Plant J: 用动态光合模型指导C4作物增产
最高产的 C4食品和生物燃料作物，如玉米、高粱和甘蔗，都利用 NADP-ME 型 C4光合作用。尽管生产率很高，这些作物远远低于理论上最大的太阳能转换效率6% 。了解这些低效的基础是生物工程和育种策略的关键，以提高这些 C4作物的可持续生产力。光合作用主要研究在饱和光下的稳态。在这些作物的田间林分中，光线是不断变化的，而且经常有快速的波动。虽然光照可能在一秒钟内改变，但光合作用的调节可能需要许多分钟，从而导致效率低下。测定了波动光照条件下玉米、高粱和甘蔗的 CO2吸收速率和气孔导度。将气体交换结果与一个新的动态光合作用模型相结合，推导出非稳态条件下的限制因子。
动态光合作用模型是在现有的玉米 C4代谢模型基础上发展起来的，它包括: 1)关键光合酶及其温度响应的翻译后调节; 2)气孔导度的动态变化; 3)叶片能量平衡。通过对三种 C4作物叶片 CO2吸收速率和气孔导度的测定，推测 Rubisco 活化酶、 PPDK 调节蛋白和气孔导度是影响 NADP-ME 型 C4光合作用在暗光转强光过渡期间效率的主要限制因素。我们认为，这些限制因子的影响程度使它们成为生物工程改良这些关键作物的地球的总光合生产力。
The most productive C4 food and biofuel crops, such as maize, sorghum, and sugarcane, all utilize NADP-ME type C4 photosynthesis. Despite high productivities, these crops fall well short of the theoretical maximum solar conversion efficiency of 6%. Understanding the basis of these inefficiencies is key to bioengineering and breeding strategies to increase sustainable productivity of these C4 crops. Photosynthesis is studied predominantly at steady-state in saturating light. In field stands of these crops, light is continually changing, and often with rapid fluctuations. While light may change in a second, adjustment of photosynthesis may take many minutes, leading to inefficiencies. We measured the rates of CO2 uptake and stomatal conductance of maize, sorghum and sugarcane under fluctuating light regimes. The gas exchange results were combined with a new dynamic photosynthesis model to infer the limiting factors under non-steady-state conditions. The dynamic photosynthesis model was developed from an existing C4 metabolic model for maize, extended to include: 1) post-translational regulation of key photosynthetic enzymes and their temperature responses; 2) a dynamic stomatal conductance; and 3) leaf energy balance. Testing the model outputs against measured rates of leaf CO2 uptake and stomatal conductance of the three C4 crops, inferred that Rubisco activase, the PPDK regulatory protein and stomatal conductance are the major limitations to the efficiency of NADP-ME type C4 photosynthesis during dark-to-high light transitions. We propose that the level of influence of these limiting factors make them targets for bioengineering improved photosynthetic efficiency of these key crops.
10.1111/tpj.15365
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