Centromere inactivation and epigenetic modifications of a plant chromosome with three functional centromeres
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A chromosome with two functional centromeres is cytologically unstable and can only be stabilized when one of the two centromeres becomes inactivated via poorly understood mechanisms. Here, we report a transmissible chromosome with multiple centromeres in wheat. This chromosome encompassed one large and two small domains containing the centromeric histone CENH3. The two small centromeres are in a close vicinity and often fused as a single centromere on metaphase chromosomes. This fused centromere contained approximately 30% of the CENH3 compared to the large centromere. An intact tricentric chromosome was transmitted to about 70% of the progenies, which was likely a consequence of the dominating pulling capacity of the large centromere during anaphases of meiosis. The tricentric chromosome showed characteristics typical to dicentric chromosomes, including chromosome breaks and centromere inactivation. Remarkably, inactivation was always associated with the small centromeres, indicating that small centromeres are less likely to survive than large ones in dicentric chromosomes. The inactivation of the small centromeres also coincided with changes of specific histone modifications, including H3K27me2 and H3K27me3, of the pericentromeric chromatin.
KeywordsWheat Chromosome Dicentric Chromosome Pericentromeric Heterochromatin Pachytene Chromosome Centromeric Chromatin
We thank Dr. Yufeng Wu for statistical analysis of the data in Table 2 and Dr. Kelly Dawe for his comments on the manuscript. This research was partially supported by grants DBI-0603927 and DBI-0553417 from the National Science Foundation.
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