CAPP: Combining Algal and Plant Photosynthesis

在大多数植物中，生长速度受到光合作用过程中从大气中吸收二氧化碳并转化为糖的速度的限制。负责这一过程的第一步的酶Rubisco在目前大气中存在的二氧化碳水平下不能发挥其潜在的最大效率。如果水平高得多，光合作用就会更快，植物也会生长得更快。这种光合作用的加速将在未来50年左右的时间里自然发生，因为人类活动导致大气中的二氧化碳水平上升。然而，迫切需要提高作物生产率，为地球上不断增长的人口提供粮食。我们的项目解决了这个问题。我们正在研究一种存在于微小绿藻中的机制，这种机制会导致光合作用细胞中高浓度的二氧化碳(称为碳浓缩机制，或CCM)，使Rubisco能够以最高效率工作。我们最近发现了有关这一机制的重要新信息，我们发明了新的快速方法来发现与此有关的藻类基因。我们有两个相辅相成和平行的目标。首先，我们将应用我们的新方法来识别藻类在细胞内实现高浓度二氧化碳所需的所有基因，我们将发现这些基因到底是如何工作的。其次，我们将把最重要的基因转移到一种植物中，并研究是否可以在一片叶子中重建相同的CCM。如果可以，我们预计我们的实验植物将有更高的光合作用速率，因此比正常植物有更高的生长速度。这项工作将为植物和藻类如何从大气中获取和利用二氧化碳提供新的见解，对于预测和应对当前大气和气候的快速变化具有重要意义。这项工作还将有助于加强全球粮食安全的战略，因为它将指明提高作物生产率的新方法。

In most plants, growth rate is limited by the rate at which carbon dioxide from the atmosphere is taken up and converted to sugars in the process of photosynthesis. The enzyme responsible for the first step in this process, Rubisco, does not work at its potential maximum efficiency at the current levels of carbon dioxide present in the atmosphere. If levels were much higher, photosynthesis would be faster and plants would grow faster. This speeding-up of photosynthesis will happen naturally over the next fifty years or so as atmospheric carbon dioxide levels rise due to human activities. However, there is an immediate requirement for increased crop productivity to provide food for the rising population of the planet. Our project addresses this problem. We are studying a mechanism present in tiny green algae that results in high concentrations of carbon dioxide inside their photosynthesising cells (called a Carbon Concentrating Mechanism, or CCM), enabling Rubisco to work at maximum efficiency. We have recently discovered important new information about this mechanism, and we have invented new and rapid methods to discover algal genes that contribute to it. We have two complementary and parallel aims. First, we will apply our new methods to identify all of the genes required by the algae to achieve high concentrations of carbon dioxide inside the cells, and we will discover exactly how these genes work. Second, we will transfer the most important genes into a plant, and study whether the same CCM can be recreated inside a leaf. If it can, we expect that our experimental plant will have higher rates of photosynthesis and hence a higher rate of growth than normal plants. This work will provide new insights into how plants and algae acquire and use carbon dioxide from the atmosphere, of great importance in predicting and coping with the current rapid changes in the atmosphere and hence in climate. The work will also contribute to strategies to increase global food security, because it will indicate new ways in which crop productivity can be increased.