Thiol-based redox switch in plant flavonoid biosynthesis

该奖项由化学部的生命过程化学项目资助。来自怀特黑德生物医学研究所的翁景科博士调查了一种与氧的化学反应对调节植物酶的影响。所有陆地植物都利用查尔酮合成酶产生一种叫做类黄酮的分子。黄酮类化合物是植物在陆地上生存的重要物质，具有抵御紫外线、抵御食草动物和吸引传粉者等多种作用。利用高分辨率技术测定结构，查尔酮合成酶被观察到进化出一个调节开关，当它与氧反应时影响其活性。通过比较各种植物（如简单的陆地植物和开花植物）的查尔酮合成酶，本研究有助于描述类黄酮生物合成如何进化以帮助植物适应各种陆地栖息地的生活。这些知识有可能在未来改善植物的性状。该项目允许研究生获得多学科前沿技术的实践训练。该项目还整合了初中和高中的外展项目，向学生介绍植物生理学和化学。蛋白质中半胱氨酸侧链的氧化在所有生物体中广泛发生，通常是活性氧（ROS）水平增加的结果。本研究的目的是获得查尔酮合成酶（CHS）的活性是如何在酶和系统水平上由其催化半胱氨酸的氧化失活控制的机制理解，查尔酮合成酶是植物类黄酮生物合成的第一个承诺酶。利用x射线晶体学和酶活性分析对来自不同陆地植物谱系的CHS同源物进行了体外表征，以研究催化半胱氨酸的氧化还原电位如何受到同源物之间附近氨基酸差异的影响。通过对表达不同CHS同源基因的转基因拟南芥在不同氧化应激条件下的体内代谢追踪和蛋白质组学研究，研究了CHS氧化对类黄酮生物合成的影响，并深入了解其对陆地植物进化的功能影响。由于CHSs与β -酮酰-（酰基-载体蛋白）合成酶同源，并在进化上衍生自β -酮酰-（酰基-载体蛋白）合成酶，因此该研究对了解细胞氧化还原状态波动对脂肪酸生物合成的影响具有深远的影响，这是一个与多种学科相关的未充分开发的研究课题，例如逆境条件下种子作物的产油。

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.