Embryogenesis is a brief but potentially critical phase in the tree life cycle for adaptive phenotypic plasticity. Using somatic embryogenesis in maritime pine (Pinus pinaster Ait.), we found that temperature during the maturation phase affects embryo development and post-embryonic tree growth for up to three years. We examined whether this somatic stress memory could stem from temperature- and/or development-induced changes in DNA methylation. For this, we developed a 200 Mb custom sequence capture bisulfite analysis of genes and promoters to identify differentially methylated cytosines (DMCs) between temperature treatments (18, 23, and 28°C) and developmental stages (immature and cotyledonary embryos, shoot apical meristem of 2-year-old plants) and investigate if these differences can be mitotically transmitted from embryonic to post-embryonic development (epigenetic memory). We revealed a high prevalence of temperature-induced DMCs in genes (8-14%) compared to promoters (less than 1%) in all 3 cytosine contexts. Developmental DMCs showed a comparable pattern but only in the CG context and with a strong trend towards hypomethylation, particularly in the promoters. A high percentage of DMCs induced by developmental transitions were found memorized in genes (up to 45-50%) and promoters (up to 90%). In contrast, temperature-induced memory was lower and confined to genes after both embryonic (up to 14%) and post-embryonic development (up to 8%). Using stringent criteria, we identified ten genes involved in defense responses and adaptation, embryo development, and chromatin regulation that are candidates for the establishment of a persistent epigenetic memory of temperature sensed during embryo maturation in maritime pine. Here, we provide evidence that DNA methylation marks established during the embryonic phase are transmitted to the post-embryonic plant development phase.

中文翻译：

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2 年生海松体胚成熟过程中感知的温度表观遗传记忆


胚胎发生是树木生命周期中适应性表型可塑性的一个短暂但可能关键的阶段。利用海洋松 （Pinus pinaster Ait.） 的体细胞胚胎发生，我们发现成熟阶段的温度会影响胚胎发育和胚后树木生长长达三年。我们检查了这种体细胞应激记忆是否可能源于温度和/或发育诱导的 DNA 甲基化变化。为此，我们开发了一种 200 Mb 定制序列捕获亚硫酸氢盐的基因和启动子分析，以鉴定温度处理（18、23 和 28°C）和发育阶段（未成熟和子叶胚胎，2 年生植物的顶端分生组织）之间的差异甲基化胞嘧啶 （DMC），并研究这些差异是否可以从胚胎有丝分裂传递到胚胎后发育（表观遗传记忆）。我们揭示了在所有 3 种胞嘧啶情况下，与启动子 （不到 1%） 相比，基因中温度诱导的 DMC 的普遍率 （8-14%） 很高。发育性 DMC 显示出相似的模式，但仅在 CG 环境中，并且具有强烈的低甲基化趋势，尤其是在启动子中。发现发育转变诱导的 DMC 中有很大比例被存储在基因 （高达 45-50%） 和启动子 （高达 90%） 中。相比之下，温度诱导的记忆较低，并且局限于胚胎发育后 （高达 14%） 和胚胎后发育 （高达 8%） 后的基因。使用严格的标准，我们确定了 10 个参与防御反应和适应、胚胎发育和染色质调节的基因，这些基因是建立海松胚胎成熟过程中感知到的温度的持久表观遗传记忆的候选者。 在这里，我们提供了证据表明，在胚胎期建立的 DNA 甲基化标记会传递到胚胎后植物发育阶段。