Efficient, Integrated Carbon Fixation Allocation Export and Sink Metabolism

在自然的每日光循环下，叶片在逐渐变化的光合作用和黑暗代谢之间交替，但它们提供稳定的蔗糖供应，以维持植物生长部分的不间断发育。为了做到这一点，叶片必须在低光照时期利用储存的碳水化合物，并在高光合作用时期在输出和更新储存之间分配碳水化合物。调节叶片碳水化合物代谢和源叶输出提供了满足这些需求的手段。缺乏合成或降解淀粉能力的突变体植物显著减少了种子产量，这证实了在低光合作用时期输出储存的碳水化合物的重要性。这个研究项目将研究树叶维持出口蔗糖稳定供应的关键过程。该项目旨在识别和理解碳分配、转运和分配的规律，以增加改善作物作物所需的基础知识。这些过程通过向经济上重要的碳汇提供碳直接影响作物生产力。PI的方法是研究这些过程的生理和生物化学及其综合调控，为这些过程的遗传和分子操作提供基础。在模拟自然白天的正弦光照条件下，叶片碳代谢对光合速率变化的响应表明，多种碳源对维持白天的输出速率至关重要。将研究这些来源，以确定参与其调节和协调的生化和分子机制。将只使用淀粉或蔗糖和淀粉维持出口的植物进行比较，以确定这些差异的基础。淀粉合成和降解与光合速率的协调对于在整个正弦光状态下维持稳定的蔗糖合成速率是重要的。研究了新固定碳和淀粉中的碳转化为蔗糖的途径。进一步的计划目标是分离和维持改变淀粉代谢的植物突变体，以研究淀粉合成和降解的调节。

Leaves alternate between periods of gradually changing photosynthesis and dark metabolism under the natural daily cycling of light, yet they provide a steady supply of sucrose to sustain the uninterrupted development of growing parts of the plant. To do this, leaves must utilize stored carbohydrate during periods of low light and distribute carbohydrate between export and renewal of storage during periods of high photosynthesis. Regulation of leaf carbohydrate metabolism and export from source leaves provides the means to meet these demands. Mutant plants which lack the ability to synthesize or degrade starch have markedly reduced seed production, which confirms the importance of export of stored carbohydrate during periods of low photosynthesis. This research project will study key aspects of processes by which leaves maintain this steady supply of sucrose for export. The program is aimed at identifying and understanding regulation of carbon allocation, translocation, and partitioning with a view to increasing basic knowledge needed for improving crop plants. These processes affect crop productivity directly by supplying carbon to sinks of economic importance. The PI's approach is to investigate the physiology and biochemistry of these processes and their integrated regulation needed to provide a basis for genetic and molecular manipulation of these processes. The response of leaf carbon metabolism to changes in photosynthesis rate during a sinusoidal light regime, which simulates a natural day, demonstrates the importance of multiple sources of carbon in maintaining export rate during the day. These sources will be studied to identify the biochemical and molecular mechanisms involved in their regulation and coordination. Plants that use either starch exclusively or sucrose and starch to maintain export will be compared to determine the basis of these differences. The coordination of starch synthesis and degradation with photosynthesis rate is important in maintaining a steady rate of sucrose synthesis throughout a sinusoidal light regime. The pathways by which newly- fixed carbon and carbon from starch are converted to sucrose will be investigated. A further program goal is to isolate and maintain plant mutants having altered starch metabolism for studying the regulation of starch synthesis and degradation.