METABOLIC FATE OF SECONDARY METABOLITES : INVOLVEMENT OF CELL WALLS

次级代谢物的代谢命运：细胞壁的参与

基本信息

批准号：
17580095
负责人：
ISHIHARA Atsushi
金额：
$ 2.37万
依托单位：
Kyoto University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2005
资助国家：
日本
起止时间：
2005 至 2007
项目状态：
已结题

项目摘要

The metabolic fates of secondary metabolites were investigated in gramineous plants, oats, and a model plant Arabidopsis thaliana.In oats, it has been demonstrated that their phytoalesxins, avenanthramides, are incorporated into cell walls. lb know the incorporation processes in detail, the metabolites that are derived from avenanthramides were investigated. The avenanthramide metabolites that are genrerated by the action of peroxidase were found to be present in oat leaves. The analysis of their chemical structures revealed that they are dehydrodimers of avenanthramides. The spectroscopic analysis revealed that they have unique carbon skeletons that have not been found in natural products. These compounds are considered to be units for the incorporation of avenanthramides into cell walls.In Arabidopsis thaliana, indole-3-carboxylic acid (ICA) has been indicated to bound to the cell walls. We found that the amount of ICA increases in the leaves infected by A. brassicicola. The biosynthetic pathway of ICA was analyzed by using stable isotope labeled putative precursors and mutants that exhibit modified tryptophan metabolism. First, Arabidopsis leaves were fed with labeled tryptophan and the conidia of A. brassicicola were inoculated. The leaves were extracted with methanol and the incorporation of tryptophan into ICA was analyzed by LC-MS/MS. The labeled tryptophan was effectively incorporated into ICA, indicating de novo synthesis of ICA in the infected leaves. Next, we analyzed ICA contents in multiple lines that have altered tryptophan metabolism. The increase of the amount of ICA in the cell walls was found in pad 3 mutant line. pad 3 line larks the accumulation of indolic phytoalexin, camalexin. Thus, this finding strongly suggests that ICA is not directly derived from camalexin, and that the biosynthetic pathway of ICA is shared by the pathway for camalexin.

在禾本科植物、燕麦和模式植物拟南芥中研究了次生代谢物的代谢命运。在燕麦中，已证明其植物抗毒素（燕麦生物碱）融入细胞壁中。在详细了解掺入过程后，我们对源自燕麦生物碱的代谢物进行了研究。发现燕麦叶中存在通过过氧化物酶作用产生的燕麦生物碱代谢物。对其化学结构的分析表明它们是燕麦生物碱的脱氢二聚体。光谱分析表明它们具有天然产物中未发现的独特碳骨架。这些化合物被认为是将燕麦生物碱掺入细胞壁的单元。在拟南芥中，吲哚-3-羧酸 (ICA) 已被证明与细胞壁结合。我们发现受 A. 芸苔菌感染的叶子中 ICA 的量增加。通过使用稳定同位素标记的假定前体和表现出色氨酸代谢改变的突变体来分析 ICA 的生物合成途径。首先，用标记的色氨酸喂养拟南芥叶，并接种甘蓝菜的分生孢子。用甲醇提取叶子，并通过 LC-MS/MS 分析色氨酸掺入 ICA 的情况。标记的色氨酸有效地掺入 ICA 中，表明 ICA 在受感染的叶子中从头合成。接下来，我们分析了多个改变色氨酸代谢的品系中的 ICA 含量。在 pad 3 突变系中发现细胞壁中 ICA 量的增加。垫3线云雀积累吲哚植物抗毒素、camalexin。因此，这一发现强烈表明ICA并非直接源自camalexin，并且ICA的生物合成途径与camalexin途径共享。