Sugar-Modulated Expression and Developmental Control of Genes for Sucrose Metabolism

9507681科赫形态适应性可塑性是多细胞植物最显著的特征之一。这种灵活性的至少一个因素似乎是特定植物基因对糖水平的敏感性(即。光合作用的有效性)。其中包括蔗糖代谢酶的基因。生长器官对蔗糖的输入受蔗糖代谢能力的强烈影响，而蔗糖代谢能力只由两条已知的途径(转化酶和可逆蔗糖合成酶反应)催化。在之前的美国国家科学基金会的资助下，科赫博士已经证明，玉米中编码这两种酶的基因是碳水化合物反应的，这为粗略调整蔗糖利用能力提供了一种潜在的机制，相对于其总体可获得性。此外，新克隆的蔗糖合成酶同工酶基因表现出与蔗糖合成酶同工酶基因惊人的相似性，表现出不同的碳水化合物反应。在这个项目中，科赫博士将使用分子、遗传学和生理学相结合的方法来阐述这些发展的重要性。转化酶基因家族(可能是可溶的)的探针提供了一个机会来解决糖反应基因表达与可溶性转化酶通过新扩展的库区组织在初始生长中的广泛作用之间的关系。

9507681 Koch Adaptive plasticity of form is one of the most remarkable features of multicelled plants. At least one contributor to this flexibility appears to be the sensitivity of specific plant genes to sugar levels (ie. photosynthate availability). Among these are the genes for sucrose metabolizing enzymes. Import of translocated sucrose by growing organs can be strongly affected by the capacity for sucrose metabolism, which is catalyzed by only two known pathways in plant (invertase and the reversible sucrose synthase reaction). Under previous NSF grant, Dr. Koch has demonstrated that genes encoding both these enzymes in maize are carbohydrate-responsive, providing a potential mechanism for coarse adjustment of capacity for sucrose use relative to its overall availability. In addition, the newly cloned isozyme genes for invertase exhibit a differential carbohydrate responsiveness with surprising similarity to that observed among isozyme genes of sucrose synthase. In this project, Dr. Koch will address the significance of these developments using a combined molecular, genetic and physiological approach. Probes for an invertase gene family (putatively soluble) provide an opportunity to address the relationship between sugar-responsive gene expression and the widespread role of soluble invertases in initial growth by newly expanding sink tissues.