Data_Sheet_1_Chemical Priming by Isothiocyanates Protects Against Intoxication by Products of the Mustard Oil Bomb.docx

In Brassicaceae, tissue damage triggers the mustard oil bomb i.e., activates the degradation of glucosinolates by myrosinases leading to a rapid accumulation of isothiocyanates at the site of damage. Isothiocyanates are reactive electrophilic species (RES) known to covalently bind to thiols in proteins and glutathione, a process that is not only toxic to herbivores and microbes but can also cause cell death of healthy plant tissues. Previously, it has been shown that subtoxic isothiocyanate concentrations can induce transcriptional reprogramming in intact plant cells. Glutathione depletion by RES leading to breakdown of the redox potential has been proposed as a central and common RES signal transduction mechanism. Using transcriptome analyses, we show that after exposure of Arabidopsis seedlings (grown in liquid culture) to subtoxic concentrations of sulforaphane hundreds of genes were regulated without depletion of the cellular glutathione pool. Heat shock genes were among the most highly up-regulated genes and this response was found to be dependent on the canonical heat shock factors A1 (HSFA1). HSFA1-deficient plants were more sensitive to isothiocyanates than wild type plants. Moreover, pretreatment of Arabidopsis seedlings with subtoxic concentrations of isothiocyanates increased resistance against exposure to toxic levels of isothiocyanates and, hence, may reduce the autotoxicity of the mustard oil bomb by inducing cell protection mechanisms.

十字花科（Brassicaceae）植物中，组织损伤会触发芥子油炸弹（mustard oil bomb）效应：即通过黑芥子酶（myrosinases）激活硫代葡萄糖苷（glucosinolates）的降解，使损伤位点快速积累异硫氰酸酯（isothiocyanates）。异硫氰酸酯属于亲电活性物质（reactive electrophilic species, RES），可与蛋白质和谷胱甘肽（glutathione）中的巯基发生共价结合。该过程不仅对草食动物和微生物具有毒性，还可诱导健康植物组织发生细胞死亡。此前已有研究表明，亚毒性浓度的异硫氰酸酯可诱导完整植物细胞发生转录重编程（transcriptional reprogramming）。此前有研究提出，RES介导的谷胱甘肽耗竭导致氧化还原势（redox potential）失衡，是RES信号转导的核心且普遍的机制。本研究通过转录组分析（transcriptome analyses）发现，将液体培养的拟南芥幼苗暴露于亚毒性浓度的萝卜硫素（sulforaphane）后，数百个基因的表达发生调控，且未引起细胞内谷胱甘肽库的耗竭。热激基因是上调幅度最为显著的基因类别之一，且该应答依赖于经典热激因子A1（HSFA1）。HSFA1缺失型拟南芥相较于野生型植株，对异硫氰酸酯的敏感性更高。此外，用亚毒性浓度的异硫氰酸酯预处理拟南芥幼苗，可提升其对毒性浓度异硫氰酸酯的抗性，因此该处理可通过诱导细胞保护机制，降低芥子油炸弹的自体毒性。