Molecular Basis for Organization of Photosynthetic Functions through Plant Body

1.在土壤中存在硝酸盐时，细胞分裂素起着器官间信号的作用，从根传递到地上部。鉴定了对细胞分裂素有反应的敏感蛋白激酶。与细胞分裂素信号转导有关的组氨酸-天冬氨酸磷酸传递系统的其他组成部分(即反应调节器和含组氨酸的磷传递体)也被鉴定和表征。此外，还鉴定了与植物昼夜节律的产生有关的伪反应调节因子。在拟南芥中发现了编码细胞分裂素生物合成酶-腺苷酸异戊烯基转移酶的基因，表明植物激素是由植物合成的，而不是由共生微生物合成的。结果表明，水稻韧皮部汁液中含有硫氧还蛋白h等蛋白质和几种不同的基因。进一步的研究表明，这些大分子中至少有一部分是在伴随细胞中合成的，并通过胞间连丝转移到筛分元件上。一组特殊的谷氨酰胺合成酶和谷氨酸合成酶同工酶分别位于叶片维管束和成熟籽粒中，它们在叶片氮素的动员和向水稻籽粒的转移中发挥着重要作用。编码硫酸盐转运蛋白和硫酸盐同化酶的基因在拟南芥等植物中已被鉴定。硫同化途径和氮同化途径之间的调控联系被发现。

1. Cytokinin was shown to act as the organ-to-organ signal, transmitted from the root to shoot, for the presence of nitrate in the soil. The sensor kinase responsive to cytokinin was indentified. Other components of the His-Asp phosphorelay system (i. e. response regulators and His-containing phophotransmitters), implicated in transduction of the cytokinin signal, were also identified and characterized. In addition, pseudo-response regulators, implicated in generation of circadian rhythm in plants, were identified and characterized.2. The genes encoding adenylate isopentenyltransferase, a cytokinin biosynthesis enzyme, were identified in Arabidopsis thaliana, demonstrating that the plant hormone is synthesized by the plant and not by symbiotic microorganisms.3. Phloem sap of rice was shown to contain certain proteins, including thioredoxin h, and several mRNA species. It was further shown that at least some of these macromolecules are synthesized in the companion cell and transferred to the sieve element via plasmodesmata.4. A particular set of glutamine synthetase and glutamate synthease isozymes, which are localized in the vascular bundle of leaf blade and maturing grains, respectively, was found to play an important role in mobilization of leaf nitrogen and its transfer to rice grains.5. Genes encoding sulfate transporters and sulfate assimilating enzymes were identified in A. thaliana and other plants. Regulatory links between the sulfur- and nitrogen-assimilating pathways were found.