Indolic secondary metabolites play an important role in pathogen defense in cruciferous plants. In Arabidopsis (Arabidopsis thaliana), in addition to the characteristic phytoalexin camalexin, derivatives of indole-3-carbaldehyde (ICHO) and indole-3-carboxylic acid (ICOOH) are synthesized from tryptophan via the intermediates indole-3-acetaldoxime and indole-3-acetonitrile. Based on feeding experiments combined with nontargeted metabolite profiling, their composition in nontreated and silver nitrate (AgNO3)-treated leaf tissue was comprehensively analyzed. As major derivatives, glucose conjugates of 5-hydroxyindole-3-carbaldehyde, ICOOH, and 6-hydroxyindole-3-carboxylic acid were identified. Quantification of ICHO and ICOOH derivative pools after glucosidase treatment revealed that, in response to AgNO3 treatment, their total accumulation level was similar to that of camalexin. ARABIDOPSIS ALDEHYDE OXIDASE1 (AAO1), initially discussed to be involved in the biosynthesis of indole-3-acetic acid, and Cytochrome P450 (CYP) 71B6 were found to be transcriptionally coexpressed with camalexin biosynthetic genes. CYP71B6 was expressed in Saccharomyces cerevisiae and shown to efficiently convert indole-3-acetonitrile into ICHO and ICOOH, thereby releasing cyanide. To evaluate the role of both enzymes in the biosynthesis of ICHO and ICOOH derivatives, knockout and overexpression lines for CYP71B6 and AAO1 were established and analyzed for indolic metabolites. The observed metabolic phenotypes suggest that AAO1 functions in the oxidation of ICHO to ICOOH in both nontreated and AgNO3-treated leaves, whereas CYP71B6 is relevant for ICOOH derivative biosynthesis specifically after induction. In summary, a model for the biosynthesis of ICHO and ICOOH derivatives is presented.

中文翻译：

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Indole-3-Carbaldehyde 和 Indole-3-Carboxyic Acid 衍生物在拟南芥中的生物合成途径。

Indolic 次生代谢产物在十字花科植物的病原体防御中起重要作用。在拟南芥 (Arabidopsis thaliana) 中，除了特有的植物抗毒素 camalexin 外，还通过中间体 indole-3-acetaldoxime 和 indole-从色氨酸合成吲哚-3-甲醛 (ICHO) 和吲哚-3-羧酸 (ICOOH) 的衍生物。 3-乙腈。基于饲养实验结合非靶向代谢物分析，综合分析了它们在未处理和硝酸银 (AgNO3) 处理的叶组织中的组成。作为主要衍生物，鉴定了 5-羟基吲哚-3-甲醛、ICOOH 和 6-羟基吲哚-3-羧酸的葡萄糖结合物。葡萄糖苷酶处理后 ICHO 和 ICOOH 衍生物池的定量表明，响应 AgNO3 处理，它们的总积累水平与camalexin相似。ARABIDOPSIS ALDEHYDE OXIDASE1 (AAO1)，最初讨论参与吲哚-3-乙酸的生物合成，发现细胞色素 P450 (CYP) 71B6 与 camalexin 生物合成基因转录共表达。CYP71B6 在酿酒酵母中表达，并显示可有效地将 indole-3-乙腈转化为 ICHO 和 ICOOH，从而释放氰化物。为了评估两种酶在 ICHO 和 ICOOH 衍生物生物合成中的作用，建立了 CYP71B6 和 AAO1 的敲除和过表达系，并分析了吲哚代谢物。观察到的代谢表型表明 AAO1 在未处理和 AgNO3 处理的叶子中 ICHO 氧化为 ICOOH 中起作用，而 CYP71B6 与诱导后的 ICOOH 衍生物生物合成相关。总之，提出了 ICHO 和 ICOOH 衍生物的生物合成模型。