Thives Santos William, Dwivedi Varun, Ngoc Duong Ha, Miederhoff Madison, Vanden Hoek Kathryn, Angelovici Ruthie, Schenck Craig A
Department of Biochemistry, Interdisciplinary Plant Group, University of Missouri, Columbia, Missouri, USA.
Department of Biological Sciences, Interdisciplinary Plant Group, University of Missouri, Columbia, Missouri, USA.
Plant J. 2024 Dec;120(6):2904-2918. doi: 10.1111/tpj.17154. Epub 2024 Dec 3.
Plants have an amazing capacity to outcompete neighboring organisms for space and resources. Toxic metabolites are major players in these interactions, which can have a broad range of effectiveness by targeting conserved molecular mechanisms, such as protein biosynthesis. However, lack of knowledge about defensive metabolite pathways, their mechanisms of action, and resistance mechanisms limits our ability to manipulate these pathways for enhanced crop resilience. Nonproteogenic amino acids (NPAAs) are a structurally diverse class of metabolites with a variety of functions but are typically not incorporated during protein biosynthesis. Here, we investigate the mechanism of action of the NPAA azetidine-2-carboxylic acid (Aze), an analog of the amino acid proline (Pro). Using a combination of plate-based assays, metabolite feeding, metabolomics, and proteomics, we show that Aze inhibits the root growth of Arabidopsis and other plants. Aze-induced growth reduction was restored by supplementing L-, but not D-Pro, and nontargeted proteomics confirm that Aze is misincorporated for Pro during protein biosynthesis, specifically on cytosolically translated proteins. Gene expression analysis, free amino acid profiling, and proteomics show that the unfolded protein response is upregulated during Aze treatment implicating that Aze misincorporation results in accumulation of misfolded proteins triggering a global stress response. This study demonstrates the mechanism of action of Aze in plants and provides a foundation for understanding the biological functions of proteotoxic metabolites.
植物具有惊人的能力，能够在空间和资源方面胜过邻近的生物体。有毒代谢物是这些相互作用中的主要参与者，它们通过靶向保守的分子机制（如蛋白质生物合成）可以具有广泛的作用效果。然而，对防御性代谢物途径、其作用机制和抗性机制的了解不足，限制了我们操纵这些途径以增强作物抗逆性的能力。非蛋白质氨基酸（NPAAs）是一类结构多样的代谢物，具有多种功能，但通常不会在蛋白质生物合成过程中被掺入。在这里，我们研究了NPAA氮杂环丁烷-2-羧酸（Aze）的作用机制，它是氨基酸脯氨酸（Pro）的类似物。通过结合基于平板的测定、代谢物饲喂、代谢组学和蛋白质组学，我们表明Aze抑制拟南芥和其他植物的根生长。补充L-脯氨酸（而不是D-脯氨酸）可恢复Aze诱导的生长减少，非靶向蛋白质组学证实Aze在蛋白质生物合成过程中被错误掺入脯氨酸，特别是在胞质翻译的蛋白质上。基因表达分析、游离氨基酸谱分析和蛋白质组学表明，在Aze处理期间未折叠蛋白反应上调，这意味着Aze的错误掺入导致错误折叠蛋白的积累，引发全局应激反应。这项研究证明了Aze在植物中的作用机制，并为理解蛋白毒性代谢物的生物学功能提供了基础。
