Gene body methylation (gbM) is a widely conserved epigenetic feature of plant genomes. Efforts to delineate the mechanisms by which gbM contributes to transcriptional regulation remain largely inconclusive, and its evolutionary significance continues to be debated. Curiously, although steady-state gbM levels are remarkably stable across mitotic and meiotic cell divisions, the methylation status of individual CG dinucleotides in gbM genes is highly stochastic. How can these two seemingly contradictory observations be reconciled? Here, we discuss how stochastic processes relate to gbM maintenance dynamics. We show that a quantitative understanding of these processes can shed deeper insights into the molecular and evolutionary biology of this enigmatic epigenetic trait.

基因体甲基化（gbM）是植物基因组广泛保守的表观遗传特征。描述 gbM 促进转录调控机制的努力在很大程度上仍然没有定论，其进化意义仍然存在争议。奇怪的是，尽管稳态 gbM 水平在有丝分裂和减数分裂细胞分裂中非常稳定，但 gbM 基因中单个 CG 二核苷酸的甲基化状态却是高度随机的。如何调和这两个看似矛盾的观察结果？在这里，我们讨论随机过程如何与 GBM 维护动态相关。我们表明，对这些过程的定量理解可以更深入地了解这种神秘的表观遗传特征的分子和进化生物学。