Thiol-based redox switch in plant flavonoid biosynthesis

化学部的生命过程化学项目为该奖项提供资金。怀特黑德生物医学研究所的翁静可博士研究了与氧气的化学反应对调节植物酶的影响。所有的陆生植物都能产生一种叫做类黄酮的分子，这种分子利用一种叫做查耳酮合成酶的酶。植物的香味对于植物在陆地上的生存非常重要，并且发挥许多作用，例如保护免受紫外线照射，防御草食动物和吸引传粉者。使用高分辨率的结构测定技术，查耳酮合酶被观察到已经进化出一个调节开关，当它与氧反应时，会影响其活性。通过比较查耳酮合酶从各种植物，如简单的陆地植物开花植物，这项研究有助于表征类黄酮生物合成如何演变，以帮助植物适应生活在各种各样的陆地栖息地。这些知识有可能在未来改善植物性状。该项目允许研究生获得多学科尖端技术的实践培训。该项目还整合了初中和高中的外展计划，向学生介绍植物生理学和化学。蛋白质中半胱氨酰侧链的氧化广泛发生在所有活生物体中，通常是由于活性氧（ROS）水平增加。本研究的目的是获得一个机制的理解，如何查耳酮合成酶（CHS），在植物类黄酮生物合成的第一个关键酶，是由其催化半胱氨酸的氧化失活控制在酶和系统水平。来自不同陆地植物谱系的CHS直系同源物在体外使用X射线晶体学和酶活性测定来表征，以检查催化半胱氨酸的氧化还原电位如何受到直系同源物之间的附近氨基酸差异的影响。在体内的研究涉及代谢示踪和蛋白质组学的转基因拟南芥表达不同的CHS直系同源物，并进行各种氧化应激条件下检查的影响，CHS氧化类黄酮的生物合成，并提供深入了解其功能的影响陆地植物的进化。由于CHS与β-酮脂酰基-（酰基载体蛋白）脱氢酶同源，并且在进化上衍生自β-酮脂酰基-（酰基载体蛋白）脱氢酶，因此所提出的研究对于理解脂肪酸生物合成如何受到波动的细胞氧化还原状态的影响具有深远的影响，这是与不同学科相关的一个未充分探索的研究课题，例如在胁迫条件下种子作物的油生产。

The Chemistry of Life Processes Program in the Chemistry Division funds this award. Dr. Jing-Ke Weng from the Whitehead Institute for Biomedical Research investigates the impact of a chemical reactions with oxygen in regulating a plant enzyme. All land plants produce a class of molecules called flavonoids, using the enzyme known as chalcone synthase. Flavonoids are important for plants to survive on land and play many roles such as protection against ultraviolet light, defense against herbivores, and attraction of pollinators. Using high resolution techniques for the determination of structure, chalcone synthase was observed to have evolved a regulatory switch that affects its activity when it reacts with oxygen. By comparing chalcone synthase from a variety of plants such as simple land plants to flowering plants, this research helps characterize how flavonoid biosynthesis has evolved to help plants adapt to life in a wide variety of terrestrial habitats. This knowledge has the potential to improve plant traits in the future. This project allows graduate students to acquire hands-on training in multidisciplinary cutting-edge techniques. This project also integrates middle-school and high-school outreach programs to introduce students to plant physiology and chemistry. Oxidation of the cysteinyl side chain in proteins occurs widely in all living organisms, often as a result of increased levels of reactive oxygen species (ROS). The goal of this research is to gain a mechanistic understanding of how the activity of chalcone synthase (CHS), the first committed enzyme in plant flavonoid biosynthesis, is controlled by oxidative inactivation of its catalytic cysteine at both the enzyme and systems levels. CHS orthologs from diverse land plant lineages are characterized in vitro using X-ray crystallography and enzyme activity assays to examine how the redox potential of the catalytic cysteine is impacted by nearby amino acid differences between orthologs. In vivo studies involving metabolic tracing and proteomics on transgenic Arabidopsis thaliana expressing different CHS orthologs and subjected to various oxidative stress conditions examine the impact of CHS oxidation on flavonoid biosynthesis, and provide insight into its functional impact on the evolution of land plants. Because CHSs are homologous to, and evolutionarily derived from, the beta-ketoacyl-(acyl-carrier-protein) synthases, the proposed research has far-reaching impact for understanding how fatty acid biosynthesis may be influenced by fluctuating cellular redox status, which is an underexplored research topic relevant to diverse disciplines, e.g. oil production in seed crops under stress conditions.