Terminal regions of wheat chromosomes select their pairing partners in meiosis

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 homoeologues. 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 the Ph1 locus has no effect on such associations. Although centromeres indeed undergo a switch from non-homologous 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: homologues 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 the subtelomeric regions that are involved in the correct partner recognition and selection.

Key Words: Centromeres, FISH, Pairing, Ph1, Subtelomeric regions

Online ISS 1091-6490
Copyright 2008 by the Genetics Society of America
phone: 412-268-1812   fax: 412-268-1813   email: genetics-gsa{at}andrew.cmu.edu