The Biosynthetic Pathway of Indole-3-Carbaldehyde and Indole-3-Carboxylic Acid Derivatives in Arabidopsis
The Biosynthetic Pathway of Indole-3-Carbaldehyde and Indole-3-Carboxylic Acid Derivatives in Arabidopsis
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DOI：
10.1104/pp.114.235630
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发表时间：
2014-06-01
期刊：
影响因子：
7.4
通讯作者：
Glawischnig, Erich
中科院分区：
文献类型：
--
作者：
Boettcher, Christoph;Chapman, Alexandra;Glawischnig, Erich
吲哚类次生代谢产物在十字花科植物的病原菌防御中起着重要作用。在拟南芥中，除了植物抗凝蛋白外，色氨酸还通过中间体吲哚-3-乙醛和吲哚-3-乙腈合成吲哚-3-甲醛(Icho)和吲哚-3-羧酸(ICOOH)的衍生物。在饲喂实验的基础上，结合非靶向代谢产物谱分析，对未处理和硝酸银(AgNO3)处理的叶片组织中的化学成分进行了综合分析。作为主要的衍生物，确定了5-羟基吲哚-3-甲醛、ICOOH和6-羟基吲哚-3-羧酸的葡萄糖偶联物。对葡萄糖苷酶处理后的Icho和ICOOH衍生库的定量研究表明，AgNO3处理后，它们的总积累水平与Camalexin相似。最初被认为参与吲哚-3-乙酸生物合成的拟南芥醛氧合酶1(AAO1)和细胞色素P450(CYP)71B6被发现与Camalexin生物合成基因在转录水平上共表达。在酿酒酵母中表达了细胞色素P71B6，并能有效地将吲哚-3-乙腈转化为Icho和ICOOH，从而释放氰化物。为了评价这两种酶在Icho和ICOOH衍生物生物合成中的作用，建立了CyP71B6和AAO1基因敲除和过表达系，并对吲哚代谢物进行了分析。观察到的代谢表型表明，AAO1在未经处理和AgNO3处理的叶片中都参与了Icho氧化为ICOOH的过程，而CyP71B6与诱导后ICOOH衍生物的生物合成有关。综上所述，本文提出了Icho和ICOOH衍生物的生物合成模型。
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.