Keyte Anna L, Percifield Ryan, Liu Bao, Wendel Jonathan F
Department of Biology, Duke University, Durham, NC 27710, USA.
J Hered. 2006 Sep-Oct;97(5):444-50. doi: 10.1093/jhered/esl023. Epub 2006 Sep 20.
Cytosine methylation is important in the epigenetic regulation of gene expression and development in plants and has been implicated in silencing duplicate genes after polyploid formation in several plant groups. Relatively little information exists, however, on levels and patterns of methylation polymorphism (MP) at homologous loci within species. Here we explored the levels and patterns of methylation-polymorphism diversity at CCGG sites within allotetraploid cotton, Gossypium hirsutum, using a methylation-sensitive amplified fragment length polymorphism screen and a selected set of 20 G. hirsutum accessions for which we have information on genetic polymorphism levels and relationships. Methylation and MP exist at high levels within G. hirsutum: of 150 HpaII/MspI sites surveyed, 48 were methylated at the inner cytosine (32%) and 32 of these were polymorphic (67%). Both these values are higher than comparable measures of genetic diversity using restriction fragment length polymorphisms. The high percentage of methylation-polymorphic sites and potential relationship to gene expression underscore the potential significance of MP within and among populations. We speculate that biased correlation of methylation-polymorphic sites and genes in cotton may be a consequence of polyploidy and the attendant doubling of all genes.
胞嘧啶甲基化在植物基因表达和发育的表观遗传调控中起着重要作用，并且在多个植物类群的多倍体形成后参与重复基因的沉默。然而，关于物种内同源位点甲基化多态性（MP）的水平和模式的信息相对较少。在这里，我们利用甲基化敏感扩增长度多态性筛选方法，并选取了20个陆地棉（Gossypium hirsutum）种质，这些种质具有遗传多态性水平和关系的相关信息，来探究异源四倍体棉花陆地棉CCGG位点的甲基化多态性多样性的水平和模式。陆地棉中存在高水平的甲基化和MP：在检测的150个HpaII/MspI位点中，有48个在内侧胞嘧啶处发生甲基化（32%），其中32个是多态性的（67%）。这两个值均高于使用限制性片段长度多态性的遗传多样性可比测量值。甲基化多态性位点的高比例以及与基因表达的潜在关系强调了MP在种群内和种群间的潜在重要性。我们推测，棉花中甲基化多态性位点与基因的偏向相关性可能是多倍体以及所有基因随之加倍的结果。
