Threonine and Methionine Metabolism in Arabidopsis

氨基酸苏氨酸和蛋氨酸不仅是必需的蛋白质结构单元，而且还作为其他重要植物代谢物的前体。虽然已经确定了植物中甲硫氨酸和苏氨酸合成的基本生化途径，但对这些氨基酸的催化作用及其在下游代谢网络中的分配知之甚少。对具有增加的种子苏氨酸和甲硫氨酸水平的拟南芥品系的工作确定了两个突变，这两个突变是正在进行的研究的主题。其中一个突变是在苏氨酸醛缩酶，苏氨酸分解代谢酶，以前没有在植物中研究。进一步的研究将实现以下目标：1.研究拟南芥苏氨酸醛缩酶的生化特性、该酶在植物氨基酸代谢中的作用以及拟南芥苏氨酸醛缩酶基因突变的影响;将表征引起种子甲硫氨酸和苏氨酸增加十倍的第二突变，并确定该基因在植物氨基酸代谢中的功能。更广泛的影响：蛋氨酸和苏氨酸是人类和其他动物不能合成的两种必需氨基酸。许多农作物，特别是豆类，对于哺乳动物饮食具有次优水平的甲硫氨酸或苏氨酸。因此，人们对发现新的植物基因感兴趣，这些基因可以通过生物技术或植物育种来提高作物中这些氨基酸的水平。该项目还将为高中生、本科生和研究生提供研究机会。一个既定的暑期实习计划将被用来招募学生，包括代表性不足的少数民族，从当地高中和大学在美国各地。这些学生将接受代谢生物化学和分子遗传学的最现代技术的培训，为他们未来在工业或学术界的职业生涯做好准备。

The amino acids threonine and methionine are not only essential protein building blocks, but also serve as precursors for other important plant metabolites. Although the basic biochemical pathways for the synthesis of methionine and threonine in plants have been identified, relatively little is known about the catabolism of these amino acids and their partitioning into downstream metabolic networks. Work on Arabidopsis lines with increased seed threonine and methionine levels identified two mutations that are the subject of ongoing research. One of the mutations is in threonine aldolase, a threonine catabolic enzyme that has not been previously studied in plants. Further research will accomplish the following goals: 1. The biochemical characteristics of Arabidopsis threonine aldolase, the role of this enzyme in plant amino acid metabolism, and the effects of mutations in the Arabidopsis threonine aldolase genes will be investigated; and 2. A second mutation causing ten-fold increases in seed methionine and threonine will be characterized, and the function of this gene in plant amino acid metabolism will be determined. Broader Impact: Methionine and threonine are two of the essential amino acids that cannot be synthesized by humans and other animals. Many crop plants, in particular legumes, have sub-optimal levels of methionine or threonine for the mammalian diet. Therefore, there is interest in discovering new plant genes that can be employed to raise levels of these amino acids in crops through biotechnology or plant breeding. The project will also provide research opportunities for high school, undergraduate, and graduate students. An established summer internship program will be used to recruit students, including underrepresented minorities, from local high schools and from colleges throughout the USA. These students will be trained in the most modern techniques of metabolic biochemistry and molecular genetics to prepare them for future careers in industry or academics.