Background: Plants subjected to the novel environment of spaceflight show transcriptomic changes that resemble aspects of several terrestrial abiotic stress responses. Under investigation here is whether epigenetic modulations, similar to those that occur in terrestrial stress responses, have a functional role in spaceflight physiological adaptation. The Advanced Plant Experiment-04 – Epigenetic Expression experiment examined the role of cytosine methylation in spaceflight adaptation. The experiment was conducted onboard the International Space Station, and evaluated the spaceflight-altered, genome-wide methylation profiles of two methylation-regulating gene mutants [methyltransferase 1 (met1-7) and elongator complex subunit 2 (elp2-5)] along with a wild-type Col-0 control.

Results: The elp2-5 plants suffered in their physiological adaptation to spaceflight in that their roots failed to extend away from the seed and the overall development of the plants was greatly impaired in space. The met1-7 plants suffered less, with their morphology affected by spaceflight in a manner similar to that of the Col-0 controls. The differentially expressed genes (DEGs) in spaceflight were dramatically different in the elp2-5 and met1-7 plants compared to Col-0, indicating that the disruptions in these mutants resulted in a reprogramming of their spaceflight responses, especially in elp2-5. Many of the genes comprising the spaceflight transcriptome of each genotype were differentially methylated in spaceflight. In Col-0 the majority of the DEGs were representative of the now familiar spaceflight response, which includes genes associated with cell wall remodeling, pathogen responses and ROS signaling. However, the spaceflight transcriptomes of met1-7 and elp2-5 each presented patterns of DEGs that are almost completely different than Col-0, and to each other. Further, the DEGs of the mutant genotypes suggest a more severe spaceflight stress response in the mutants, particularly in elp2-5.

Conclusion: Arabidopsis physiological adaptation to spaceflight results in differential DNA methylation in an organ-specific manner. Disruption of Met1 methyltransferase function does not dramatically affect spaceflight growth or morphology, yet met1-7 reprograms the spaceflight transcriptomic response in a unique manner. Disruption of elp2-5 results in poor development in spaceflight grown plants, together with a diminished, dramatically reprogrammed transcriptomic response.

背景：在太空飞行的新环境中的植物表现出类似于几种陆地非生物胁迫反应的转录组学变化。这里正在研究的是表观遗传调制，类似于那些发生在地球压力反应中的调制，是否在航天生理适应中具有功能作用。Advanced Plant Experiment-04 – 表观遗传表达实验检查了胞嘧啶甲基化在航天适应中的作用。该实验在国际空间站上进行，并评估了两个甲基化调节基因突变体 [甲基转移酶 1 (遇到 1-7) 和伸长复合体亚基 2 (elp2-5)] 以及野生型 Col-0 对照。

结果： 这 elp2-5植物对太空飞行的生理适应受到影响，因为它们的根无法从种子延伸出去，植物的整体发育在太空中受到极大的损害。这遇到1-7植物受到的影响较小，它们的形态受太空飞行的影响类似于 Col-0 对照。太空飞行中的差异表达基因（DEGs）在elp2-5 和 遇到1-7 植物与 Col-0 相比，表明这些突变体的破坏导致它们的航天反应重新编程，尤其是在 elp2-5. 构成每种基因型航天飞行转录组的许多基因在航天飞行中发生了差异甲基化。在 Col-0 中，大多数 DEG 代表了现在熟悉的航天反应，其中包括与细胞壁重塑、病原体反应和 ROS 信号传导相关的基因。然而，太空飞行转录组遇到1-7 和 elp2-5每个都呈现出与 Col-0 几乎完全不同的 DEG 模式，并且彼此之间。此外，突变基因型的 DEG 表明突变体有更严重的航天应激反应，尤其是在elp2-5.

结论：拟南芥对航天的生理适应导致以器官特异性方式差异 DNA 甲基化。Met1 甲基转移酶功能的破坏不会显着影响航天飞行的生长或形态，但遇到1-7以独特的方式重新编程航天转录组反应。中断elp2-5 导致航天植物的发育不良，以及减少的、显着重编程的转录组反应。