Holokinetic Drive in the Karyotype Evolution of Monocots
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| Year of publication | 2013 |
| Type | Conference abstract |
| Citation | |
| Description | Two alternative chromosomal structures have evolved in eukaryotes: (i) monocentric chromosomes characterized by a single localized centromere/kinetochore region, and (ii) holokinetic chromosomes that assemble the kinetochore along almost the whole length of chromosomal body. In flowering plants, the vast majority (> 90%) of holokinetic species belong to monocot families Cyperaceae and Juncaceae and the genus Chionographis (Melanthiaceae). Holokinetic structure of chromosomes has a substantial impact on the evolution of whole karyotypes and genomes. Even between closely related species, holokinetics share unique karyological characteristics, which are observed also in Cyperaceae and Juncaceae, mainly exceptional and often almost continual variation in chromosome numbers, extreme divergence in chromosome sizes and negative correlations between the chromosome number and nuclear DNA amount. So far, the sufficient explanation for these observed karyological patterns is lacking. To fill this gap, we propose a new evolutionary mechanism referred to as holokinetic drive, which is based on the competition of homologous chromosomes during female meiosis for preferential inclusion into the megaspore. In competition between homologs, the success depends on chromosome size, which can be changed by chromosomal fusion/fission or by repetitive DNA proliferation/removal. We argue that holokinetic drive facilitates (i) the synergism of chromosomal fission with repetitive DNA removal (or any segmental deletion) or (ii) the synergism of chromosomal fusion with repetitive DNA proliferation (or any segmental duplication). |
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