Regulation of Pathogen-Triggered Tryptophan Metabolism in Arabidopsis thaliana by MYB Transcription Factors and Indole Glucosinolate Conversion Products
Regulation of Pathogen-Triggered Tryptophan Metabolism in Arabidopsis thaliana by MYB Transcription Factors and Indole Glucosinolate Conversion Products
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DOI：
10.1016/j.molp.2016.01.006
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发表时间：
2016-05-02
期刊：
影响因子：
27.5
通讯作者：
Bednarek, Pawel
中科院分区：
文献类型：
--
作者：
Frerigmann, Henning;Pislewska-Bednarek, Mariola;Bednarek, Pawel
MYB34、MYB51 和 MYB122 转录因子被认为是吲哚芥子油苷 (IG) 生物合成的决定性调节因子，对编码 CYP79B2 和 CYP79B3 酶的基因表达产生强烈影响，这些酶将色氨酸冗余地转化为吲哚 3-乙醛肟 (IAOx)。该中间体代表了 IG 生物合成的分支点，以及导致 camalexin 和吲哚羧酸 (ICA) 的途径。在这里，我们研究这些 MYB 如何影响病原体触发的色氨酸代谢。我们的实验表明，这三种 MYB 不仅影响 IG 的产生，还影响其他 IAOx 衍生代谢物的组成型生物合成。引人注目的是，渗透 2 (PEN2) 依赖性 IG 代谢产物（在 myb34/51/122 和 pen2 突变体中不存在）对于 flg22 介导的其他 IAOx 衍生化合物的完全诱导是不可或缺的。然而，尽管 IG 水平大幅降低，但在 myb34/51/122 植物中，病原体感染后 ICA 和camalexin 的基因诱导和积累并未受到损害。因此，与缺乏所有 IAOx 衍生代谢物的 cyp79B2/B3 相比，我们发现 myb34/51/122 是分析 IG 对坏死性真菌病原体黄瓜圆球菌 (Plectosphaerella cucumerina) 抵抗力的理想工具。 myb34/51/122的敏感性与pen2相似，但远低于cyp79B2/B3的敏感性，表明MYB34/51/122仅通过IG生物合成来抵抗黄瓜青霉，并且PEN2是响应微生物病原体而激活叶黑芥子酶的主要IG。
MYB34, MYB51, and MYB122 transcription factors are known as decisive regulators of indolic glucosinolate (IG) biosynthesis with a strong impact on expression of genes encoding CYP79B2 and CYP79B3 enzymes that redundantly convert tryptophan to indole-3-acetaldoxime (IAOx). This intermediate represents a branching point for IG biosynthesis, and pathways leading to camalexin and indole-carboxylic acids (ICA). Here we investigate how these MYBs affect the pathogen-triggered Trp metabolism. Our experiments indicated that these three MYBs affect not only IG production but also constitutive biosynthesis of other IAOx-derived metabolites. Strikingly, the PENETRATION 2 (PEN2)-dependent IG-metabolism products, which are absent in myb34/51/122 and pen2 mutants, were indispensable for full flg22-mediated induction of other IAOx-derived compounds. However, gene induction and accumulation of ICAs and camalexin upon pathogen infection was not compromised in myb34/51/122 plants, despite strongly reduced IG levels. Hence, in comparison with cyp79B2/B3, which lacks all IAOx-derived metabolites, we found myb34/51/122 an ideal tool to analyze IG contribution to resistance against the necrotrophic fungal pathogen Plectosphaerella cucumerina. The susceptibility of myb34/51/122 was similar to that of pen2, but much lower than susceptibility of cyp79B2/B3, indicating that MYB34/51/122 contribute to resistance toward P. cucumerina exclusively through IG biosynthesis, and that PEN2 is the main leaf myrosinase activating IGs in response to microbial pathogens.