Moore G, Abbo S, Cheung W, Foote T, Gale M, Koebner R, Leitch A, Leitch I, Money T, Stancombe P
Cambridge Laboratory, Norwich, United Kingdom.
Genomics. 1993 Mar;15(3):472-82. doi: 10.1006/geno.1993.1097.
Unlike mammalian genomes, cereal (Gramineae) genomes exhibit little suppression of CpG dinucleotides. In cereal genomes, however, most of the numerous potential recognition sites for CpG methylation-sensitive restriction enzymes are methylated. Analysis of cereal genomic libraries and of regions flanking genes indicates that unmethylated NotI sites are useful landmarks for regions containing genes/single-copy sequences. Studies of a rye chromosome arm indicate that its pericentromeric region has a reduced density of unmethylated NotI (and MluI) sites and therefore of genes. Unmethylated MluI and NruI sites are distributed nonrandomly in the genomes of wheat, barley, and rice. Analysis of the genomic blocks defined by these sites in wheat and barley indicates that they are most likely to have arisen by amplification. These observations form the basis of a proposed model for the organization and evolution of the wheat, barley, and rice genomes.
与哺乳动物基因组不同，禾本科（Gramineae）基因组对CpG二核苷酸的抑制作用很小。然而，在禾本科基因组中，众多对CpG甲基化敏感的限制性内切酶的潜在识别位点大多被甲基化。对禾本科基因组文库和基因侧翼区域的分析表明，未甲基化的NotI位点是包含基因/单拷贝序列区域的有用标记。对黑麦染色体臂的研究表明，其着丝粒周围区域未甲基化的NotI（和MluI）位点密度降低，因此基因密度也降低。未甲基化的MluI和NruI位点在小麦、大麦和水稻基因组中呈非随机分布。对小麦和大麦中由这些位点定义的基因组区域的分析表明，它们很可能是通过扩增产生的。这些观察结果构成了一个关于小麦、大麦和水稻基因组组织与进化的模型的基础。
