Defining the Tyrosine Biosynthetic Pathways in Plants

植物中酪氨酸生物合成途径的定义

• 批准号: 1354971
• 负责人: Hiroshi Maeda
• 金额: $ 45万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-09-01 至 2018-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1354971&HistoricalAwards=false
• 关键词: Defining; Tyrosine; Biosynthetic; Pathways; Plants

Non-technical summary:Plants synthesize an aromatic amino acid tyrosine (Tyr), which is an essential nutrient in human diets and a key precursor of numerous plant specialized compounds. These Tyr-derived plant natural products have profound impacts on plant growth, development and environmental responses, and also have important nutritional and pharmacological activities in humans (e.g., vitamin E, morphine). Despite their importance in both plant and human biology, we still do not know how Tyr is synthesized in plants. Therefore, this project will gain fundamental knowledge to enhance the nutritional quality or pharmaceutical values of crops and medicinal plants, and can potentially improve plant growth and stress responses for sustainable production of food and biomass. An outreach event, "Pigment-Art", will take advantage of attractive and beneficial plant pigments derived from aromatic amino acids (e.g., betalains). While younger children will appreciate the beautiful and complex colors in natural pigments, parents and older children will have opportunities to learn about how these pigments are synthesized by plants. Technical Description of the Project:Accumulating evidence suggests that many plants synthesize Tyr via the intermediate arogenate and therefore differ from microbial models that usually use 4-hydroxyphenylpyruvate as an intermediate. However, significant variations appear to exist for the Tyr biosynthetic routes among different plant species. The goals of this project are to define the Tyr biosynthetic route(s) in plants and determine their compartmentalization and crucial regulatory step(s). The proposed research will build upon PI's recent isolation of Arabidopsis and legume genes encoding arogenate and prephenate dehydrogenases (ADH and PDH), key enzymes of the Tyr pathway. Arabidopsis ADHs have strong substrate specificity toward arogenate, are localized in the plastids and inhibited by Tyr. In contrast, legume dehydrogenases specifically use prephenate, lack a plastid transit peptide, and are insensitive to Tyr. The primary hypothesis of this study is that Arabidopsis mainly uses the plastidic arogenate pathway that is regulated by Tyr, whereas legumes synthesize Tyr via both arogenate and 4-hydroxyphenylpyruvate with unknown localization and regulatory mechanism. In this project, kinetic analysis and localization studies are first planned for the newly identified legume PDHs (Aim 1). In planta functions of PDHs and ADHs will be investigated and compared using two contrasting plant models, Medicago truncatula (Aim 2) and Arabidopsis thaliana (Aim 3). Targeted metabolite profiling and stable-isotope feeding experiments will be further conducted in the generated mutants and transgenics to directly measure the distribution of carbon flow among the alternative Tyr pathways. Although primary metabolism is generally assumed to be conserved across plant species, our preliminary data indicate otherwise. This project will directly test this assumption and address how Tyr biosynthesis, a primary metabolic pathway, has evolved in different plants to support the enormous chemical diversity that exists in the downstream specialized metabolism.

摘要：植物合成一种芳香氨基酸酪氨酸（Tyr），它是人类饮食中必需的营养物质，也是许多植物特化化合物的关键前体。这些tyr衍生的植物天然产物对植物的生长、发育和环境反应具有深远的影响，并且在人体中具有重要的营养和药理活性（如维生素E、吗啡）。尽管它们在植物和人类生物学中都很重要，但我们仍然不知道Tyr是如何在植物中合成的。因此，该项目将获得提高作物和药用植物营养质量或药用价值的基础知识，并有可能改善植物生长和应激反应，以实现粮食和生物质的可持续生产。外展活动“色素艺术”将利用从芳香氨基酸（如甜菜碱）中提取的有吸引力和有益的植物色素。虽然年幼的孩子会欣赏天然色素中美丽而复杂的颜色，但父母和年龄较大的孩子将有机会了解这些色素是如何由植物合成的。项目技术描述：越来越多的证据表明，许多植物通过中间的炔雌酸酯合成Tyr，因此不同于通常使用4-羟基苯基丙酮酸酯作为中间体的微生物模型。然而，Tyr的生物合成途径在不同的植物物种之间似乎存在显著差异。本项目的目标是确定Tyr在植物中的生物合成途径，并确定它们的区区化和关键调控步骤。该计划的研究将建立在PI最近分离的拟南芥和豆科植物基因的基础上，这些基因编码酪氨酸途径的关键酶——砷酸盐和预苯酸脱氢酶（ADH和PDH）。拟南芥ADHs对芳香酸酯具有很强的底物特异性，定位于质体中并受Tyr抑制。相比之下，豆科脱氢酶专门使用预苯酸盐，缺乏质体转运肽，并且对Tyr不敏感。本研究的初步假设是拟南芥主要通过由Tyr调控的可塑性炔原酸途径合成Tyr，而豆科植物通过炔原酸和4-羟基苯基丙酮酸合成Tyr，但其定位和调控机制未知。在本项目中，首先计划对新鉴定的豆科植物PDHs进行动力学分析和定位研究（Aim 1）。在植物中，PDHs和ADHs的功能将通过两种截然不同的植物模型，Medicago truncatula （Aim 2）和Arabidopsis thaliana （Aim 3）进行研究和比较。在生成的突变体和转基因体中，将进一步开展靶向代谢物分析和稳定同位素喂养实验，以直接测量碳流在替代Tyr途径中的分布。虽然初级代谢通常被认为在植物物种中是保守的，但我们的初步数据表明并非如此。该项目将直接验证这一假设，并解决Tyr生物合成这一主要代谢途径如何在不同植物中进化，以支持下游专门代谢中存在的巨大化学多样性。

项目成果

Role of cytosolic, tyrosine‐insensitive prephenate dehydrogenase in Medicago truncatula

胞质、酪氨酸不敏感的预苯酸脱氢酶在蒺藜苜蓿中的作用

• DOI: 10.1002/pld3.218
• 发表时间: 2020
• 期刊: Plant Direct
• 影响因子: 3
• 作者: Schenck, Craig A.;Westphal, Josh;Jayaraman, Dhileepkumar;Garcia, Kevin;Wen, Jiangqi;Mysore, Kirankumar S.;Ané, Jean‐Michel;Sumner, Lloyd W.;Maeda, Hiroshi A.
• 通讯作者: Maeda, Hiroshi A.