Unraveling plasmodesmata formation in C4 plant Gynandropsis gynandra

解开C4植物白花菜胞间连丝的形成

• 批准号: BB/X010015/1
• 负责人: Tina Schreier
• 金额: $ 51.8万
• 依托单位: University of Oxford
• 依托单位国家: 英国
• 项目类别: Fellowship
• 财政年份: 2023
• 资助国家: 英国
• 起止时间: 2023 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=BB%2FX010015%2F1
• 关键词: Unraveling; plasmodesmata; formation; C4; plant

Feeding the rapidly growing human population requires continuous increases in crop yield. An important strategy towards higher crop productivity is to improve the efficiency of photosynthesis in plants, so that plants capture CO2 more efficiently from the atmosphere and sequester it into biomass. A small number of plant species already perform a more efficient type of photosynthesis than others - called C4 photosynthesis. C4 photosynthesis evolved independently over 60 times in different plant lineages and involves modified biochemistry that occurs between two cell types in the leaf: the mesophyll and bundle sheath cells. In C4 plants, CO2 is initially fixed in mesophyll cells into a four-carbon acid, which is then transferred into bundle sheath cells. There, the acid is decarboxylated and CO2 is regenerated, thus forming a pump action that concentrates CO2 in the bundle sheath cells. The CO2 is then fixed primarily within these bundle sheath cells, where the high CO2 concentration increases photosynthetic efficiency by up to 50% in comparison to non-C4 plants. It is therefore a major goal of plant biotechnology to engineer C4 photosynthesis into non-C4 crop species (e.g: rice, wheat, potatoes) to improve their productivity and yield.The exchange of metabolites between the mesophyll and bundle sheath cells is central to the biochemistry of C4 photosynthesis. Typical C4 plants therefore have specialised leaf anatomy that maximises physical connections between these two cell types, with numerous pores named plasmodesmata that mediate metabolite exchange. Despite the critical importance of cell-to-cell connectivity in facilitating C4 metabolism, almost nothing is known about how the large numbers of plasmodesmata form between the mesophyll and bundle sheath cells. My research is focused on this process in the C4 plant Gynandropsis gynandra, where I discovered that light is the cue that triggers the rapid and numerous formation of plasmodesmata at the mesophyll-bundle sheath interface during leaf development.In my fellowship project, I will aim to understand the cell biological mechanisms underpinning plasmodesmata formation at the mesophyll-bundle sheath interface in G. gynandra and its importance to photosynthetic efficiency. Since G. gynandra is the closest known C4 relative to the non-C4 model plant Arabidopsis thaliana, I will use the latest findings on plasmodesmata formation in Arabidopsis as a starting point. Plasmodesmata are known to contain components of the cytoskeleton, as well as plasma membrane with specialised lipid composition (lipid microdomains), and previous work in Arabidopsis suggests that both cytoskeleton and lipid microdomains are involved in plasmodesmata regulation. I will further explore this in the context of the mesophyll-bundle sheath interface in G. gynandra, testing the impact of specific chemical inhibitors of the cytoskeleton and lipid microdomains on plasmodesmata formation. I will also use gene editing in G. gynandra to generate knockout mutants in three candidate genes that could link plasmodesmata formation to the cytoskeleton and lipid biosynthesis. The effect of the gene knockouts on plasmodesmata formation at the mesophyll-bundle sheath interface, and consequences on photosynthetic efficiency, will be assessed. Finally, I also aim to discover novel candidate genes in plasmodesmata formation in G. gynandra using proximity labelling to find novel proteins associated with known plasmodesmata localised proteins. The role of these proteins will be investigated in future independent work. Overall, my findings will not only create new understanding of how plasmodesmata form in C4 plants, but reveal new cell biological and biochemical mechanisms that underpin plasmodesmata formation in plants. The knowledge can be used in the global effort to engineer C4 photosynthesis in major crops to increase photosynthesis and yield.

养活迅速增长的人口需要不断提高粮食产量。提高作物产量的一个重要策略是提高植物光合作用的效率，这样植物就能更有效地从大气中捕获二氧化碳并将其封存到生物质中。少数植物物种已经进行了一种比其他植物更有效的光合作用——C4光合作用。C4光合作用在不同的植物谱系中独立进化了60多次，涉及到发生在叶片中两种细胞类型：叶肉细胞和束鞘细胞之间的生化修饰。在C4植物中，CO2最初在叶肉细胞中被固定为四碳酸，然后被转移到束鞘细胞中。在那里，酸被脱羧，二氧化碳被再生，从而形成一个泵作用，将二氧化碳集中在束鞘细胞中。然后，二氧化碳主要被固定在这些束鞘细胞内，与非c4植物相比，高二氧化碳浓度可使光合效率提高50%。因此，植物生物技术的一个主要目标是将C4光合作用改造成非C4作物物种（如水稻、小麦、土豆），以提高它们的生产力和产量。叶肉细胞和束鞘细胞之间代谢物的交换是C4光合作用生物化学的核心。因此，典型的C4植物具有专门的叶片解剖结构，可以最大限度地实现这两种细胞类型之间的物理连接，其中有许多称为间连丝的孔，可以调节代谢物交换。尽管细胞间连通性对促进C4代谢至关重要，但对于叶肉细胞和束鞘细胞之间大量的间连丝是如何形成的，我们几乎一无所知。我的研究重点是C4植物gyynandropsis gyynandra的这一过程，我发现在叶片发育过程中，光是触发叶肉-束鞘界面快速和大量形成间连丝的线索。在我的奖学金项目中，我将致力于了解黄杨叶肉-束鞘界面间连丝形成的细胞生物学机制及其对光合效率的重要性。由于G. gyynandra是已知的与非C4模式植物拟南芥（Arabidopsis thaliana）最接近的C4植物，我将以拟南芥中plasmodesmata形成的最新发现作为起点。众所周知，胞间连丝含有细胞骨架的成分，以及具有特殊脂质成分（脂质微结构域）的质膜，先前对拟南芥的研究表明，细胞骨架和脂质微结构域都参与胞间连丝的调节。我将在黄芪叶肉-束鞘界面的背景下进一步探讨这一点，测试细胞骨架和脂质微域的特定化学抑制剂对胞间连丝形成的影响。我还将使用G. gyynandra的基因编辑技术在三个候选基因中产生敲除突变体，这些基因可能将胞间连丝的形成与细胞骨架和脂质生物合成联系起来。基因敲除对叶肉-束鞘界面间连丝形成的影响以及对光合效率的影响将被评估。最后，我还打算利用接近标记来发现与已知的胞间连丝局部蛋白相关的新蛋白，以发现在G. gyynandra胞间连丝形成中的新的候选基因。这些蛋白质的作用将在未来的独立工作中进行研究。总的来说，我的发现不仅将为C4植物间连丝的形成提供新的认识，而且将揭示植物间连丝形成的新的细胞生物学和生化机制。这些知识可以用于全球努力在主要作物中设计C4光合作用，以增加光合作用和产量。