Genetic and mechanical approaches to enhancing crop seed vigour

种子是人类绝大多数农业的起点和终点。目前，全球每年的种子贸易额超过340亿GB，高质量种子的生产和销售是这一行业的基础。在作物形成之前，种子在田间经历一系列的逆境。这些因素包括低水分应力和压实土壤的机械阻抗。种子活力是指种子在广泛的环境条件下发芽和成苗的能力，并决定着作物在田间建立的成功与否。这是产量的关键决定因素，因为没有植株会导致没有最终产品可供收获。改善作物的这一特性是农业的主要目标，但其潜在的活力机制仍不清楚。植物细胞的生长是一个由内部膨胀压力推动周围细胞壁的机械过程。当周围的细胞壁变弱时，细胞变得更大，并对内部膨胀做出反应。编码蛋白质的基因已经被识别出来，这些蛋白质分泌到细胞壁，并改变其结构组成和强度。一旦这种蛋白质被命名为Expansin，它就会起到松散细胞壁结构的作用，允许细胞生长。种子到幼苗的转变完全通过细胞扩张来驱动，而不是细胞分裂。产生足以抵消外部压力的机械力的能力决定了幼苗在广泛的环境条件下站立的能力，从而具有旺盛的生命力。增加膨胀素的表达可以使幼苗在胁迫条件下建立，而胁迫条件通常会限制这一过程。因此，种子活力可以被认为是一种机械驱动的农艺性状，而控制膨胀素的表达是一个目标。该项目采用跨学科的方法来揭示种子向幼苗过渡的遗传因素和机械基础，以及种子活力。我们以前发现了代表Expansin基因表达的高置信度候选调节因子的蛋白质。增加Expansin基因的表达可以增加种子活力，使这些遗传靶点增强种子活力。这些基因将在模式植物拟南芥系统中进行探索。这些发现将被推广到提高作物品种甘蓝种子活力。新鉴定的活力基因中的突变将在不同的十字花科植物中被识别。与工业合作伙伴先正达一起，这些新的油菜种子的活力将得到表征。这将导致确定可直接用于育种计划的品种，以提高幼苗建立、大田作物表现和产量。我们之前已经证明，细胞的大小、形状和排列可以影响种子萌发的早期阶段，以响应生长促进基因的表达，如Expansin。这一观察结果强调了机械约束对植物生长的存在。然而，这些限制因素是如何影响幼苗生长的，目前尚不清楚。了解种子到幼苗转换的力学基础对于了解作物在田间的建立和种子活力具有重要意义。利用三维图像分析和力学建模相结合的方法，将生长促进基因表达与幼苗生长之间的关系建立起来。通过这种方式，将揭示幼苗建立和种子活力的机械基础。在这个快速气候变化的时期，增强油菜种子活力将增加作物产量和粮食安全。该项目中的发现可能反过来也可能推广到其他作物物种。

Seeds are the start and end point for the vast majority of human agriculture. The annual global seed trade is currently valued at over £34 billion, and the production and sale of high quality seeds which germinate uniformly and rapidly underpin this industry. Seeds experience a range of stresses in the field prior to crop establishment. These include low water stress and mechanical impedance from compact soils. Seed vigour refers to the ability of seed to germinate and establish seedlings across a wide range of environmental conditions, and defines the success of crop establishment in the field. This is a key determinant of yield as the absence of a plant leads to no end product to harvest. Improving this trait in crops is a primary goal of the agricultural industry, however the underlying mechanisms of vigour remain poorly understood.The growth of plant cells is a mechanical process driven by internal turgor pressure pushing against the surrounding cell wall. Cells get bigger when the surrounding cell wall is weakened and yields in response to internal turgor. Genes which encode proteins that are secreted to the cell wall and modify its structural composition and strength have been identified. Once such protein is named expansin, and acts to loosen cell wall structures, permitting cell growth.The seed to seedling transition is driven exclusively through cell expansion in the absence of cell divisions. The ability to generate of mechanical force sufficient to counteract external stresses defines the ability of a seedling to establish across a wide range of environmental conditions, and hence be vigorous. Increasing the expression of expansin enables seedling establishment under stress conditions which normally limit this process. Seed vigour may therefore be considered a mechanically driven agronomic trait and the control of expansin expression a target. This project takes an interdisciplinary approach to uncover the genetic factors and mechanical basis of the seed to seedling transition, and seed vigour. We previously identified proteins which represent high confidence candidate regulators of expansin gene expression. Increasing expansin gene expression can increase seed vigour making these genetic targets to enhance seed vigour. These genes will be explored in the model plant system Arabidopsis. These findings will be extended to enhance seed vigour in the crop species Brassica oleracea. Mutations within newly characterized vigour genes will be identified in different Brassica plants. Together with industrial partner Syngenta, the vigour of these new Brassica seeds will be characterized. This will lead to the identification of varieties which can be used directly in breeding programs to enhance seedling establishment, field crop performance and yield. We have previously shown that the size, shape and arrangement of cells can influence the early stages of seed germination in response to growth-promoting gene expression, such as expansin. This observation highlighted the presence of mechanical constraints on plant growth. How these constraints affect the growth of seedlings however remains unknown. Understanding the mechanical basis of the seed to seedling transition is of central importance to understanding the establishment of crops in the field and seed vigour. Using a combination of 3D image analysis and mechanical modelling, the relationship between growth promoting gene expression and seedling growth will be established. In this way the mechanical basis of seedling establishment and seed vigour will be uncovered.Enhancing Brassica seed vigour will increase both crop yields and food security during this period of rapid climate change. The findings in this project may in turn may in turn be extended to other crop species.