The Meristem in Context: a multilevel systems approach to improving plant growth under changeable environments

气候变化正在影响植物的生长方式，导致全球生产的可消耗卡路里总量逐年减少。虽然植物的生产力通常被认为是在生物体水平，产量最终取决于在植物的芽和根的生长尖端发现的干细胞的小团体。茎顶端分生组织（SAM）产生所有的叶、花和茎，构成植物的地上结构。其特化的圆顶结构通过充分描述的移动的转录因子和信号分子系统来维持，所述转录因子和信号分子平衡细胞生长和分裂与分化和器官起始。由于新器官的形成遵循一系列特定的几何规则，因此SAM的大小和细胞结构非常重要。例如，由许多细胞组成的大SAM可以比较小的SAM或由更少、更大的细胞组成的SAM在中央干细胞池周围容纳更多数量的新器官原基。事实上，许多作物物种的分生组织比它们的野生亲戚更大，这被认为是导致它们更高产量的一个因素。尽管SAM结构对植物产量的重要性，但我们对SAM的结构如何受到现实世界环境条件的影响和调节知之甚少。例如，驯化的较大的自组装膜对环境压力的敏感性是否比野生亲缘动物的较小的自组装膜更高或更低？而且，我们能否通过降低SAM结构中的环境可塑性来提高作物产量的稳健性？我们对SAM如何响应胁迫缺乏了解的一个原因是SAM通常在组织培养中进行研究，缺乏植物及其环境的背景。这意味着关于SAM如何整合环境和发育信号的关键信息丢失了。为了解决这个问题，我设计了一种方法，将细胞生物学与大规模表型和多级建模相结合，开始在其正常生理和环境背景下构建SAM的图片。我将研究如何定义明确的细胞生长，分裂和信号转导通路在应激反应过程中被修改，以及这些变化对SAM结构和生产力的影响。这将使我能够开发一个框架，通过该框架，我们可以可靠地预测SAM将如何应对多变的现实世界条件，并确定将提高其生产力的遗传修饰。重要的是，这种多层次的方法将使我能够使用细胞水平的修改，使可预测的变化，植物的整体架构和桥梁之间的现有差距，在细胞水平上收集的基础知识的财富和整个植物水平，我们希望能够进行有针对性的修改。我的研究将集中在干旱作为一个重要的例子植物胁迫反应。干旱胁迫是英国和世界范围内作物损失的主要原因，与气候变化相关的温度和降雨模式的变化正在加剧这一问题。春季炎热干燥的时期对英国冬季谷物作物如油菜来说尤其成问题，这些作物必须在春季快速生长，以最大限度地提高种子产量。因此，对极端和多变天气条件更具耐受性的新作物品种将支持英国农业，并有助于养活不断增长的世界人口。因此，我将使用模式物种（拟南芥）和作物物种（甘蓝型油菜-冬季油菜）进行研究，以确保我的研究结果的普遍性。在未来，我将能够使用相同的方法来研究其他压力，如热和食草动物的影响，并确定是否有共同的解决方案，这些相关的问题。

Climate change is impacting the way plants grow, resulting in year on year reductions in the total consumable calories produced worldwide. Although plant productivity is often viewed at the organism level, yields are ultimately dependent on small groups of stem cells that are found in the growing tips of the plant's shoots and roots. The shoot apical meristem (SAM) produces all of the leaves, flowers, and stems that make up the plant's above-ground architecture. Its specialised domed structure is maintained through a well described system of mobile transcription factors and signalling molecules that balance cell growth and division against differentiation and organ initiation. Since new organs are initiated following a set of specific geometric rules, the size and cellular structure of the SAM are extremely important. For example, a large SAM comprised of many cells can accommodate a larger number of new organ primordia around the central stem cell pool than a smaller SAM, or a SAM comprise of fewer, larger cells. Indeed, many crop species have larger meristems than their wild relatives, a factor that is thought to contribute to their higher productivity. Despite the importance of SAM structure to plant yields, we know little about how the structure of the SAM is impacted and modulated by real-world environmental conditions. For example, are the larger SAMs of domesticated more or less sensitive to environmental stresses than the smaller SAMs of their wild relatives? And, can we improve robustness in crop yields by reducing environmental plasticity in SAM structure?One reason for our lack of understanding of how the SAM responds to stress is that the SAM is often studied in tissue culture, devoid of the context of the plant and its environment. This means that crucial information about how the SAM integrates environmental and developmental signals is lost. To address this problem I have devised an approach that will integrate cell biology with large scale phenotyping and multilevel modelling to start building a picture of the SAM within its normal physiological and environmental context. I will examine how well-defined cell growth, division and signalling pathways are modified during stress responses and what the effects these changes have on SAM structure and productivity. This will allow me to develop a framework through which we can reliably predict how the SAM will respond under to changeable, real-world conditions and identify genetic modifications that will improve its productivity. Importantly, this multilevel approach will allow me to use cell level modifications to make predictable changes to the overall architecture of the plant and bridge an existing gap between the wealth of fundamental knowledge collected at the cell level and the whole plant level at which we want to be able to make targeted modifications.My research will focus on drought as an important example plant stress response. Drought stress is a major cause of crop losses in the UK and worldwide and altered temperatures and rainfall patterns associated with climate change are exacerbating this problem. Hot, dry periods during spring are especially problematic for UK winter grain crops such as Oilseed Rape, which must undergo rapid shoot growth in spring to maximise seed yield. New crop varieties that are more tolerant of extreme and changeable weather conditions would therefore support UK agriculture and help feed the growing world population. I will therefore conduct my research using both a model species (Arabidopsis thaliana) and a crop species (Brassica napus - Winter Oilseed Rape) to ensure the generality of my findings. In the future I will be able to use the same approach to study other stresses such as the impact of heat and herbivory and identify whether there are common solutions to these related problems.