Postdoctoral Research Fellowship in Plant Biology

高等植物的非光合组织（碳汇）对碳代谢的调节知之甚少，尽管这些组织构成了世界上大部分的食物供应。光合作用产生的碳通常作为蔗糖转运到碳汇，但一旦卸除，可能会以不同的方式进行处理。进口的蔗糖主要用于生物合成和呼吸作用，或者以蔗糖或淀粉的形式储存起来，这取决于碳汇的类型。我们对完成这种分配的生化机制知之甚少。这些研究将为了解汇组织碳代谢这一亟待发展的植物生物学领域做出重要贡献。果糖2,6-二磷酸（F2,6P2）是一种在光合细胞中控制碳分配的调节分子，也可能在碳汇中发挥相关作用。F2,6P2的浓度由果糖6-磷酸2激酶（F6P, 2K）和果糖2,6-二磷酸酶（F2,6P2ase）的活性决定，它们合成并降解F2,6P2。研究员将从各种类型的汇中纯化F6P，2K和F2,6P2ase，以确定酶的特性差异是否与不同的碳分配模式相关。用纯化的制剂，酶对底物的亲和力和对代谢物效应物的敏感性将被测量。研究人员将确定库F6P、2K和F2、6P2ase是否像在叶片中一样位于不同的蛋白质上，并测试这些酶是否可能受到共价修饰（例如磷酸化）的调节。

The regulation of carbon metabolism in non-photosynthetic tissues (sinks) of higher plants is poorly understood, despite the fact that these tissues constitute the bulk of the world's supply of food. Photosynthetically derived carbon is generally translocated to sinks as sucrose but, once unloaded, may be processed in different ways. Depending on the type of sink, the imported sucrose may be used predominately in biosynthesis and respiration, or stored, either as sucrose or starch. Little is known about the biochemical mechanisms by which this partitioning is accomplished. These studies will make significant contributions to the understanding of carbon metabolism in sink tissues, an area of plant biology in urgent need of development. Fructose 2,6-bisphosphate (F2,6P2), a regulatory molecule shown to control carbon partitioning in photosynthetic cells, may play a related role in sinks as well. The concentration of F2,6P2 is determined by the activities of fructose 6-phosphate, 2-kinase (F6P, 2K) and fructose 2,6-bisphosphatase (F2,6P2ase), which synthesize and degrade F2,6P2. The Fellow will purify F6P,2K and F2,6P2ase from a variety of sink types to determine whether differences in the properties of the enzymes correlate with different patterns of carbon partitioning. With the purified preparations, the affinity of the enzymes for their substrates and their sensitivity to metabolite effectors will be measured. It will be determined whether sink F6P,2K and F2,6P2ase reside on separate proteins as in leaves, and tested whether the enzymes might be regulated by covalent modification (for example, phosphorylation).