Rapid Centromere Evolution in Potato: Invasion of the Satellite Repeats

摘要

In contrast to the gene-rich chromosome arms, the sequence of a typical plant centromere contains a large amount of repetitive DNA, most commonly large tracts of tandemly repeated sequences, or satellite DNA. However, the question of how this arrangement of sequences comes about is still a matter of active debate (reviewed in Malik and Henikoff, 2009). Centromere sequence evolves rapidly, possibly in response to competition among centromeres during female meiosis, where only one out of four meiotic products survives in the oocyte. Recombination, which may homogenize centromere repeats, acts in opposition to mutation and transposon insertion, which alter centromere repeats. Expansion of centromere repeat domains, selected for by competition to survive female meiosis, is counterbalanced by mechanisms to prevent distortion of segregation. In addition to having dynamic sequence and size, centromeres can move, either changing position gradually or forming in other regions of the chromosome (reviewed in Birchler et al., 2011), including regions without typical centromere sequence composition. Epigenetically defined, centromeres can also become inactive to prevent formation of dicentric chromosomes.