Department of Genetics, University of Georgia, Athens, 30602, USA.
Chromosome Res. 2012 May;20(4):403-12. doi: 10.1007/s10577-012-9284-1. Epub 2012 May 3.
It has been known for decades that centromere size varies across species, but the factors involved in setting centromere boundaries are unknown. As a means to address this question, we estimated centromere sizes in ten species of the grass family including rice, maize, and wheat, which diverged 60~80 million years ago and vary by 40-fold in genome size. Measurements were made using a broadly reactive antibody to rice centromeric histone H3 (CENH3). In species-wide comparisons, we found a clear linear relationship between total centromere size and genome size. Species with large genomes and few chromosomes tend to have the largest centromeres (e.g., rye) while species with small genomes and many chromosomes have the smallest centromeres (e.g., rice). However, within a species, centromere size is surprisingly uniform. We present evidence from three oat-maize addition lines that support this claim, indicating that each of three maize centromeres propagated in oat are not measurably different from each other. In the context of previously published data, our results suggest that the apparent correlation between chromosome and centromere size is incidental to a larger trend that reflects genome size. Centromere size may be determined by a limiting component mechanism similar to that described for Caenorhabditis elegans centrosomes.
几十年来，人们已经知道着丝粒大小在物种间存在差异，但涉及设定着丝粒边界的因素尚不清楚。为了解决这个问题，我们在包括水稻、玉米和小麦在内的十个禾本科物种中估计了着丝粒的大小，这些物种在 6000 万至 8000 万年前分化，基因组大小差异达 40 倍。测量是使用广泛反应性的水稻着丝粒组蛋白 H3（CENH3）抗体进行的。在全物种比较中，我们发现总着丝粒大小与基因组大小之间存在明显的线性关系。基因组大且染色体少的物种往往具有最大的着丝粒（例如黑麦），而基因组小且染色体多的物种具有最小的着丝粒（例如水稻）。然而，在一个物种内，着丝粒大小却惊人地均匀。我们从三个燕麦-玉米添加系中提供了支持这一说法的证据，表明在燕麦中传播的三个玉米着丝粒中的每一个彼此之间都没有可测量的差异。根据先前发表的数据，我们的结果表明，染色体和着丝粒大小之间的明显相关性是偶然的，反映了更大的趋势，反映了基因组大小。着丝粒大小可能由类似于描述的秀丽隐杆线虫中心体的限制成分机制决定。
