Bioenergetics of C4 Photosynthesis

该奖项支持杰拉尔德·爱德华兹博士(华盛顿州立大学)和鲍里斯·伊万农博士(俄罗斯科学院)之间的研究合作。在光合作用过程中，被叶绿体吸收的太阳能通过电子传递、膜能化和磷酸化转化为同化力(ATP和NADPH)，而水的氧化和氧气的产生提供了还原力。关于另外两种形式的光化学是否在植物的光合作用中起作用，也就是假环和/或循环电子流，正在引起争论。假环电子流通过水的氧化发生，线性电子流最终以氧气而不是NADP作为最终电子接受者。循环电子流在没有水的氧化和氧气的产生的情况下发生。本项目的目标是确定在对ATP的需求不同的条件下，玉米叶绿体中这两种光化学形式中的一种或两种是否起作用。叶绿体中抗坏血酸的供应是否调节假环电子流的能力将被研究。分析方法将包括使用从玉米中分离的叶绿体来测量膜能量、光化学的量子产率和碳代谢中代谢物的转化。这项研究将有助于我们理解光合作用转换太阳能的效率，光合作用对维持地球上的生命至关重要。

This award supports research collaboration between Dr. Gerald Edwards (Washington State University)and Dr. Boris Ivanon (Russian Academy of Sciences). During photosynthesis solar energy absorbed by chloroplasts is converted into assimilatory power (ATP and NADPH) via electron transport, membrane energization, and phosphorylation with reductive power provided by oxidation of water and production of oxygen. Debate is ensuing over whether two other forms of photochemistry, pseudocyclic and/or cyclic electron flow, have a role in photosynthesis in plants. Pseudocylic electron flow occurs via oxidation of water with a linear flow of electrons culminating with oxygen, rather than NADP, as the final electron acceptor. Cyclic electron flow occurs without oxidation of water and generation of oxygen. The objectives of this project are to establish whether one or both of these forms of photochemistry function in mesophyll chloroplasts of the maize under conditions which place varying demands on the requirement for ATP. Whether the supply of ascorbate in the chloroplasts regulates the capacity for pseudocyclic electron flow will be investigated. Methods of analysis will include measurements of membrane energization, quantum yields of photochemistry and conversions of metabolites in the carbon metabolism using mesophyll chloroplasts isolated from maize. This research will contribute to our understanding of the efficiency of the solar energy conversion by photosynthesis, which is crucial to sustaining life on earth.