Lysine Biosynthesis in Plants

本提案的目的是了解植物是如何合成赖氨酸的。赖氨酸是限制用于动物饲料的作物营养价值的关键氨基酸之一。植物中赖氨酸生物合成所需的全套基因尚不清楚。总的来说，人们认识到植物合成赖氨酸的途径包括化合物二氨基苯甲酸（DAP）。细菌也使用这种化合物。然而，细菌使用三种不同的DAP途径，目前尚不清楚植物是否使用其中的任何一种。初步证据表明,植物包含小说在单个步骤酶,这种酶催化的反应,细菌大肠杆菌需要三种不同的酶,dapC的产物,dapD, dapE基因。据推测，该植物酶可由四氢二吡啶酸合成L，L-二氨基苯甲酸酯。这种酶存在于玉米、豌豆、拟南芥和一种苔藓中。L，L-二氨基磺酸氨基转移酶的发现表明植物产生赖氨酸的机制可能不同于所有已知的机制。本实验拟克隆L，L-二氨基磺酸氨基转移酶基因。研究了该酶催化的反应。转氨酶在赖氨酸生物合成中的作用将通过观察该基因的敲除突变是否产生需要赖氨酸喂养才能生长的菌株来证实。我们将研究L，L-二氨基乳酸转氨酶基因的表达，以确定其表达模式是否与其他赖氨酸生物合成基因相比较。本研究将使用的生物是拟南芥和拟南芥。这项被提议的工作可能最终解决植物如何产生赖氨酸的长期悬而未决的问题。这些信息可能有助于制定提高作物营养价值的战略。更广泛的影响声明拟议的活动将为博士后、本科生和高中生提供研究和培训。本科生和高中生的实验室经验对于培养未来的科学家、决策者和知情公民是必要的。

The objective of this proposal is to learn how lysine is synthesized by plants. Lysine is one of the key amino acids that limit the nutritional value of crops used for animal diets. The complete set of genes needed for lysine biosynthesis in plants is not known. In broad outline it is recognized that plants synthesize lysine using a pathway that includes the compound diaminopimelic acid (DAP). Bacteria also use this compound. However, bacteria use three different variations of the DAP pathway and it is unknown which, if any, of them is used by plants.Preliminary evidence indicates that plants contain a novel enzyme that catalyzes in a single step a reaction that in the bacteria Escherichia coli requires three different enzymes, the products of the dapC, dapD, and dapE genes. It is hypothesized that the plant enzyme synthesizes L,L-diaminopimelate from tetrahydrodipicolinate. This enzyme is found in corn, pea, Arabidopsis thaliana and a moss, Physcomitrella patens. The discovery of L,L-diaminopimelate aminotransferase indicates that plants may produce lysine differently than all previously known mechanisms.In the proposed experiments the gene encoding L,L-diaminopimelate aminotransferase will be cloned. The reaction catalyzed by the enzyme will be studied. The role of the aminotransferase in lysine biosynthesis will be confirmed by observing whether a knockout mutation of the gene produces a strain that requires lysine-feeding to grow. The expression of the L,L-diaminopimelate aminotransferase gene will be studied to determine whether its expression pattern compares with other genes for lysine biosynthesis. The organisms that will be used in this study are A. thaliana and P. patens.Intellectual Merit StatementThe proposed work may finally solve the longstanding open question of how plants produce lysine. The information may prove useful in developing strategies to improve the nutritional value of crops. Broader Impact StatementThe proposed activities will provide research and training to a postdoctoral fellow, undergraduates, and high school students. Laboratory experiences for undergraduates and high school students in particular are necessary for the training of future scientists, policy makers, and informed citizens.