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农作物产量，以养活不断增长的全球人口。农作物之所以能够生长，是因为它们利用阳光的能量将大气中的二氧化碳转化为生物质。这一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获更多的阳光。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光区域。然而，近年来，人们发现了几种进行类似植物光合作用的蓝细菌菌株，它们可以产生修饰形式的叶绿素，吸收光谱中远红区域的光。如果这些远红叶绿素可以在植物中制造并在光合作用装置中正确组装，则可用于驱动光合作用的光子数量最多可增加 19%，效率将大幅提高。吸收远红光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表征合成 Chl f 的蓝藻酶。在最近的一项突破中，Don Bryant 和美国的同事表明 Chl f 合成依赖于 ChlF 蛋白亚基，令人有些惊讶的是，该亚基被发现与经过充分研究的光系统 II 复合物中存在的一种蛋白质有关，该复合物催化光系统 II 的合成。植物光合作用的光驱动水氧化为氧气的特征。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，我们将其称为超级流氓 PSII 复合体。超级流氓 PSII 复合体与常规 PSII 表现出明显的相似之处，但已进化为制造 Chl f，而不是将水分解为氧气。 Chl f 是由 Chl a 色素通过分子氧的氧化反应制成的；但这一过程中涉及的化学成分目前尚不清楚。在此应用中，我们建议以前所未有的细节研究新发现的超级流氓 PSII 复合体的结构和机制。我们的目的是研究超级流氓复合物是否具有光化学活性，并将检验超级流氓 PSII 复合物将分子氧激活成反应形式的假设，该反应形式氧化与超级流氓 PSII 复合物中特定位点结合的叶绿素 a 分子。该项目涉及一组具有微生物学、分子生物学、生物化学和光谱学技能的科学家。我们的实验方法多种多样，涉及生化纯蛋白质复合物的研究以及表达 Chl f 的蓝藻突变体的研究。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，该复合体将为未来在农作物中生产叶绿素 f 的工作奠定基础。

项目成果

The Photosynthetic Electron Transport Chain of Oxygenic Photosynthesis

产氧光合作用的光合电子传递链

• DOI: 10.1089/bioe.2023.0003
• 发表时间: 2023-03-01
• 期刊: Bioelectricity
• 影响因子: 2.3
• 作者: Man Qi;Ziyu Zhao;P. Nixon
• 通讯作者: 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: http://dx.10.1093/pcp/pcad027
• 发表时间: 2023
• 期刊: Plant & cell physiology
• 影响因子: 4.9
• 作者: Masuda T