Resolving the key photoprotective switch in photosynthetic electron transport

解决光合电子传输中关键的光保护开关

基本信息

批准号：
BB/R004838/1
负责人：
Guy Hanke
金额：
$ 49.65万
依托单位：
Queen Mary University of London
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2018
资助国家：
英国
起止时间：
2018 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=BB%2FR004838%2F1
关键词：
Resolving key photoprotective switch photosynthetic

项目摘要

We aim to understand the way in which plants are able to adapt to fluctuations in the environment by studying a specific example that has the potential to improve crop plant tolerance to stress. In the final step of photosynthetic electron transfer, the enzyme ferredoxin:NADP(H) oxidoreductase (FNR) uses photosynthetic electrons to reduce NADP+ to NADPH, which is then used in multiple reactions and is essential for C fixation. The amount of this enzyme has a strong effect (a high coefficient of control) on the entire pathway of photosynthesis (0.7 at low light and 0.94 at saturating light (1)). Interestingly, it has also been shown that the amount of FNR also strongly correlates with the ability to tolerate multiple environmental stresses in tobacco (2,3), although the reasons for this are not yet clear. One contributing factor could relate to the free radicals produced by photosynthetic electron transport (PET). We recently showed that variable FNR content and location results in disrupted free radical production, and that this could be responsible for "priming" the plant, and inducing defence mechanisms (4). Although FNR has been well studied as an enzyme, its location within chloroplasts is highly dynamic, with many interaction partners. The reason for these multiple interactions, the activity of the enzyme at these different locations and the relationship of these complexes with the rest of the PET apparatus is not understood. There are three important recent developments that will enable us to answer these important questions. Firstly, we have produced transgenic Arabidopsis plants with FNR proteins localised to different complexes within the chloroplast (5). This means we can now compare the activity of the enzyme, and its associated metabolic pathways, when it is bound to different places. Introduction of cyanobacterial FNR to higher plants has been patented as a means of improving stress tolerance in crop plants, but the interactions of this prokaryotic enzyme in higher plant chloroplasts are unknown. Our novel plants will allow us to pinpoint the interactions responsible for stress tolerance. Secondly, new equipment has been developed that will allow us to monitor the activity of the enzyme inside a living leaf (6), which is much more accurate than working with semi-purified systems, where important components or regulatory events may be lost. Thirdly, we have promising preliminary results from a microscopy approach, that will help us image where in the chloroplast membranes these events occur. This is important, as many regulatory events in chloroplasts can only be understood in the context of spatial organisation between different parts of the organelle, or are too weak to detect with standard biochemical methods.Using these tools we aim to discover how dynamic redistribution of FNR is able to regulate PET and promote stress tolerance. Plants have limited resources available to them, and must allocate these to ensure the greatest chance of survival and reproduction. Improving the efficiency of switching between protective states and assimilatory states will therefore improve the chances of the plant not only surviving stressful conditions, but conducting rapid photosynthesis afterward and achieving a high harvest index. Better understanding of this regulation may help to design or breed plants able to withstand specific stresses, or rapidly respond to the presence and absence of stresses in order to achieve survival but maintain high yields.(1) Hajirezaei MR, et al. (2002) Plant J 29(3):281-93.(2) Palatnik JF, et al. (2003) Plant J 35(3):332-41.(3) Rodriguez RE, et al. (2007) Plant Physiol 143(2):639-49.(4) Kozuleva M, et al. (2016) Plant Physiol 172: 1480-1493.(5) Twachtmann M, et al. (2012) Plant Cell 24(7):2979-91.(6) Klughammer C, et al. (2016) Photosynth Res 128(2):195-214.

我们的目标是通过研究一个有潜力提高作物对胁迫耐受性的具体例子，了解植物适应环境波动的方式。在光合电子转移的最后一步，铁氧还蛋白：NADP(H) 氧化还原酶 (FNR) 使用光合电子将 NADP+ 还原为 NADPH，然后用于多个反应，对于 C 固定至关重要。这种酶的量对光合作用的整个途径有很强的影响（高控制系数）（低光下为 0.7，饱和光下为 0.94 (1)）。有趣的是，研究还表明，FNR 的量也与烟草耐受多种环境胁迫的能力密切相关 (2,3)，尽管其原因尚不清楚。其中一个影响因素可能与光合电子传输（PET）产生的自由基有关。我们最近表明，可变的 FNR 含量和位置会导致自由基产生中断，这可能是“启动”植物并诱导防御机制的原因 (4)。尽管 FNR 作为一种酶已得到充分研究，但它在叶绿体中的位置是高度动态的，具有许多相互作用伙伴。这些多重相互作用的原因、酶在这些不同位置的活性以及这些复合物与 PET 装置其余部分的关系尚不清楚。最近的三个重要进展将使我们能够回答这些重要问题。首先，我们生产了转基因拟南芥植物，其 FNR 蛋白定位于叶绿体内的不同复合物 (5)。这意味着我们现在可以比较酶结合到不同位置时的活性及其相关的代谢途径。将蓝藻 FNR 引入高等植物已获得专利，作为提高作物植物胁迫耐受性的一种方法，但这种原核酶在高等植物叶绿体中的相互作用尚不清楚。我们的新型植物将使我们能够查明负责耐受胁迫的相互作用。其次，我们开发了新设备，使我们能够监测活叶内酶的活性（6），这比使用半纯化系统准确得多，因为半纯化系统可能会丢失重要成分或调节事件。第三，我们通过显微镜方法获得了有希望的初步结果，这将帮助我们对叶绿体膜中这些事件发生的位置进行成像。这很重要，因为叶绿体中的许多调控事件只能在细胞器不同部分之间的空间组织背景下才能理解，或者太弱而无法用标准生化方法检测。使用这些工具，我们的目标是发现 FNR 的动态重新分布如何能够调节PET并促进应激耐受力。植物可用的资源有限，必须分配这些资源以确保最大的生存和繁殖机会。因此，提高保护状态和同化状态之间的转换效率不仅可以提高植物在胁迫条件下生存的机会，而且可以提高植物随后进行快速光合作用并获得高收获指数的机会。更好地理解这一调节可能有助于设计或培育能够承受特定胁迫的植物，或对胁迫的存在和不存在快速做出反应，以实现生存并保持高产量。(1) Hajirezaei MR, et al. (2002) Plant J 29(3):281-93.(2) Palatnik JF 等人。 (2003) Plant J 35(3):332-41.(3) Rodriguez RE 等人。 (2007) 植物生理学 143(2):639-49.(4) Kozuleva M 等人。 (2016) 植物生理学 172: 1480-1493。(5) Twachtmann M 等人。 (2012) 植物细胞 24(7):2979-91.(6) Klughammer C 等人。 (2016) 光合作用研究 128(2):195-214。