REGULATION OF PLANT GENES INVOLVED IN MODULATION OF NH3 ASSIMILATION

大多数具有营养意义的生物固氮作用是 由根瘤菌/慢生根瘤菌、仅固氮的细菌进行 它们在豆科植物的根部形成的根瘤中。 我们的长期目标 是为了提高固定效率和扩大宿主范围， 非豆科植物 这里提出的研究是为了了解最初的 宿主与共生体之间的相互作用以及植物如何利用 还原氮。 建议主要集中在两个方面：（一） 确定类黄酮在根瘤形成中的作用;（ii）确定 如果氨的同化作用能够得到改善， 对植物的总体N状态的影响。 对于我们项目的第一部分， 重点是苯丙烷类化合物中关键酶的基因编码 类黄酮合成途径-苯丙氨酸解氨酶 (PAL)、查耳酮合成酶（CHS）和查耳酮异构酶（CHI）。 研究 包括研究家庭中不同成员的调节 以及关键成员的过表达/表达不足对结节形成的影响。 谷氨酰胺合成酶（GS）是氨同化的关键酶， 我们对氨同化的理解的核心，是主题， 第二部分。 我们的研究结合了分子和生物化学 理解职能作用和监管机制的方法 不同GS基因成员的潜在表达。 而且 不同GS基因成员的下调和上调对 氨同化和固氮的效率正在研究中。 第二个项目旨在提高豆类的营养质量 种子和饲料，这是在实验室追求，是引入到 这些植物高表达编码高硫氨基酸的基因， proteins. 总之，实验室中的项目利用了最先进的技术， 分子生物学、生物化学和细胞生物学， 植物生物学中对人类营养有直接影响的问题。

Most of the nutritionally significant biological nitrogen fixation is carried out by Rhizobia/Bradyrhizobia, bacteria that fix nitrogen only within the nodules they form on the roots of legumes. Our long-term goal is to improve the efficiency of fixation and to broaden the host range to nonlegumes. The research proposed here is to understand the initial interaction between the host an the symbiont and how the plant utilizes the reduced nitrogen. The proposal focuses on two major aspects: (i) to determine the role of flavonoids in nodule initiation; (ii) to determine if ammonia assimilation can be improved and if that would have an impact on the overall N-status of the plant. For the first part of our project, the focus is on genes encoding for key enzymes in the phenylpropanoid pathway leading to flavonoid synthesis - phenylalanine ammonia lyase (PAL), chalcone synthase (CHS) and chalcone isomerase (CHI). The study involves studying the regulation of the different members of the family and the effect of over/under expressing key members, on nodule initiation. Glutamine synthetase (GS), the key enzyme in ammonia assimilation, is central to our understanding of ammonia assimilation and is the theme of the second part. Our research combines a molecular and biochemical approach to understand the functional role and regulatory mechanism underlying expression of different GS gene members. Furthermore, the effect of down and up regulation of different GS gene members on the efficiency of ammonia assimilation and N2-fixation, is being studied. A second project aimed towards improving the nutritional quality of legume seeds and forage, that is being pursued in the lab, is to introduce into these plants highly expressing genes encoding for high sulfur amino acid proteins. Altogether, the projects in the lab utilize state-of-the-art techniques in molecular biology, biochemistry and cell biology to address important issues in plant biology that have a direct impact on human nutrition.