Probing the structure and function of a super-rogue photosystem II complex involved in chlorophyll f synthesis

探讨参与叶绿素 f 合成的超级光系统 II 复合体的结构和功能

• 批准号: BB/V002007/1
• 负责人: Peter Nixon
• 金额: $ 75.7万
• 依托单位: Imperial College London
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2021
• 资助国家: 英国
• 起止时间: 2021 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=BB%2FV002007%2F1
• 关键词: Probing; structure; function; super; rogue

There is an urgent need to develop new strategies to improve crop yield to feed the ever-growing global population. Crop plants grow because they use the energy of sunlight to drive the conversion of atmospheric carbon dioxide into biomass. This process of photosynthesis is relatively inefficient with much less than 1% of the incident solar energy converted into stored chemical energy. One straightforward way to improve photosynthetic efficiency is to capture more of the sunlight in the first place. Plants rely on chlorophyll pigments (as well as some accessory pigments) to absorb light to drive photosynthesis. The chemical nature of the chlorophyll pigments found in plants necessarily means that photosynthesis is restricted to the visible region of the solar spectrum. In recent years, however, several strains of cyanobacteria, which perform plant-like photosynthesis, have been discovered that make modified forms of chlorophyll that absorb light in the far-red region of the spectrum. If these far-red chlorophylls could be made in plants and assembled correctly in the photosynthetic apparatus, the number of photons of light that could be used to drive photosynthesis could be increased by up to 19%, a considerable increase in efficiency. One of the far-red absorbing chlorophylls is chlorophyll f (Chl f). In order to make Chl f in plants, an important first step is to identify and characterise the cyanobacterial enzyme that synthesises Chl f. In a recent breakthrough, Don Bryant and colleagues in the USA showed that Chl f synthesis was dependent on the ChlF protein subunit which, somewhat surprisingly, was found to be related to one of the proteins present in the well-studied photosystem II complex which catalyses the light-driven oxidation of water to oxygen characteristic of plant photosynthesis. In follow-up work, we have discovered that ChlF does not act alone, as was originally thought, but is part of a new type of PSII complex, which we term the super-rogue PSII complex. The super-rogue PSII complex shows clear similarities to regular PSII but has evolved to make Chl f rather than split water into oxygen. Chl f is made from the Chl a pigment through an oxidation reaction involving molecular oxygen; but the chemistry involved in this process is currently unknown. In this application, we propose to study the structure and mechanism of the newly identified super-rogue PSII complex in unprecedented detail. We aim to investigate whether the super-rogue complex is photochemically active and will test the hypothesis that the super-rogue PSII complex activates molecular oxygen into a reactive form that oxidises a Chl a molecule bound to a specific site in the super-rogue PSII complex. The project involves a team of scientists with skills in microbiology, molecular biology, biochemistry and spectroscopy. Our experimental approaches are diverse and involve working on biochemically pure protein complexes as well studying cyanobacterial mutants expressing Chl f. Ultimately our studies will provide important new knowledge on a new type of photosystem II complex that will underpin future work producing Chl f in crop plants.

迫切需要制定新的战略来提高作物产量，以养活不断增长的全球人口。农作物之所以生长，是因为它们利用太阳光的能量来推动大气中的二氧化碳转化为生物质。这种光合作用过程的效率相对较低，只有不到1%的入射太阳能转化为储存的化学能。提高光合作用效率的一个直接方法是首先捕捉更多的阳光。植物依靠叶绿素色素(以及一些辅助色素)吸收光线来驱动光合作用。植物中发现的叶绿素色素的化学性质必然意味着光合作用仅限于太阳光谱的可见区域。然而，最近几年，人们发现了几种执行植物般的光合作用的蓝藻，它们可以产生修饰形式的叶绿素，在光谱的远红区吸收光线。如果这些远红光的叶绿素能够在植物中制造并在光合作用装置中正确组装，可以用于驱动光合作用的光子数量可以增加高达19%，这将大大提高效率。远红外线吸收的叶绿素之一是叶绿素f(Chl F)。为了在植物中制造Chl f，重要的第一步是鉴定和鉴定合成Chl f的蓝藻酶。在最近的一项突破中，Don Bryant和他的美国同事证明Chl f的合成依赖于Chlf蛋白亚基，令人惊讶的是，它被发现与光系统II复合体中存在的一种蛋白质有关，光系统II复合体催化光驱动的水氧化为植物光合作用的特征。在后续工作中，我们发现ChlF并不像最初认为的那样单独作用，而是一种新型PSII复合体的一部分，我们称之为超级无赖PSII复合体。超级无赖的PSII复合体与普通的PSII有明显的相似之处，但已经进化成Chl f，而不是将水分解为氧气。Chl-f是由Chl-a色素通过分子氧参与的氧化反应制成的，但这个过程中涉及的化学成分目前尚不清楚。在这一应用中，我们提议对新发现的超级无赖PSII复合体的结构和机制进行前所未有的详细研究。我们的目标是研究超级无赖复合体是否具有光化学活性，并将检验这一假设，即超级无赖PSII复合体将分子氧激活为活性形式，将结合到超级无赖PSII复合体中特定位置的Chl分子氧化成活性形式。该项目涉及一个拥有微生物学、分子生物学、生物化学和光谱学技能的科学家团队。我们的实验方法多种多样，包括研究生化纯蛋白质复合体以及研究表达Chl f的蓝藻突变体。最终，我们的研究将为新型光系统II复合体提供重要的新知识，这将为未来在作物中生产Chl f的工作奠定基础。

项目成果

The Photosynthetic Electron Transport Chain of Oxygenic Photosynthesis

• DOI: 10.1089/bioe.2023.0003
• 发表时间: 2023-03
• 期刊: Bioelectricity
• 影响因子: 2.3
• 作者: Man Qi;Ziyu Zhao;P. Nixon

Accumulation of Cyanobacterial Photosystem II Containing the 'Rogue' D1 Subunit Is Controlled by FtsH Protease and Synthesis of the Standard D1 Protein.

含有“Rogue”D1 亚基的蓝藻光系统 II 的积累受 FtsH 蛋白酶和标准 D1 蛋白合成的控制。

• DOI: 10.1093/pcp/pcad027
• 发表时间: 2023
• 期刊: Plant & cell physiology
• 影响因子: 4.9
• 作者: Masuda T