Methylome variation across clonal seagrass shoots

Factors influencing variance of DNA methylation in vegetatively reproducing plants, both terrestrial plants and aquatic seagrasses, is just beginning to be understood. Improving our knowledge of these mechanisms will increase understanding of transgenerational epigenetics in plant clones, of the relationship between DNA methylation and seagrass development, and of the drivers of epigenetic variation, which may underly acclimation in clonally reproducing plants. Here, we sampled leaves, rhizomes and roots of three physically and spatially separated ramet sections from a clonally propagated field of the seagrass Zostera marina. Using reduced methylome sequencing, we studied variations in the methylome of seagrass Zostera marina between the sampled tissue types and across age groups. Our analysis of ramets of different ages showed variations in methylation between older and younger samples in both specific methylation patterns and global methylation levels. Our analysis of tissue types showed a marked differentiation of the roots from the rhizomes and leaves, which showed more similar methylation patterns. These findings are in agreement with the strong connection of DNA methylation and plant development and tissue differentiation. We also suggest an effect of differential environmental exposures on the methylome of the younger versus the older ramets due to the forming of molecular stress memories.

关于营养繁殖植物（涵盖陆生植物与水生海草）的DNA甲基化（DNA methylation）变异影响因素，学界目前尚处于初步认知阶段。深化对这些调控机制的认知，将有助于我们理解植物克隆群体的跨代表观遗传学（transgenerational epigenetics）、DNA甲基化与海草发育的关联，以及表观遗传变异（epigenetic variation）的驱动因素——而后者或是克隆繁殖植物适应性驯化（acclimation）的分子基础。本研究从克隆繁殖的大叶藻（Zostera marina）野外种群中，采集了三个物理与空间上相互隔离的分株（ramet）区段的叶片、根状茎与根系样本。本研究采用简化甲基化组测序（reduced methylome sequencing）技术，分析了大叶藻不同组织类型以及不同年龄组的甲基化组（methylome）变异特征。针对不同年龄分株的分析显示，无论是特异性甲基化模式还是全局甲基化水平，年长样本与年轻样本之间均存在显著甲基化差异。针对组织类型的分析则显示，根系与根状茎、叶片之间存在显著的甲基化组分化，而后两者的甲基化模式更为相近。上述研究结果与DNA甲基化与植物发育、组织分化之间存在紧密关联的结论相一致。本研究还提出，由于分子应激记忆的形成，差异化的环境暴露会对年轻与年长分株的甲基化组产生不同影响。