A stable isotope-assisted mass spectrometry-based platform was utilized to demonstrate that the plant hormone, salicylic acid, is catabolized to catechol, a widespread secondary plant compound. The phytohormone salicylic acid (SA) plays a central role in the overall plant defense program, as well as various other aspects of plant growth and development. Although the biosynthetic steps toward SA are well documented, how SA is catabolized in plants remains poorly understood. Accordingly, in this study a series of stable isotope feeding experiments were performed with Silene latifolia (white campion) to explore possible routes of SA breakdown. S. latifolia flowers that were fed a solution of [2H6]-salicylic acid emitted the volatile and potent pollinator attractant, 1,2-dimethoxybenzene (veratrole), which contained the benzene ring-bound deuterium atoms. Extracts from these S. latifolia flowers revealed labeled catechol as a possible intermediate. After feeding flowers with [2H6]-catechol, the stable isotope was recovered in veratrole as well as its precursor, guaiacol. Addition of a trapping pool of guaiacol in combination with [2H6]-salicylic acid resulted in the accumulation of the label into catechol. Finally, we provide evidence for catechol O-methyltransferase enzyme activity in a population of S. latifolia that synthesizes veratrole from guaiacol. This activity was absent in non-veratrole emitting flowers. Taken together, these results imply the conversion of salicylic acid to veratrole in the following reaction sequence: salicylic acid > catechol > guaiacol > veratrole. This catabolic pathway for SA may also be embedded in other lineages of the plant kingdom, particularly those species which are known to accumulate catechol.

中文翻译：

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来自稳定同位素标记的证据表明，儿茶酚是 Silene latifolia (white campion) 花中水杨酸分解代谢的中间体

利用基于稳定同位素辅助质谱的平台来证明植物激素水杨酸被分解代谢为儿茶酚，这是一种广泛存在的次生植物化合物。植物激素水杨酸 (SA) 在整个植物防御计划以及植物生长和发育的各个其他方面发挥着核心作用。尽管朝向 SA 的生物合成步骤有据可查，但 SA 如何在植物中分解代谢仍然知之甚少。因此，在本研究中，用 Silene latifolia（白色野草）进行了一系列稳定同位素喂养实验，以探索 SA 分解的可能途径。喂食 [2H6]-水杨酸溶液的 S. latifolia 花释放出挥发性强的传粉引诱剂 1,2-二甲氧基苯（藜芦），其中含有苯环结合的氘原子。这些 S. latifolia 花的提取物显示标记的儿茶酚可能是一种中间体。用 [2H6]-儿茶酚喂花后，在藜芦醇及其前体愈创木酚中回收了稳定同位素。添加愈创木酚的捕获池与 [2H6]-水杨酸的组合导致标记积累到儿茶酚中。最后，我们为从愈创木酚合成藜芦醇的阔叶树种群中的儿茶酚 O-甲基转移酶活性提供了证据。这种活动在非藜芦发射花中不存在。总之，这些结果表明水杨酸转化为藜芦醇的反应顺序如下：水杨酸 > 儿茶酚 > 愈创木酚 > 藜芦醇。