occurred in only a single chromosome in the homoeologous group 1 and group 5 chromosomes, in two homoeologues in the group 2 chromosomes and in all three homoeologues in the group 4, 6, and 7 chromosomes. However, if pericentromeric inversions had taken place in all three homoeologous chromosomes in euploid CS, genes that were encompassed by all three inversions would appear as being nonrearranged, that is would be located on, for example, chromosome arms 6AS/6BS/6DS and 6AL/6BL/6DL or, in case of the group 4 chromosomes, on 4AL/4BS/4DS and 4AS/4BL/4DL. Consequently, the occurrence of pericentric rearrangements in all three chromosomes within a homoeologous group would yield only four patterns of nonstandard arm locations. For example, if pericentromeric inversions occurred on chromosomes 6A, 6B, and 6D, with the size of the inverted segments on both the short and long arms being larger on 6D than on 6B than on 6A, one would expect to find markers with the nonstandard arm locations 6AS/6BS/6DL, 6AS/6BL/6DL, 6AL/6BS/6DS, and 6AL/6BL/6DS (fig. 3A). The same nonstandard arm locations would be obtained if pericentromeric inversions occurred in two of the three homoeologs (i.e., in chromosomes 6B and 6D with the 6D inversion spanning a larger region than the inversion on 6B). Arm locations will vary depending on the chromosomes involved and on the relative size of the inverted segments (fig. 3B), but the maximum number of nonstandard arm locations that can be obtained from a single genotype is four. The fact that at least five patterns of nonstandard arm locations were identified on the group 4, 6, and 7 chromosomes strongly suggests that at least some of these rearrangements are not present in euploid CS but occurred during the generation of the ditelosomic or double ditelosomic lines.Fig. 3.—
Affiliation: CSIRO Agriculture Flagship, St Lucia, Queensland, Australia Triticeae Research Institute, Sichuan Agricultural University, Wenjiang, Chengdu, China.