COLLABORATIVE PROJECT: MAGIC - A multi-tiered approach to generating increased carbon dioxide for photosynthesis

合作项目：MAGIC - 为光合作用产生更多二氧化碳的多层方法

基本信息

批准号：
BB/I02450X/1
负责人：
Nigel Burroughs
金额：
$ 25.36万
依托单位：
University of Warwick
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2011
资助国家：
英国
起止时间：
2011 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=BB%2FI02450X%2F1
关键词：
COLLABORATIVE PROJECT MAGIC multi tiered

项目摘要

Photosynthesis is at the core of virtually every aspect of society, from food production to industrial construction. Terrestrial photosynthesis is intimately connected with our use of other natural resources, and it exerts major controls on the water, mineral and carbon cycles of the world. For example, plant transpiration is thought to have contributed to recent changes in fresh-water availability associated with the global rise in CO2, and it is at the centre of a crisis in water availability expected over the next 20-30 years. Over this same period it is estimated that a 50% increase in global food production will be required to keep pace with the increase in human population. Crop yields have matched population growth until recently, but the gains from cereal cultivars bred in the Green Revolution were realised in full a decade ago. Thus it is vital that routes to further improvements in photosynthetic efficiency are sought now. In most species, CO2 is fixed by Ribulose Bisphosphate Carboxylase/Oxygenase (RuBisCO) in the Calvin-Benson cycle to generate a three-carbon compound. RuBisCO is remarkably poor in its substrate selectivity and promiscuously fixes both CO2 and O2, a fact that makes RuBisCO arguably the most inefficient step in photosynthesis. One way of reducing O2 use by RuBisCO is to raise the partial pressure of CO2 (pCO2). So-called carbon concentrating mechanisms (CCMs) have evolved multiple times in nature, albeit not as a feature of most common crop species. Thus, comparisons suggest roughly a 50% increase in overall yield might be realised if O2 use by RuBisCO were bypassed in crops. Significant resources have gone into engineering RuBisCO for increased CO2 selectivity and introducing a single-celled version of C4 photosynthesis in rice, but these approaches have yet to see a step change in photosynthetic efficiency. One new set of strategies yet to be explored is to co-opt light-driven pumps, anion exchange transport and substrate channelling to supply CO2 to RuBisCO. To date none of these processes is known to facilitate photosynthesis, although all three occur naturally and have been employed synthetically in biology. It is our goal to develop the equivalent of a 'two-stage pump': placing in series (1) a transport mechanism to concentrate HCO3- in the chloroplast powered by the light-driven ion pump halorhodopsin (hR) from the archeon Halobacterium halobium, and (2) substrate channelling within the chloroplast using one or more molecular 'building blocks' from Clostridium or cyanobacteria to carry HCO3- or a four-carbon intermediate to RuBisCO. This two-stage strategy is expected to maximise CCM gain driven independently with light energy absorbed by hR, and it has the added potential for engineering hR to tap the unused asset of light beyond the photosynthetic spectrum. Furthermore, an overarching feature of this approach is in its modular nature: it will be possible to develop each stage of the two-stage pump in parallel, and to assess its functionality separately at molecular, cellular and whole-organismal levels, combining the components thereafter for final validation. This modular approach ensures the maximum efficiency and speed in realising our goal within the three-year period.

光合作用几乎是社会各个方面的核心，从粮食生产到工业建设。陆地光合作用与我们对其他自然资源的利用密切相关，它对世界的水、矿物质和碳循环发挥着重要的控制作用。例如，植物蒸腾作用被认为是造成近期与全球二氧化碳浓度上升相关的淡水供应变化的原因之一，并且它是预计未来 20-30 年水资源供应危机的核心。同期，预计全球粮食产量需要增加 50%，才能跟上人口增长的步伐。直到最近，农作物产量才与人口增长相匹配，但绿色革命培育的谷物品种的收益在十年前就已全部实现。因此，现在寻找进一步提高光合作用效率的途径至关重要。在大多数物种中，CO2 在卡尔文-本森循环中被核酮糖二磷酸羧化酶/加氧酶 (RuBisCO) 固定，生成三碳化合物。 RuBisCO 的底物选择性非常差，并且混杂地固定 CO2 和 O2，这一事实使得 RuBisCO 可以说是光合作用中效率最低的步骤。减少 RuBisCO 使用 O2 的一种方法是提高 CO2 分压 (pCO2)。所谓的碳浓缩机制（CCM）在自然界中已经进化了多次，尽管这并不是大多数常见作物物种的特征。因此，比较表明，如果作物中不使用 RuBisCO 的 O2，总产量可能会增加大约 50%。人们投入了大量的资源来设计 RuBisCO 以提高 CO2 选择性，并在水稻中引入单细胞 C4 光合作用，但这些方法尚未看到光合作用效率的阶跃变化。一套尚待探索的新策略是采用光驱动泵、阴离子交换传输和底物通道向 RuBisCO 提供 CO2。迄今为止，尽管这三个过程都是自然发生的，并且已在生物学中综合应用，但尚无已知的这些过程可以促进光合作用。我们的目，和（2）叶绿体内的底物通道，使用来自梭状芽胞杆菌或蓝藻的一种或多种分子“构建块”，将 HCO3- 或四碳中间体携带到鲁比斯CO。这种两阶段策略预计将通过 hR 吸收的光能独立驱动的 CCM 增益最大化，并且它具有工程 hR 的额外潜力，可以利用光合光谱之外未使用的光资产。此外，这种方法的一个总体特征在于其模块化性质：可以并行开发两级泵的每一级，并结合组件在分子、细胞和整个有机体水平上分别评估其功能此后进行最终验证。这种模块化方法确保了在三年内实现我们目标的最大效率和速度。