Regulation of Pathogen-Triggered Tryptophan Metabolism in Arabidopsis thaliana by MYB Transcription Factors and Indole Glucosinolate Conversion Products

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• 作者：Henning Frerigmann¹ ; Mariola Piślewska-Bednarek² ; Andrea Sá ; nchez-Vallet³ ; ⁵ ; Antonio Molina³ ; Erich Glawischnig⁴ ; Tamara Gigolashvili¹ ; Paweł Bednarek² ; ^{bednarek@ibch.poznan.pl" class="auth_mail" title="E-mail the corresponding author}
• 关键词：indolic glucosinate ; Plectosphaerella cucumerina ; MAMP-triggered immunity ; Trp metabolism ; indole-3-carboxylic acids ; camalexin
• 刊名：Molecular Plant
• 出版年：2016
• 出版时间：2 May 2016
• 年：2016
• 卷：9
• 期：5
• 页码：682-695
• 全文大小：1750 K

文摘

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.