Functional Analysis of Maize Genes for Sucrose Metabolism

蔗糖字面上是“植物的生命之血”，从光合作用的叶子转移到生长的细胞和组织中。生长最快的器官是那些具有高糖代谢能力的器官。蔗糖和/或其代谢产物也可以影响许多基因的表达。因此，控制蔗糖代谢可以在多个水平上对植物产生深远的生理和发育影响。只有两种已知的蔗糖裂解途径，分别由转化酶和可逆蔗糖合成酶催化。由于多个基因、其蛋白产物的不同功能以及基因对环境、代谢和发育信号的敏感性，解剖所涉及的过程一直很困难。来自我们实验室和其他地方的新材料现在使我们处于一个很好的位置，来剖析玉米中特定基因对蔗糖代谢的作用和调节。突变体、生理和玉米作为谷物模型的相关性的结合使其成为本研究项目的理想物种。拟议的研究涉及分析i)“敲除”的突变体只缺乏一个蔗糖合酶基因（sus1）， ii)新发现的第三个蔗糖合酶基因（Sus3），以及iii)表达转化酶基因（Ivr2-GUS）的转基因玉米植株，该基因被设计成在基因被诱导时产生蓝色。我们将利用这些工具结合特定的发育、遗传和生理扰动，利用玉米植物的独特特征使之成为可能。提出的工作将提供一种以前不可用的方法来解决基因在蔗糖代谢中的作用和调节。

Sucrose is literally "the life-blood of plants" and moves from photosynthetic leaves to growing cells and tissues. The most rapidly growing organs are those that have a high capacity for sucrose metabolism.Sucrose and/or its metabolic products can also affect expression of many genes. Control of sucrose metabolism can thus have profound physiological and developmental consequences for the plant at multiple levels. There are only two known paths for sucrose cleavage, catalyzed by either invertases or the reversible sucrose synthase reaction, respectively. Dissection of the processes involved has been difficult due to multiple genes, diverse functions of their protein products, and sensitivity of the genes to environmental, metabolic, and developmental signals. New materials from our lab and elsewhere now put us in an excellent position to dissect roles and regulation of specific genes for sucrose metabolism in maize. The combination of mutants, physiology, and relevance of maize as a grain model make this an ideal species for this research project. The proposed studies involve analysis of i) "knock-out" mutants deficient in only one of the sucrose synthase genes (sus1), ii) a newly identified gene for a third sucrose synthase (Sus3), and iii) transgenic maize plants expressing an invertase gene (Ivr2-GUS) designed to generate a blue color when the gene is induced. We will use these tools in combination with specific developmental, genetic, and physiological perturbations made possible using distinctive features of the maize plant. The proposed work will provide a previously unavailable means of addressing the roles and regulation of genes for sucrose metabolism.