An environment with strong gravitational and magnetic field alterations synergizes to promote variations in Arabidopsis thaliana callus global transcriptional state

Using diamagnetic levitation, we have exposed A. thaliana in vitro callus cultures to five environments with different levels of effective gravity (from levitation i.e. simulated mg* to 2g*) and magnetic fields (10.1 to 16.5 Tesla) and we have compared the results with those of similar experiments done in a Random Position Machine (simulated micro g) and a Large Diameter Centrifuge (2g) free of high magnetic fields. Microarray analysis indicates that there are changes in overall gene expression of the cultured cells exposed to these unusual environments but also that gravitational and magnetic field produce synergic variations in the steady state of the transcriptional profile of A. thaliana. Significant changes in the expression of structural, abiotic stress and secondary metabolism genes were observed into the magnet field. These results confirm that the strong magnetic field, both at micro g* or 2g*, has a significant effect on the expression of these genes but subtle gravitational effects are still observable. These subtle responses to microgravity environments are opposite to the ones observed in a hypergravity one. seven-condition experiment, MM2D Arabidopsis culture callus control vs. Treatment (altered gravity simulation, GBF). Three GBF were used (LDC (2g) + control, RPM (mg) + control and Magnet (mg*, 0.1g*, 1g*, 1.9g*, 2g*) + control). Biological replicates: 3 replicates in all conditions and controls except 1.9g* (2 replicates)

本研究采用抗磁悬浮（diamagnetic levitation）技术，将拟南芥（Arabidopsis thaliana）体外愈伤组织培养物暴露于5种有效重力水平（从悬浮状态下的模拟微重力*至2倍重力*）与不同磁场强度（10.1至16.5特斯拉）的环境中，并将实验结果与随机定位机（Random Position Machine，模拟微重力）及无强磁场的大直径离心机（Large Diameter Centrifuge，2g重力）上开展的同类实验结果进行对比。基因芯片（Microarray）分析结果显示，暴露于这些非常规环境的培养细胞整体基因表达发生改变，且重力与磁场对拟南芥转录组稳态的变化存在协同调控效应。在磁场环境下，我们观察到结构基因、非生物胁迫（abiotic stress）相关基因及次生代谢（secondary metabolism）相关基因的表达出现显著变化。本研究结果证实，无论是模拟微重力*还是2倍重力*环境下，强磁场均会对上述基因的表达产生显著影响，但微弱重力效应仍可被观测到。这类对微重力环境的微妙响应与超重（hypergravity）环境下观测到的响应恰好相反。本次七条件对照实验以MM2D培养基培养的拟南芥愈伤组织为材料，设置对照组与处理组（重力模拟改变实验，GBF），共包含3类GBF处理方案：大直径离心机（2g重力）+对照组、随机定位机（微重力）+对照组，以及磁场处理组（模拟微重力*、0.1g*、1g*、1.9g*、2g*）+对照组。除1.9g*处理组仅设置2次生物学重复外，其余所有处理组与对照组均设置3次生物学重复。