Böttcher Christoph, Chapman Alexandra, Fellermeier Franziska, Choudhary Manisha, Scheel Dierk, Glawischnig Erich
Leibniz Institute of Plant Biochemistry, Department of Stress and Developmental Biology, 06120 Halle/Saale, Germany (C.B., D.S.); andLehrstuhl für Genetik, Technische Universität München, 85354 Freising, Germany (A.C., F.F., M.C., E.G.).
Leibniz Institute of Plant Biochemistry, Department of Stress and Developmental Biology, 06120 Halle/Saale, Germany (C.B., D.S.); andLehrstuhl für Genetik, Technische Universität München, 85354 Freising, Germany (A.C., F.F., M.C., E.G.)
Plant Physiol. 2014 Jun;165(2):841-853. doi: 10.1104/pp.114.235630. Epub 2014 Apr 11.
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 (AgNO)-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 AgNO 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 AgNO-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.
吲哚类次生代谢产物在十字花科植物的病原体防御中发挥着重要作用。在拟南芥中，除了特征性的植物抗毒素camalexin外，吲哚 - 3 - 甲醛（ICHO）和吲哚 - 3 - 羧酸（ICOOH）的衍生物是通过中间体吲哚 - 3 - 乙醛肟和吲哚 - 3 - 乙腈由色氨酸合成的。基于饲喂实验并结合非靶向代谢物谱分析，对未处理和硝酸银（AgNO）处理的叶片组织中它们的组成进行了全面分析。作为主要衍生物，鉴定出了5 - 羟基吲哚 - 3 - 甲醛、ICOOH和6 - 羟基吲哚 - 3 - 羧酸的葡萄糖共轭物。糖苷酶处理后对ICHO和ICOOH衍生物库的定量分析表明，响应AgNO处理，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化酶1（AAO1）和细胞色素P450（CYP）71B6被发现与camalexin生物合成基因转录共表达。CYP71B6在酿酒酵母中表达，并显示能有效地将吲哚 - 3 - 乙腈转化为ICHO和ICOOH，从而释放出氰化物。为了评估这两种酶在ICHO和ICOOH衍生物生物合成中的作用，建立了CYP71B6和AAO1的敲除和过表达系，并分析了吲哚类代谢物。观察到的代谢表型表明，AAO1在未处理和AgNO处理的叶片中均参与将ICHO氧化为ICOOH的过程，而CYP71B6仅在诱导后与ICOOH衍生物的生物合成相关。总之，本文提出了ICHO和ICOOH衍生物生物合成的模型。
