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Originally published as Genetics Published Articles Ahead of Print on August 24, 2007.

Genetics, Vol. 177, 699-706, October 2007, Copyright © 2007
doi:10.1534/genetics.107.078121

Terminal Regions of Wheat Chromosomes Select Their Pairing Partners in Meiosis

* Departamento de Genética, Facultad de Biología, Universidad Complutense, 28040 Madrid, Spain and {dagger} Department of Botany and Plant Sciences, University of California, Riverside, California 92521

1 Corresponding author: Departamento de Genética, Facultad de Biología, Universidad Complutense, José Antonio Novais, 2, 28040 Madrid, Spain.
E-mail: toranjo{at}bio.ucm.es

Many plant species, including important crops like wheat, are polyploids that carry more than two sets of genetically related chromosomes capable of meiotic pairing. To safeguard a diploid-like behavior at meiosis, many polyploids evolved genetic loci that suppress incorrect pairing and recombination of homeologues. The Ph1 locus in wheat was proposed to ensure homologous pairing by controlling the specificity of centromere associations that precede chromosome pairing. Using wheat chromosomes that carry rye centromeres, we show that the centromere associations in early meiosis are not based on homology and that the Ph1 locus has no effect on such associations. Although centromeres indeed undergo a switch from nonhomologous to homologous associations in meiosis, this process is driven by the terminally initiated synapsis. The centromere has no effect on metaphase I chiasmate chromosome associations: homologs with identical or different centromeres, in the presence and absence of Ph1, pair the same. A FISH analysis of the behavior of centromeres and distal chromomeres in telocentric and bi-armed chromosomes demonstrates that it is not the centromeric, but rather the subtelomeric, regions that are involved in the correct partner recognition and selection.




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