Tapping the Unused Potential of Photosynthesis

光合作用是地球上关键的生物反应，为我们提供食物和呼吸的氧气，并从大气中清除二氧化碳。光合作用由两个反应组成：光反应吸收来自太阳的光能，并利用这一反应将水(H2O)分解为电子、质子和氧气，暗反应利用光反应产生的电子和质子将大气中的二氧化碳固定为单糖，这是食物链的基础。重要的是，光反应的能力比暗反应高得多，导致大部分吸收的光能被耗散，而不是被用来固定二氧化碳。在这个建议中，我们将使用合成生物学方法来设计光反应和暗反应之间的额外酶(细胞色素P450，CYP)。这将重新连接光合作用，以便更多吸收的光被用来为有用的化学反应提供动力。因此，这项工作代表了一项创新，在蓝藻和植物中，一系列额外的有价值的化学反应可以由太阳提供动力。我们之前已经开发了一个“平台”蓝藻细胞系，其中光合作用的“浪费”电子被重新布线(使用CYP)来降解污染物阿特拉津(一种用于农业的除草剂)。虽然阿特拉津在欧盟被禁止，但在一些地下水系统中，阿特拉津仍然是最普遍的农药之一。在这项建议中，我们的目标是进一步发展CYP在重新连接光合作用方面的使用，以便我们能够改善和调节所需产品的产量，以及增强可由光驱动的产品的多样性。此外，我们将充分描述工程细胞系的生理学特征，以便我们能够询问这种光合作用电子转移的基本机制。此外，我们的目标是将这项技术转移到高等植物拟南芥模型中，作为提高作物物种光合作用潜力的第一步。我们的目标是将“附加值”引入蓝藻和植物中，这可能是利用光合作用物种产生“生物燃料”的商业实现的关键一步，有朝一日可能会取代我们目前对化石燃料的依赖。

Photosynthesis is the pivotal biological reaction on the planet, providing the food we eat and the oxygen we breathe, and removing CO2 from the atmosphere. Photosynthesis consists of two reactions: the light reactions absorb light energy from the sun and use this to split water (H2O) into electrons, protons and oxygen, and the dark reactions use the electrons and protons from the light reactions to 'fix' CO2 from the atmosphere into simple sugars that are the basis of the food chain. Importantly, the light reactions have a much higher capacity than the dark reactions, resulting in much of the absorbed light energy being dissipated rather than being used to 'fix' CO2.In this proposal we will use synthetic-biology methods to engineer an additional enzyme (a cytochrome P450, CYP) in-between the light reactions and the dark reactions. This will 'rewire' photosynthesis such that more absorbed light is used to power useful chemical reactions. This work therefore represents an innovation whereby a range of additional valuable chemical reactions can be powered by the sun in cyanobacteria and plants. We have previously developed a 'platform' cyanobacterial cell line where the 'wasted' electrons of photosynthesis are rewired (using a CYP) to degrade the pollutant atrazine (a herbicide used in agriculture). Atrazine while banned in the EU is still one of the most prevalent pesticides in some groundwater systems. This cell line may be used in the efficient bioremediation of such polluted wastewater areas.In this proposal we aim to further develop the use of CYP in rewiring photosynthesis such that we can improve and regulate the yield of the desired products, as well as enhance the diversity of products that can be powered by light. Further, we will fully characterise the physiology of engineered cell lines such that we can interrogate the fundamental mechanism of this photosynthetic electron transfer. In addition, we aim to transfer this technology to the model higher plant Arabidopsis as a first step in improving photosynthetic potential in crop species.The 'added value' we aim to introduce into cyanobacteria and plants may be a critical step toward the commercial realisation of using photosynthetic species to generate 'biofuels' that may one day replace our current dependence on fossil fuels.